Simviation Forum - Can't take off!

Jan 2^nd, 2004 at 8:51pm

Sterk Offline
Colonel

Posts: 316

Hi all!
It's me again,and now with another problem with my
aircraft model...
Finally,after several days of hard work on aircraft flight dynamics parameters, I GOT her stand on ground!!!
Ufffff-it was not easy at all...

But now I cant take off-I mean aircraft takes off,but very very difficult and almost without pitching-with fuselage paralell to ground and after several seconds of flight,plane starts shivering like mad and fall...
All the parameters like elevators area,wing area,engine
thrust ,weight and so on are real aircraft params-but looks like plane has no enough lift power,reaching
dangerous speed yet on runway...

Logically I could think that there is not enough elevator's
area but it pretty close to other planes' params of the similar class...

I even tried to increase elevator's area but even doubling it has almost no effect...

Any idea,guys?

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Reply #1 - Jan 2^nd, 2004 at 9:23pm

Sterk Offline
Colonel

Posts: 316

Anyway-at least she is standing firmly on the ground and I am glad to even such kind of achievment...

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Reply #2 - Jan 2^nd, 2004 at 9:28pm

Sterk Offline
Colonel

Posts: 316

Hmm,no picture...

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Reply #3 - Jan 2^nd, 2004 at 10:19pm

Woodylepic Offline
Colonel
Quebec Canada

Posts: 330

send us the aircraft.cfg text we will check that and see what doing wrong ???

There is a 100pixle wide, and 10kb large, size limits on Avatars.&&&&Thank you for doing your part to make this a better place for all who visit by observing these guidelines.

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Reply #4 - Jan 2^nd, 2004 at 10:46pm

Sterk Offline
Colonel

Posts: 316

Ok,just a moment.
And thanx for your wish to help!

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Reply #5 - Jan 3^rd, 2004 at 10:54am

Sterk Offline
Colonel

Posts: 316

Here it is...
http://www.simviation.com/yabbuploads/TU334CFG.zip

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Reply #6 - Jan 3^rd, 2004 at 11:15am

Sterk Offline
Colonel

Posts: 316

If you find it useful,I could send you all the aircraft folder including flying(hardly:-)) model,so you could check it's behaviour in sim.

One note-current cfg is slightly improved one so now
there is no this mad aircraft shivering in flight...but plane is still hardly controllable...

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Reply #7 - Jan 4^th, 2004 at 2:23am

Milton Offline
Colonel
Props forever!

Gender:
Posts: 301

Sterk,

The aircraft sounds nose heavy. Based on you aircraft.cfg Geometry section data, it appears that the wing_pos_apex_lon = -3.900 is off by about 4 feet.

This number should be approximately 1/4 of the wing root chord distance in front of the 25% MAC (mean aerodynamic wing chord).

The wing_root_chord = 18.750 / 4 = 4.6875
Your empty_weight_CG_position = -3.200 + 4.6875 = 1.4875

This is the number that should go here:
wing_pos_apex_lon=1.4875

This tells the sim how far in front of the CoG the leading edge of the wing is. It also helps define for the sim, therefore, the proper position of the CoG/CoLift.

With this set, the aircraft CoG should be at 25% MAC and the nose heaviness should be minimal.

Visually you can check the Fuel/Cargo Loading window to see where FS places the circle over the wing. It should now show about 1/4 way back from the ;eading edge of the wing.

Hope this helps.

Milton&&Dash 7, Aero Commanders, Howard 500, D18S, Spartan, XP47J, Beechcraft A28 (Grizzly)

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Reply #8 - Jan 4^th, 2004 at 6:41am

Sterk Offline
Colonel

Posts: 316

Thanx a lot,Milton,I'll check it soon! Wink

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Reply #9 - Jan 4^th, 2004 at 5:37pm

Sterk Offline
Colonel

Posts: 316

Ok,you completely right about this,problem is wing position,but I moved this point even more forward,now it's about 6.5,because with param you gave me CoG is still right on nose...

Thanx a lot for real help,now my bird is taking off!

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