Correcting Stall Characteristics

[blazer003]

After years of avid Flight Simulator use, I recently purchased my first airplane, and am in the process of getting lessons.

The airplane I purchased is an 2001 OMF Symphony 160. About the same time I was setting up this purchase, I purchased a payware Symphony (the only FS version I could find).

The one biggest difference between the real thing and the FSX aircraft is the stall characteristics. In real life the plane stalls oh so gently. It's tough to even get it to stall, often time ending up mushing more than stalling.

When you do get it into a stall, it's very easy to gently drop the nose straight back down.

In FSX this plane behaves quite differently. The nose drops dramatically off to the left and you cannot get the nose to drop straight down. Pushing forward on the stick at the brink of a stall has very little effect on the plane.

Anyway, just would like any suggestions you might have.

[flaminghotsauce]

Heh. I suggest you fly it up to KIRK and take me up in it! ;-)
k
I don't have any real advice for adjusting stall characteristics. I've not done any of that type surgery.

[louross]

Interesting point, I found the same issue with the Twin Otter in fs9. Modeling of engine failures in heavy twins is not programed into the basic MS code for fs9 nor fs 2000. Probably the same for fsx, including actual stall characteristics.
lr.

[Tom Goodrick]

I don't have FSX and so I can't say for sure what you need to do. But it may be sufficiently similar to FS9 for these suggestions to work. They would solve the problem in FS9.

First, you need a program that enables editing of the .air file. I have used AAM (Aircraft Airfile Manager) in FS8 and FS9. Several other programs have been added recently.

Second there are two tables or graphs that you need to check. CL versus Alpha is table 404. Check that the peack CL curve just to the right of Aplha = 0 is a gradual peak and not a sharp peak. the value of CL at the peak determines the stall speed without flaps extended.

Third, and most likely the source of your problem, id the table of Cm versus Alpha (Table 473). Both this table and the previous table apply to the entirety of orientations: from Alpha = -180 (2 pi) to Alpha = +180 (2 pi) and please note that -180 is the same orientation as +180 so values must agree at those two points. The graph of Cm versus Alpha is often made very strange around the stall point (about +.26 to .35 radians). For a smooth stall as you describe, there should be only a slight bend in the Cm versus Alpha curve, not a sharp turn or a reversing turn.

Hopefully someone with FSX who has done this sort of thing can help you. If it were in FS9, I'd have it fixed in a few minutes. But usually I go the other way. FS stalls are too gentle so I make the plane fall out of the sky if you goof up the recovery on something like the Baron.

[Tom Goodrick]

Lou, if you would send me an email (or posy in the FS2004 section) describing the various stalls of the Twin Otter - twin power oN/OFF, single-engine, flaps up or flaps down - I should be able to get it closer to what you want. I'll send you what I get and you can test and I'll retry until we get a significant improvement.

What I am usually lacking is good sescriptions from people like you having experience with the particular aircraft.

I agree that few of the aircraft in FS are properly "programmed" for stall. But the solutions are not too hard though it gets complicated with the one-engine-out twins. Tables 404 and 473 are still involved but so are the lateral and directional stability derivatives.

[louross]

Okay. However, I think I've eliminated any Twin Otters I had, will have to check. There is a website- maybe PAD or something, that has a whole slew of DHC6's and other a/c. I'll see if I can find it, and do some tests, but it will take some time, maybe a week.
One thing I found about those from PAD was the frame rates were poor. I have the Dreamfleet 727 and the PMDG744 which has better frame rates than the PAD group. Also, as we talked about before, there are other problems with the Otter set up, which I don't understand since many other a/c for FS are rather well programmed.

lr.

[Tom Goodrick]

OK but you don't have to go too far to find a good DHC-6. You can get a Blue Grass version at:

www.bluegrassairlines.com/bgas/hangar/2004_turbo-prop.html

I got one there back in FS2002 and the file was a lot smaller than the one they show now. i converted the one I got to FS2004 and revised the flight dynamics files considerably. The size of a file has very little to do with how well it flies. The file size today relates to how many doors open, how much furniture you can see inside and whether any trucks come out to service the aircraft. I don't care about that stuff. Whatever aircraft you get, I'll just ask you to email the aircraft.cfg file and the (a/c_name).air file. I can plug those into my aircraft and fly it with them. Then I can change those to get the performance you want to see and send them back to you.

I'll start a thread in the FS9 section to describe what I saw in some brief testing this morning. That might be one starting place.

[louross]

Okay, I've just downloaded the DHC6 from the above Bluegrass link. I'll check on it when I can during the week.
lr.