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
*****
Simaholic
WWW Email Instant Message
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 »
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
*****
Simaholic
WWW Email Instant Message
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 »