Hop-A-Long Airplane Problem

[falcon409]

I have been flying a very nice update version of the SimTECH Do-335. If I load a default Cessna first (running) and then load the Do335, everything is fine but if I load the Do335 straight away and try to do a cold start it starts bouncing all over the place the instant the engine cranks.

I made some necessary corrections to the contact points thinking that would fix it, but no joy. What else would cause this to happen?

[MrZippy]

Have you tried any adjustments under [weight and balance] MOI settings? Had to do this on several aircraft that seemed to bounce and hop while on the runway at engine startup.

example: This is NOT your aircraft but an example of where to look.

empty_weight=89748.0
empty_weight_roll_MOI=931400.000000
empty_weight_pitch_MOI=1100000.000000
empty_weight_yaw_MOI=1000000.000000
empty_weight_coupled_MOI=0.000000

[Milton Shupe]

I have been flying a very nice update version of the SimTECH Do-335. If I load a default Cessna first (running) and then load the Do335, everything is fine but if I load the Do335 straight away and try to do a cold start it starts bouncing all over the place the instant the engine cranks.

I made some necessary corrections to the contact points thinking that would fix it, but no joy. What else would cause this to happen?

Ed, in my experience, there are two things that typically cause this:

1) Yaw MOI value in aircraft.cfg is too low - should be generally about twice the sum of pitch and roll MOI's;

2) CoG is off a bit and/or suspension is way too stiff ( Worse on some after-market sceneries).
This is identifiable by looking at contact points for nose and main gear. Either the compression is very short (like less than 10% of total suspension movement), or the max-static ratio is too high (well above 2.5)

I use to have this aircraft for the RTWR but have since deleted all those aircraft.

Can be an easy fix if I had it.

[falcon409]

Thanks for your input Milton, always great to hear from you. I did make a few adjustments based on your suggestions (Yaw MOI was a bit low and CG was moved a bit). The problem remains, however I found that starting using the autostart method (I have a button on my joystick for auto start and auto shutdown) does not produce the wild bouncing effect. So I'll use that rather than the switches for now. Hope you are doing well Milton.

[spokes2112]

Hi Ed,

Just to add another thought on top of Milton's ideas.
Perhaps starter_torque, maybe way over the top of what is really needed to start it?
The reason of this idea.. When CTRL-E is used the sim's internals ramps up the torque until it reaches max or starts, whichever comes first. A nice and smooth application.
Using the starter controls applies the all the torque instantly.

This is, of course, assumes the torque from the starter is applied to the aircrafts physics as a whole..

Going down a similar idea path... Propellor MOI? For the same reasons.

The propellor / starter forces, when started, may be too much to handle in regards to the MOIs in the weight and balance section.

Hope all is well,
Roman

[mal998]

I too have run into this problem before. I always thought it had something to do with the magnitos, but could never nail it down. I ran into this issue when I built the airfile and cfg for Virtavia's B-29. If I didn't follow the correct sequence for cold dark start-up the plane would go crazy.

[falcon409]

I too have run into this problem before. I always thought it had something to do with the magnitos, but could never nail it down. I ran into this issue when I built the airfile and cfg for Virtavia's B-29. If I didn't follow the correct sequence for cold dark start-up the plane would go crazy.

I have tried all the suggestions and have been unable to get it fixed so it has been relegated to the trash heap. I have far too many other airplanes that function properly to waste any more time with this one.

[Shessi]

F,
Just go and get this, it's been updated for FSX...so all done for you!

https://simviation.com/1/download?fi...p&fileId=54862

Cheers

Shessi

[falcon409]

I think that's the one I have. Used this individuals email addy. . .rodolfovalery@gmail.com? I had to convert many of the VC and gear strut textures because they were 256 color which displays as invisible so the VC was missing and the struts and a few other parts of the exterior were missing. Not exactly FSX ready. Once I converted those textures and the others to dds everything was fine. The bouncing airplane is irritating so it's gone.


Update: Yep, verified that this is the same one I already have. I did download again and there was no change, it bounces like crazy the instant the engine start switch is activated. Auto start works periodically but not consistent enough to make me want to keep messing with it.