Simviation Forum - Editing FDEs.....how do I learn?

Jun 12^th, 2007 at 10:33pm

JBaymore Offline
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I am wanting to fix some stuff in the flight model of an aircraft (Jon Murchison BAe 146-200).

Where do I begin to learn how to do this?

best,

...................john

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Reply #1 - Jun 12^th, 2007 at 10:35pm

G-Fire25 Offline
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I think you need the source file....

RIP miltestpilot&&RIP Sean Taylor

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Reply #2 - Jun 13^th, 2007 at 7:30am

Felix/FFDS Offline
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To edit the FDE (i.e. aircraft.cfg and *.air files) you should start off at avhistory.com - the famous 1% spreadsheet, and/or Jerry Beckwith's Air Wrench (modest payware) are excellent tools.

Felix/FFDS

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Reply #3 - Jun 13^th, 2007 at 10:07am

JBaymore Offline
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Thanks Felix.

I am finding that when I cut the throttles to flight idle at the TOD on my 146-200, that the descent IAS speed seems very slow with the aircraft in a rather nose high trim out when set at an appropriate FPM descent rate. It should not be that nose high, which I think is affecting the airspeed with the extra drag.

best,

.......................john

Intel i7 960 quad 3.2G LGA 1366, Asus P6X58D Premium, 750W Corsair, 6 gig 1600 DDR3, Spinpoint 1TB 7200 HD, Caviar 500G 7200 HD, GTX275 1280M, Logitec Z640, Win7 Pro 64b, CH Products yoke, pedals + throttle quad, simpit

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Reply #4 - Jun 13^th, 2007 at 1:49pm

Brett_Henderson Offline
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It's a geometric thing... many variables.. and changing one usually means changing a few others (In what will seem like illogical and unrealted ways ..lol )

For example, in your case you "might" want to try increasing parasitic drag.. which would mean reducing induced drag (to keep cruise airspeed right)... which might be followed by adjusting the wing incidence.

I remember flying an FS2004 BAE146 quite a bit. If the aircraft.cfg locates the engines properly (higher than most passenger jets), there's got to be a built in incedence (negative (increases pitch)), to keep the plane level under power. When power is reduced, the nose should pitch up.. requiring nose-down trim by the pilot... and possibly more nose-down pitch during descent. Obviously I've never piloted a 146, but it wouldn't surprise me if a real 146 pilot confirmed this.

I'd imagine that if you trimmed the nose down, the airspeed/descent might go too high.. That's were parasitc and induced drag come in. You'll probaly end up tinkering with thrust and and changing flap pitch/lift/drag too...

A single gaol in FDE editing ususally takes several paths..

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Reply #5 - Jun 13^th, 2007 at 1:53pm

JBaymore Offline
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Brett_Henderson wrote on Jun 13^th, 2007 at 1:49pm:

I'd imagine that if you trimmed the nose down, the airspeed/descent might go too high.. That's were parasitc and induced drag come in. You'll probaly end up tinkering with thrust and and changing flap pitch/lift/drag too...

A single gaol in FDE editing ususally takes several paths..

Brett,

Yup...... if I trim the nose down, the airspeed comes up to what I'd typically expect.....but the FPM descent rate goes thru the roof at the same time. Not right.

best,

.......................john

Intel i7 960 quad 3.2G LGA 1366, Asus P6X58D Premium, 750W Corsair, 6 gig 1600 DDR3, Spinpoint 1TB 7200 HD, Caviar 500G 7200 HD, GTX275 1280M, Logitec Z640, Win7 Pro 64b, CH Products yoke, pedals + throttle quad, simpit

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Reply #6 - Jun 13^th, 2007 at 2:05pm

Brett_Henderson Offline
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That will be a tricky one to resolve.. Probably a good one to cut your teeth on. I'd offer to help, or do it for you, but I've not FS9 running right now.

You could cheat and just lower the location of the engines (start-up smoke will look funny) and then just fiddle with the incidence and/or make a mental note for the new trim settings...

If you go at this head on... you'll end up adjusting the paramters I've mentioned.. and likely; tweak the heck out of the "Flight Tuning" paragraph (you wanna keep that to a minimum... once you go too far there, your plane's flight envelope will barely resemble the airplane you started with)..

It's not as time consuming as 3D modeling, but FDEs can be just as challenging..

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Reply #7 - Jun 13^th, 2007 at 2:13pm

Brett_Henderson Offline
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One more important thought. If you are gonna do this, consider starting with a clean slate.

Go through the aircraft.cfg file to get a feel for it.. then go get all the EXACT numbers in front of you..

Most important are; Wing/stabilizer area/span, wing/control-surface apexes, engine locations, COG, flap-span, wing and tail incidences, and of course weights and MOIs.

To MSFS' credit.. if that "model" is accurate, you're way ahead of the game. Just tweaking specific parameters in an innacurate foundation, can leave you chasing your tail..

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