Flight Model?

[Jekyll]

Funked, would not torque ALSO be proportional to propellor pitch?

I would imagine the coarser the prop pitch, the greater the resultant torque effect.

[BBGunn]

The term "dumbed down" used above may not have been a good choice of words, but seems mild compared to some of the metaphors being posted.  Anyway I found a reprint of an F6F pilot manual and noticed the following.  "Trim tab settings for takeoff: elevator-1 degree down; ailerons-neutral; and rudder 30 degrees right." "Following takeoff at high gross weight, it is necessary to hold hard right rudder pressure until the flaps are raised even though full right rudder tabs are used".  Torque and the other related force factors (P-factor and corkscrew effect) were obviously an important issue on take-off.  Clearly I do not wish to make anyone angry but I was a bit surprised that torque etc does not seemed to be modeled in for carrier take-off.

[Maverick]

 

Originally posted by Jekyll:
Funked, would not torque ALSO be proportional to propellor pitch?

I would imagine the coarser the prop pitch, the greater the resultant torque effect.

The answer to your question is no. Pitch doesn't impact torque. Pitch impacts amount of air displaced by the blades and correspondingly the number of RPM's of the engine due to loading the prop beyond the engines ability to produce enough horse power to maintain RPM. Lower rpm means LESS torque as the mass the engine is spinning is going slower. The amount of the mass is the same so the only variable is the speed of the prop.

Frankly the whole issue of torque on the bbs astounds me. The only time it becomes a "real" factor in flying in the GAME is if you are not using auto take off. There is no real reason for a go around on landing so torque on sudden increase of power is not an issue. If you are flying at full stall you are doing something very wrong as you will very soon be out of control of the aircraft. This is not good in a fight.

As a real pilot of a real plane (complex, retract and variable pitch prop) torque is not a big factor in flying. You learn to deal with it and apply the minimal amount of rudder needed to keep you lined up on take off. After that it becomes a very small consideration including an aborted landing.

In short, I think the "torque fanatics" need to get a life here.

Mav

[ispar]

AFAIK, and please tell me (nicely) if I'm wrong, torque is the effect caused by Newton's Third Law of Motion, i.e., for every action there is an equal and opposite reaction. Torque is the airframe trying to spin in the opposite direction of the propellor. The effect caused by displaced air is, I think, the P-factor/slipstream. P-factor is part of what causes most twin engined planes to have a "critical engine" (the one on the left).
I'm probably at least partly wrong. Let me know. What I'm basically trying to say is that torque isn't a problem until you are in the air. I think.

I'm done talking now   .

[This message has been edited by ispar (edited 12-31-2000).]

[chisel]

I think the word "power" takes into account the propellers pitch.

[Jekyll]

 

Pitch impacts amount of air displaced by the blades and correspondingly the number of RPM's of the engine due to loading the prop beyond the engines ability to produce enough horse power to maintain RPM.

Don't forget that AH models constant speed propellors.  It would seem to my poor dim mind the following:

1.  Constant speed prop = prop is always revolving at same rotational rate.
2.  If prop is in coarse pitch, it is displacing more air than if in fine pitch
3.  If it is displacing more air, then Newton's Third Law suggests that torque effect would be greater for an engine in coarse pitch than in fine pitch.

Too many brandys to think this through any further.  Over to the aerodynamicists  

 

The only time it becomes a "real" factor in flying in the GAME is if you are not using auto take off.

Hell, does ANYONE really use EZ Takeoff other than in the TA?

[This message has been edited by Jekyll (edited 01-01-2001).]

[Pyro]

There were no flight model changes aside from what was written in the readme and that just covered some ordnance details.  My world would sure be nice if I had so much spare time that I could go make all the phantom changes that gets purported by people, but the fact is I can't even get through the list of known problems I need to look at.  



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Doug "Pyro" Balmos
HiTech Creations

[funked]

Jekyll the power of the engine (or any rotating machinery) is proportional to torque times rpm.  Other than a little bit of reduction gear friction, all of the power of the engine is absorbed by torques from forces acting perpendicular to the axis of prop rotation.  So torque is almost precisely proportional to power divided by rpm.

In the example you describe, increasing the pitch at a constant rpm would require a power increase to maintain rpm.  Otherwise the torque times rpm would exceed engine power and rpm would have to decrease.

[This message has been edited by funked (edited 01-01-2001).]

[AKDejaVu]

 

If you think the FM's are fine, try this quick test. Grab an F4U or F6F on a carrier. Turn EZTrim off and then adjust rudder trim so that it is exactly centred and in line with aileron trim. Start engine, hit full throttle and WEP and do not touch your rudders or ailerons.

If you think the fm is dummed down based on this.. try the exact same thing from a land base.

Its not the FM being dummed down.. its a bug.

AKDejaVu

[AKDejaVu]

Actually.. don't even know that its a bug... that's just an assumption.

Hard to tell how sudden the torque effect happens (how many feet).  I do know the F6F was farther left that the F4u.. though both actually were left of center.  The F6F actually dropped on gear off the edge prior to clearing the front of the carrier.  The Hurricane 2 dropped that gear about 10 feet sooner.

Don't really know how a 25 mph headwind would affect this... so I'm just guessing that something is wrong on the CV Deck.

AKDejaVu

[Maverick]

 

Originally posted by Jekyll:
 Hell, does ANYONE really use EZ Takeoff other than in the TA?

[This message has been edited by Jekyll (edited 01-01-2001).]

Jekyll,

Usage of constant speed prop is not how you imagined it.

You set the desired RPM of the prop / engine by using the propeller control. Once the RPM is set the prop will maintain that rpm as you manipulate the throttle. More power to the prop means the prop will coarsen the pitch to maintain the preset RPM. If you lower power (throttle) the prop will fine pitch to it's built in limit at which point the rpms will drop as the engine is not putting out enough horses to maintain the RPMs. If you coarsen the pitch sufficiently the engine will bog down and lose RPM's. In my Comanche it is possible to coarsen the pitch enough in the preflight checks to kill the engine.

Prop control is maintained in two ways. Either by an electric hub or a hydraulic hub. The electric was an early version and was extensively used in WW2 bombers. That is the prop that could "run away" (go to ultra fine pitch) and destroy the engine if it couldn't be shut down fast enough. It also required the plane have a functioning generator to maintain enough electrical power to operate the prop.  The battery will not hold for very long.

The hydraulic hub uses engine oil under pressure through the crankshaft or a separate line that maintains pitch by using the set pressure from the oil. A valve either opens or restricts oil flow / pressure to change blade angle. When the engine stops, the blades revert to the setting intended by design and the restraining springs in the hub. In small single airplanes it is usually fine pitch. In a multi engine plane it may feather to reduce the drag in case of an inflight engine failure.

Power is a function of the engine and how much throttle you are using. The constant speed prop regulates the RPMs as opposed to a fixed prop plane where the only control you have is the throttle.

If you change the pitch only, the engine RPMs will fluctuate unless the throttle is moved in a coordinated manner with the prop pitch control. This is because the load on the engine changes with the pitch.

Constant speed props mean you can fine tune the performance of your plane to best use the horsepower from the engine and get best efficiency from the plane. You can have a "climb prop" when climbing and a "cruise prop" when cruising which is not possible in a fixed prop plane.

Finally in answer to your last question, yes I use easy take off in MA. I see no reason not to at this time. If I need to abandon the runway on takeoff all I have to do is move my stick. I do try to avoid capped fields and the attendant vulchers however.

I hope this helps you to understand that the constant speed prop is not effective in controlling or manipulating torque.

Mav

[Sunchaser]

WOW Pyro, am I glad to hear that, appearantly my skills majically matured between the releases.

It got easier for me to takeoff in a Corsair from 1 day to the next.

I am not trying to be a smartass....much.... but that is a fact.

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When did they put this thing in here and WTF is it for?

[Pyro]

Sunchaser, you can reinstall 1.04 into a different directory and see if there is a difference taking off from a normal field.  Taking off from a carrier would be different because you have a good amount of airspeed before you even start to move.  

There can easily be something off in what everyone refers to as "torque".  But true torque is actually the easiest thing in this to calculate within reason.  The hardest thing about this is trying to figure out what effect a revolving mass of airflow from the propwash has on the plane.  What a lot of people don't realize is that you're dealing with multiple factors from both sides.  How many people realize that the corkscrewing propwash decreases the effective angle of attack on a portion of one wing while increasing it on the other?  And that this is effect is counteractive to torque?  How many people realize that the tailplane usually has a built in incendence angle?

There's also a lot of misunderstanding about what true torque is and what it does and how it applies to constant speed aircraft engines.  Take a hand-held grinder and fire it up.  You can feel the torque pull as it comes up to speed.  Once it's up to speed though, the torque is not something you have to fight.  You can see the same thing with your car.  Rev it in neutral and watch one side sink as it speeds up but once you get hold the rpm, it settles.

But that's kind of an aside, what most people want to think of as torque is really slipstream effect.  It would be easier to exaggerate an effect that people expect to be of a certain magnitude, but we really are trying to calculate it accurately.



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Doug "Pyro" Balmos
HiTech Creations

[wells]

 

How many people
                realize that the corkscrewing propwash decreases the effective angle
                of attack on a portion of one wing while increasing it on the other?
                And that this is effect is counteractive to torque?

This is only true if the angle of attack (plus induced angle from slipstream) doesn't exceed that of the stall.  What happens when you're flying slow and the wings are already at high angle of attack?  The angle increases on the left wing, decreases on the right wing, what happens?  It's not counteractive to torque in that case!

[niklas]

I read a story from an german aviation author, i think his name was Baumann. He flew the FW190 in the war.

He wrote about a common accident during their training on the FW190.

Earlier they were trained on a Arado aircraft with about 4-500HP. When they came into a critical situation (during landing approch, slow flight) they got used to push the throttle full forward. No Problem with 500HP.

The next aircraft what they did fly was already the FW190. 1300HP more power. When someone wasnīt careful, he reacted in the same situation in the same way, like in the Arado and pushed the throttle quickly forward.
This let the Fw190 immediatly roll on itīs head, and they crashed. He wrote that he saw many dying this way.

This is of course no "steady state". I think it has something to do with the change of the RPM. How fast can a constant-speed-mechanism adjust the RPM? In AH itīs always constant, no matter how fast you change your power setting. I remember the mechanism of the P40 from zenoswarbirdsvideos, it worked pretty slow. That would mean if you open your throttle very fast you can reach 4000,5000 RPM for a short time right?

niklas