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View Full Version : Torque,dead stick landings and unexpected results with 4.00.



Chadburn
06-13-2005, 09:07 PM
Tried a couple of dead stick landings to see the effect the new torque modelling has when the engine is shut down in a single engine plane.

I tried it in the 109 G6 and the Spitfire IXe. Both planes exhibited the same characterstics in the test, but there are some surprises that someone with real flight experience may be able to explain. Here's the stages I tested and I'll use the Spit Mk.IXe's speeds:

1. Engine on 100% - left wing drops due to engine torque (clockwise spinning prop when viewed from the cockpit) until cruise speed is achieved around 450kph. Just some slight nose down trim required for level flight and no stick pressure. This all makes sense so far.

2. Throttle back to zero power and the right wing begins to drop. This seems to make sense too, since the plane should be trimmed to counter the engine's torque effect, so when the engine is idled down, the left wing rises. The plane will behave this way right down to stall speed so long as the engine is running. Again, this generally makes sense to me.

3. Now the surprises. Let the Spit's speed drop with engine idling to about 300kph. Shut off the engine and as soon as the prop stops spinning, the Spit suddenly torques left, the left wing drops while the right now rises. I had expected the plane to continue its torque to the right for the reasons mentioned above, maybe even moreso with the engine completely off, but it doesn't do that. Zero torque from the engine at this speed seems to produce the same torque effect as a running engine at 3000rpm.

4. Push the nose down and pick up some speed. At about 330 kph the prop windmills and suddenly the plane torques right again. So long as the prop is spinning (although it's only windmilling) the plane will torque right. Pull the nose up and bleed off speed, and as the speed drops to 330kph again, the prop stops windmilling and the plane suddenly returns to a left torque.

Sorry for the long post, but are there any areodynamic explanations that would account for this flight characteristic? Whether it's accurate or not, it sure makes dead stick landings a lot more interesting than in any previous patch!

Chadburn
06-13-2005, 09:07 PM
Tried a couple of dead stick landings to see the effect the new torque modelling has when the engine is shut down in a single engine plane.

I tried it in the 109 G6 and the Spitfire IXe. Both planes exhibited the same characterstics in the test, but there are some surprises that someone with real flight experience may be able to explain. Here's the stages I tested and I'll use the Spit Mk.IXe's speeds:

1. Engine on 100% - left wing drops due to engine torque (clockwise spinning prop when viewed from the cockpit) until cruise speed is achieved around 450kph. Just some slight nose down trim required for level flight and no stick pressure. This all makes sense so far.

2. Throttle back to zero power and the right wing begins to drop. This seems to make sense too, since the plane should be trimmed to counter the engine's torque effect, so when the engine is idled down, the left wing rises. The plane will behave this way right down to stall speed so long as the engine is running. Again, this generally makes sense to me.

3. Now the surprises. Let the Spit's speed drop with engine idling to about 300kph. Shut off the engine and as soon as the prop stops spinning, the Spit suddenly torques left, the left wing drops while the right now rises. I had expected the plane to continue its torque to the right for the reasons mentioned above, maybe even moreso with the engine completely off, but it doesn't do that. Zero torque from the engine at this speed seems to produce the same torque effect as a running engine at 3000rpm.

4. Push the nose down and pick up some speed. At about 330 kph the prop windmills and suddenly the plane torques right again. So long as the prop is spinning (although it's only windmilling) the plane will torque right. Pull the nose up and bleed off speed, and as the speed drops to 330kph again, the prop stops windmilling and the plane suddenly returns to a left torque.

Sorry for the long post, but are there any areodynamic explanations that would account for this flight characteristic? Whether it's accurate or not, it sure makes dead stick landings a lot more interesting than in any previous patch!

ColoradoBBQ
06-13-2005, 11:42 PM
I'm not an expert but I figured that since propellers are just slender wings pushed through the air to generate thrust, they generate lift that pushes the plane in the other direction when moving through the air while stationary.

xTHRUDx
06-14-2005, 12:05 AM
this was present in 3.04.
it only occurs about a wingspan or wing span and a half above the runway.

it is a bug. prop pitch full or featherd, it has same effect.

NonWonderDog
06-14-2005, 12:46 AM
It really sounds like a divide by zero error. http://forums.ubi.com/images/smilies/16x16_smiley-tongue.gif

Really, this shouldn't happen. I haven't noticed it having anything to do with altitude or ground effect, it's just as soon as the prop stops, torque goes through the roof. If you dive fast enough that the prop will start turning again, the torque is gone.

Should probably go in the bug report thread.

Lixma
06-14-2005, 12:55 AM
This nasty little bugger caused me to pancake a landing while damaged this evening.

There is a definate 'hole' in FM, here. There should be no reason whatsoever for the plane to kick violently to one side just because a prop that has been happily windmilling at very low rpm decides to stop.

AerialTarget
06-14-2005, 01:18 AM
It's always been present in the game. Apperantly, it is now more noticeable now that torque is magnified.

I think that the entire flight model code needs to be completely rewritten from the ground up for Battle of Britain, not just rehashed again. Don't get me wrong; I'd be on thin ice saying this about a free patch. But for Battle of Britain, we really should get a completely redone code.

Chadburn
06-14-2005, 08:25 AM
Thanks for reading through my long post. I never noticed it in 3.04, so the new torque model must have magnified it to the point where I do notice it now.

I agree that I can't think of any aerodynamic reason this should happen, so it's probably a bug in the fm or a limit of the current model.

At least now that I'm aware of what to expect on a dead stick approach, I'll be ready.

ucanfly
06-14-2005, 09:12 AM
YOu ought to post this in the bug report thread if you haven't already.

Chuck_Older
06-14-2005, 10:06 AM
Yes, report it.