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Post by Bill Von Sennet on Sept 9, 2008 13:00:38 GMT -5
I wish you and Nicole a safe journey.
Now that I'm feeling better I've been thinking about a journey to Alaska.
I found a place that will give me a brand new motor home at the factory in Nappanee IN and let me drive it to Anchorage next May. My only cost is for gas, propane, oil and one oil change enroute.
If I want to take some side trips it will cost me 15 cents a mile for every mile over 3,900 and $100 a day for every day over 9.
The cost of fuel could nix the deal.
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Post by Bill Von Sennet on Sept 1, 2008 20:01:06 GMT -5
Post your September Screenshots here.
You may change the Subject to something that describes the flight.
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Post by Bill Von Sennet on Aug 28, 2008 10:34:28 GMT -5
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Post by Bill Von Sennet on Aug 27, 2008 13:44:23 GMT -5
Time at gate CYVR 10:38 PT KSEA 11:33 PT
fuel at gate CYVR 1200# fuel on reaching 5,500' cruise altitude 1088# fuel at gate KSEA 726#
Fuel used 474#
I'd say there is something way out of kilter with your flight dynamics.
My route was CYVR RW12.YVR.PAE.KSEA RW16R
mY fsnav setting
Cruise 140 kts Climb 120 kts Touchdown 90 kts
Fuel flow Cruise 90 gph Clumb 155 gph Touchdown 60 gph
My plan for this flight estimated 496.7 # of fuel actual usage was 474#
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Post by Bill Von Sennet on Aug 27, 2008 12:27:08 GMT -5
Sounds like your aircraft dynamics aren't set up correctly.
A real DC-3 and my FS2004 model consumes about 90 gal and hour on cruise with power settings of 30"map and 2050 rpm.
Which DC-3 are you flying.
I will be happy to send you my air file and the appropriate section of my aircraft.cfg file.
I'm going to load up with 1200# and fly from cyvr to ksea and let you know how I do.
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Post by Bill Von Sennet on Aug 27, 2008 12:19:45 GMT -5
Sorry to hear about your fatigue problems Tom.
I have a lift chair/recliner now, and I'm still using a wheelchair with leg lifts at the computer. So I don't have to go back to bed as often as I did before. I Still have some trouble with swelling in the legs and feet. I'm on lasix to take care of the excess water.
Other than that I'm doing great. My hip surgeon saw me last week and is very happy with my progress. I am pain free in my hip for the first time in about 10 years.
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Post by Bill Von Sennet on Aug 27, 2008 9:41:57 GMT -5
Hi Flaming,
I concur with your personal freedom ethic. We need less of the government telling us what we can and cannot do.
In this case, we have kids driving golf carts in our neighborhood, and not causing any problems. We also have kids on quads roaring up and down the street wreaking havoc on our peace and quiet and just waiting for an accident to happen. I thinks its a matter for parents to supervise their own kids, we certainly don't need any new laws.
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Post by Bill Von Sennet on Aug 24, 2008 14:14:24 GMT -5
The system corrected it automatically.
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Post by Bill Von Sennet on Aug 23, 2008 13:23:14 GMT -5
PWA444 has arrived in Springfield IL
Obamas big jet arrived earlier, but it doesn't show up on flightware.com
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Post by Bill Von Sennet on Aug 23, 2008 11:14:49 GMT -5
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Post by Bill Von Sennet on Aug 22, 2008 22:30:37 GMT -5
Tom Goodrick Fs Piloting Skills « on: Mar 11th, 2007, 7:00pm »
We will discuss piloting skills both from the point of view of general flight mechanics applicable to real aircraft to specific issues for FS aircraft and controls. We will advocate use only of FS aircraft to study and practice these methods. For example, in the case of every aircraft from a J-3 Cub to a 747, the pilot uses a power setting and an airspeed to control the airplane in the vertical plane - that is, climbing, cruising and descending. Some people think it can't be that simple but, indeed, this is what real pilots do. Of course there are some practical differences between the Cub and the 747. The speeds and power for a Cub are simple while those for the 747 depend on the instantaneous weight and atmospheric conditions. When you set power and trim for a particular indicated airspeed, the plane will fly with a corresponding vertical speed. You don't have to look at vertical speed but in some cases you need to for reasons of comport. Also you may need to fly a particular glide path as when using an Instrument Landing System (ILS). You will generally fix airspeed and adjust power to get either the descent rate or the path in line with a requirement. The pitch trim adjusts the speed and the throttle adjusts the vertical speed. You might ask why I did not mention the joystick or yoke. That is because you only need to use this control to make a turn, to rotate for takeoff or to make a flare for landing. « Last Edit: Mar 11th, 2007, 7:02pm by Tom Goodrick »
Tom Goodrick Re: Fs Piloting Skills « Reply #1 on: Mar 11th, 2007, 9:30pm »
Why is indicated Airspeed so important to the proper control of an aircraft? This can be explained mathematically with some difficulty and complexity. I have seen and have used the math. But it is a bit messy so most people don't want to see it. For those who do want to see the math in as straight-forward a fashion as possible, find the book "Introduction to Aircraft Performance, Selection and Design" by Francis J Hale of North Carolina State University. I had other books in college that were much more obtuse. This one I picked up at Auburn University while waiting for a football game to start. (My youngest son was a student there.) The reason Indicated airspeed is vital to the control of an aircraft is that only indicated airspeed relates directly to the pressure causing the forces and moments acting on an aircraft. It is also directly related to the angle of attack from which the lift and drag can be separately determined. Thus, if you fly at certain indicated airspeeds, you will be assured of safe and efficient operation. let's go just a little into the fundamental physics on which this is based. Most normal flight is conducted very near steady state and very close to straight and level. In this condition, lift equals weight. Based on the equation used to calculate lift, this gives an equation in which airspeed is directly related to the lift coefficient which is, in turn, directly proportional to the angle of attack. Now within this equation is a factor called the dynamic pressure which is related to the pressure that can possibly act on a surface because of air moving near the surface. The instrument that measures airspeed actually senses this dynamic pressure. Now dynamic pressure can relate to true airspeed using the local air density or to indicated airspeed using the standard men sea level density. This is because in the airspeed instrument, the standard mean sea level density is used in the calibration. Thus a measurement of density is not required for the airspeed indicator to work. With this relation, the indicated airspeed is directly related to the aerodynamic forces regardless of altitude. We can use the indicated airspeed to tell when a plane is about to stall at any altitude. Thus, in summary, we use indicated airspeed as an indicator of both dynamic pressure and angle of attack. we don't need to know those other parameters as long as we operate within limits of indicated airspeed specied for the airsraft. The low limit would be the stall speed and the high limit would be VMO or max operating airspeed at which a simple upset could tear off the wings. The bad things that can happen - stall and wings falling off - are also related to the gross weight of the aircraft. These speeds are also tied to the weight. But we can use the speeds given at max gross weight which are higher than the speeds that would apply to lesser weights and be safe because the speeds for lesser weights would be lower. Thus if you test for stall in a plane where clean stall occurs at 65 KIAS, you may find it stalls at only 60 knots. But if you stay above 65 KIAS all the time to avoid stall, you won't stall at the lighter weight or the heavy weight. Don't think that True Airspeed is never used. It is always used as the spec for cruising speed. When somone says "The cruise speed of the X-97 is 400 knots, they mean the cruise speed is 400 KTAS. That is the speed at which it moves through the air at cruise. You must subtract the wind vector to get the ground speed. (Or, you can peek at the Garmin.) True airspeed will always be faster than Indicated airspeed. salesmen love to use True airspeed. It does have an important technical aspect in that it is used to determine the Mach number of jets. The Mach number is a ratio of True airspeed to the local speed of sound - the speed of sound at the same position and altitude. Stability, controllability and performance of jets depends on Mach number once you are above 30,000 ft. Indicated Airspeed for takeoff is chosen as 1.3 times the clean stall speed at gross weight. For jets where a very large percent of the gross weight is in fuel which can change, the safe takeoff speed V2 is calculated based on the actual takeoff weight. it varies with the square root of the weight ratio. Commercial pilots are required to make this calculation for every takeoff. I have saved the FS jet pilot the trouble by including a calculation made by the computer and displayed on the panel next to the airspeed indicator when the aircraft is on the ground. Indicated Airspeed for landing is also based on 1.3 time stall speed but in this case the configuration used is flaps down and the weight is maximum landing weight (normally much less than the max takeoff weight meaning a jet must fly and burn fuel before landing if it took off near max gross weight). This airspeed for landing is called Vref and is flown during final approach with full flaps. Again, I made a gauge that calculates and displays this for jets based on actual weight. (A fancy computer with weight sensors used on the ground and fuel-on-board calculations makes this Vref calculation. The result is displayed next to the airspeed indicator when the landing gear is lowered. Unfortunately, Microsoft has thoroughly screwed up the matter of Indicated and True airspeed. They specify that true airspeed is to be used for stall conditions. They also say that using indicated airspeed rather than true airspeed diminishes the realism. They have some ignorant employees. At least they were kind enough to let us use indicated airspeed. Make sure you have that set under "Realism." « Last Edit: Mar 11th, 2007, 9:32pm by Tom Goodrick »
Tom Goodrick Re: Fs Piloting Skills « Reply #2 on: Mar 12th, 2007, 9:27pm »
Use of controls and control sensitivity are areas in which FS differs from the real world. The physical connection to the aircraft for the pilot is rather different in the sim. You must understand this and be prepared to make adjustments that will suit you with your equipment. There are also control procedures that real pilots use that are not what some simmers expect. Of course the first thing you must add is a control input device. In theory you can use the keyboard for everything. But this does not work well. You cannot input more than one control at a time using the keyboard. Flying requires that you do this in several instances - pitch inputs at the same time roll and yaw inputs are made. A good control interface can also reduce the unnatural aspects of sim flying. You need to be able to look outside and back at the panel. You must always be able to read the panel instruments accurately though you must also be able to look out and spot the runway as you line up for an approach. The controller must have axes for pitch and roll. I like a stick because I first learned to fly an airplane with a stick. Now on FS i fly many aircraft that in reality have yokes. But many aircraft do have sticks which are making a comeback to some extent. A stick is particularly well-suited if you want to do aerobatics. The stick will still work well for normal flying. A yoke is not too good for aerobatics. The best answer is to get one of each and use them as appropriate. (This may be a hard sell to the wife. Rudder pedals are important. As a student pilot you would be taught very early to use the rudder properly in making turns. The pedals are also used to steer on the ground. Most prop aircraft have a storng left yaw tendency when you add full power for takeoff. this is normally counteredt with rudder. If you have to use the stick or yoke for this it makes things difficult. It is unnatural. Similarly, many aircraft should be slipped a little on final approach, expecially in a crosswind. This requires that the roll be set opposite to the yaw - not possible without rudder pedals. You will need to have a good and quickly effective throttle control. I am happy sing the keyboard for this though I have a control on the joystick I could use. My reason is I can make very precise control inputs with the keys which I need to set the power exactly. i have learned to do this quickly. Most throttle controls built into joysticks or yokes seem to me to be very cheap. people have reported problems flying airplanes I fixed up. Then we find it is a noisy throttle control. Ther are good separate throttle controls and even quadrants with throttle, prop and mixture levers for one or two engines. These look great but they are expensive. Still, I might pop for one of them one day - before I pop for a sim upgrade! A good controller should also have extra buttons and switches that you can define as needed. I like a button for nose-up and for nose-down trim. It is very realistic. I use mine all the time when flying. I also have a hat switch I use to quickly look left or right. To look half left or half right, I use the number keys on the right numpad. I also use keys for landing gear, spoilers and pairs of F keys for prop, mixture, flaps and brakes. I have changed many of the key assignments so these lie in order across the top of my keyboard. I made a simple paper label that I tape across the top of the keyboard F1 through f4 are the throttle keys as set by defult. These controlelrs must first be calibrated using the Windows calibration scheme. You may also have a disk or Cd furnished with the controller that should be run before calibration is attempted. It will set drivers and some special Windows calibration software. Once the initiial calibration is completed, start FS and go flying, using an aircraft with which you are very familiar. This is no time to try a fancy new aircraft. Turn off the wind using Clear Weather. While doing this indoctrination flight, check the control sensitivities and null widths set within FS. The "joystick" control sensitivity and null width can only be set within FS itself. Go to Options, Select Controls and then Sensitivities. Click on Advanced. Bear in mind what works for me may not be to your liking. But you will probably want something other than the default settings. When making these changes, test with a very familiar aircraft that you have flown a lot. These adjustments are meant to take out peculiarities in your controller that are not related to any specific aircraft. Note first that your control device should be shown in the window. Mine says "CH Flightstick Pro". next there are sliders for sensitivity and for null width on each of the main control axes - ailerons, elevator and rudder. There could be others such as throttle if you have that set in the calibration of your device. (This is to be done after you have calibrated the device.) My settings for sensitivity are for ailerons 50%, for elevator 25%, for rudder 33%. The settings for all null widths are 25%. The purpose of the null width is to handle any chatter you may have in the controller - digital or analog noise. I have had several sticks go bad sending noise into the controls. There is one more sensitivity that gives a lot of people trouble, particularly for those transitioning to rudder pedals for the first time. This is the nose wheel turn angle. It is set in the aircraft.cfg file for each aircraft in the section labeled "[contact_points]'. (Note that any .cfg file is simply a text file you can read and edit using Note Pad. tech your computer to treat these files as .txt files.) Not all files have a key telling you the components of a line in the contact_points section. Check a default aircraft like a Boeing to find the key. You can copy the key into any other aircraft .cfg file since it is just a series of remarks. On an airplane that is difficult to keep straight during takeoff, reduce the wheel angle by editing the line in the .cfg file. I seldom set the turn angle for the nose wheel less than 20 degrees. But, often I'll find values of 60 to 90 degrees in downloaded aircraft. I always reduce them to 30 degrees or less. But you can get used to anything after a while. Often, by the time I have tested an aircraft enough to get other bugs worked out, I have learned to live with a large angle. You don't need a large angle here, even if there is one in the real aircraft. Also, if you have an aircraft you really like and want to fly it a lot but are having some problems controlling it, it pays to look in the aircraft.cfg file for the "[flight_tuning]" section and play with the aileron, elevator and rudder sensitivity scalars. (A scalar is a number of about 1 that is a factor to the actual control parameter. 1.0 means no change, 0.9 means a 10 percent reduction and 1.1 means a 10 percent increase.) I find that elevator sensitivity is usually too high. Sometimes aileron is too high as well. This will improve the handling of only that particular aircraft. I find often that FD designers have over -cooked the control sensitivities, notably the elevator sensitivity. You just want to be able to raise the nose adequately on takeoff when the proper amount of pitch trim has already been set for takeoff. Don't leave so much sensitivity for elevator that you can rotate without regard to the trim setting.
Tom Goodrick Re: Fs Piloting Skills « Reply #3 on: Mar 12th, 2007, 10:15pm »
Pitch trim setting is a major aspect of pilot control technique that many non-pilots have no knowledge about. Pilots themselves almost forget that they use it all the time. it becomes second nature, like using rudder in a turn. But it is vital to proper control of the aircraft. The forward or backward motion of the stick or yoke only has a limited range of control. The pitch trim must be used to augment this control. For takeoff there is usually a setting marked in real aircraft. I usually put a remark in the checklist as to what pitch trim setting to use for takeoff. Sometimes it varies with different weight or CG position. The value is in degrees. I give you a pitch trim value on the panel shown in degrees as well as weight and CG position if that is needed. Set the trim for takeoff. The pitch control should be set for spring centering at neutral. A control that outputs forces is not necessary and not desireable in my opinion. Just spring centering is needed. After takeoff, with a slight pitch input needed to rotate, set the speed for climb using the stick or yoke. Then dial in enough pitch trim to take out the stick force so it will fly without your hand on the stick. This will work during most of the climb. I usually turn on the wutopilot at this point having set the cruise altitude and either a flight heading or with a flight plan entered I'll turn on NAV mode (set the NAV/GPS switch to GPS) and let the autopilot control pitch trim to maintain a particular rate of climb and heading or as needed to follow the path on the flight plan. I just adjust the power between climb and cruise. If you are flying manualy, you have a lot of work to do and you will probably never do it perfectly. You must level off at cruise altitude, reduce power slowly to cruise power as the speed increases. Here you don't set a speed, you set only the power and the speed happens, depending on your weight, whether flying manually or on autopilot. But on autopilot the steady cruise condition is reached very quickly because the autopilot responds quickly and with just the right amount of conrol change to get to equilibrium flight with all forces balanced. You will probably chase the phugoid for quite a while. The phugoid is the undulating motion that happens when the lift does not balance the weight. Though this is a pitch motion, the angle of attack remains constant during phugoid motion. The lower lift causes a slight descent which adds speed starting a levelling off with the lift greater than the weight. It then starts a slight climb. Then it will slow down with the lift less than the weight The damping of this motion depends on the drag if the controls are not changed. Clean airplanes with little drag will oscillate for a long time. The solution is quick and short pitch trim inputs when the speed is at a medium value. The autopilot does this very well. Whenever I want to test a plane in cruise to lsee if its speed is corect, I use the autopilot. I don't waste time trying to stop the phugoid. On a draggy plane like a Cub or a Champ, the phugoid is well-damped so you can get it to fly steadily without much trouble. When I was flying real aircraft in the real world (which is fairly bumpy), I don't think I every had the plane in steady cruise for very long. I always had a hand on the stick or yoke and was "diddling" with it continuously. I had no autopilot. I also never had the aircraft precisely "on" its specified cruise speed. It was probably close but off by a couple of knots. So don't feel bad if you can't hand fly an airplane steadily in FS. Use the autopilot like a pro would.
Tom Goodrick Re: Fs Piloting Skills « Reply #4 on: Mar 15th, 2007, 3:38pm » NOTES ON USING THE MIXTURE CONTROL IN FS9 If you fly a plane in FS9 that has a normally-aspirated engine, you must learn to use the mixture control in order to climb and fly above 4,000 ft. But if you fly a tubocharged aircraft, you should do nothing except leave the mixture on full rich (fully in against the panel). If you don't know which way a plane is set up, check the aircraft.cfg file. If the aircraft is normally aspirated, like this C172SP, you'll find this line in the [piston_engine] section: turbocharged= 0 //Is it turbocharged? 0=FALSE, 1=TRUE If it is turbocharged as this Mooney Bravo is, you'll find this line: turbocharged= 1 and then you should look for this line: fuel_air_auto_mixture= 1 //Automixture available? 0=FALSE, 1=TRUE This has not always been the case so, if you see turbochaged=1 and fuel_air_auto_mixture=0, you should change it to =1. The reason is that real pilots of turbocharged aircraft are taught to push the Mixture to full rich to begin and to maintain a climb at any altitude. Thus the operation will be realistic. Unfortunately, in real life, the pilot can adjust the mixture once he gets to cruise altitude where we cannot. But both the piloting technique and the performance is more realistic for tubocharged aircraft if auto mixture is used. There is a slight departure from realism when using the mixture control with non-turbo aircraft. Real pilots (and some notes in FS documentation) are told to adjust the mixture to get a max on the EGT and then go beyond the max on the lean side. But in FS this does not work well. The thing that does work well is to adjust the mixture to see a maximum fuel flow. That coresponds to the maximum power you can get from the engine at that condition. That means you'll get good performance and will be treating the engine well for long life. There is a big myth in aviation that pilots should lean for economy. They are probably even told to do that by the companies that own the airplane. But to lean for best economy, you would lean beyond max power to a higher temperature (EGT). This can easily cause engine wear and it does not save as much fuel as simply setting a lower throttle position would give you. There have been many cases reported where post-crash analysis showed engines were burned out when they failed by the leaning practices of the pilots. As you climb in a normal aircraft, leaning to max fuel flow will keep you climbing as well as you can. Failure to do anything will leave you down low and slow. Note that you cannot tell if an airplane is turbocharged by any means other than checking the aircraft.cfg file. One clue is that turbocharged engines usually have a TIT gauge for Tubine Inlet Temperature. This can cause problems if the mixture is not adjusted properly. Mooney made the Bravo and the 231 with turbocharging but the 201 and MSE did not have turbocharging. I have four versions of the Skylane, two with turbocharging and two without. « Last Edit: Mar 15th, 2007, 3:39pm by Tom Goodrick »
Ed_Burke Re: Fs Piloting Skills « Reply #5 on: Mar 15th, 2007, 6:35pm »
" Real pilots (and some notes in FS documentation) are told to adjust the mixture to get a max on the EGT and then go beyond the max on the lean side." I knew a chief engineer of an air charter business who threatened to nail any of his pilots to the wall by their dangly bits if they used that leaning method, despite it apparently getting the ok in some ops manuals. He reckoned the risk of detonation was too high and the extra fuel was engine insurance. Peak the EGT and then drop it on the rich side was his instruction. Ed « Last Edit: Mar 15th, 2007, 6:38pm by Ed_Burke »
ED B
flaminghotsauce Re: Fs Piloting Skills « Reply #6 on: Mar 15th, 2007, 8:07pm »
I was taught that as well. Tom's method is simpler to implement, and works well for power, so I do it that way now. Our fleet of 172's were not equally equipped, and I only recall a couple having an EGT. We were taught to adjust mix to best RPM, or peak EGT leaning to rich side. One instructor told me to never lean during a climb, leaving a richer mixture to cool the engine until reaching cruise altitude.
"Barring all differences, they're identical!"
Tom Goodrick Re: Fs Piloting Skills « Reply #7 on: Mar 15th, 2007, 10:34pm »
If you try climbing on a rich mixture in FS9, you'll reach a level near 6,000 ft where the engine will not have sufficient power to climb. I don't know if this is realistic. 6000 ft is about the altitude at which a normal engine can generate no more than 75% power even at full throttle when leaned correctly. « Last Edit: Mar 15th, 2007, 10:36pm by Tom Goodrick »
Tom Goodrick Re: Fs Piloting Skills « Reply #8 on: Mar 30th, 2007, 9:30pm »
Some thoughts on GLIDING that every pilot of a single-engine aircraft should know about: Some people talk about "Glide Angle" and others talk about Glide Ratio." I have done a lot of work in this area and understand the situation. There are two problems: 1) which is better to talk about Glide angle or Glide ratio" and 2) How can you best measure glide performance? First, it is best to use glide ratio. The two are related. The angle is the arctangent of the glide ratio. Or the tangent of the angle is the glide ratio. The reason the ratio is best to use is for practical purposes and for its strong basis in theory which leads to a simple way of testing - much simpler than trying to glide to a VOR. First we must recognize and work with the differences between indicated airspeed and true airspeed. We use indicated airspeed to set up the test. My 172 POH says the best glide comes at 80 mph. That is 69.6 knots indicated airspeed. We should use that speed to set up the test. Why? that is based on the theory of flight. For each glide speed, at a given weight (max gross is assummed here), there is a particular pair of lift and drag coefficients. There is also a particular angle of attack that pprovides these values of the coefficients but we need not bring that into the discussion. The ratio of CL/CD is the same as the ratio of the true velocity components VH/VV and is the same as the glide ratio X/H. this statement is founded in the technical definitions of lift and drag, and in the basic kinematics that speed components define the path if the ratio remains constant. Notice I did not say the speeds remain constant (although the indicated airspeed can and should remain constant). What is practical about the glide ratio? The glide ratio is the ratio of the distance travelled, X, over the height dropped, H or X/H. If the glide ratio is 8.2, then X = 8.2H or 8.2 times the altitude. From 8,000 ft, you can go 65,600 ft which is 12.4 statute miles. There was a time I relied on this. I was flying back from Provincetown, Massachusetts across Cape Cod Bay to the area near Plymouth and wanted very much to keep my feet dry. I circled over Cape Cod and climbed to 8500 ft before setting off across all that water. That meant if the engine quit before I reached 12 miles from the shore of Cape Cod, I could turn back and glide back. When within 12 miles of Plymouth, I could relax because I could glide to the mainland. To measure glide ratio, you don't have to sit in the plane and fly a constant KIAS for 20 minutes. Just start gliding at any altitude and measure your airspeed components accurately. I developed a "Turn Test Gauge" that is good to have. You can get it from my web site. It will give the true airspeed in decimal knots. Use my landing speed to get the vertical speed. Start a glide at 70 KIAS and smoothly adjust the trim to hold steady speed components. When the components are steady, regardless of altitude, read the KTAS, VA and the vertical rate VV in feet per minute. Convert each to feet per second: 1) multiply KTAS by 1.689 and 2) divide FPM by 60. Then calculate the horizontal airspeed component VH: VH = SQRT(VA*VA - VV*VV) using the FPS values of each. Then get the glide ratio: = VH/VV. What is happening during the glide: 1. If you keep the indicated airspeed constant, then the angle of attack is constant and the values of CL and CD remain constant. 2. As you descend, the vertical speed decreases in magnitude as density increases. The true airspeed also decreases by a proportional amount so that this ratio remains constant at all altitudes from start to finish of the glide. The indicated airspeed is independent of density and altitude so it can remain constant once set up with proper trim that does not change. In theory this ratio does not change with changes in weight. But that theory assumes the CG position is constant. Since partial loads can also change the CG and, thus, the trim, it would be good to test a couple of airspeeds and a couple of loadings, one CG forward and one CG aft. I have not done this test myself but it is a good thing to do. It should only take a few minutes. It would be interesting to do it for several single-engine aircraft because this is all we have when the engine goes quiet. The flaw in all this neat theory is the wind. The real glide ratio is (VH-W)/VV where W is the headwind component in feet per second. This will be worst at altitude. It is the reason pilots should pick the airport most directly underneath their position and begin maneuvers to land there when the engine goes quiet. Now I will copy this so it won't vanish when the server gets too busy.
Tom Goodrick Re: Fs Piloting Skills « Reply #9 on: Mar 31st, 2007, 10:34am »
There is a simple way to prove with geometry that L/D = Vh/Vv = X/H. Start by putting a dot on a piece of paper that represents the mass of the airplane. Then make a downward arrow of a certain length and an upward arrow of the same length. The downward arrow is the weight vector acting on the aircraft in a glide.Call it W. The upward arrow is the resultant, R, of all the aerodynamic forces acting on the aircraft. There are no other forces - no thrust because the engine is off. (The prop may produce drag but we lump that with the drag from the rest of the plane.) Now draw a long straight line slanted downward. This is the glide path. Don't lable it now. It makes an angle gamma (call it what you wish) with the horizon. This is the glide angle. Put an arrow head on that line about an inch from the dot and lable it Va. That is the airspeed vector. Next make a line going up perpendicular to the path. Make it just long enough so an arrow going back at a right angle will connect to the R vector. The upward arrow is the Lift vector, L. Make a back arrow from the mass point back in an extension of the airspeed vector and in opposition to it but only long enough to make a connection from the lift vector to the R vector in a parallelogram. Next put in horizontal and vertical airspeed vectors from the poiint going forward to connect to the end of the airspeed vector. These are Vh and Vv. Next pick any point along the line and draw a vertical line down to a point and then draw a horizontal line from that point to intercect the glide path. This is the ground. The vertical line is the altitude H and the horizontal line is the distance X over which we will glide. Now we have three over-lapping similar triangles: RDL, VhVvVa and pathHX. All have a right angle in one corner and the flight path angle gamma in another corner. They are similar but of different sizes. That means the leg ratios are constant. Hence L/D = Vh/Vv = X/H. For the typical aircraft this will be about 8. For a smooth, clean sailplane it can be as high as 50. For many airliners it is about 10. This ratio L/D is actually the ratio of the lift coefficient to the drag coefficient. It is independent of density. It plays an important part in many aspects of flight. In cruising flight it is the ratio of weight to thrust. In a climb, it influences the rate of climb for a given amount of thrust. As long as the aircraft is stable, it will naturally sit at its trim angle of attack and will generate the same pair of values of CL and CD so that ratio remains constant. The indicated airspeed will also be constant. We can use that feature to change the glide ratio if we want to. While the forces appear to be balanced, the motion is quasy-steady-state. There is a gradual deceleration as the aircraft moves into the more dense air at the low end of the glide. You control the glide ratio by picking the indicated airspeed for the glide. You want to pick an airspeed sufficiently above stall so that you can make a flair before touching the ground. 70 KIAS is the best value for a C172.
Tom Goodrick Re: Fs Piloting Skills « Reply #10 on: Mar 31st, 2007, 2:02pm »
It's always a little scary to climb on a soap box and say "This is the theory..." because some guy in the back row will yell out "Can you prove it?" I did some experimenting and the answer is "Yes, I can." But, of course, there is some variation in the experimental data. I popped a C172 SP up to 10,000 feet from its position on the parking ramp and let it glide. The engine was off. It went into a stall and by the time I got it nice and steady, the altitude was 6500 ft. This was loaded at gross of 2549 lbs and the CG was at 22.03%. I did not record the trim but I got it steady at 70.52 KIAS where I saw 77.6 KTAS and -762 FPM. This gives 10.27 for L/D. I let it glide without touching it and it became quite steady. At 5500 ft it showed 70.46 KIAS, 76.4 KTAS and -682 FPM for an L/D of 11.31. At 4500 ft it showed L/D of 11.14. I trimmed for a faster glide by setting the trim at 11.2 degrees. I got this data: 7500 ft, 75.18 KIAS, 84.0 KTAS, -832 FPM, L/D=10.18 6500 ft, 75.18 KIAS, 82.7 KTAS, -887 FPM, L/D=9.40 5500 ft, 75.08 KIAS, 81.4 KTAS, -867 FPM, L/D=9.46 4500 ft, 75.07KIAS, 80.2 KTAS, -855 FPM, L/D=9.45 I reset the load to 13.03% and 2029 lbs. At the same trim of 11.2 degrees, I saw 8500 ft, 79.92 KIAS, 90.6 KTAS, -988 FPM, L/D=9.24 Then I trimmed at 16.4 degrees and got a slower glide. 8500 ft, 70.75 KIAS, 80.3 KTAS, -887 FPM, L/D=9.12 7500 ft, 70.76 KIAS, 79.1 KTAS, -860 FPM, L/D=9.27 6500 ft, 70.75 KIAS, 77.9 KTAS, -849 FPM, L/D= 9.24 5500 ft, 70.76 KIAS, 76.7 KTAS, -836 FPM, L/D=9.24 4500 ft, 70.76 KIAS, 75.6 KTAS, -825 FPM, L/D=9.23 I checked a Piper Archer II and found similar results. At gross weight, 70.9 KIAS gave L/D=9.97. At 75.1 KIAS, I saw L/D=9.99. I have the data on a spread sheet. I recorded five sets of data at five altitudes. While the C172 glided fairly straight ahead, the Piper Archer turned steadily at about 0.5 degrees per second. A touch of rudder would have kept it straight. Here is a quick summary of several other tests I made. I'll just give a representative glide ratio (L/D) for each aircraft. But, I did take data at four or more different altitudes in each case. They are logged on my Excel sheet. Piper Cherokee 180 L/D=9.8 Cessna 182 L/D= 8.8 *Cessna 182 RG L/D= 12.16 *Mooney Bravo L/D= 9.68 *Velocity XL-5 L/D= 11.76 *Bonanza V35B *Piper Malibu Mirage L/D= 12.25 * retractable gear with gear up. All are at max gross weight. The aerodynamically clean retractable aircraft have a high L/D but are tricky to fly for this experiment because they have a long and low-damped phugoid. They oscillate in pitch all the way down rather than reaching a steady condition. The Mirage cannot use its glide ratio if the engine stops when cruising above 15,000 ft because their first job is to get down below 12,000 ft as fast as possible without exceeding the max safe airspeed. The pressurization is lost when the engine quits. Also, when I was testing the 182 RG, I got a taste of the real problem with some of these aircraft. I had finished a testat 4500 ft and was going to do a test at 3500 ft when the battery gave up. I lost all instruments except the airspeed and altitude so I set up for a landing on a handy road. But I could not extend the gear so I changed my target to a nice flat field. On final I found I could not lower the flaps either. The landing was good but a little fast - 70 KIAS. « Last Edit: Apr 1st, 2007, 11:12pm by Tom Goodrick »
Tom Goodrick Re: Fs Piloting Skills « Reply #11 on: Apr 7th, 2007, 12:15am »
In the section on sailplanes in the FS2004 thread, I mention that I made a Glide Ratio gauge and posted it on my web site. This gauge is handy on the panel of a glider. But it does not belong on the panel of a powered aircraft. Instead, it can be placed in the panel.cfg as a pull-down gauge to use when you want to study the glide chanracteristics of an powered aircraft. To put it there just insert the floowing lines in the panel.cfg: [Window02] size_mm=64,48 window_size_ratio=1.0 position=2 visible=0 ident=Glide gauge00=Digital!Glide, 0,0 The window number you assign depends on the number of other windows you have. I'd place it in a high-numbered window becaues it will seledom be used. Name the window in the top few lines of the file. Also, the name of the file can be simply "Glide" if you put it in your main Gauges Folder when you download it from my site. here I call it Digital!Glide because I have it in a sub folder of Gauges called Digital. I used it on the C182 to get the following values: Trim KIAS L/D 4.1 100 8.5 6.7 90 8.6 10.6 80 8.8 (The trim values are in degrees measured by my pitch trim gauge.)
Tom Goodrick Re: Fs Piloting Skills « Reply #12 on: Apr 13th, 2007, 3:51pm »
FUNDAMENTALS OF MEASURING AIRSPEED AND VERTICAL SPEED To make my Glide gauge work, I simply read the vairables named "True Airspeed" and "Vertical Speed" that are made available by the Mirocoft people who designed the FS9 program. But you might ask whther there is a way it can be done on real aircraft. The answer is "Yes". For sailplanes it is done all the time. It dawned on me that many FS fliers may not be familiar with the fundamentals of how aispeed and vertical rate are measured on an airplane. The whole basis for the validity of the Glide gauge described above is in the fact that these measurements are based on different aspects of the physics of motion through the atmosphere. Finding the true "Up" direction in an aircraft is very difficult. Nothing really does it well in a static sense. If you see a bubble in a tube, you must realize it is not showing "Up". You can dangle a nice plumb bob and not find "Down." The reason these do not work is that the aircraft is generally accelerated in all three dimensions. This means the plumb bob and the bubble will respond to a combination of gravity and acceleration that results from the motion of the aircraft. That does not detract from the use of the turn and bank indicator, in fact, it reinforces the utility of that gauge. When flying a steady, banked turn, the bubble indicates where local "down" is during the turn but that local "Down" is not True "Down" as you can easily see. It points to the floor when the pilot is flying the turn correctly. Sitting in a seat, you will feel the pull directly "Down" into the seat and yet the airplane may be banked at 45 degrees to the vertical! So how do we measure "vertical speed?" We measure it using a device that shows the difference between two air pressures the current pressure and the pressure that existed about 1 second before. There is a very standard and fixed gradient of air pressure in the atmosphere from the surface up to a very high altitude. This gradient, or change per unit altitude, is used to calculate the vertical rate as an aircraft climbs or descends. It is handy because it has nothing to do with the attitude of the aircraft. (It uses the pressure pushing against a port on the side of the aircraft. This can be inaccurate momentarily if you slip the aircraft significantly but is not affected by pitch attitude at zero sideslip.) You might think this method of comparing old and new pressures. Indeed there is a line in the aircraft.cfg file that enables you to set a delay in the vertical speed reading. I think it is a mistake to use that with any significant delay. In fact the reading is very responsive. I have held these devices in my hand while they were connected to a PC and have seen the change in rate as I raised and lowered my hand. I saw no indication that there was a delay. The changes at the end of thet large tube occur imediately in comparison to the pressure at the end of the small lag tube. The rate of propagation of pressure in a tube slows down with smaller diameter. This is done in tubing that is built inside the case of the vertical speed device. How do we measure True Airspeed? Airspeed is measured as described above in this section but it warrents more discussion in this context. To compare with the vertical rate which is a true speed, we need a true airspeed rather than an indicated airspeed. This can be obtained two ways. In powered aircraft, the standard way is to get the indicated airspeed by measuring the difference between the pressure at the front end of a tube pointing into the relative wind and the pressure at a hole in the side of the fuselage. Bernoulli's Law says the difference between the total pressure on a streamline that stops in the end of a tube, is higher than the "static" pressure in streamline that passes along the side of the tube. The difference is called the dynamic pressure and varies with the density and the square of the speed. Indicated Airspeed is calculated and displayed based on the use of sea level density regardless of altitude. It works fine for pilots to use to keep the plane flying at a safe speed. But to get true airspeed, there must be a connection to the altimeter and a small calculation (digital or analog) that determines the true airspeed. There is another way to measure true airspeed directly. I was able to use this alternative method in my parachute testing and sailplane pilots make use of this method routinely. I utilizes the physical principle that the frequency of vortices shed from an object protruding into the flow depends directly on the true speed of the flow. All you need is an audio circuit that detects the frequency down stream of a protrusion. The device I used ws housed in a low-aspect ratio airfoil fin that stuck out from the fuselage. (We built a sloping nose fairing on the front of our instrumentation box and the checked the calibration in a wind tunnel. The fin was sticking out of the fairing on the nose. We had to check for angle of attack effects. We were able to minimize those so that we measured true total airspeed of the box hanging below the parachute.) This fin had a rectangular channel from fron to back with a diamond section cross bar. An audio signal of know and precisely controlled frequency was injected up stream of the cross piece. A small microphone picked up the sound downstream and showed us the change in frequency caused by the flow over the cross piece. It worked very well. Its readings were linear with airspeed. That device was intended for use on helicopters and V/STOL aircraft because it could measure very low airspeeds which cannot be measured by the pitot static system. Unfortunately it did not work on those aircraft because of the extremely high noise environment. Thirty years ago I did experiments on my own that showed you could do this with a cheap microphone, tape recorder and voltmeter. With my wife driving, I would hold the mike out the window of the car and watch the voltmeter which was connected to read the average AC volts from the headphone jack on the tape recorder. I worked up a crude calibration chart. The ony problems were extraneous noises. Having good measurements of the speed components (VT and VV), we can get the glide ratio by finding VH = SQRT (VT^2-VV^2) and then calculating VH/VV. « Last Edit: Apr 13th, 2007, 4:00pm by Tom Goodrick »
Tom Goodrick Re: Fs Piloting Skills « Reply #13 on: Apr 16th, 2007, 9:30pm »
Today the wind was very gusty at many airports from the Southeat to the Northeast in the US. It made me think we need to talk about what airplanes work best in gusty winds and why. When an aircraft in cruise moves or climbs into a region of higher or lower wind, the change is slow enough so there is very little aerodynamic effect on the aircraft. The aircraft is accelerated or decelerated but at such a slow rate that the airspeed won't be seen to change. But get an airplane into gusty conditions and the airplane definitely feels the wind. Why? Read the article below. I'll have more discussion later with tables showing how different aircraft respond to wing gusts and to extreme turbulence. Then we'll pick some good airplanes for the job and go flying. I saved the RW for this morning. EQUATIONS PERTAINING TO GUST LOAD FACTORS (The simplified Goodrick Method.) Here is the basic equation that I've kept in my head for years. V = 17.16 * SQRT((W/S) / CL)_______________________________________________________{Eq 1} where V is in KIAS, W is weight in pounds, S is wing area in square feet (= span times mean chord) and CL is the lift coefficient. The constant 17.16 comes from using sea level density for which IAS is valid and converting speed from fps to knots. This applies when the aircraft is in steady, level flight. Each of these variables takes on certain values in certain cases so we have to discuss them a little. Until all are explained, let your wonders accumulate. Don't get hung up on these. One thing you should notice soon is that W and S never appear alone. They always appear as the ratio W/S in a finished equation. This ratio is called the wing loading. But we must be careful which W we use because W can be different on different flights and at different times during the same flight. It turns out this ratio is a key to good windy flying. The higher its value, the better off you are in any wind. If you can remember this, then the relatively straight-forward logic I'll discuss will get you any of the other useful equations with just a little algebra. For the first manipulation, let's turn this around so it gives the value of the lift coefficient CL because most of you are wondering how we can get that. I'll show you how we can get the ball park for that value. CL = 294.466 * (W/S) / V^2______________________________________________________{Eq2} You could look in abook or tech report that gives CL versus angle of attack for a bunch of airfoils but we'll get a ball park for this value in the following way. Use the clean stall speed (always assummed to be at max takeoff weight) to determine the highest value CL can have, called CLmax. We need to mention the significance of CLmax. It defines the stall condition. It is at the slowest speed at which the plane will fly steadily wihtout losing altitude though it is on the verge of falling from the sky. But, the fact that we can make the airplane fly level at least briefly at that speed (with lots of power) means that the stabilizing power of the tail is sufficient to make the airplane reach that lift coefficient. Indeed the fact is that the plane is capable of reaching that lift coefficient at ANY SPEED. That is how we find the max load factor. We assume we are flying along in steady conditions in level flight at some higher speed, with all forces nicely balanced and then something strange happens that makes the plane rotate quickly in angle of attack to a very high value. The plane can experience no greater force than when it reaches this lift coefficient. At a higher angle of attack it would stall and forces would drop. For the Cessna 172SP this stall speed is 53 KIAS (based on our assumption in FS9 that KCAS = KIAS). W/S = 14.66 psf. Thus CLmax is 1.536. The fastest we can fly at 75% power gives us a speed of 111.8 KIAS (measured at 3500 ft but any altitude is good if 75% power can be developed). From this value we fine CL=0.345. Thus we know that, unless we do a nose dive which no good pilot would want to do, our Cessna 172SP spends its life flying with a CL between 0.345 and 1.536. Now if you are sufficiently computationally motivated, you can plug in values of CL between these extremes in Eq 1 and see what indicated airspeed results for any CL. Now here's an eqaution from which Eq 1 was actually derived but will start with it here to go farther toward getting a load factor caused by a change in lift from either a horizontal gust or from a change in angle of attack. The lift force F at speed V (KIAS) and any value of CL for the wing reference area, S, is: F = (CL*S*V^2)/294.466______________________________________________________ __{Eq 3} where the ^2 means the speed is squared and the constant is simply our friend 17.16 squared. This just happens to be the basic definition of the lift force, F. Now we play a simple trick to get a better format for load factor. We divide both sides by the weight W. Now we have F/W = (CL / (W/S) *V^2) / 294.466________________________________________________{Eq 4} Some folks like to add 1 to this before they call it a load factor. But if you are cruising at a value V1 and insert the value for CL that you would get from Eq 1, you will get the Value F/W = 1 meaning there is only the normal 1 g load factor applied to the aircraft. That seems good enough for me. Notice that our 'algebraic slight of hand' put the W back with the S on the right side. But now let's see what can break the airplane. Let V1 be something like our speed at 75% (111.8 KIAS) and then put CLmax into Eq 4. You will get 4.45 g's. That might not be enough to break the 172 though it is close. But now suppose we are flying lightly loaded. There is only one person on board with no luggage and only 40% fuel. For this case W/S is11.218 and our steady cruise speed at 75% power is 114 KIAS. Now Clmax gives F/W = 6.04 and we have TROUBLE. In a nutshell, this is the sort of thing that got Scott Crossifeld, the famous test pilot, whose Cessna 210 came apart in a thunderstorm over northeast Georgia last summer. (He had just given a lecture to some CAP cadets at Maxwell AFB on flight safety.) We don't have to say HOW this can happen. The fact is it CAN happen. The light load lets your engine pull the plane a little faster than normal. But the sudden change in CL to CLmax that CAN occur, DID occur, probably due to a little mix of Murphy's Law and Mother Nature being a witch. Now let's go one step further and see what happens when we encounter a specific horizontal gust. We'll use V1 as our steady level flight speed again and Vg (in knots indicated) as the gust speed that Murphy's Law says we must encounter as a headwind. When hit by this horizontal gust, we assume that CL DOES NOT have time to change, and there's nothing to change W/S in the short time it takes the gust to hit. So let us take Eq 4 and divide it by itself with the 'before' condition (V=V1 and F/W=1) in the denominator and the gust load Fg/W in the numerator with V= V1+Vg. We have (Fg/W) / 1 on the left and just ((V1+Vg)^2) / (V1^2) on the right. Thus Fg/W = (1+ Vg/V1)^2________________________________________________{Eq 5} and we have our grand equation for the load factor due to the gust Vg at the steady speed of V1. For the Cessna 172SP at 75% power at a heavy weight, this is 1.39 for a 20 knot gust. That is enough to shake you a little bit but it won't break anything by itself. If you are holding the yoke lightly by two fingers as I used to, it can be a bit of a surprise. But if you are flying slowly at 80 knots it will be 1.56. The slower you fly the more of jolt you will feel. This process is independent of how you load the aircraft because W/S cancels out of the equation. It is simply a function of the change of speed. 20 knots added to a large speed is no big deal. But added to a small speed it can be a very big deal as far as contributing to a sudden upset is concerned. Aeronautical engineers who don't fly generally ignore the effects of horizontal gusts. But pilots will notice it. I'll make some more calculations for other planes. So far I have just done the Skylane which is a slight improvement over the Skyhawk. At cruise a 20 knot gust gives the Skylane a bump of 1.32 g's. But at cruise a sudden shift to max CL will give the Skylane a bump of 5.89 g's if heavy and 8.189 g's if light. You have to slow down significantly if light in bumpy air. ~~~~~~~~~~ADDENDUM~~~~~~~~~~~~~ Having lived with these equations now for a few days and having made calculations for various aircraft, I found a better way of looking at the turbulence load factor as given in Eq 4 using CLmas (which is the CL at stall). If we write Eq 2, using stall speed VS and max weight Wmax to get the CL at the clean stall speed specified for the aircraft, we can then substitute that expression for CL in Eq 4. The result is a much handier expression for the turbulence load factor: Fmax/W = (V/VS)^2 / (W/Wmax)__________________{Eq 6} « Last Edit: Apr 18th, 2007, 11:27am by Tom Goodrick »
Tom Goodrick Re: Fs Piloting Skills « Reply #14 on: Apr 18th, 2007, 11:38am »
The two main equations from the section above, Eq 5 and Eq 6, have been used to make generalized plots of load factor. In each case the load factor is plotted against speed. But in the case of turbulence, we use the speed ratio V/VS, the ratio to the official stall speed.
It is important to note that the turbulence load factor is a max possible factor that can occur only if the angle of attack is changed to the angle that gives the maximum lift coefficient by some aspect of the turbulence. This could be a vertical gust hitting the wing or it could be a gust hitting the tail that changes the pitching moment drastically. In short we don't know exactly what happens but we know something bad happens when we find a wing or tail fin miles away from the main wreckage. It is now clear why few aircraft ever fly at more than 2.5 times their stall speed. It is also clear you want to load up the airplane when you fly in turbulence and then you want to fly slower than your normal cruise. The "maneuvering speed" is published for most aircraft as a guide to keep you safe in turbulence. Go slower yet if you are flying light. At landing speeds, both the effects of turbulence and the effects of horizontal gusts are the same order of magnitude. They can break the airplane only if they both happen at the same time. The most common effect of horizontal gusts is discomfort and loss of control if you are not careful. « Last Edit: Apr 18th, 2007, 11:51am by Tom Goodrick »
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Post by Bill Von Sennet on Aug 22, 2008 22:24:54 GMT -5
Tom Goodrick Turbine Aircraft « on: Jul 6th, 2007, 10:59pm »
What does "Turbo" mean? You have to be careful with this term because it means many different things with regard to aircraft engines. In reality it is the same thing: a turbo is a mechanically driven set of fans that compresses air. In the section on flying piston-engine aircraft, we have already discussed the use of the turbo. We'll just hit the main points here. The turbo is a "turbocharger" for piston aircraft, also called a "turbonormalizer" if you want to get fancy. Its fan adds pressure to the air being fed to the engine so the engine behaves as though at a lower altitude. In an aircraft with a "normally-aspirated engine" (meaning without a turbocharger), the power starts to diminish at 6,000 ft where the most power you can get is about 75% of the maximum power you can get at sea level. Above 4000 ft you have to adjust the mixture to increase the fuel flow to get more power. You can continue to do this to about 10,000 ft where you will only have about 30% of full power. At that altitude the climb rate is slow. You can horse the aircraft up to 12,000 ft with patience. You don't gain much at these altitudes unless it becomes possible to fly OVER mountains instead of through them. You will fly at a higher speed at 30% power at 10,000 ft than you would at the same percent power at a low altitude. The reduced density makes this possible. But 30% power is still rather slow. With a turbocharged engine, you just leave the mixture set at full rich and climb the aircraft. You will have 80% power, which is normally used for extended climbs, until you reach about 16,000 ft in most aircraft. You can crusie at 75% power at up to 21,000 ft where you will find a true airspeed as much as 40% higher than you would find at 6,000 ft without a turbocharger. We must note that many "turbocharged" aircraft are not set up correctly for engine operation in FS9. This includes the default Mooney. You'd think they would have gotten that one right. Look in the [piston_engine] section of the aircraft.cfg file. If you see the line: turbocharged= 1 you should also see the line fuel_air_auto_mixture= 1 This will assure that you can follow proper operating procedure of setting mixture to full rich for all climbs. indeed, in FS9 you have no need to make further mixture adjustments in a turbocharged aircraft. If fuel_air_auto_mixture=0, then you must use mixture adjustment as you climb and the adjustment and power settings will not be correct. They get far from reality. The way you fly a turbocharged aircraft, and its basic utility for most people, depends on whether its cabin is pressurized or not. The basic performance does not change but you must use it differently if not pressurized. Without pressurization, you must breath oxygen from a canister through a mask when above 12,000 ft. This applies to passengers and pets too. There is a danger here because, if something happens to the oxygen supply while cruising at 22,000 ft or higher, it will be a real trick to get the airplane down below 12,000 ft fast enough without breaking it or losing consciousness. Also, you must trust a line boy to fill your oxygen tank from the right gas canister. Some have used nitrogen or ordinary shop air. The fact is that few people who own turbocharged, non-pressurised aircraft such as the Mooney fly them at high altitude very often. Most find value in the turbo for good climb performance on hot days from high elevation fields and use 10,000 ft as a common cruise altitude. Also, a non-pressurized aircraft must descend no faster than 500 ft/min to keep the passengers comfortable. Many people will report ear pain if you descend faster than that. Getting down from 22,000 ft at 500 ft/min will take about 40 minutes and something like 100 to 120 nm distance. The Cessna 340, Cessna 414, Piper Aerostar, Beech Duke, Piper Mirage and several other piston planes are turbocharged and pressurized. The Baron 58 was made in a pressurized version until 1982. These aircraft use their turbochargers to pressurize the air in the cabin as well as the air going into the engine intakes. A common measure of the pressurization is the altitude at which the cabin can maintain pressure equivalent to 8,000 ft altitude. This would be described as "the 8,000 ft cabin altitude" which is 20,000 ft for the Cessna 340. That means while it flies at 20,000 ft, the passengers sitting comfortably in the cabin (with no oxygen masks) will feel as if they were at 8,000 ft. (Actually, all pressurized aircraft must carry oxygen bottles and masks for all people on board in case there is a leak in the cabin. But this is stashed under the seats. Only the pilots must wear their masks so they are ready to put them on and get the plane to a lower altitude quickly in a loss-of-pressure emergency. I have made cabin altitude gauges for all of my pressurized aircraft that will show the cabin altitude anytime the aircraft is flying. You can use this for interest. But it also has a use in piloting techniue. The pressurization system depends on the engine power. If you suddenly lose power, you will lose pressure as well. If you slow down rapidly by cutting power to idel while at cruise, the cabin altitude will shoot up. You might have felt this in real planes as they prepare to descend. By reducing power in increments of about 20% spaced over several minutes, you can avoid severe spikes in the cabin pressure. Many current aircraft have automatic ways of regulating pressure reduction so this does not happen in most cases. But I feel you should learn to fly this type of aircraft with attention to the pressure so that you know what you are dealing with. Real pilots have been dealing with this complexity for decades. Turboprops, turbojets and fan jets are called "turbine aircraft" because their engines use turbines as the main motive force instead of pistons. The engines suck in the air with a forward turbine stage and compress it before it is ignited. The hot gas from the ignition serves to turn secondary turbines which power the front turbines. In the case of turbojets, a large mass of air exits the exhaust. Throwing this mass continually out the back end makes a thrust force toward the front end. The turboprop has the same internal structure except the secondary turbine, driven by the hot gasses, has a geared connection to a propeller on the front of the engine that acts like the prop on a piston aircraft and provides forward thrust. Almost all "jet engines" in use today are fan jets, not turbo jets because turbo jets are too noisy and too inefficient. The fanjet engine has a turbo inlet area about 40% larger than the turbojet. The air from the outer periphery goes into a bypass chamber that bypasses the ignition chamber. It rejoins the central flow just aft of the secondary turbine and gets sucked out with the central hot air. This has two effects. It reduces the noise considerably. It also adds more mass to the exhast given more thrust. There are more pounds of thrust per pound of fuel expended. Normal piston planes fly no higher than 10,000 ft most the time as do unpressurized turbocharged aircraft. The turbo just gets them there faster. In the section on mixture control, I have shown a comparison between the normal and turbocharged versions of the Skylane RG. There is no difference (on a standard day) up to 6,000 ft. few fly faster than 200 knots. Pressurized aircraft can come down at rates of 1000 to 1500 ft/min. They have efficiency values of 5 to 10 nmpg. Turboprop planes fly between 15,000 ft and 28,000 ft at speeds of 220 to 300 knots. They burn a little more fuel than a comparable piston aircraft. They can come down at rates of 1500 to 2500 ft/min. Smaller aircraft can have efficiency values of 2 to 4 nmpg. Fanjet aircraft fly between 28,000 ft and 51,000 ft at speeds of 370 to to 480 knots. They come down at rates of 2,000 to 5,000 ft/min. They burn quite a bit more fuel than the other types of aircraft. Their efficiency can be as high as 2.5 nmpg at the lower speeds. « Last Edit: Oct 13th, 2007, 8:20pm by Tom Goodrick »
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Post by Bill Von Sennet on Aug 22, 2008 22:23:48 GMT -5
Tom Goodrick Aircraft of Various Sizes and Capabilities « on: Jul 7th, 2007, 12:00pm »
GOODRICK'S LAW OF AERONAUTICAL SIMPLICITY Sounds dumb doesn't it. The fact is most texts on flying make it seem as difficult as possible so that you are intimidated from the start. But my intention is to let you in on a couple of little secrets that make flying any plane relatively simple in concept. These secrets are based on solid physics and aeronautical engineering so there is nothing new here. But there are, indeed, many similarities in concept between flying a Piper Cub and flying a Boeing 747. Yes, to be sure "the devil is in the details" as people like to say. But by being aware of these fundamentals, you can tackle the business of flying any aircraft made. My "Law of Simplicity" is: You need to know the energy and speed requirements to fly any aircraft. And that's about all you need to know!!! Another way of putting this is that you need to control power and speed to fly any aircraft. Put another way, if you know the fuel flow at cruise and the clean stall speed, you can fly any aircraft. First - Energy! Airplanes all need energy to fly. Gliders need energy too. They get it from being towed to a moderate altitude (giving them potential energy) so they can glide for quite a while even if they don't find "lift" from rising air. Unfortunately, like all aircraft, they lose energy due to drag as they fly. This means they can never quite regain their original release altitude unless they get help from rising air. They can swoop down and climb back or even do a loop and end up with almost as much energy as they started with. But they do lose energy eventually and must land. If you try any of the fancy gliders available for FS, you'll probably get tired of flying before you run out of altitude and just dump the lift with the spoilers to get down and land. For powered aircraft, energy comes from the engine. To control the aircraft properly, you must control the fuel flow. The engine burns fuel to make energy. The rate at which this happens is directly proportional to the power. In physics, the definition of power is the rate of change of energy. Thus power relates directly to the rate of burning fuel. If you know the fuel flow at cruise, that is all you need to know to fly the aircraft - any aircraft, any type of engine. To climb you need about 10% more power. To descend you can use about 30% less power. That means 10% more fuel flow or 30% less fuel flow. If you have a decent fuel flow meter, you are in business. Some engine management computers today show percent power directly on the panel. They are using fuel flow. I have made fuel flow gauges for many piston aircraft using this same fact. For turboprops and fanjets, I find the percent throttle setting that corresponds to the proper cruise fuel flow at a commonly used altitude. Then I base all power settings on that "throttle" or "Power Lever" or "Thrust lever" setting. Normally the cruise setting works out to be about 60%. 80% is usually good for climbing and 30% is good for descending. Of course, I watch for any engine parameter going out of the safe range. on my digital engine gauges this mean a number goes from green to red. Some people are taught that jet engines have thrust and prop engines have power. The fact is that all types of engines have both power and thrust. They could not possibly fly according to the laws of physics if this were not true. The thrust force counters the drag force. Both forces could be integrated along the path to give the energy exchange. We can use the fuel flow rate to set the power on all aircraft. By doing that properly, We will be assured of keeping the engine operating within safe limits. Too high a fuel flow means too much power and we are stressing the engine too much. Second - Speed! Given that you know VS, the stall speed in Indicated Airspeed with a clean wing (flaps up), you can safely take off at 1.3 VS, climb at 1.5 VS, cruise at about 2 VS and descend at 1.8 VS. Using Indicated Airspeed with these factors assures the aircraft will not be overstressed regardless of altitude. You might think this severely limits the speed of the aircraft. But it would be entirely normal in most cases. If you don't know the clean stall speed (many jet manufacturers don't like to give that out.), multiply the stall speed in landing configuration by 15%. If anyone is interested, I can make a table of these values for all types of civilian aircraft. The cruise speed is not locked in at 2 VS. It is whatever you can get while cruising at the particular cruising power level or fuel flow. But, you will find it is close to 2 VS. To find out why this works, consider that, the definition of stall speed is the speed at which the maximum lift coefficient is reached. Stall is defined as the slowest speed at which an aircraft can maintain level flight. This assures that the lift coefficient must be at its maximum. If an aircraft is at max gross weight flying at VS, the lift coefficient is as great as it can be so the lift force will be as great as it can be but in proportion to the square of the speed. An aircraft flying in cruise at 2 VS will be developing one G of lift or lift equal to its weight. But if something goes wrong such as a gust changing the angle of attack or a loss of control giving it a temporary high angle of attack, the max lift force can only be the square of the ratio of IAS to stall speed. So if the aircraft is at 2 VS when this happens, it will experience 4 G's and will not break because it is designed to carry this load. Nothing will even stretch too much. But if it is at 3 VS (which is close to the "never exceed" speed), it will see 9 G's. It will probably survive but may be damaged. Aerobatic aircraft are designed for up to 6 g's and fighters are designed to handle 9 G's safely. Scaling the Pattern Landings are generally made after entering and flying part of a rectangular pattern. This rectangle has a side that passes over the runway, a side that is 90 degrees to the runway in the crosswind direction, a downwind leg and a base leg that converges with final approach, lined up with the runway. you will usually be told by a tower to enter on the downwind leg. For runway 15 this would on a heading of 33. you might be told to enter on a left base which would be on a heading of 240 degrees. If it were a right base the heading would be 60 degrees. Or the towere may direct you to fly a straight-in to 15 which would be done on a heading of 150 degrees. For practice with any aircraft, you fly the entire pattern starting with a takeoff. Different aircraft will fly this at different speeds. But there is some standardization that is commonly accepted. All turns are made with a 30-degree bank. With each turn being through 90 degrees of heading change, this makes the size of each turn one radius upwind and one radius crosswind. Then people make the crosswind leg 1 minute long and the downwind leg 2 minutes long, excluding the turns. Here are the dimensions of these rectangles in statute miles for various speeds (KTAS, zero wind): Speed_Width_Length __60___1.36__2.51 (Cessna 152) __90___2.20__3.92 (Beech Baron 58) _120___3.14__5.44 (Beech King Air) _150___4.19__7.07 (Learjet) _180___5.34__8.79 (Boeing 747) The 30 degree bank is clearly marked on the attitude gauge so it is easy to hold. The times are easy to note and to execute. There is enough time to make pre-landing checks such as lowering the correct amount of flap for each stage. I see this happening every day at my local airport (KHSV) where we get everything from small Cessnas to jumbo jets with many military and commercial aircraft doing repeated practice patterns. Large aircraft flying the pattern use 180 R or 36 L which puts the downwind leg well out away from residential areas. We did have an MD11 doing the pattern to 18L once. That put the end of the downwind leg right over my house. of course I didn't mind. I was outside watching it. fed Ex likes to use KHSV for check rides. It's just a hop skip and a jump from Memphis by jumbo jet. Here is a figure shown the scaling of traffic patterns. I tried to conform to the timing and bank angle mentioned above but had to take liberties in some cases. I show the landing data mainly to indicate something about the differences between the planes. Because I don't fly jumbos very often, the landings on the jumbos are a bit rough. At least they all qualified as "satisfactory."
« Last Edit: Jul 11th, 2007, 12:30pm by Tom Goodrick »
Tom Goodrick Re: Aircraft of Various Sizes and Capabilities « Reply #1 on: Jul 9th, 2007, 2:43pm »
This is Part 1 of a "short" note on glass panels. Any aircraft cockpit for a plane that does anything beyong go up and down slowly will have a panel with a lot of "stuff" on it. The task of a panel designer is to provide the pilots with the information they need to have in a way they can quickly find what they need without being confused or mistaken. Confusion and mistakes can cost many lives and many millions of dollars. When I first built by own aircraft flight "simulator" on a TRS-80 Color Computer (in 1980), I was faced with the problem of making gauges that would give the pilot the information he needed. As I toiled with the process of making digital images that looked like analog images, it dawned on me that future engineers would be doing this with computer graphics for almost any kind of aircraft. Why not lighten up and make graphical images combined with digital images. I soon found digital values were easier to do and fit in small spaces but you have to be carefull to leave space around the digits and make them big enough to be easily read. A few years ago I was trying to learn C++ to make "analog" gauges for FS panels. There were some gauges I needed to make that were not in the default panels. It was the same thing I had done 20 years before. I found the XML language as adapted for the MS Flight Simulator that enabled me to put digital values of parameters read from the simulator in flight on the panel in any size and position. I quickly started playing with this and working on the problems of using panels that contain digital data. Any panel has lots of things for you to look at. The thing a pilot must learn is to prioritize his scan of the panel. You do not have to see all the gauges all the time. For each phase of flight, certain gauges have higher priority than others. Thus you can group the gauges and controls depending on their need in certain situations. You need to scan in cycles with high priority info gathered at frequent interval and lower prioity info gathered at lower rates. The great thing about glass panels is that the designer can use graphics to show many things in a way that emphasizes clarity. Our glass panels in FS are more limited than the real ones. The real ones have multiple sets of data shown variuosly on up to two to four interchangable screens. Where I have a map, they have an MFD - a multifunction display that can be a map one instant and a checklist the next with many combinations of engine data and navigation data. The displays are carefully designed to put information together in sets that are frequently needed in certain situations. Though every square inch is important, designers take care to avoid clutter. A friend didn't like my panels. he claimed they did not display well on his system or he could not read them. He taught himself how to design his own PFD, working in XML and taking apart the defaul Boeing 747's PFD for a start. But he ended up packing in so much additional information that it became very cluttered. I could not use it. He taught me a lot about programming in XML for FS. Some of those tricks went into my digital gauges (color warnings) and Landing Speed Gauge (storing values). His programming ability was top notch. But his human factors background was a little bit lacking. The functions a pilot must perform, in prority order are: 1. Fly the plane. 2. Monitor the health of all systems. 3. Communicate. 4. Navigate. The best way to introduce yourself to glass panels is to jump right in and fly one. But you should start with one on a slow plane like the Cessna 172 so you have time to figure things out as you go. You can download from my site the two panels to use (TG and TG2) in addition to the default panel for the 172SP. The TG panel has standard round flight gauges, the map, and a few digital engine gauges on the left. The TG2 is like my standard jet panels with a PFD, map and digital engine gauges on the right. By flying the same plane through the same situation, it will become clear how to use the glass panel. During takeoff you start out looking at the engine gauges to make sure all are working right. You look at the airspeed to see that it is functioning. Cut power and abort the takeoff if the airspeed is not registering. It may be just a bug that crawled into the tube but having no airspeed can kill you quickly. You watch for the safe takeoff speed, V2. You rotate at V2-10 and take off at V2. Then you look for the altimeter and keep track of the climb. You raise gear first and then flaps as you climb. Above 1000 ft AGL, you get cleared for departure and concern yourself with initial navigation chores. Maybe this just means turning on the autopilot that you set up before the takeoff. Cruise/climb and cruise are periods when you mainly monitor everything and make sure all is fine. This is normally all done on autopilot since it can fly the plane better and more efficiently than you can. You calculate you time to start descent as the position at 3 x H/1000 nm from the destination with maybe 10 nm slop, For example from 25,000 ft, you would start down a little beyond 75 nm from the destination. You reduce power for descent. If you have a pressurized aircraft, you must watch the cabin altimeter and not use large throttle changes which will cause spikes in the pressurization. At about 2500 to 3500 ft above the runway elevation, you begin maneuvering to a position from which you can easily line up for final approach or can enter the traffic pattern on the downwind leg. The traffic pattern is entered at 800 to 1000 ft above the runway elevation. You'll usually intercept an ILS at about 2500 ft above the runway elevation for a straight-in approach starting about 7 to 10 nm out from the runway. If using ATC in FS, they will vector you to intercept a line to the runway from about 20 nm out. In this case listen for other traffic and keep your airspeed down as told - usually 150 knots in a turboprop - so you don't over run any aircraft ahead of you. If you do you'll scratch the approach and have to go around again. On final using an ILS, your eyes are locked on the center of the PFD where you keep watching airspeed, localizer alignment, the glideslope and the altitude until you can see the runway. In designing a glass panel we keep these functions and their priority in mind. The first thing that gets your attention is the "PFD" or Primary Flight Data display. It includes on one screen, airspeed, attitude and altitude across the top, navigation info, directional info and relation to a path or glide slope below in the middle and climb info in the lower right. Once on the final ILS approach, your vision is focused on the center area of the PFD. You see the Attitude above center and the alignment with the localizer below center. You see airspeed just above and left. You see the glideslope indicator just above right with the altitude. Your buddy in the right seat can be watching engine data, setting flaps, throttles brakes and other things as you land the plane. Nothing makes this easier than a good PFD. The PFD I use is the one given to us with theLearjet 45. It is a common instrument made by Honeywell and used in many jets. I have seen it in cockpit photos of many jets. it was designed with many levels of human factors in mind. one feature i do not like will soon be gone from such gauges. It is the imitation of vertically moving tape indicators for altitude and airspeed. These were used to ease the transition of some pilots accustomed to old jet instruments. Many fresh modern instruments use more direct and informative indicators without ambiguities. To the right of the PFD on my panels you find the GPS map. This is an accurate representation by Microsoft of the Garmin 530 GPS nav computer. It performs many of the functions of the actual device but not all. Having this on the panel for view all the time helps considerably in many nav operations. It tells you a good departure route to fly after takeoff to converge with your climb and cruise routes. During cruise you can monitor your progress. One of my digital gauges on all panels tells you how many decimal hours of flight time you have remaining at the current power and altitude. look at the GPS Map and you will see the time remaining to the destination if you have used a direct GPS route as when crossing oceans. It is reassuring to see the flight time left significantly greater than the time required to get there, especially on transoceanic flights. At the end of cruise you are 3 x H/1000 nm out from the airport with 10 nm for maneuvering. The map shows you how to maneuver in an efficent way so you can get lined up for the approach to the runway in use. You can call ATIS from 40 nm out to get the runway in use. To the right of the map is a rectangular panel with an orderly column of digital engine data for each engine. This works with one, two, three or four engines. My digital gauges are all set to change color when a value is out of the normal operating range. In most cases, when a value is slightly above normal, the value turns from light green to yellow. When dangerously above normal, the value turns red. On the radar altimeter, Green numbers are above 500 feet. Yellow numbers are between 100 and 500 feet above the ground. Red numbers are below 100 ft and you'd better be ready to land! I provide many values that you can ignore if you want to. The weight and CG position are shown. Every pilot must know both his loaded weight for every flight and the CG position. In many real aircraft, tables of numbers help you determine where the CG is and whether that is a safe position or not. When out of the safe range the aircraft may not be safe to fly. A terrible example is the crash of a transport carrying a rock group out of the Bahamas a few years ago. After takeoff the nose just kept going up and then the aircraft stalled and crashed, killing all on board. It turned out the pilot was not qualified to fly that airplane. Being qualified to fly means you can figure out whether it ia safe to take off. In many aircraft, the weight to take off is higher than the weight to land so a pilot must figure out what his landing weight will be before attempting to land. Otherwise the gear could collapse. Also each jet pilot must calculate V speeds for every flight based on the weight. Vr is rotation speed and I estimate that as 10 knots less than V2. V2 means it is safe to take off, Vref means it is safe on final approach for landing with full flaps . I provide digital gauges next to the airspeed on the PFD showing V2 if you are taking off and Vref if you are landing. (The gauge code figures which you are doing and measures the weight to calculate the speeds.) With many jets, fuel is such a big part of the weight that these values vary by 10's of knots on different flights for the same aircraft.
Tom Goodrick Re: Aircraft of Various Sizes and Capabilities « Reply #2 on: Jul 9th, 2007, 2:45pm »
This is Part 2 of my "short" note. Other values you can ignore are the wind speed as determined by the GPS nav computer in flight as a difference between the ground speed vector and the airspeed vector. The real Garmin 530 GPS displays this info on its map screen. But MS chose to ignore that. I give it to you as two separate digital values shown somewhere on the panel. It will be in different locations on different aircraft so look for it if you want to use it. It can be useful information. Another value is the angle of attack and another is the trim angle. The trim angle is vital to good piloting. Most aircraft have a mark for the trim setting for takeoff that must be checked and set before any takeoff. I tell you what the trim angle should be in the checklist I write for most aircraft. Taking off with a badly set trim can be very embarassing. The angle of attack is of some interest if you every get into a deep stall. recovering from a deep stall can be impossible in some aircraft. Knowing when the angle of attack is in a flyable range is very helpful to managing a recovery. For your education, set up the autopilot to fly level at some low power setting. Note the KIAS, the Angle of attack and the trim angle. increase power and record these same values when everything becomes steady. Increase power again and record these same values. Note also the loaded weight. Try the same thing again with the same set of power settings at a different weight. It is interesting. That's how airplanes work. Most of the piston aircraft I have worked on have a power gauge, made specifically for them, that show the percent max power when you set the throttles, prop and mixture. You may have noticed taht, with a constant speed prop, certain combinations of throttle (manifold pressure) and RPM give the same power setting. The power gauge takes the mystery out of this. This is a stand-alone gauge that can be stuck various places on the panel. I usually try to stick it with the engine instruments. Another gauge on some aircraft shows nm per gallon. This is handy when looking for the most efficient cruise condition with various power settings and altitudes to choose from. On many piston panels these are stand-alone gauges. On most jet panels these reside at the bottom of the engine data between the two throttle position numbers (percent values) and just below the flight time remaining. This was a recent addition and may not be on many of my downloads. Let me know if you want this gauge and don't have it. Other digital gauges you can get from my web site and stick on any aircraft are the Flight Time gauge and the Landing Speed gauge. The FTime gauge is usually tacked on the panel some place and the landing gauge is put on a pull-down window. You need not pay attention to these except near the end of a flight. before landing, make the landing speed gauge visible. This activates it so that it displays continuous values of Indicated Airspeed (KIAS) and vertical speed (fpm). After the main wheels touch these values are frozen for review. But you must view them and write them down BEFORE COMING TO A STOP. At the same time you pause to write down the landing speeds, note the flight time too. That shows the time during which the airspeed was fatser than 35 KIAS which is a good measure of your actual flying time. During taxi if you get hit by a wind gust, this gauge may be reset and you will lose the flight time. We have found this flight time useful in rallys where we count the time flown on each leg toward the final score. To get used to flying "glass panels" it is a good idea to train in an aircraft where you have both the old and new types of panels available. Such a plane is my version of the Cessna 172SP. You can download it from my web site. The simple way to change between two or more panels is to have the panels in the aircraft's specific folder, identified by different extensions. The extensions on the Panel Folder name may be .TG or . TG2 for any of my panels. The default panel would be left with the folder name Panel with no extension. Then, before loading the plane for flight, you select the panel by editing the aircraft.cfg file in the line showing "PANEL= " and saving the file. this lets you add glass panels as you wish but keep the original panels available until you decide which type you prefer to work with. I am a firm believer in commonality in panel designs. All my glass panels look alike as much as possible. All my panels for a particular type and number of engines look the same. That wy I can get into any one of them and fly with a quick look at the checklist. Recently I had to change the windshield design and the placement of some gauges on my jets in order to accommodate needed light switches. Some aircraft that self-installed itself walked over my good switch gauges and ruined them so I had to change to Baron switches for the jets. A temporary fix has been installed in all my handared aircraft. Downloads are another matter. Also I think the new panel can be improved but have not yet done so. Making all required updates is a real pain. Today in real life, you can buy everything from a Cessna 172 to a King Air and Learjet with a glass panel. Many people take their first flight lessons with glass panels. Probably in just a few years, you won't be able to buy a new airplane with any other type of panel and most old airplanes will be retrofitted with glass panels. For the fun of it, go for a ride at night with a glass panel. When 50 nm away from your home airpot, cause the electrical system to fail. Land the plane. The people like Cessna and Beech have tried to handle this in many ways. First, many glass panels give you mechanical gauges in some corner of the panel for airspeed, attitude and altitude. Second the component most prone to failure - the gyro - has been replaced by an "AARS" or Artificial Attitude Reference System" that uses micro accelerometers to track all rotations and accelerations since takeoff to estimate your present attitude. With the Flight Simulator, your PC has been tracking all the computed translational and rotational accelerations you have made since takeoff so it knows which way the aircraft is pointed. The AARS does the same thing only it measures the accelerations instead of estimating them. The gyro vacuum pump tended to burn out every year or two at the least opportune moment. It was probably responsible for the death of John Kennedy and his wife and sister-in-law near Martha's Vineyard on a hazy night. Of course the AARS still depends heavily on the electrical system. Aircraft manufacturers ahve handled that problem with redundancy and isolating circuits. Planes have two generators and two sets of batteries with fault-sensing devices that can isolate problems and conserve power to get you safely down. In FS the only time something fails is when you do something dumb or when you decide to set up an intentional failure. Incidentally, a special "dumb" thing we have all fallen victim to once or twice is the loss of power in a turboprop about two minutes after you have started the engines and taken off. The proper turboprop starting procedure is: 1) Use shift+3 to pull down a window showing electrical control switches for each engine for the start. Before start they should each be OFF. 2) Watch the switches when starting with Ctrl-E. 3) After starting the first engine, the left switch will go to OFF instead of GEN. Set it to GEN. If you have a sudden darkness after a takeoff while climbing out, you can use shift+2 to see mechanical instruments while you use Shift+3 to see the switches. Set each switch to GEN and the lights will come back on.
Tom Goodrick Re: Aircraft of Various Sizes and Capabilities « Reply #3 on: Jul 10th, 2007, 10:21am »
I must add that, when I was doing early experiementation with the PFD and the Map on the same panel, Chuck Dome contacted me and sent a copy of a panel he was working on. It had certain digital engine instruments on the right combined with analog bar graph indicators for the values. I liked it and we discussed various parameters that could be shown digitally. He tried to help me get into C++ coding for gauges but then I discovered XML programming which was much simpler. I found I could pack more engine data into that spot on the right by making digital gauges with no bar graph. He went back to doing it his way and I developed the digital XML gauges farther. I called the panels "DG" panels for Dome/Goodrick. Since then many other features have been added such as the V speeds, CG and weight. 216.180.4.190 Tom Goodrick Administrator *****
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Posts: 3589 Re: Aircraft of Various Sizes and Capabilities « Reply #4 on: Jul 11th, 2007, 6:31pm » Quote Quote Modify Modify Remove Remove When I wrote the notes on the glass panel above, I wanted to have some illustrations. But I thought my web space memory was full. I found some old photos I could dump and found these two photos already there used for another story. These show the left and right halves of the panel for my Cessna 414 or 340. Study them and you'll be able to find most of the gauges in the new panel layout. At first I thought these were for the Baron. But then I saw the Cab Alt Gauge that is only used on pressurized aircraft like the Cessna 340 or 414. The aircraft is shown on final to KHSV.
Note the FASP and GASP airspeed lights. These indicate when the airspeed is low enough to drop the flaps or the gear. I find them very handy - better than marks on an airspeed tape. « Last Edit: Jul 11th, 2007, 6:33pm by Tom Goodrick »
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Post by Bill Von Sennet on Aug 22, 2008 22:21:13 GMT -5
Tom Goodrick Understanding The Autopilot « on: Mar 6th, 2008, 12:18am »
How Automatic is the Autopilot? PART 1 Several questions recently have prompted me to discuss the matter of the autopilot. How automatic is it and how should it be used in FS9? I found an old article I wrote on autopilots in 2003 and it had a bunch of obsolete information. So it is time for a new article. I looked into how the autopilot works and how you can control it in its several modes. I tried to find how you can adjust it to fit particular aircraft. In this I was mainly unseccessful. Mostly, it works. If it does not work with a particular aircraft, the solution lies in adjustment of the FD the same way we do for better handling and for realistic performance. If an aircraft works well when you fly it manually, it will work well on autopilot. Do not hesitate to use the autopilot when flying cross-country. It offers the best way of managing climb to cruise altitude, holding cruis altitude and attaining and maintaining the best speed, and flying the best track to the destination. It can also be used very well to fly vectors during a departure or an approach. In some cases it will do an ILS approach but you are better off flying approaches manually. Part 1 is an introduction to the "hardware" you see in the panel. Part 2 covers the altitude mode or ALT mode. Part 3 covers the heading mode or HDG mode. Part 4 covers the navigation or NAV mode. Part 5 covers the SPD/MACH modes. Part 6 covers the the approach mode and other odds and ends such as LWL, BC, and YD. Below we will discuss the use of the Autopilot in ALT mode, HDG mode, NAV mode, SPD mode and APR mode. I'll use some examples involving the Baron 58, the Beechcraft King Air 350 and the Learjet 45. For each of these there is a download on my web site that improves the FD. For the Learjet 45, the download is especially helpful because the original FD causes it to behave poorly on autopilot. For simple Cessnas, the autopilot is of little use and isseldom necessary. But, it could be considered necessary if you fly solo IFR in any airplane. it certainly is needed in more complex aircraft to reduce the pilot's work load. Many jets are not certified to be flown without a working autopilot or must be operated low and slow if the autopilot is malfunctioning. Using the autopilot in no way reflects poorly oin your pilot abilities. It is a necessary tool when flying complex aircraft with high cruise and approach speeds. it is vital to the new reduced altitude separation rules where aircraft on opposite headings may be separated in altitude by only 1000 ft. In FS there are several different "control heads" for the autopilots. These are units you see in the panel by which you can control the autopilot. There are the old ones that were used in singles in a pull-down image that included the radio stack. In my panels I use the more sophisticated units that were mounted in jets. I think you need the control head mounted as a permantent part of the panel because you always need to be able to see what the settings are at a glance. You cannot cover up another vital part of the panel by pulling something down on top of it. Of course thei requires a PFD display to show all the vital flight instruments in a compact manner so there is enough space to put the control head as well as the GPS map which should always be visible as well. But you should know that the control head must work with elements in the air file for the particular aircraft. Not all the switches and settings will work with all aircraft. The gauge coding relates to settings in the air file. Some parameters are in the aircraft.cfg file. It is not clear how these work. But can the autopilot be trusted to fly the airplane completely with no supervision? No, not in many cases. A competant pilot, fully able to take manual control at any stage, must be watching all gauges all the time. He must interrupt at any unexpected deviation from normal procedure and performance. He can guide the procedure with heading adjustments, thrust adjustments and vertical speed adjustments. The first rule for using an autopilot is DO NOT ACTIVATE IT until you are sure you are ready. An autopilot should NEVER be turned on when the plane is on the ground. That mistake has killed many people. In FS it can mess you up so that you don't know what is happening. Of course I have done that. I have interrupted a flight while the autopilot is on, popped the airplane down to a location on the end of the runway at a faraway airport and then tried to takeoff, wondering why the plane is climbing to a stall and turning furiously to the left. Always prepare the autopilot by setting the parameters for whatever mode you intend to use before you activate the mode and/or the autopilot. When activated, the autopilot will try very hard to do what you have commanded. make sure you are ready for that. In my Baron, the autopilot "head" is always visible. This is the part you use to control the autopilot. On the left are two buttons AP and FD for Autopilot and Flight Director. For now we can ignore FD. We will click on or "press" AP when we want to turn the autopilot ON. To the right of FD is a window with a number in it and below that is a CRS knob. In real life you rotate the knob to change the course to be displayed. In FS you put your mouse pointer on the left or right side of the number and press the mouse button to decrease or increase the number. This applies only to the Instrument Landing System (ILS) localizer. That number agrees with the heading you will fly toward the runway. To the right of it is anothe number with a knob below labelled "HDG. This can hold the heading you want the aircraft to fly in HDG mode. Between the two numbers is a button labelled "NAV" that turns on NAV mode. To the right of the heading number is a button labelled "HDG". Press this to get into HDG mode. You can change the heading number and all other numbers on the autopilot by putting the mouse arrow on one end of the number and clicking or holding the mouse button. Below HDG is APP, another button that turns on APP mode. In the column of buttons to the right of HDG is BC (turns on "back Course", LVL (turns on the wing leveler) to keep the wings level, YD (turns on the Yaw Damper) that reduces unwanted yaw oscillations, and to the right of those buttons are MACH (setting Mach speed limit) and IAS (setting indicated airspeed speed limit). A number to the right of MACH can hold the Mach limit or the airspeed limit. Next you see ALT, a button that sets ALT mode. To its right is a number showing the altitude you want the autopilot to hold and farther to the right is a window showing the vertical rate limit you want to impose during the transition to that altitude.
Tom Goodrick Re: Understanding The Autopilot « Reply #1 on: Mar 6th, 2008, 12:19am »
PART 2 ALT MODE The most basic autopilot mode is ALT mode in which the autopilot attempts to make the airplane climb or descend to a particular altitude and then maintains that altitude as long as the autopilot is ON and ALT mode is ON. To use ALT mode you must set an altitude to be held and a vertical rate limit to be used to get to that altitude. This is the key to controlling the aircraft for safe flight. The autopilot does not know what power is needed or what airspeed is safe to fly. You must set the power and monitor the airspeed. You can change the allowed vertical rate as you fly to keep the right airspeed. You can adjust the throttle to maintain the climb or to avoid over-speeding during descent or getting too slow during a climb. How does the autopilot control climb? It simply increases or decrease the pitch trim until the vertical rate reaches the value set in the window. Then it continues to adjust the trim to maintain that rate until the altitude set in the window is nearly reached. It reduces the vertical rate slightly before reaching the selected altitude and then works to hold the altitude. I tried setting various values in the aircraft.cfg file for the pitch parameters. Nothing seemed to make a difference. I doubled them and increased them by 10x. There was no change in climb performance. I would assume that, if the FD is set for proper CG and for proper pitch trim sensitivity, the autopilot will work well during climb or descent. But it requires that you know how to adjust the proper in a reasonable way during climb or descent. You must select a reasonable vertical rate and then must set the power properly. In the case of a normally-aspirated engine like the Baron's, you must also adjust the mixture as the aircraft climbs to maintain the max fuel flow or power. When descending you must set a sensible power setting . For the Baron this would be 15 inches and 2100 rpm. BARON Lets do a basic climb on autopilot that is commonly done on takeoff in IFR conditions. The controller will instruct you to "Maintain runway heading and climb to 8000 feet." We will do this in the Baron while taking off from runway 18L at KHSV. While the Baron is parked, set 8000 in the altitude window and 1000 in the vertical rate window. The aircraft can safely handle this rate while accelerating and while you check that the gear is up and bring the flaps up. Later during the climb we will raise this to 1000. The FD designer has left a value in the files that the aircraft will go to if you don't have anything in the window. But it is best to think ahead and put a positive number in there the aircraft can handle. I have been unpleasantly surprised to find a negative climb rate in there several times. When you are trying to get a few hundred feet above the ground and clear of the trees, power lines and hills beyond the runway, you don't need a negative climb rate. We set the heading 180 in the HDG window because from runway 18, that is the heading we will be flying. You should also think ahead and put the number 180 in the course window and dial the freq 111.9 in the Nav 1 frequency slot. That way you will have the return ILS all set in case an emergency develops and you have to go around and land as soon as possible. The last thing you need with an emergency is to be changing numbers or even looking them up with smoke in the cockpit, etc. We make the takeoff as we normally would and get the gear up. (Flaps up if you use them.) As we pass 400 feet on the radar altimeter (or 1000 ft on the baro altimeter) we punch the HDG and ALT buttons. We see the green lights and punch the AP button. (I unpunch the FD button because I don't like using it. I know what to do to fly the airplane. I don't want anything needlessly cluttering up the instruments.) I begin adjusting the power while watching the airspeed. I reduce the RPM to 2500 and then adjust the throttle looking at the power meter to set about 84%. Anything over 80% but less than 85% works for the initial climb. The power decyas rapidly as we get toward 5000 ft. I have to begin adjusting the mixture to maximize the fuel flow. Otherwise the airspeed will decay. At about 3500 ft I can set full throttle ad the power will stay in the right range though I must keep leaning the mixture a bit to keep the fuel flow and the power from declining significantly. As the aircraft reaches 5000 feet, I adjust the mixture a final time for max fuel flow and then back off on the throttle to set 75% power. During the climb on autopilot I have to know how to keep the power properly adjusted. The procedure would be different for an aircraft with turbcharged engines like the Mooney Bravo or my Cessna 340. In that case no mixture adjustment would be required but I would have to reduce the throttle properly to keep the power level in the same range (80 to 85%). I must also watch the EGT or CHT temperatures. (I made sure before takeoff that the cowl flaps were open.) If those temperatures go high during climb, I must reduce the vertical rate to increase the airspeed and give the engines better cooling. You can save this Baron flight situation (level at 8,000 ft) for future demonstrations. Next we will repeat the same takeoff and autopilot climb in the King Air 350 though we'll climb to 15,000 ft. BEECH 350 Set up the King Air at KHSV 18L. (Weather should be on Clear for all test flights - no winds and no clouds). Note that the checklist for the 350 specifies flaps optional for takeoff. We will not extend the flaps. We must set 7 degrees elevator trim and use only 90% throttle for takeoff. The speed for rotation is 95 KIAS and takeoff is 105 KIAS. Set the autopilot up once again for 15000 ft altitude and 180 degree heading. This time use 1800 fpm for vertical rate as noted in the checklist for climb that you must read before takeoff). The condition levers should be at low idle. (Use the "mixture" to adjust this. It becomes the condition lever in a jet turboprop like the 350.) Throttle to 90%, watch for 95 KIAS, rotate and let it fly off. I set the stop watch on the timer as I shoved the throttles to 90%. Just as the aircraft was climbing through 400 ft, I turned on the AP. The aircraft accelerated to 210 KIAS and climbed smoothly. I noticed that 90% throttle gave 92% power. In a turboprop, ITT is the parameter to watch on takeoff and climb. It should never exceed 800 C. The value peaked near 750 and settled down during the climb to about 640C. In 8 minutes we were level at 15000 ft. There was no fuss about the climb airspeed, the temperatures or the airspeed. The 350 is a very well-behaved aircraft. Set 80% power for cruise at 15000 ft and then save the flight for later use. LEARJET 45 Next look under the Bombardier menu and select the Learjet 45. Put it on runway 18L at KHSV. Set the AP altitude at 15,000 ft and the heading at 180. Set the vertical rate at 4000 fpm. Do not turn on the autopilot. (Make sure it is off.) Bring up the checklist and go through it. Weight is very important in jets. While we will make a takeoff at MTOW, we will have to dump fuel if we want to land. The checklist says to make sure the weight is below 21500 lb. Yours probably is not below that weight. That is because FS always puts 100% of fuel into the center tank. Look at the page for fuel and payload. It will show someting like 715 gallons is the max fuel load you can carry this trip. Look at the fuel. Subtract the amount in the left and right tanks from 715 gallons. The result is the max you can put in the center tank. Enter that value (in gallons) into the center tank. Now you should be ready for a takeoff at MTOW. Leave the AP set for HDG and ALT with the numbers listed above in the windows. But leave the main AP switch OFF for takeoff. The checklist says to set one notch of flaps (8 degrees) and 8 degrees of elevator trim. Do that. Note that you see 124 KIAS in the window on the left of the airspeed indicator on the PFD for V2. You will rotate at 124-10 and fly off at 124 KIAS with the present weight. The checklist says you will raise gear on positive climb and accelerate to 180 KIAS before reducing thrust to 80% and going to 4000 fpm climb. That is when you can hit Z to turn on the autopilot. Let's do that. My takeoff was fine but the transition to climb was not smooth. I had to unset and reset both the HDG and ALT buttons after turning on the autopilot. I guess we should leave those off until we turn on the AP. Then hit AP, HDG and ALT at the same time. The airspeed should never exceed 250 KIAS until we are above 10,000 ft. Then, as the checklist indicates we go to 2000 fpm and 100% throttle. But we will stay at 2000 fpm and 80% throttle until we level off at 15,000 ft for maneuvers. If you have trouble with any of these exercises, do them until you are satisfied. Climbing steadily in the Learjet is the toughest, especially when you go all the way to 41,000 ft. For now throttle back to 50% and save the aircraft in level flight at 15,000 ft for the next set of exercises.
Tom Goodrick Re: Understanding The Autopilot « Reply #2 on: Mar 6th, 2008, 12:21am »
PART 3 HDG MODE BARON HDG mode is the simplest turning control mode. You set a compass heading into the "HDG" window. Then the autopilot will try to turn the aircraft to that heading. Return to the Baron in level flight at 8,000 ft and make sure it really is in steady flight. Then set 090 into the HDG window. (The HDG button should already be on and a turn to the left will commence.) You are in both HDG and ATL mode as the autopilot holds altitude and turns to a heading of 090 (east). The autopilot calculates the diferents between the present heading and the desired heading, treats that difference as an "error" value and takes steps to drive that error to zero. It does this by rolling in the direction according to the sign of the difference (right for positive difference, left for negative difference). There is a max bank angle in the aircraft.cfg file that is held by the autopilot until it gets near the desired heading. As the difference diminishes to a key value, the bank angle becomes proportional to the difference. This results in a smooth roll out on the new heading. You may notice that, during the Baron's turn, its airspeed decreases slightly and the pitch trim changes slightly. This is because it loses some lift coefficient while banked (that lift is helping to turn the aircraft) and must compensate for the loss of lift by increasing the pitch trim. This will in turn slow it down slightly as drag increases in the pitch change. When the turn is completed the speed comes back and the pitch trim returns to its value before the turn was started. The max bank angle is normally set at 25 degrees because that works for a smooth turn in most aircraft. However, I have changed it to 35 degrees in many jets because of the low turn rate at high jet speeds. But this must be checked in various conditions because it can lead to an upset condition. The turn rate depends both on bank angle and on true airspeed. Hold bank angle constant and increase airspeed and the turn rate will decrease notably. Hole true airspeed constant and increase bank angle and the turn rate will increase. But the amount of pitch-up required to maintain altitude will also increase resulting in a loss of airspeed. It gets complicated quickly so this is something to be careful about. At high altitude where jets normally cruise, this speed upset becomes very significant and can even result in the autopilot losing control. Now with the Baron flying east at 8,000 ft, set the heading to 270 and see how well it manages both the turn and holding altitude. OK. That was easy. Now set a heading of 60 degrees and an altitude of 4000 ft. Set a vertical rate of 500 fpm. (This is the max downward rate you should use in any non-pressurized aircraft like the Baron 58.) We will give the autopilot a challenge of making both a turn and a descent at the same time. But will will have to help by adjusting the power properly. Set 20 inches and 2100 rpm. As you reach about 4500 ft, start a left turn to 360. Then when reaching 4000 ft, set 2500 RPM and 75% power which will be reached at 23.5 inches. But then remember you must adjust mixture again to get maximum fuel flow. Do this and then readjust the throttle to give 75% power. I ended up with 23.77 inches, 17.56 gph, 2500 RPM and 74.99% power. Continue and let the aircraft get fully steady. Next set a heading of 090 and an altitude of 9,000 ft. Use 1000 fpm as a climb rate. Set full throttle. Don't forget to lean the mixture for max fuel flow every 2000 ft or so. Again, the Baron just does what you want it to do with no fuss. It is a very nice aircraft for those who need to carry more weight than a fast single will carry or who want the extra engine when flying over water, over desert, over mountains and at night and general IMC. BEECH 350 Go through the same turn exercises in the Beech 350 - level from 180 to 90 and then to 270. For a level flight power setting, reduce the RPM until N2 is below 100%. You can set 80% power. Mine did those turns with ease. Now try turning to 060 and descending to 8,000 ft. Set set -1500 fpm and adjust the throttle to keep the airspeed at 230 KIAS. Level off with 70% throttle and turn to 360. Next set 80% power, 15,000 ft with 1500 fpm and turn to 090. My aircraft does this also with no problems. LEARJET 45 Return to the Learjet we left in level flight at 15,000 ft. i set 55% so the airspeed became steady at 280 KIAS. Now turn from 180 to 090 degrees. Now turn to 270 degrees. Mine did a good job with these. Now set the altitude at 40,000 ft, the climb rate at 4000 fpm and the throttle at 90%. As you pass 25,000 ft, turn to 360 degrees. As the airspeed drops below 300 KIAS, set the climb rate at 3500 fpm. Set 3000 fpm as airspeed drops through 295 KIAS. Continue with this adjustment as needed. Mine was climbing at only 1000 fpm from 31,000 ft upward. But remember that we started at full gross weight. We made it to 40,000 ft for cruise. Many jets cannot climb that high after a full gross weight takeoff. They must level at something like 35,000 ft and burn off some fuel before continuing. Aceelerate to Mach 0.80 and then reduce the thrust to about 80%. To optimize range in the Learjet 45, you must work up to higher altitudes as fuel burns off. The max altitude for cruise is 51,000 ft. I have never gotten the Learjet 45 that high. It always seemed that the fuel burned in climbing was not worth the reduced fuel consumption at higher altitude once the aircraft was cruising in the low 40,000 ft range. Now we have another turn check. When the aircraft is steady at 40,000 ft. do a turn to 180 degrees. Well, this was another ho-hum for this aircraft. If you are flying a default Learjet, you might have another story to tell. Save the Flight with the Learjet steady at 40,000 ft. We can use this when talking about SPD mode. AP TURN PARAMETERS The parameters in the aircraft.cfg file pertaining to turns are: max_bank=25.0 max_bank_acceleration=1.8 max_bank_velocity=3.0 These are the same for the Baron 58, the Beech 350 and the Learjet 45. They are even the same for the Boeing 737-400 and the Cessna 172SP. This seems to suggest that you don't have any reason to make adjustments to them. I fixed a problem in the Learjet 45 from the default FD files. But I did it not in the AP lines but in the pitch trim sensitivity. It seems that the trim sensitivity can make it difficult for both you and the autopilot to control the aircraft.
Tom Goodrick Re: Understanding The Autopilot « Reply #3 on: Mar 6th, 2008, 12:22am »
PART 4 NAV MODE A few years ago I was warning people not to use NAV mode. I thought it did not properly correct for wind. I was wrong. It does correct for wind better than you can. (It senses and adjusts to wind changes continually as you fly if you have loaded Real Weather.) Now I use it most of the time on most cross-sountry flights in RW. I set and use HDG mode for departure and for arrival in the vicinity of the destination airport. To use NAV mode, you must create a flight plan for the trip from the departure airport to the destination airport. It can have none or several waypoints between those two airports. (The need for waypoints can be for fuel stops or to stay out of restricted areas.) if you use ATC while flying IFR, you will be given vectors for departure and arrival. These must be flown in HDG mode. ALT mode handles all altitude assignments. But after the initial one or two vectors after takeoff, the controller will say something like navigate at your descretion or he will give a heading that matches the heading on the flight plan. Even if you are slightly off the path set for the flight plan on the GPS, you can activate NAV mode on your autopilot. To activate NAV mode you must set two switches: 1) Set NAV/GPS to GPS. 2) Click the NAV button on the autopilot head. When NAV mode is properly activated, the aircraft will disregard the heading number and will turn in such a way that it intercepts the path for the flight plan. You can watch this happen on the GPS map. You will still have to adjust power as needed for any climbs or descents and to enter cruise. The autopilot will head into the wind just enough to keep the flight path straight along the flight plan. In RW, the wind speed and direction change with both altitude and time. You could not possibly do as well as the autopilot in NAV mode. When you get close to the destination, ATC will give you vectors for the approach. If not using ATC, you can give yourself vectors to get setup for the approach. If you stay with the autopilot in NAV mode too long, the aircraft will fly over the target and begin circling. That does not help you any unless you are away from the computer (shame on you!). Set the correct heading and go into HDG mode to handle the approach vectors. Also, be sure to turn the NAV/GPS switch back to NAV so you can see the ILS indications properly. If you see on the map that you should be close enough to see the ILS needles move but they do not seem right, you have probably forgotten to throw the NAV/GPS switch back to NAV. You can do your own experiments with NAV mode. Use on your next cross-country trip. Use Real Weather too so the trip is more realistic. NAV MODE in AIRCRAFT.CFG These are the lines in the aircraft.cfg file that pertain to NAV mode: nav_proportional_control=9.00 nav_integrator_control=0.25 nav_derivative_control=0.00 nav_integrator_boundary=2.50 nav_derivative_boundary=0.00 They are initially set the same for all aircraft. I have changed the first line a little for really big aircraft such as the A380 and C133. They generally work fine. For many years, FS was ahead of the real world in navigation enhancements. We have had flight visualization for many years. That allows you to fly an ILS approach usiing an artificial display of rectangles. All you do is manage power, flaps and gear while keeping the plane flying through a series of rectangles down to the runway. This works great in very low ceilings as in fog and snow. I read recently that this is available now in general aviation aircraft for following the flight plan in NAV mode. But we cannot yet do that. We must connect the display to either NAV1 or NAV2 radios, not to the GPS. Maybe FSX can do that. The experienced pilot who described using this system (Richard Collins of FLYING), like it.
Tom Goodrick Re: Understanding The Autopilot « Reply #4 on: Mar 6th, 2008, 12:23am » PART 5 SPD/MACH MODE This mode is of use to you only if you are flying a jet like the Learjet 45. Even then it is not always necessary. But if you fly jets, you should at least learn about it. SPD mode means you want to lock in an indicated airspeed. MACH mode means you want to lock in a particular Mach number. You can do either. No, they are NOT the same thing. We will presume that with your interest in jets, you are sufficiently experienced in flying to know about dynamic pressure - the basis for calculating all aerodynamic forces and moments acting on the airplane. By locking in an indicated airspeed, you are locking in a dynamic pressure at which the aircraft and engine(s) work well in cruise. To keep things simple, instead of talking about the dynamic pressure you are using, we talk about the indicated airspeed you are using. In jets, the fuel burn as you cruise is very significant if you are going very far. You may want to lock in an airspeed so that you are locking in a particular performance level and so you can make reasonable predictions about when you will get where you are going. You will, of course, be locking in a particular true airspeed as well since that remains a particular proportion of your indicated airspeed as long as the altitude remains constant. As a general rule, jets fly based on KIAS below 30,000 ft and based on Mach above 30,000 ft. MACH is new to pilots moving up to jets from lower and slower aircraft. The Mach number is the ratio of the true airspeed to the local speed of sound. By "local" I mean the speed of sound that would occur in the air imediately outside the aircraft. This varies with the temperature. The true airspeed as a proportion of the indicated airspeed varies with density. Both density and temperature vary with altitude. Here's a short table to think about. sea level 250 KIAS 250 KTAS SoS 662 KTAS Mach 0.38 20,000 ft 250 KIAS 343 KTAS SoS 615 KTAS Mach 0.56 40,000 ft 250 KIAS 505 KTAS SoS 591 KTAS Mach 0.85 Since the proportion of true airspeed to indicated airspeed doubles between sea level and 40,000 ft while the speed of sound decreases by 11 %, it is easy for high-flying pilots to become confused about how fast they are flying! You can see that both the numerator and the denominator in the Mach number are varying as you fly upward. that is why I said that a Mach limit is not exactly a speed limit. The reason Mach becomes important is that many characteristics of the aircraft change with Mach. These affect stability and controllability, two very big concerns. Also, the effects of Mach are extremely peculiar to particular designs because they are based on the actual distribution of pressure over the body surfaces near ailerons, elevators and rudders. The jet engine performance also varies significantly with Mach number. This can be scary stuff - especially when you find the ailerons fluttering and flying off the wing because you exceeded a critical Mach number. Fortunately, for pilots of many jets, including the Learjet 45, this can be simplified by remembering one simple number - 0.80. Just set this as a limit during cruise and you will be in good shape. I have heard jet pilots say the speed they fly depends on the temperature. Temperatures at altitude higher than normal mean a slower cruise speed. This only applies if you are flying with a Mach limit. If you hold a speed and let Mach vary a little, there would be no difference. The big question is "Can you hold speed constant rather than Mach?" Most pilots are taught to honor Mach over speed. I am not sure that is necessary for the slight variations one would encounter. I would honor fuel flow more than Mach. How does fuel flow vary? In order to hold either a Mach limit or a speed (KIAS) limit, the autopilot will adjust the throttles. This brings up a problem of how to set a Mach limit in the AP control head. Setting a speed limit is easy. I was concerned about how you set a Mach limit and switch to Mach mode. I just did it in the LJ45 and it did not crash though its cruise was interrupted a bit. I saw only 000 in the window. There was no way to enter .80. When I clicked on the MACH button, this display changed to .00 but the throttles were suddenly pulled back. By the time I clicked the number up to .800, the aircraft had slowed considerably to M.74. There is a better way. SETTING A KIAS LIMIT With the aircraft flying on autopilot near the desired speed condition, just click on the numbers in the SPD window until they show the desired number. If you are flying your LJ45 at 40,000 ft, use 245. Then click on the SPD button. Be sure to set the speed value BEFORE clicking the SPD button. Don't touch the throttles because the autopilot will be controlling them. You can set a KIAS limit and then do a climb or descent. The autopilot will try hard to hold the limit. But if you have selected a speed too high to be maintained during a climb, the throttles will go to full thrust and your limit will not be held. After trying this for both a climb and a descent, I'd say you are better off just turning off SPD or MACH mode, making the climb just using altitude hold and a manual throttle adjustment, and then turning on the SPD or Mach mode after the change in altitude has been made. Trying to hold Mach or Speed does not seem advantageous. SETTING A MACH LIMIT The smooth way to do this is to set a SPD limit first. Pick a KIAS value close to what you are flying, enter it and turn on SPD mode. Then click on the MACH button. The current Mach number will replace the speed value you had set. This way there is no disruption in the thrust. I tried to develop some exercises to show how this mode works. The Baron and the Beech 350 do not have this mode. It is not in their sim program. This mode - SPD or MACH - can only be used with the jets. So I tried a constant airspeed climb in the Learjet. It didn't work. I normally do a max rate climb in jets. This is similar to the optimal climb schedules produced by the theoreticians but it becomes a bit crude in practice. Above 10,000 ft where the 250 KIAS limit does not apply, you reduce the climb rate in HDG and ALT mode and let the aircraft accelerate to some speed above 300 KIAS but well below its VMO. Then you set the climb rate high - 4000 fpm for the Learjet 45. As you climb you lose airspeed so you drop the climb rate in 500 fpm increments until you are climbing at about 1000 fpm above 35,000 ft for a max gross takeoff. Some people say you should be able to do this holding about 220 KIAS all the way. Thrust would be about 90% and the climb rate would start very high and then would decrease gradually. But it does not work out that way. Starting slow means your induced drag is high and that limits your ability to climb. I tried this in the Learjet 45. I was trying to use ALT mode as well and that may have caused some conflict. But the main culprit was the SPD mode control law that depends on thrust to control speed. In a climb in a jet, you need full thrust all the way or at least as much thrust as the engines can develop safely. (Setting 90% throttle seems to be okay.) You regulate speed not by thrust but by climb rate and the resulting pitch angle. I tried this constant speed climb again using manual control. I did set the autopilot in HDG mode so I would not have to worry about staying on course. My intention was to just use the stick to control speed and climb rate. I held 220 KIAS after takeoff and cleanup and used 90% thrust. The vertical speed was 4000 fpm at first. But I was fighting the trim. I kept pushing it nose down and it kept coming back. With only HDG mode engaged I could not understand what the autopilot was doing. Finally I turned off the autopilot and managed fairly well to about 24,000 ft. I was hoping to go all the way to 40,000 ft. But it gets tricky in the mid 20's. Vertical rate has to drop a fair amount and the tendency is to drop it too much and then get into a phugoid. Use the autopilot in HDG and ALT mode is the most orderly way to climb a jet. You continuously reduce the set climb rate limit to keep airspeed from dropping too quickly. Your airspeed will start at about 310 KIAS and drop to about 230 KIAS at 30,000 ft. Then you can climb steadily at 1000 fpm to 40,000 ft or just above for an initial climb. Some jets like the Gulfstreams and the Falcons have plenty of climb power so you can use higher airspeeds and climb rates longer into the climb. Still, if those are flown on international flights with full fuel, your climb will be staged - 35000, 39000, 43000 and maybe 45000. At each stage you burn off fuel. on domestic flights with full pax they will zoom right up to 45000 ft in grand style. This simply means it will take longer before you have to drop the climb rate by 500 FPM.
Tom Goodrick Re: Understanding The Autopilot « Reply #5 on: Mar 6th, 2008, 12:25am »
PART 6 APP MODE APP mode is one I seldom use. I have used it occasionally in past versions of FS but not recently. There are two reasons. First You have to land most planes anyway so it is best to be in control all the way down final. The second reason is that not all aircraft can use the approach mode. To see what happens in FS9, I set the Baron up in an interesting scenario. I put it at Albany, New York and did some VFR flying in the vicinity. There are some tall hills in that area so 2500 ft is a good minimum altitude when flying generally though you can fly the approach to KALB runway 1 down to 100 ft with the proper equipment. I turned on the Visual Flight Path and set medium size rectangles and medium length. Then I flew a downwind leg out to 10 miles and turned to intercept the ILS localizer at 30 degrees to its central direction (heading 040 to enter from the southwest). I had trouble getting the aircraft to enter the approach mode properly. I flew the approach manually. I decided to do some testing of the parameters marked "gs" in the aircraft,sfg file. I also decided to make it interesting by setting the weather to "Heavy Snows." I set up an entry point and heading for the approach and saved that Flight situation. I tried several value changes of parameters and thought some helped. But the main difference was how I entered the approach. I had to be fairly well off the center, flying to intercept the centerline at about 30 degrees to it. In several instances the aircraft lined up properly but was high, flying well above the boxes. I had to take control early, cut the power and drop down steeply to make a landing. There was one case that worked all right. I had flown under the glideslope before turning on APP mode but speed wa already quite low. The plane lined up and flew down the center of the glideslope. I gave up trying to find adjustments to the parameters. I put the Beech 350 and the Learjet 45 into the same situation as the Baron. They did fine. I was busy managing power, gear and flaps. But, they intercepted the localizer and flew down the the glideslope in the center of the rectangles. There was a notable crosswind and they were heading right of the track. The track was straight. Taking over manual control was very easy. I turned off the autopilot but no immediate change in control setting was required. I simply waited to get low enough to start the flare and then made a nice smooth landing. I still do not expect to use this mode much. But if you want to try it, just be aware that you must do your own flaps, gear and power. Arm the spoiler in the jets. I recommend using the rectangles on any approach. Just keep the speed right and keep the plane centered in the rectangles. If the AP does not do this right, do it yourself. The parameters were exactly the same for the Baron, Beech 350 and Learjet 45 yet they all worked - the last two working best. It makes you wonder what the parameters do. The Baron lands at about 86 KIAS, the Beech 350 lands at about 98 KIAS and the Learjet lands at about 129 KIAS. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~ YD Mode The AP has a YD or Yaw Damper mode. This can be used independent of any other mode you are using, including manual control. It simply reduces the yaw excursions that may happen during bumpy air conditions. Many jets MUST be flown with YD ON above 30,000 ft for safety. Yaw instability is common at the high altitudes. A slight yaw oscillation can get larger and become troublesome. If you turn on the YD mode and nothing seems to happen, look at the aircraft.cfg file. You should see the line: yaw_damper_gain = 1.0 This is all you need to make the yaw damper work. I have played with the directional stability of some planes, making it worse than it normally is. The Yaw Damper makes it behave well. Some aircraft need it whenever you fly in RW. ~~~~~~~~~~~~~~~~~~~~~~~~ BC and LVL mode: BC just means "back course". It reverses the sense of the localizer display. On an ILS this cannot be used because the glide slope points to the wrong end of the field. It is used in an approach where there is only a localizer showing where the runway is. LVL just keeps the wings fairly level. I never use it because I want to be sure the airplane is going where I want it to go. It can turn slightly in LVL mode but not in HDG mode. Use HDG mode and "diddle" the heading numbers with your mouse to make turns.
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Post by Bill Von Sennet on Aug 22, 2008 22:17:26 GMT -5
Tom Goodrick USING REAL WEATHER « on: Aug 16th, 2008, 11:53pm » uote Quote Modify Modify Remove Remove The Real Weather feature of FS9 is one of its greatest features. If you have not tried using it, you have been missing something. Using it is easy. You don't have to know how to fly an instrument approach or even an ILS approach to use this feature. Clouds and variable winds are a big part of real flying. As a real pilot, you sneak a lot of looks at the sky during the day you will fly. You check the weather forecast and look at the sky and wonder if they agree. As you walk to your airplane you look closely at the sky. That's where you will be in a few minutes. Is it good flying weather? When you get into the air, you can see farther and may see some clouds on the horizon. At first a few clouds on the horizon strike fear into the student pilot's heart. I was lucky. During my early solo flying, I encountered broken scud layers while practicing in the pattern. I just kept going because i saw enough holes so I knew I could get down. It worked and gave me a sense I coud live with some clouds. But some places the clouds are hiding rocks or steel towers. So how do you survive as a real-world pilot? The first step is to learn how to do it safely. You can do that in FS9 with RW. To get RW, select Weather under the World Menu and then select Download Real Weather. When you click on it, your system will try to connect to the Internet. Let it do so or help it if you have to. It connects to just a special site and does not use your Browser. (Somepeople like me cannot use their Browser at the same time as FS9. Don't worry. This will work fine.) The software goes to a special place operated by Jeppeson Company, a well-known aviation company with an excellent reputation. One thing you may not like is that Microsoft intervenes and quickly reads some data about your system. I have never seen evidence this will cause harm. The software downloads a short line of weather data from each airport with a weather station in the world. Then it arranges the data in a way that FS9 can use it. The entire process takes about two minutes on my rather slow dial-up system. But it would take you days of work to concoct an equivalent weather system for a 1000 nm flight using the methods of building weather manually. Then you would not get it close to "right." What does "right" mean? It means if you look out your window, the weather you will see in FS9 at a nearby airport is similar to what you see out the window with a few exceptions. It will be weather you have experienced on the surface in the past 15 minutes. The weather at altitude will be a mathematical montage of weather reported by sets of stations and measured at altitude at least four times a day. Weather between stations will be formed by interpolation of data over the space between stations and measurement points. But weather is done in sections. Occasionally you will see strange things as you move between sections. Unfortunately nothing tells you the boundaries of the sections. It is not uncommonon to start a final ILS approach 8 nm out in weather above the clouds where you can see the lights for the runway. Then you pass through various clouds layers losing sight of the runway. Then finally, about a mile out the runway pops into view. To fly RW without having to make an ILS approach, load the RW. Then use "Go To Airport" to place yourself at the destination. Look around in spot view. You might want to move out to 6000 ft from the airplane. Check visibility along the approach to the runway in use (most into the wind). When you determine that a visual approach can be made from a reasonable altitude like 2000 ft into your destination, then you are good to go on your trip. Pop back to your original airport and go. You don't have to have good visibility to take off, just to land. If your first choice for a destination looks bad, pick another until you find a good one. The main value of RW is that it gives you a complex weather system all the way between the start and destination airports at all levels you will use (up to 51,000 ft). As you fly, the weather changes in various ways so it matches the weather reported at the airports you pass. The usual way to use RW is just to get a file and fly with it. Your computer can be disconnected from the internet after you get the download. This works fine for practicing weather flying, for local flights and for short trips of up to two hours. For longer trips or for out and back trips over a period of 3 to 5 hours, you can either get continuous updates automatically, or you can get a second download half way through. There is a mode which reads updates the weather every 15 minutes and makes smooth transitions as you fly. For this you leave the computer connected to the Internet during the entire flight. I have used this on loong jet flights where I know the weather will change significantly during the flight. I may be going from one continent to another or from a norther city to a southern city in the winter with a flight starting in the morning and ending in the afternoon. We can expect significant changes in the weather due to the time of day as we fly such a trip. If you are not comfortable flying an ILS, there are several ways to learn. First pick an airport near your home that has a full ILS - both a localizer and a glideslope. The localizer guides you by direction to line up with the runway and the glideslope guides you along a sloping line as you lose altitude regularly (about 300 fpm) to the runway. Pick any airplane you are comfortable flying that has the instruments required for IFR flight (heading and attitude indicators and an ILS receiver (Nav1). Stick to that one airplane until you are a pro at ILS landings. Move to other airports with full ILS capability. You can also turn on a visual aid that displays recatangles along the path for you to fly through. They make it much easier to fly the ILS becaues you do what ever you need to to keep the airplane passing through the center of each rectangle. I use these when landing in dense fog or slow with zero ceiling. Just make sure you are at landing speed when you reach the last rectangle. This gives you the ability to go anyplace anytime (at least in FS where the thunderstorms will not kill you and your wings will never ice up from real weather.) One of the drawbacks to RW is that it often will set rain instead of snow. It will even do this when the surface temp is 25F and will not give you surface ice. There will often be sharp changes in winds even at high altitudes as the interpolation breaks down in certain conditions. Keep "Crash due To Structural Failure" turned off. It is unfortunate that nothing in FS RW will cause you to lose control and the things that will break your airplane are generally not realistic. It is not realistic to see a sudden shift on 180 degrees in wind direction with a high constant wind speed like 50 knots or even 100 knots. You'll notice this but you will not lose control. Instead of varying direction by itself, they should vary the speed componenst which would result in more reasonable directional variation. Any airplane would break if a 50 knot headwind suddenly became a 50 knot tailwind. That cannot occur in the real atmosphere except in a tornado. flaminghotsauce Re: USING REAL WEATHER « Reply #1 on: Aug 18th, 2008, 5:56am » How good we have it these days! Downloading real weather for the simulator and having it reproduce what is outside the window as accurately as it does... priceless. I keep thinking about the future of flight simulation. Imagine what computers will be able to handle in a decade or so. A flight simulator will come that will have us flying over photo-real land (which can be done today, although an arduous task), weather will be far better than it already is.... The weather simulation could take up an awfully huge processor setup all by itself. But there's already multiple core, multiple processor machines produced today that, if the software could properly access them, would do a tremendous job. It's only going to get better, too. I used to have a great situation saved at KIRK that included heavy clouds with multiple layers, some wind, and some rain that was just merely a RW download but it was fantastic and I had set it up to be the default flight. I changed it I guess and lost that weather scenario. I haven't captured it again since then. Once in a while, while driving at work, I'll see some of that and I have wanted to call home and have someone boot my computer, simulator, and walk them through it, so I can save the situation. "Barring all differences, they're identical!" BudsBud Re: USING REAL WEATHER « Reply #2 on: Aug 18th, 2008, 10:36am » RW weather has been one of my favorite things about FS9. I almost always have it on because in the real world you can not fly without being aware of the local conditions as Tom has said. One of my first flights from our local airport, KMCO, we had intermittent local thunder storms in progress. I was making an approach on the downwind leg when a large lighting strike crashed just out side of my window and about the same instant I was blasted in the headphones with a loud thunder clap. It was absolutely unreal how close to the real thing this RW is in the simm. But the downside is what Tom called attention to, that of sudden wind shifts at altitude. They wont bend your bird but they do throw you around a bit. JohnL Re: USING REAL WEATHER « Reply #3 on: Aug 18th, 2008, 1:54pm » If you have FSUIPC www.schiratti.com/dowson.html, you can set it to "slow down" any wind strength/directional changes, though I think you need the "all-singing all-dancing" payware version to do this. As I can't/won't fly while my current PC is hooked up to the net, I use FSMetar personal.telefonica.terra.es/web/fsmetar to provide RW. It's freeware and I've been using it since FS98, and have a library of Metars (most of 2007 at 4-hour intervals), so if I want some unseasonal RW it's no problem. « Last Edit: Aug 18th, 2008, 1:54pm by JohnL » JohnL (bgad017) Tom Goodrick Re: USING REAL WEATHER « Reply #4 on: Aug 18th, 2008, 5:42pm » I can get "unseasonal RW" if I want to break out of the winter blahs. I have saved weather files over several years, getting several in each month. I am more likely to tire of the heat of summer so I select a day in December. I do not understand what having the metars does for you. What do you do with them? Is there a way of feeding the data into the same routines that interpolate between stations to get weather for a cross-country? If the use of Metar files directly gives the same result as getting RW, what is the advantage? I have to think getting RW is at least easier. I may end up with a lot of weather that I don't use but it costs nothing of significance in time or memory. One thing I do if I am hoping to fly in some "interesting waether" is to get an RW download after studying a weather map. Then I go looking for the type of weather I want to fly in - a hurricane, a bunch of bad thunderstorms with tornadoes, a snowstorm, etc. I have found some very strong winds that made it impossible to operate from ground to air or air to ground. You can still fly through them. I have seen 50 knots on the ground and well over 100 knots in the air. « Last Edit: Aug 18th, 2008, 6:55pm by Tom Goodrick » flaminghotsauce Re: USING REAL WEATHER « Reply #5 on: Aug 18th, 2008, 10:49pm » Well, Tom, you're in luck! Another tropical storm this way comes. May go all hurricane on 'em. "Barring all differences, they're identical!" BudsBud Re: USING REAL WEATHER « Reply #6 on: Aug 19th, 2008, 10:17am » Ok so we now have a …small TS moving up on us here in central Florida. I thought it would be interesting to fly through the thing in RW as a real hurricane hunter does. Pooo nothing but light rain 15 – 17 knts winds. I was disappointed to say the least. I know as storms that we have through here this one is pretty weak but heck I expected much more Tom Goodrick Re: USING REAL WEATHER « Reply #7 on: Aug 19th, 2008, 10:47am » You have to get lucky in that high winds must occur at a reporting station within the past 15 minutes of your download. Sometimes winds aloft data are good for storms but often not. I have two files, one yesterday afternoon and one just a few minutes ago. I'll go looking through them for winds and hard rain. Allen_Peterson Re: USING REAL WEATHER « Reply #8 on: Aug 19th, 2008, 10:28pm » Thanks for the encouragement to use Real Weather, Tom. I downloaded RW and then went to my local airport (KCOE) and looked around. All I could see was clear sky and sunshine, so I didn't think RW was working. Then I realized that the real weather in Cd'A really was sunny with not a cloud in the sky. I took off and everything was still clear around the area, so I went to NWWW to check it out. I had previously flown up to NWWC in clear weather. This time it was different, clouds down to about 3000' with some of the higher peaks poking up through the clouds. I flew VFR to NWWH at 2500', picking my way up through valleys and around peaks using the GPS map. You're right, it does add a new dimension to flying! I saved the flight after landing, hopefully the same RW file will be used when I continue on to NWWD. I still have a lot to learn about IFR, ILS, etc. A couple of questions: 1. Where does the sim put the RW file? 2. Does the sim overwrite the old file the next time RW is downloaded? 3. If I find the "current" RW file I assume I must at least rename it save it. How then do I use the saved file in another flight? Have a good day. Allen Ed_Burke Re: USING REAL WEATHER « Reply #9 on: Aug 20th, 2008, 3:11am » Hi Allen, just wandering by and saw that I can answer your queries. RW is indeed a great thing. 1.... C:\Documents and Settings\name maybe\My Documents\Flight Simulator Files" For each flight there are two files, a .FLT file and a .WX file You can rename the .WX file to replace any existing wx file so that is one way of getting the weather you want. 2.... It sure does. 3.... If you save a flight with the 15 minute update you are also saving the instruction to continue with 15' updates. You will have a short, sweet flight before the wx changes to the current conditions. Your saved file is still where you left it but it's no use for an extended flight. The shot is to save a 'static' weather situation with a name that pins it down. My saved flight name looks like this....... wx080313frontalYBMC ........ or something similar which reminds me why I fancied the weather and where I was. The 6 figure group is YY/MM/DD which ensures that the files are listed chronologically. To fly in that weather simply load the saved flight. You are then free to change aircraft if you wish or to drag the aircraft in world/map view to the airfield of your choice should you want a new start. You have saved a snapshot of weather world-wide so poke around and have some fun. Ed ED B Tom Goodrick Re: USING REAL WEATHER « Reply #10 on: Aug 20th, 2008, 12:17pm » Yes... what he said. But to keep it simple, I only save flights with the fixed weather - a single RW download. Where your system stores the .FLT file, it will also store a corresponding WX file. It does this anyway, even if the file is Clear all Weather. So when you elect to resume a flight at that saved condition, you will get the weather. But you can change the aircraft and the airport for the next flight. You'll still have that same weather file. If I am making a flight of about two hours out and then returning, I get the RW at the start and then get RW again before doing the return flight. That gives me enough variation in weather to match pretty well what I would see in real life. If you save the flight named "BEST_DARN_FLIGHT" you will find two files in the storage directory: BEST_DARN_FLIGHT.FLT and BEST_DARN_FLIGHT.WX. You do not have a choice in naming the RW file differently. Fot this reason I have a bunch of flights named similar to "Aug 20 08" with a note in the commentary saying something about the weather. You may also see that flight plans (.PLN files) are stored in the same directory. This is so that you can save a flight with a specific flight plan and it will be loaded when you load the "Flight", in addition to the weather. If I want to send you a flight I have saved because of the weather, I would zip the pair of files .FLT and .WX. You would put those files into your directory with the other .FLT files. But I may have saved the flight with an aircraft you don't have. You'll get an error message. Just continue with whatever aircraft you had selected from your hangar and it will work all right. To avoid this I usually try to save flights with default aircraft. « Last Edit: Aug 20th, 2008, 12:33pm by Tom Goodrick »
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