how long for real torque efect ?

[J_A_B]

The engines wouldn't stop working if run at full power for 40-50 minutes.  They'd just need to be overhauled much sooner.  

Now running on WEP for that long might have adverse effects on the engine, but we can't do that in AH.

J_A_B

[FLS]

Originally posted by Dago
how about "p-factor"?  Why isnt anyone discussing P-factor?

P-factor is what pushes your nose to the left on takeoff roll, and pushes your nose around when you are slow and slam in the power.

Does anyone else understand the differance?  HT models p-factor but doesnt add a lot of  if, so it seems anyway.

dago

Dago if you'd like to calculate the amount of yaw force applied to the aircraft by P-factor and compare it to the amount applied by spiral slipstream I'm sure we'd all be interested in the result.

--)-FLS----
Musketeers

[CyranoAH]

Just adding some anecdotical data here, but my aerobatics instructor is also an Air Tractor pilot.

The Air Tractor is an 8-ton 1200HP turboprop, tail-dragger, and in the airport where I fly, it's used for fire extinguishing missions.

He told me that he had to apply full rudder AND some brake to counteract the tendency of the aircraft to veer to the left.

This is the closest aircraft in terms of performance to a WW II Warbird that I can see flying in my airport, and judging from this evidence, I'd say some planes in AH are lacking some p-factor.

Just my € .02

Daniel

[bloom25]

I may be totally wrong with what I say, but since I'm in engineering I did have to take some classes in statics and dynamics.  (Although it's been a while...   )

"Torque," as some people here are defining it, is a combination of many factors:  

There's the effect of the rotating propellor and engine parts.  This is actually what, in engineering, would be called torque.  The direction of the force is determined by the "right-hand rule", meaning if the prop is rotating counterclockwise (viewed from the cockpit), the plane is going to experience a force that would tend to turn the nose to the left.

The angle at which the propellor meets the air is also going to contribute.  ( I *believe* this is what some of you are calling p-factor ??? )  If the plane was in a nose up attitude at takeoff this is going to also try to cause the plane to turn left.  (Again, counterclockwise propellor rotation.)  This effect would diminish as the tail came up.  This effect would also be present whenever the propellor was not pointed directly in the direction of motion.

There are also going to be effects from the air coming off the propellor itself rotating.  (Slipstream effects? )  Unless I got it backwards, this is actually going to want to turn the plane to the right, opposite of the torque and p-factor effects.

Gyroscopic effects are also going to be present.  Raising the tail should (if I got the direction right) again try to twist the plane to the left.  (By the way, it is this effect that allows an arificial horizon indicatior to work.  Satellites also use this effect to orient themselves.)

HT, which (maybe all?) of these effects does AH currently model?  Obviously you have torque, I think I've read p-factor is there too.    

I'd love it if someone with some real Aeronautical engineering experience to let me know if I got it right.

[FLS]

Bloom25

You're not totally wrong, just a little mixed up.

The left turning tendency is from a clockwise rotation. The prop rotates clockwise so the aircraft wants to rotate counterclockwise. This is easy to see by pulling the wings off.

The spiral slipstream pushes the vertical stabilizor to the right with clockwise rotation so the nose goes left. Since it's a rotating force I think you can call it torque.

Asymmetrical thrust, known as P-factor, increases the thrust on the descending blade in a nose up attitude so with clockwise rotation the nose goes left.

Gyroscopic precession results in yaw from a pitch change and a pitch change from yaw. With clockwise rotation the tail rising on takeoff would cause a yaw to the left.

--)-FLS----
Musketeers

[hitech]

Just for clairification on torque, just change your left turning to left rolling, is easyer to understand.


All 4 eng/prop effects there.


Slip stream effects have more effects than just producing yaw. They also tend to counter act some of the torque do to the slip stream angle as it flows over the wings.

[funkedup]

Minus don't feel so bad.  HT spanked me twice this week when I posted whiny BS.  You only got spanked once.  

[bloom25]

HT, if you don't mind, could you tell me how gyroscopic effects are calculated.  I guess more to the point how does AH take it into account?  I'm trying to figure out how you model the prop itself.  (I suppose the rotating engine parts would be significant as well.)

I dug out my old dynamics book, but there wasn't anything useful in there on gyroscopic effects.  (Of course slipstream wasn't in there either, but that's fairly easy to figure out from a fluids point of view.)

Kind of an off-topic issue, but how did you ever figure this stuff out?  I think you told me once that you used to do something with controllers for furnaces or refrigerators or something like that, which I'm assuming was an Electrical type of thing.

It's truely impressive what you've accomplished.  Comparing the AH flight model to boxed sims (where it's obvious only minimal effort was spent implementing these effects and then it's often just kind of tossed in there) really shows you do your research.  From an economic standpoint there really isn't anything forcing you to model these things in detail, but yet you do.  That's something to be commended, and I'm sure most of us engineering type people really appreciate it.

[funkedup]

I studied aircraft dynamics and control a little in school.  It wasn't my major, but I learned just enough to know that HT and Pyro have hard job and they do amazing things considering how little data there are for some of these planes.