Pyro's opinion on 3 flight modelling items?

[funked]

Don't forget the tailwheel guys.  When the tail is on the ground, the tailwheel (free, locked, or steering) has a major effect on directional control and stability.  AH seems to have tailwheel steering, but I think most of the WW2 taildraggers had a free tailwheel that could be locked in some planes.  Anyways a lot of this stuff about "torque" and rudder effectiveness means diddly squat if the tailwheel is keeping her straight.

[Yoj]

 

Originally posted by hitech:

Roll Torque on the plane is very easy to calculate it's simply current HP / prop rpm.

HiTech

Thanks HT.  I was curious about the comment on Roll Torque though.  From what you say it would appear that Roll Torque would be the same regardless of the prop's mass - or even without a prop installed (assuming the engine could be run that way).  If that's true then I would think it would be of no interest at all to the pilot - only to a propulsion specialist.  Did I get what you meant?

Yoj

[niklas]

 

Originally posted by Yoj:
Thanks HT.  I was curious about the comment on Roll Torque though.  From what you say it would appear that Roll Torque would be the same regardless of the prop's mass

If you watch the RPM gauge then youŽll see that your RPM is always constant until you change it manually. Mass is only important when you accelerate it - this is not the case here. So torque seems to be only modelled due to drag effects of the blades.
IŽm wondering myself why the number of blades and the length of the blades is not important for this roll torque? I mean a 4-bladed prop produce ~33% more torque than a similar 3-bladed one, right? And torque is force*distance, so a larger propeller should produce more torque than a smaller one, right? So why has the 109 with a small 3-bladed propeller one of biggest torque effects?

And aillerons are not affected by the slipstream. Why has the N1k still good ailleron control in a vertical zoom when you slow down to less than 50mph?? Ailleron torque is based on lift, right? And lift is a function of speed.

niklas

[funked]

Niklas the torque is just action/reaction.  The prop exerts a torque on the atmosphere and the atmosphere exerts a torque on the prop.  To balance that, the engine/gearbox exerts on the prop a torque equal to shaft power divided by rotational speed.  The rotational speed is not the engine crankshaft rpm, but the rpm of the reduction gearbox output shaft.

Also try moving the throttle in AH when you are at very low speeds.  The rpm will change.  They still don't have a full dynamic model of the prop governor but it's better than it used to be.

[hitech]

Yoj Prop mass has nothing to do with the torque on the plane, whats realy happening is we are concerned with the torque at the prop shaft,
that torque is either going into thrust/prop drag or it's going into accelerating the prop, Either way the force on the plane remains the same for any HP/rpm combination, the thing to relize is that the HP of the eng is increasing as the rpm increases.
Threw most mid RPM ranges the eng tourqe output is fairly constant and HP is increasing with RPM.

HiTech

[Torque]

I see that i'm the subject of much debate.

[Pepe]

Hehehe, just as I was writing a post stating that I did not undertand the mass thingy, the light struck me.....i guess  

Bearing in mind that we are talking about constant rpm props, now I can imagine that prop mass and prop diameter has only slight consequences on generated torque. It would if we change rpm, but since we are only varying the prop pitch, the propwash effect would be far more intense than the one generated by the change in the pair of forces (dunno if that's the right translation, but tech english is quite schematic here  ) produced by the prop spin and derived from the change in blades' angle.

Now the question is....did the light really struck me, or I'm even more lost?  

On a side note....I like a lot these thech discussions....food for my thoughts  

Cheers,

Pepe

[Yoj]

 

Originally posted by Pepe:
Hehehe, just as I was writing a post stating that I did not undertand the mass thingy, the light struck me.....i guess    

Bearing in mind that we are talking about constant rpm props, now I can imagine that prop mass and prop diameter has only slight consequences on generated torque. It would if we change rpm, but since we are only varying the prop pitch, the propwash effect would be far more intense than the one generated by the change in the pair of forces (dunno if that's the right translation, but tech english is quite schematic here   ) produced by the prop spin and derived from the change in blades' angle.

Now the question is....did the light really struck me, or I'm even more lost?  

On a side note....I like a lot these thech discussions....food for my thoughts    

Cheers,

Pepe

I agree - your comments clicked with HT's and a lightbulb went on.  

[Pepe]

n.m. answer to this one was on Htc. first post...gyroscopic precession

Cheers,

Pepe



[This message has been edited by Pepe (edited 05-11-2001).]