I am retired and spend all day on my computer. I am available to help anyone with FS9 and the FS navigator . I use several messenger programs plus SKYPE . We can use our team speak. The best way to learn is by talking to each other . Typing is a very hard way to learn anyway . I have been using the flight simulator for over seven years .I have a real pilot ticket plus flew with the US NAVAL AIR as a flight engineer .
Post by Tom Goodrick on Mar 14, 2009 13:24:13 GMT -5
Welcome to this side of the BGA Forum, Pappy. We can always use more info. The FS2004 Forum has not been very busy lately as you can tell. You can start by looking over what we have discussed in the past and adding any comments you think helpful.
I generally prefer just email or with comments on this Forum. When we discuss a topic on the Forum, it may just be between us but others may also be interested. I have tried various messaging systems in the past but found them very hard to live with. When I am wroking on a plane or gauge like the Ice Gauge I did recently, I am busy flying and editing and flying and editing so when I get to posting a revision on the Forum, I don't like being hit with a bunch of Instant Messages before I can complete the post. However, I noticed that Skype is available on my new lap top. That might be interesting to try.
These days I have found other projects to do other than FS flying so I have been busy off-line. I am copying old family videos on two types of media to DVD and I have been making audio recordings with a new high-quality mic on this laptop to compare different horns and accessories. (I play trumpet, trombone, tenor sax and soprano sax as well as keyboard.) I guess you could say I've become a multi-media person! I almost don't have time to play golf on the Nintendo Wii anymore. (I am due on the tee at Doral in a few minutes!)
My background is I have a private ticket and a degree in aeronautical engineering with 30 year's experience between the US Army and NASA.
Do you have experience flying turboprops? That is a sticky area we've gotten into lately. It seems FS does not model correctly the turboprop engine in relation to ITT.
Post by Tom Goodrick on Mar 16, 2009 9:53:20 GMT -5
Pappy, I have a question you might answer. We have problems setting the right value for gear drag. Most developers tend to err on the high side which makes it easy to slow down for landing.
Yesterday, while setting this value on a Beech Queen Air, I tried testing the change in steady flight speed when gear is lowered and the power remains the same. This generally was a big speed difference (25 KIAS) which seemed a bit much to me. But the gear speed is a rather low 140 KIAS and so the aircraft is near the bottom of the power curve. Thus if the added drag is not balanced by a slight power increase, it tends to push the aircraft toward the backside of the power curve. I think if the aircraft could lower its gear at a higher speed, there would be less of a difference.
Does this make sense? Does it agree with your experience? I have never flown a real aircraft with retractable gear - just fixed gear, mainly Cessna's.
Signed up a week or so ago and am just now reading the posts here. I flew for a co. that had Twin Otters and then left to go with a company flying Beech 99s- those were PT6a engines. Responding to a point in the upper post MSFS does a very poor job of modeling the PT6a- can't comment on the other turbo-prop engines. Remember a good amount, but also have forgotten a lot. Was type rated on 727 but only flew them a very short while and flew the 732 a very short while so remember virtually nothing. Maybe I could help you with questions you might have about the turboprops. Enjoy playing a lot with MSFS with the "right" addons, but to be frank, don't have much respect for the program as far as simulating a/c aerodynamics goes. lr.
Post by Tom Goodrick on Oct 28, 2009 0:07:52 GMT -5
I am a former small plane pilot and an experienced aeronautical engineer with an emphasis on aerodynamics and flight mechanics. I don't know much about engines except what I read in the aviation press.
But I can assure you the aerodynamics and flight mechanics in this sim are very accurate. The problem is that most people, incliding those who work for Microsoft, do not know much about setting up the flight dynamics files. So, most airplanes you download will fly with poor realism. It is not the fault of the sim.
I have run several tests on the sim for realism. The standard density and temperature profile is very good.
Getting accustomed to the view and control interface with the computer takes a while and can be helped with some adjustment. We have worked at that.
The only technical fault is the lack of realism in spins. This is because the sim assumes that lift always occurs at the center of the aircraft - not distributed across the wind which can be unbalanced in real life. So you can't do snap rolls with any realism. But otherwise all the flight mechanics aspects are properly simulated if properly set up. I have managed to get a decent spin out of the Piper Cub which I used to like doing as a kid.
I take it very seriously. I have a number of model files as free downloads on my web site (click first icon under my photo).
Most interesting point by you. MSFS does not model engine failures (MEL a/c)- is that an MSFS limitation, or the person who makes the FDE file for the a/c? Take final approach. At a particular weight, the airplane will have a particular pitch, power setting, and fuel flow to hold the approach speed. These parameters do not show correctly in FS. Is this again due to programming by the a/c developer, of a limitation by MSFS? Why doesn't FS model ice on the runway? Would it be possible? lr.
Post by flaminghotsauce on Oct 28, 2009 14:33:20 GMT -5
Also Tom, about spins. If the sim doesn't model it correctly, how did you get the cub to do it right? I just posted about the A2A simulations Cub and how real life Cub pilots were happy that it spins correctly.
I've struggled with the Cub because I cannot seem to be able to taxi. Landing is a deathtrap! It's a rare landing I don't crash. Consequently , I don't get much time in it. I've yet to try to spin it, so I'm in uncharted waters here.
Post by Tom Goodrick on Oct 28, 2009 23:00:01 GMT -5
Flaming, you must not have been flying my FD in the Cub. It can taxi. The FD has been on my web site for years. It spins when you do a power-on stall and hold full rudder. It is a realistic motion.
Lou wrote the following: "MSFS does not model engine failures (MEL a/c)- is that an MSFS limitation, or the person who makes the FDE file for the a/c? Take final approach. At a particular weight, the airplane will have a particular pitch, power setting, and fuel flow to hold the approach speed. These parameters do not show correctly in FS. Is this again due to programming by the a/c developer, of a limitation by MSFS? Why doesn't FS model ice on the runway? Would it be possible?"
All of these items are, indeed, faults of poor FD files. By not moddelling engine failures I guess you mean it does not show the proper immediate yaw response to loss of engine power. If the directional stability is too strong, you don't see the proper response. That is common in poor FD. Sometimes the engine positions are not properly givens so there is not the proper offset to left or right. This can be easily corrected.
Pitch, power and fuel flow on approach are commonly unrealistic. This is rather complex but I have corrected it to my satisfaction in several cases. The pitch is partly a matter of adjusting the lift curve, partly a matter of getting the CG placed correctly and partly a matter of flap pitching moment. If you have a specific example from my web site, then I can make an ajustment to fix the problem. I have notes on what I did and why I did it.
Not only is ice not modelled correctly but lateral wheel friction is not modelled corectly in FS. But we live with that.
There is a lot of info on this stuff in various parts of this Forum.
Most of the aircraft you can download have good-looking profiles, panels with various degrees of relism and operating gizmos like opening doors. But the FD files are generally copis of files for some other aircraft that is close. Few people have much of an understanding of what is going on in real flight dynamics so they apply mistaken ideas they heard from somebody.
Take the effect of flap deflection on pitch. Many pilots think the flap cause the nose to pitch upward. The flap does two things: 1) the change in moment causes the nose to pitch down; 2) the flap adds lift that causes the aircraft to fly upward and to point upward along the new path. The balance between these tendencies varies of course between aircraft. Most FD files make the nose ride high. But this is also a matter of the curve for lift versus angle of attack. This effect was changed for FS9 when they deleted the effect of wing incidence. We have to create the proper effect by shifting the lift to higher values at a given low angle of attack. We are fighting a lot of ingorance on the part of Microsoft programmers and managers.
I set the view over the standard 2D panel so the pilot can see the runway numbers on a standard glide slope from 2 or 3 miles out but you lose that view as you cross the fence. Then you aim farther down the runway and may actually lose sight of even the end of the runway as you flare. But in doing this it is more than just adjusting the pilot's eyeball. all aspects mentioned above are involved.
As you can see these things are not simple. I suggest you take examples of problems you find and discuss them in sepoarate threads on the FS2004 portion of this Forum where you'll get several comments. But I caution that, for legal reasons, I will not comment on any commercial or "payware" aircraft.
Just a quick clarification: My point on engine failures was concerning V speeds. I've pulled an engine on at least several different twin-engine transport category jets (MSFS) at or just above V1- both free and payware- and they will not fly. The magic number in FS seems to be 180 kts, obviously way high. Flaps- when you lower flaps on the Twin Otter or the Beech 99, you need to trim nose down. The lowering flaps moves the CG to the rear.
Post by Tom Goodrick on Oct 29, 2009 9:24:23 GMT -5
Flaming, I have written quite a bit about how I did that. FS has stability derivtives that let you make the plane do a lot of things in response to certain motioms. I was able to get the particular spin of the J-3 Cub but my method would not apply in general to other aircraft. Also, because the sim does not model laterally unbalanced lift, we cannot make aircraft perform incipient spins, where the pilot does not cross the controls or do something to yaw the aircraft incorrectly at low speed.
Lou, you have been flying junk.
I'll grant you that lowering the flaps can make the airplane behave as though a copule of pro football players are wandering in the aisle but the flaps obviously cannot move the CG. As I said, their are two opposing reactions to flap deflection. One dominates in one design and the other dominates in other designs. But if you look at any chart on airfoil performance, the pitching moment moves the nose down. But the lift goes up by a factor of at least 2. So you have a nose-down pitching moment and a lifting of the flight path. If I have nothing else to go on, I generally make the plane behave nicely so the pilot's workload is not high on final approach. But I try to model planes for which I have pilot reports in magazines. If those reports indicate a particular response, I put that into my model.
In the particular case of the DHC6, the flaps are very effective at producing lift so they enable slow and fairly steep approaches. Hige lift enables slow flight. But that also means that before the aircraft slows as needed, it wants to go up. You have to counter that with nose-down trim. Otherwise it would rise up and run out of speed and then drop you.
Information like you bring is very valuable. I have a model of the Twin Otter. I'll check to make sure it behaves like that.
I'm going to say that there is an obvious misunderstanding here someplace. I have about 2,000 hrs flight time in real world Twin Otters with a commuter airline and also about 3,500 hours real world time with a commter airline in the Beech 99. That is left seat time. So I suppose it's safe to say I know how to fly these 2 a/c. I am specifically stating that when you put the flaps down on either of those planes, you must trim forward. Well, you don't have to, but if you don't, you will have a very difficult time holding the nose down. If you are disagreeing on that point, obviously you're mistaken. As far as MSFS goes, I've pulled and engine on the default 737, the Dreamfleet 737, and numerouse other 737's, and they do not fly at V1. I don't rember what the PIC 767 did.
Post by Tom Goodrick on Oct 29, 2009 22:03:07 GMT -5
Let me make this perfectly clear. I have nevr been in the left seat of a DHC6. Put me there and I couldn't find the cabin light switch.
But I know aerodynamics and flight mechanics. In what I wrote above, I said that, in general, a plane could go either way - nose-up or nose-down when the flaps are extended and transients have died out. What you do not seem to get is that we can make these airplanes behave "as they should" but only if someone like you tells us what they should do.
I tested my DHC6 tonight briefly and found it had too much of a nose-down moment when the flaps were extended. I had a full load of passengers and 60% fuel in the maintanks. The CG was at 15%. I reduced the nose-down moment by 50% and moved the CG back to 24%. It was more like you describe. There was a much stronger initial nose-up moment as it tried to climb but after that transient went away (I descended through several hundred feet), it required a slight nose up trim to hold a shallow glide. I was doing this 7500 ft above terrain with no intent to land.
Two things are happening here. If doing this on an approach, obviously I would trim nose down while extending the flaps and then land. But I suspect that I don't have the CG right yet. If I put it at 30% or more, then it might b ehave exactly as you describe.
We can change the behavior completely by changing numbers in the FD files (aircraft.cfg and .air file).
Let's go to the FS2004 section and work on the DHC6 until we get it right.
Okay. I have 1 or 2 DHC6's, I think they are from Premium Air Design. I'm not at my computer now, so can't say for sure. Let me know which one you want to use and I'll download it, but I'm sure you're aware that the avsim library is out to lunch. One thing that might be important, in case you're not aware, is that when you do a power off stall the Twin Otter (control column is in your lap) will recover just by adding full power- you don't have to "push the stick" forward. CG is noticeably affected- if for example there are 5 people in the last five seats rather than 5 in the front five seats. Can't give you any MAC % because I don't remember the numbers. lr.