Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: Straiga on December 07, 2004, 05:08:11 AM
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Im not understanding the trim in AHII.
Here I take a plane up and trim it at a set power setting for a given altitude, trim the ball center, trim aileron (I still dont Know WHY), and trim elevator. Then do some turns and bring the airplane back to the same airspeed and altitude, then plane should be trimmed but its not, I still have to trim the plane. The plane should already be trimmed, for the airspeed and altitude.
The plane should show some right rudder trim and some nose down trim, and nuetral aileron trim, for a single engine airplane in straight and level unaccelerated flight. But all the trims are centered, except the airleron trim, it shows right airleron, I guess this is for Torque (wrong). This I dont understand. If you think you trim in aileron because of torque this is wrong, you use rudder to counter torque.
So show me some written documents that prove me wrong about the torque. You guys know I have P-51 time and you dont counter torque with aileron. And please dont show me a picture of a helicopter again theres a big difference when you have a 80 ft. rotor span compared to a 11 ft prop disks, when talking about torque. You ought to know the diference between the way a helicopters flys compared to an airplane. Its like day and night, if you think its the same, start reading some more.
I have a lot of airplane sims, and why is this the only sim that uses aileron trim the way it does. When you trim the ailerons in a real airplane its because of a possible fuel embalance, or have a bomb still hanging on one side, or trim because in a multi-engine airplane you lost one engine. Trim the dead engine into the good one about five degrees up.
With the autopilot set for best climb, the elavator trim, it shows full up. Theres no trim left. In a real plane, you trim for a climb and theres a lot of trim wheel left. You should also see right rudder being used, with nuetral aileron. This I dont understand.
When my dad and brother were flying AHII over Thanksgiving, they couldnt stop laughing and picking the sim apart, because they never had to trim so much in there life, just to keep the plane flying true. Although they were impressed with the planes skins and terrain.
My dad said if a fighter pilot had to trim so much as in AHII, he would not have time to line up someone to shoot at. Trimming an airplane in 3D and having to use throttle, stick and rudder constantly in combat good luck. Its to busy, just point the plane and shoot.
He said trim for cruise and use the stick and rudder pedals, and some elavator trim if needed and leave the airlerons in nuetral trim. Thats all you need to do.
My dads A retired General USAF
36 mission in Korea (P-51, F-86)
112 missions over N. Vietnam (F-105, F-111)
Later Straiga
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Hi,
Torque is not modeled in AH. The trim is not 'completely realistic'. The trim used is an abstraction of what is really used in an aircraft.
Trim modeling *is* incorporated, however. That added level of detail is a further step towards realism. But, it is not perfect. Lepturns web site (in the AH links) has a useful discussion on trim used in AH.
Combat trim allows pilots to fly around without constantly 'fiddling' with the trim. Manual trim is useful in the flight envelope edge when flying certain planes and landing. The AH flight models are not perfect, but they are the best I have found. If you know of any better, myself and many others would be interested (including HiTech I bet).
I recommend similar posts be placed in the 'Help and Training' forum. Also, you would be wise to spend some time in the training arena. Posting here just sounds like a rant... which I don't believe was your intention.
Have fun,
Malta
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No it was not my intention to rant, but I have no prob with flying in AHII. But its just a major hassle to constantly trim, trim, trim, trim.
Just put the ailerons to nuetral and lets just trim elavator and use the rudder with a little trim. This would be closer to the real thing.
Straiga
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Torque Is completely modeled in AH.
As far as how trim is modled it is very representative of triming an aircraft. We have some trims that the real counter part didn't have, but in the real counter parts you had to maintain stick input to typicly fly level.
As far as Straiga's question, depends if you had combat trim on or off.
HiTech
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Combat trim off
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And ah trimm changes the amount of elevator authority you have.
Trimming aircraft for lvl flight at 400mph and pulling full up yields less g turn than trimming nose up and pulling up.
Is that authentic?
That also gives a great disadvantage flying in combat trim than in manual trim.
ciao schutt
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Yes it is authentic schutt. At fast speeds you can not pull hard enough on the stick to reach it's full defelection. Adjusting trim moves the zero for point of the stick. And you get the same amount of stick force from the zero point, hence you call pull more g's.
At slower speeds adjust trim does not effect turn performance at all. Because no matter where the trim is set, you can pull the stick to the stops.
HiTech
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What I meant to say was that In AH, low speed torque induced flight characteristics can not be found as described in articles such as:
http://home.att.net/~ww2aviation/Bentwings.html (http://home.att.net/~ww2aviation/Bentwings.html)
I have not seen the 'ensign eliminator' effect in any of the F4U's. Not having the tail wheel locked on landing can cause a crash, but that is not what I consider a flight characteristic. Fwiw, I don't remember ever seeing low speed torque effects modeled in any flight sim.
Regards,
Malta
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Its nice to be able to trim the plane in all axises.
But the point I trying to make is that trimming the aileron as much as we have to do, it is not nessasary. WWII and todays airplanes set the aileron trim to nuetral and leave it alone, now is this hard to understand.
In 30 years of flying I may have only trimmed a hand full of airplanes with the aileron trim. Once was a DC-10 because it had a very bad bios in that the way it flew.
The big war birds use a lot of right rudder trim and even more rudder on takeoff while the aileron trim is set to nuetral. Hmm. It make you wonder doesnt it.
When you trim an airplane say for cruise speed and at a set altitude you should be able to do loops, turns, climbs and desents then put the plane back at that altitude and speed and it should be trimmed already. Do you see my point.
Straiga
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Originally posted by Straiga
The big war birds use a lot of right rudder trim and even more rudder on takeoff while the aileron trim is set to nuetral. Hmm. It make you wonder doesnt it.
That depends upon the airplane and the circumstances.
For example: For takeoff, all tabs are set at neutral for the P-40. Not so for the F4U-4
According to one F4U-4 pilot:
" I checked various settings. Full flaps. Cowl flaps open. Hook up. Trim 6 degrees nose right, 1 degree nose up, 6 degrees right wing down. Tailwheel locked. Cockpit canopy open and locked. Shoulder straps and seat belt tight. Prop control full forward for maximum revolutions per minute (rpm). Mixture auto rich. Supercharger neutral. Wings locked. Controls move freely."
This is just one example and it applies to carrier deck runs, but it seems to establish that there are no absolutes.
My regards,
Widewing
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I dont buy it.
US NAVY
Flight opperations manual
F-4U-5/ F-4u-5N/F-4U-5NL/F4U-5Px
Emergencey Takeoff
A. Shoulder harness and safty belts secure and locked
B. Canopy open
C.Tail wheel lock
D. Fuel selector ON
E. Fuel transfer switch ON
F. Aux (Boost) fuel pump switch HIGH check fuel pressure
G. Rudder tab 6 degrees NOSE RIGHT
H. Elevator tab 1 degree nose up
I. Aileron tab Nuetral
Same for carrier takeoffs (catapult or non catapult Takeoffs)
Full flaps required
2-50 Tabs settings
The rudder force required maintain a straight run will be high unless the rudder tab has been set to at approximately 6 degrees nose right prior to takeoff run. (nothing said about ailerons or aileron trim)
1-7 Tabs
The tabs on the control surface consist of the balance tabs on each airleron. A trim tab on the left aileron, and combonation spring and trim tabs on the rudder and elevators.
The airleron balance tabs are deflected automatically in a direction opposite to that of the ailerons when the ailerons are deflected. This reduces the stick force to opperate the ailerons. Same as in previous F-4U models.
P-51D Mustang
Takeoff
Rudder 61/2 degrees nose right
Elevator 2 degrees nose down
Aileron nuetral
B-17G
Takeoff
Rudder 5 1/2 dgrees nose right
Elevator 2 degrees nose up
Airleron Nuetral
Straiga
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Originally posted by Straiga
I dont buy it.
US NAVY
Flight opperations manual
F-4U-5/ F-4u-5N/F-4U-5NL/F4U-5Px
I don't know if it's important but Widewing wrote about the F4U-4 not the F4U-5
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The F-4U-4 and F-4U-5 have the same airframe but the 5 has a bigger engine. If you dont need airleron trim in the 5 you dont need it in the 4. LOL
Trim: P-51D same as P-51C, F-14A same as F-14D, P-38L same as P-38J. DC-10-10 same as DC-10-30 LOL
B-24D
Takeoff
Elevators 1 degree nose up
Rudder 2- 2 1/2 nose right
Aileron nuetral
Straiga
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no need to be ironic , I was just makiing a point.
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So my point is if you dont need aileron trim on takeoff which is the highest torque producing range and at the point for the most amount of rudder application is needed to counter torque, you dont need aileron trim in the air, it should be nuetral.
King Air E90, B200, B300, B350
Takeoff
Elevator trim 2 up
Rudder trim nuetral
Aileron trim nuetral
At cruise
Elevator trim 5 down
Rudder trim 2 nose right
Airleron trim nuetral
Straiga
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I don't think so, if the designer of a plane spend time and money designing a aileron trim it's certainly because it has a purpose.
I don't know IRL but in AH when diving the 190 show a tendancy to roll and ailreon trim is very usefull to counter act this roll.
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Stop the roll with rudder. So why does it roll to begin with. I dont think its modeled right.
Airleron trim is useful for fuel embalance, one bombing hanging on the plane, good for multi-engines with an engine out. Alot of WWII planes did not have certain trims at all.
Straiga
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All planes are different. You should check out what the Combat Trim is doing in all the different planes in varying situations.
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Iam sorry I dont fly combat trim on, so I dont know.
Straffo one prob you might have is you dont know IRL. I know different airplanes fly differently. But I also know, that a plane that has to fly with aileron trim to keep it flying true, wings level creates a lot of drag on the airframe.
So here we have a plane in straight and level flight with right aileron trim induced to counter torque, which makes the plane yaw to the left because of the aileron deflection.
Now understand the right aileron is deflected up, which decreases lift on that wing which inturns increases in airspeed, because a decrease in lift, is a decrease in drag. So the wing moves forward, and pushing the nose to the left. The left airleron is deflected down which increases the lift on that wing, a increase in lift is also a increase in drag, which also decreases airspeed, so the wing moves rearward, which also moves the nose to the left.
So now the planes yaws to the left, just because of aileron deflection. Now to counter the yaw you need to use right rudder to center the ball.
Now in real life, aircraft maufactures try to design airplane to fly with little trim as nessasary which decrease drag because of induced drag from the flight controls. The less trim needed is good for a more efficeint airframe. Plus at cruise airspeeds and unaccelerated flight the airframe is rigged to fly as straight as possable with out trim, it still might need some rudder trim and elevator trim for a given pitch or airspeed. The airframe should counter the torque as much as possible which is at it lowest point in straight and level unaccelerated flight.
Wouldnt it be more efficeint to have the ailerons nuetral and to counter torque with rudder alone, if torque was increased or decreased. What I described above is ailerons deflected and more rudder then nessasary being used to counter the ailerons and the torque. Think about that, the planes yawing to the left because of the aileron thats countering the torque and now you have to add more rudder then nessasary to counter the torque and the aileron deflection together, just to have directional stability. Look at all the induced drag. Why not just use rudder alone.
Just a reminder torque is at its greatest on takeoff and at anykind of power increase to a varying degree. In straight and level flight unaccelerated, torque is at its lowest point. The airframe is designed to fly true, at the airplanes best cruise airspeed with little trim.
I have read that ME-109 pilots had no rudder trim tabs at all in some models, so how tired do you think his right foot gets, but theres no mention of aileron deflection to counter torque to keep directional stability. I guess these guys turn more to left and desended then climbing right turns, I guess because of there dead right feet.
Straiga
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Here is a relevant article I looked up on the F4U flight characteristics detailed by a former pilot.
http://www.museumofflight.org/news/newsletter/Aloft_MayJun04_p09.pdf
Torque roll causes a plane to roll in the direction of the engine rotation. For single engine aircraft, such as the F4U, that is along the longitudinal axis. Ailerons on the wings counteract that motion by creating aerodynamic forces to cancel the torque forces. Yaw is created because of the aileron positions, as described above.
Torque roll will cause a plane to bank without aileron input and more rudder would be needed to get the plane to 'crab' through the air and maintain a straight course. That would cause more drag than applying ailerons to cancel the roll with rudder to correct for the yaw offset.
I will offer a suggestion. Adjust the dead zone on your stick. Adjustments are available in AH and under the games controllers section. All controllers drift slightly and the 'dead zone' adjustment is to compensate for the drift.
The 'problems' you are seeing in AH are most likely due to your setup. High end controllers, such at Thrustmaster, CH Products, etc. offer alternate ways to trim out your controller. After all, that is what you are doing. The only piece of hardware available to adjust is your controller. The plane is virtual.
Regards,
Malta
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Straiga from an complete unscientific view (and backed only with my intuition :)) wouldn't it be more efficient to counter roll with aileron trim than rudder ?
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Wouldnt it be more efficeint to have the ailerons nuetral and to counter torque with rudder alone, if torque was increased or decreased. What I described above is ailerons deflected and more rudder then nessasary being used to counter the ailerons and the torque. Think about that, the planes yawing to the left because of the aileron thats countering the torque and now you have to add more rudder then nessasary to counter the torque and the aileron deflection together, just to have directional stability. Look at all the induced drag. Why not just use rudder alone.
Whether it's rudder trim or aileron trim, using trim creates drag.
Torque creates a rolling effect that would be counteracted with aileron, and aileron trim if it were available.
P-factor and slipstream effects would normally be corrected with rudder.
Rudder can be used on some aircraft to correct for rolling moments, but this is dependent on the aircrafts stability about the longitudnal axis and if this means yawing the aircraft to counteract roll it can be far less efficient than correcting with aileron (the slip skid indicator can give you an idea of whether or not rudder is efficient.)
Ideally an aircraft will be rigged so as to need only minimal amounts of trim; but only in one phase of flight (usually at normal cruise speed) and obviously an aircraft can only be perfectly rigged at one pressure altitude, airspeed, weight configuration; so trim is a neccessary evil.
I don't agree with your evaluation of AH trim. Compared to any other PC based flight sim I've used (and the list is extensive) my opinion is the AH flight model, overall, is the best I seen in any flight sim; especially when compared in the slow flight and stall regimes.
I would suggest that the trim position indicators actual position be ignored and the aircraft trimmed so it flies straight with minimal control input.
I don't use combat trim. I usually autotrim most aircraft on speed = 220 before entering into combat. I rarely ever need to touch the trim again after that unless I'm going on an extended climb or level cruise (and either case usually only requries elevator trim, or minor aileron trim if the speed has changed dramaticaly.)
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The later models 0f the F4U had the engine mounted nose down and to the right which is offset from the logitudenal axis (the crank shaft is not inline with the longitudinal axis), this is why aileron and aileron trim is not needed for takeoff. This was another way to rigg the airframe to counter torque. There is a lot of airframes designed this way.
Yes Torque is a rolling motion counter clock wise to the prop rotation, not in the same rotation of the prop [stantond]. But how do you counter torque on the ground (were torque is high), when at a zero airspeed there is no airflow across the airlerons(w/rudder). Airlerons become effective, only when enough airflow moves across the wing, this happens at about 45 -50 MPH, so until this happens how do you counter torque on the ground (w/ Rudder) and also an even application of power.
Also you can not roll an airplane over on the ground. You can only ground loop it. You will compress the left landing gear strut which creats friction on the tire and pulls the airplane to the left and ground looping it, with to much torque.
Using rudder alone to counter torque is not crabbing its called directional control. Rudder can be used to roll an airplane very well with out aileron. It can also be used to counter torque roll well.
Do I understand, would you guys only use aileron only to counter torque?
Then how can you hold a heading?
How do you counter yaw due to aileron deflection?
I have taken a P-51D and set the trim for takeoff based of the POH (pilots opperating hand book), which is
Aileron trim Nuetral
Rudder Trim 6 degrees right
Elevator trim 2 degrees up
Then I go fly.
In AH the trim setting should reflect this but look at it on autotakeoff, its not even close. The trim shows elevator nuetral (no torque countering at all) Airleron trim, it should be nuetral but its trying to counter torque (so it shows to the right), but how can this be if theres no airflow across the ailerons to be effective to counter torque. Elevator trim goes full up when trimmed for autoclimb for Vy.
In a real P-51D if you trim for Vy you would still have 7 trim wheel revolutions nose up left, but not full up like in AH. The real P-51 Vy, its only about 1 degree up trim. The Vy on my dads P-51 dosent match Vy in the book. Its gross weight is less than that of a factory P-51, so it has a better Vy.
I wish you guys could fly the real P-51D, I have, and my experiences flying it is what im telling you about. Yes torque is a rolling moment, and when your in cruise and adding power, and increasing torque, believe me it can be countered by rudder only.
This is what the trim is set at for a real P-51D at cruise
Rudder 3 1/2 right
Elevator 4 down
Aileron nuetral
Look what AH shows. This is what I dont understand. If this is supposed to be a real accurate sim about WWII fighters than explain something like this. I cant get any body who can explain this. The turn cordinator and ball with the trim tabs should show accurately what the plane is doing in flight. Shouldnt it?
After I trim the P-51 for cruise, now I can go dog fighting and use rudder pedals, some elevator trim and just move the stick were I want to go.
Straiga
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The later models 0f the F4U had the engine mounted nose down and to the right which is offset from the logitudenal axis (the crank shaft is not inline with the longitudinal axis), this is why aileron and aileron trim is not needed for takeoff. This was another way to rigg the airframe to counter torque. There is a lot of airframes designed this way.
I don't know for sure, but I thought the down and right canting of engines in their mounts was to off set to combined left turning forces of torque, p-factor, slipstream, and the canting is set to balance the forces at cruise airspeeds.
Yes Torque is a rolling motion counter clock wise to the prop rotation, not in the same rotation of the prop [stantond]. But how do you counter torque on the ground (were torque is high), when at a zero airspeed there is no airflow across the airlerons(w/rudder). Airlerons become effective, only when enough airflow moves across the wing, this happens at about 45 -50 MPH, so until this happens how do you counter torque on the ground (w/ Rudder) and also an even application of power.
Also you can not roll an airplane over on the ground. You can only ground loop it. You will compress the left landing gear strut which creats friction on the tire and pulls the airplane to the left and ground looping it, with to much torque.
Agreed, you counter left turning forces on the ground with rudder. The propeller slipstream over the rudder is your only method of controlling direction at the start of the takeoff roll.' With the wheels planted firmly on the ground the aircraft isn't prone to roll. (Although I know I read somewhere in some very high power aircraft, such as the P-51, a sudden application of full power could produce enough torque to flip you over when the aircraft is sitting on the ground.) Proper use of controls in taildragger aircraft do have you use aileron deflection as well as rudder to counter crosswinds (something we don't have to deal with in AH.)
Using rudder alone to counter torque is not crabbing its called directional control.
On the ground this is true
Rudder can be used to roll an airplane very well with out aileron. It can also be used to counter torque roll well.
Depends on the aircraft. Rudder can be used to roll most aircraft and is the recommended method at certain times (while recovering from a stall for instance) but in most aircraft I've flown (and I have never flown a WWII fighter) rudder is not an efficient way to roll into or out of a turn. However, some of the older aircraft I have flown do like you to lead the turn with rudder and use only enough aileron to keep the turn coordinated (as compared to most modern GA aircraft which like you to turn using aileron and keep it coordinated with rudder.)
Do I understand, would you guys only use aileron only to counter torque?
Then how can you hold a heading?
How do you counter yaw due to aileron deflection?
In the air its all a matter of aileron and rudder coordination. If something is out of trim and is causing the aircraft to roll, correct with aileron and/or aileron trim. If it's necessary to use rudder or rudder trim as well to keep everything coordinated adjust that as well. Likewise if something is out of trim and the aircraft is yawing, correct with rudder and/or rudder trim, and again, it might be neccessary to also adjust aileron trim.
I've heard some people talk "aileron does this and rudder does that" and the truth is that each control has a unique function, but nothing is ever cut and dry where you can change one and not have to change the other, however minutely.
On the ground, use rudder to track straight during takeoff and after landing. In the air, use both all the time to keep the plane flying coordinated.
I have taken a P-51D and set the trim for takeoff based of the POH (pilots opperating hand book), which is
Aileron trim Nuetral
Rudder Trim 6 degrees right
Elevator trim 2 degrees up
Then I go fly.
In AH the trim setting should reflect this but look at it on autotakeoff, its not even close. The trim shows elevator nuetral (no torque countering at all) Airleron trim, it should be nuetral but its trying to counter torque (so it shows to the right), but how can this be if theres no airflow across the ailerons to be effective to counter torque. Elevator trim goes full up when trimmed for autoclimb for Vy.
In a real P-51D if you trim for Vy you would still have 7 trim wheel revolutions nose up left, but not full up like in AH. The real P-51 Vy, its only about 1 degree up trim. The Vy on my dads P-51 dosent match Vy in the book. Its gross weight is less than that of a factory P-51, so it has a better Vy.
I wish you guys could fly the real P-51D, I have, and my experiences flying it is what im telling you about. Yes torque is a rolling moment, and when your in cruise and adding power, and increasing torque, believe me it can be countered by rudder only.
I wish I could fly a real p-51 too! Do you have access to one? Are you offering? :)
This is what the trim is set at for a real P-51D at cruise
Rudder 3 1/2 right
Elevator 4 down
Aileron nuetral
Look what AH shows. This is what I dont understand. If this is supposed to be a real accurate sim about WWII fighters than explain something like this. I cant get any body who can explain this. The turn cordinator and ball with the trim tabs should show accurately what the plane is doing in flight. Shouldnt it?
After I trim the P-51 for cruise, now I can go dog fighting and use rudder pedals, some elevator trim and just move the stick were I want to go.
Straiga
As I said earlier, I'd ignore what the trim indicator settings look like, and make whatever adjustments need to be made to make the aircraft fly right (both in AH and in real life)
AH isn't a perfect P-51 simulator (or simulator of any particular aircraft.) I think you are expecting too much of it.
IMHO, Hitech and company have done a great job with the flight model as a whole. I think they've also done a great job with relative aircraft performance. Then they took these simulated aircraft and put them together in a way that allows huge numbers of people to get together and kill each other in them on a fairly level playing field despite the vast differences in internet connection types and PC performance.
I guess what I'm saying Straiga is that while I see your point about the AH P-51 not operating exactly as the real P-51 POH says it should, over all though it still performs like a P-51 (or that I'd imagine it does.) There is a place in Florida that will let you fly a P-51, but it is thousands of $$$ for a 1 hour flight. Too rich for my blood. I asked them what you can do while flying it. The responce was "anything you like." I guess its a tough aircraft to break.
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I just trying to find answers about my questions this was said to be avery accurate flight sim. They spend more time a guess on the roll rates and other things, but showing what the trim does in the airplanes I guess it wasnt aprority.
Yes my dad owns a P-51D and I have about 560 in it. It takes about $3400 an hour to fly w/ fuel, maintainance, insurance.
Straiga
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Straiga I noticed something while taking off in a 109. I was watching the control surfaces and combat trim movements.
They did not correspond to what was actually happening. CT showed almost full right aileron deflection but the ailerons showed little movement.
What was interesting about this was the rudder movement, I looked out back and the rudder was almost fully deflected as was expected to counter torque as speed built up CT showed rudder neutral or almost neutral.
Try it out with the P51 maybe you'll get similar results. In other words as muerto hinted at (if I read correctly). The trim position may not be showing what's actually happening.
I don't agree with your evaluation of AH trim. Compared to any other PC based flight sim I've used (and the list is extensive) my opinion is the AH flight model, overall, is the best I seen in any flight sim; especially when compared in the slow flight and stall regimes.
I would suggest that the trim position indicators actual position be ignored and the aircraft trimmed so it flies straight with minimal control input.
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Thanks Kaz
Thought it was just me.
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Stragia,
I never meant to imply you were wrong (although only using rudder to counter cruise torque I still don't understand). AH has a flight model where trim is incorporated. It is not perfect.
Picking on the flight model will not make it better. Providing information from the pilot’s flight handbook for the P51 may be useful in making an argument for a change. Also, and I mean this sincerely Straiga, have you ever considered taking a creative writing course?
One thing I have found for all Military Generals, such as your dad, they can communicate very effectively! Your writing skills could be better. I know mine can improve and I am working on that.
It would be nice to see the AH flight model become even more realistic. However, I have neither the time nor energy to pursue that goal. Seeing torque roll would be really cool, but it's an isolated aerobatic maneuver that I can live without.
The trim indicators can have a visual effect on the control surfaces. One of the ways to get a damaged plane back to base is to use full trim to compensate for a loss of aileron and wing surface. You can look out the window and see the (remaining) elevator physically deflected under those conditions due to trim.
Having aircraft flight manual information and comparing it to what is seen in AH could make for a compelling argument. Conveying the information may be the most challenging part of that goal. Fwiw, I am pretty sure the F4U ‘torque’ rotation is backwards in AH. However, since torque is not modeled to affect the roll rate or vertical stabilizer offset for normal cruise, rotational direction is not important.
I would be happy to see the trim system revised, but like torque direction, its imperfections do not significantly affect the flight model. That is not to say it is not important when flying a real plane. The AH flight model is not perfect, but as I have said many times before, it’s the best I have found.
Regards,
Malta
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Stantond: Torque is completely modeled and is not backwards on the f4.
HiTech
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HiTech, do you have a list of the V speeds used for the AH aircraft that you could publish? It would be nice to know Vy for all AH aircraft.
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Originally posted by hitech
Stantond: Torque is completely modeled and is not backwards on the f4.
HiTech
"At this slow speed, just a few knots above stalling, it took a lot of right rudder, even though in a left turn. And you didn't dare add power quickly since the powerful engine turning that large prop could make the aircraft roll uncontrollably to the left-the dreaded "torque roll." [ Fred Blechman on F4U-4]
http://home.att.net/~ww2aviation/Bentwings.html
"The aircraft stalls like a Piper Cub. Though a wing tends to drop, there isn't the slightest mean streak in it unless you cob the power, which produces a very violent torque roll" [ Jeff Ethell on Spitfire]
http://www.supermarine-spitfire.co.uk/flying.html
"I remember telling everyone I ever checked out in the Mustang to take it up high, lower the gear and flaps, then back it off to about 15 inches with the prop up to 3 grand... slow it down easy to about 130 mph... then SLAM in 61 inches fast. The resulting torque roll might have helped save a few lives on full power go-arounds" [Dudley Henriques on P-51]
http://www.warbirdalley.com/p51pr.htm
Can you really say torque in AH feels like in these quotes ?
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The auto speed is set to Vy at sea level on all aircraft.
HiTech
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I think I am confused. Is there a setting for enabling torque that I do not have turned on?
I can consistently take off in a F4U-1 using this step by step process with no rudder or aileron inputs:
1. 25-75% fuel, clean, engine at idle.
2. elevator trim centered, rudder trim centered, aileron trim centered.
3. 2 notches flaps.
3. hold stick back 1/2 way to engage tail wheel lock.
4. 100% throttle & wep as quick as controls will allow.
5. Roll down runway (note that plane does veer slightly to left).
6. Airborne as soon as 100 mph speed is attained while still on runway.
There just doesn't seem to be much torque I am seeing here (if torque is what I am seeing). The P51 can be flow from takeoff using the exact same process but has slightly more of a veer to the left effect which has to be countered with a couple of right brake taps (but no rudder or aileron) to stay on the runway.
Once airborne, the P51 tends to roll to the left. The F4u seems neutral, sometimes wanting to roll left, sometimes right. The F4U direction of roll to the right (that I though might be due to torque) was after setting trim to level flight then going to manual trim.
Am I alone on this?
Regards,
Malta
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Am I alone on this?
That certainly is not my experience. Any aircraft I fly needs constant rudder input to track during takeoff. Some aircraft, a heavily loaded P-47 for instance, can be a real b***h to control during takeoff.
Do you have auto-takeoff switched on?
Is there still and easy flight mode in AH?
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Wait one moment please
Before everyone continues to go around in circles again and again about trim, does no one realise:
The computer joystick in AH is not modeled the same as a real life aircraft stick. Therefore trim does not work the same as a real aircraft
What?
1. In Aces High, trim changes the center position of the stick
ie...... if I am fast at 320 MPH I set trim to level flight.....my stick is sitting in the neutral center position.
........ if I am flying 100 MPH slow, I put full up trim, I can now again fly level with the stick in the neutral center position.
2. In Real Life, my trim never changes my stick position. It only changes the Weight of the stick that my arms have to hold.
ie........ If I am fast, I set a small angle of attack, my arms hold that AOA for the speed. If I dial in some trip. IT DOES NOT CHANGE THE STICK POSITION. It just moves a tap on the elevator that takes the LOAD off my arms.
....... If I am real slow doing 70 MPH, I have a LOT of AOA, my stick is WAY back, nearly at max angle of attack (nealy stalled). If I give full up trim, my stick position STILL WILL NOT CHANGE. Only the effort needed to hold that Angle of Attack.
One more example to clarify.
Climbing in AH. Point nose up. Add up trim, until you return your stick to center. Let go of stick..... drink beer. Grab joystick again.
Climbing on real life. Point nose up. Stick comes back until you reach the right angle. Let go of stick....drink water.....plane nose drops... oops. Point nose up. Stick comes back until you reach right angle. Dial in up trim until no weight felt on stick. Let go of stick . Drink water. STICK STILL IS IN A UP ELEVATOR POSITION. Grab stick again.
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In summary:
- Aces high does not model control stick/trim inputs like real life.
- In real life, trim does not change your stick position. It changes the weight that you are holding for a given speed/AoA
- In Aces high, trim CHANGES your stick position to let you return your joystick to center.
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P.S. I have fire-proof undies. Flame away. :D
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Umm Brendo sorry to say but maybe the airframe you fly doesn't move the stick but that doesn't mean it doesn't on others. The F-15s stick and rudders will move when trim is applied. It's how the system is designed as to whether or not you will have corresponding movements when trimming. Your little "reality check" isn't 100% correct.
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Yeah I know that Cobra..... im talking 'old school' stuff here.
Do you remember the movie 'The final countdown' from the '80s? :lol
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brendo: In real aircraft that are normaly trimed , i.e. tab on control surface, changing trim position will always move the stick. Typicly you will percive this as just removing force, but think what would happen if you let go of that force with out triming, obviously the stick would move. Move the trim to remove the force, then let go, the stick dosn't move. Hence the trim has realy moved the stick center.
Your are correct AH dosn't move the stick center because it is just not posible with a spring return to center joy stick.
HiTech
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Brendo,
I agree with your statements about trim. My last post was about the effect of torque, not about trim. Apparently, either no one reads my posts (which is probably true) or I cannot effectively communicate what I am trying to say. I expect the latter may be true as well.
To rephrase my previous post, if the tail wheel is locked, torque effects (which I keep hearing from HiTech are modeled fully) do not show up. A step by step process was written down in my previous post so anyone who wanted to repeat what I have noticed could. The takeoff process involves using manual trim with all the trim settings centered. No rudder or aileron inputs are needed, which should be, to counter torque on takeoff.
Apparently, the torque effects only appear when in combat trim during takeoff. Is that because the tail wheel is not locked? That's what it looks like to me.
I must confess, I am not certain what Stragia (who started this thread) was talking about. I think he noticed differences between the trim settings in AH and a R/L P51. I am not going to try and speak for him.
My confusion comes from not being able to see torque which is supposed to be modeled. Do I not have the torque enabled setting toggled? I did not know there was one, but if there is, how do you enable it?
Can someone explain why no torque appears when the trim is set so the tailwheel can be locked on takeoff? Is this a bug?
Regards,
Malta
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Stantond I don't think trim are neutral (at 0) at take off.
I think they are setup for climb out.
HT will confirm or invalidate :)
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stantond: The effects of locking a tail wheel change what you think would happen. Try this pop on runway, throttle low, pull stick back and release to make sure auto take off is off. Now advance throttle with no control input, what happens?
HiTech
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HiTech,
Roger that, I already know what happens... the plane spins in what would be considered a ground loop. My question is, why does that not happen with the tail wheel locked? Is there not enough torque for a ground loop to occur with the tail wheel locked or is something else (like prop wash) causing the ground loop? Locking the tail wheel removes all the ground loop effects regardless of power setting or change in rpm.
That is where I got the notion that torque was not modeled in AH, while primarily flying the F4U. After all, what pilot would try to taxi or take off in a plane without the tail wheel locked? The F4U pilot’s manual tells you that! Once the tail wheel is locked, all ground loop effects are gone!
The torque effects I keep thinking about are due to a change in the engine speed, such as at take off or 'blipping' the throttle. The ground loop effect happens with the engine at a constant speed, which is why I though it might be prop wash, or something else. I believe you when you say torque is modeled. I just don't quite see how it is modeled.
Not to prattle on aimlessly, but I am very impressed by the flight model. Being able to use the F4U pilot’s manual to successfully take off and land the plane is very cool. I have thoroughly enjoyed flying it! Minor discrepancies such as torque and trim positions I have ignored. Even as I write, I do not consider them significant details. I do appreciate the interest you show in the flight models.
Regards,
Malta
Some history about how I got to this point:
Landing with combat trim on makes for quite an adventure with the F4U, usually ending with a busted plane. Using manual elevator trim centered while landing allows locking the tail wheel on touchdown and a normal landing, just as described in the pilot’s manual. Without the tail wheel locked, the F4U (in particular) is pretty much impossible to taxi with. As an aside, I have never used auto take-off.
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stantond: Start from the basics.
The 4 forces generated by the engine are.
1. Torque. a rolling force.
2. Slip stream, produces both roll force oposit torque and yaw force.
3. P Factor produces both pitch and yaw forces.
4. Gyroscopic both pitch and yaw forces.
Torque by itself does not produce a yaw tendency, only a roll, as straiga describs it does produce a secondary yaw force do to increase load on 1 tire but this is very minor force.
The major force involved when starting a take off roll is only slip stream.
P factor and gyro, do not have any effect at the start of a take off roll.
Torque is computed simply
(Current HP) / RPM * 5252
Also torque is produce fairly linar to the throttle setting and is effected very little by the engine speeding up or slowing down.
HiTech
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Originally posted by stantond
Landing with combat trim on makes for quite an adventure with the F4U, usually ending with a busted plane. Using manual elevator trim centered while landing allows locking the tail wheel on touchdown and a normal landing, just as described in the pilot’s manual. Without the tail wheel locked, the F4U (in particular) is pretty much impossible to taxi with. As an aside, I have never used auto take-off.
Malta,
got a spare copy of that F4U manual :-)
for those that use Auto Take Off, as soon as you launch to the runway if you quickly move your stick you will knock off the auto take off feature before it retrims the plane for auto take off........
anyhow, taking off and landing without locking tail wheel is easy once you get the hang of it, low throttle and rudder use ( rudder back and forth ) until speed picks up and raises tail of the deck, then u set to go, when landing do a flare landing at around 100 IAS/TAS and cut throttle to 0 at touch down, then alternate braking C & V keys
don't use CT as you said, and if you try to use the tail wheel lock in game and are to fast on landing you gonna bounce and break up the landing....
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HiTech,
Indulge me for a moment. I will be happy to discuss torque physics and math with you if you want, but a more experimental and everyday experience approach might be clearer. If you have a power drill, such as one made by Black and Decker or Makita at home... or better yet an angle grinder, try this out.
Hold the drill with your hand along the axis where the electric motor turns. For a hand drill, that would be the axis where the chuck rotates. An angle grinder's motor axis would be the cylinder you grip.
Turn them on and off quickly. The effect is very brief because the transient is fast. That rotational movement surge against your hand is dynamic torque. An angle grinder usually has more dynamic torque than a hand drill and you normally have to hold it more firmly. A dremel motor tool also shows dynamic torque.
Mathematically, dynamic torque is defined as:
T=I*a, where T is torque in ft-lb, I is rotational moment of inertia and a is the rotational acceleration.
Not surprisingly this equation has the same form as F=ma (force = mass * acceleration).
So, like pulling g's in a drag racer or when turning an aircraft, dynamic torque is a transient effect. The torque seen and talked about related to horsepower is a transient effect when you are trying to stop or slow down an engines rotation by applying a load. That deceleration in rotation generates torque. The more torque an engine has the faster it can accelerate a rotational load, or convert that rotational torque to changing the rotating speed of a propeller on an aircraft.
My point being, there is a dynamic torque due to an acceleration of inertia just like there is a dynamic force due to acceleration of mass (or pulling g's). That dynamic comes from changing the engine speed. Without a change in engine speed, there is no dynamic torque. That is the torque I am talking about. That is also the torque describing the 'ensign eliminator' effect for the F4U.
Sorry that was not clear earlier. Unfortunately, I do not have numbers for the rotational inertia of a R2800 P&W engine.
Regards,
Malta
p.s. TC, I will email you or contact you through the Damned email list.
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Electric motor are not same torque curve as a gas motor, basicly an electric motor produces more torque when slower then set speed, It is the same as if you were running at full speed then started pushing the drill into somthing, the drill slows slightly,causing less resistance in mag field, more current drawn, hence more torque.
Gas motors torque is releated to throttle input. But the engine torque is what is either accelerating the prop, or generating thrust. Not the other way around. Unlike a electric motor a gas motor will keep accelerating if not underload as long as you keep the throttle in it, and most probably explode.
Gas motors do not have a 100% flat torque curve, but they are relativly flat in the rpm ranges airplane motors use.
HiTech
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2. Slip stream, produces both roll force oposit torque and yaw force.
Slip stream is a left turning force. The prop slip stream hits the vertical stabilizer from the left and pushes the nose to the left. Not in the oposit from torque or yaw. Prop rotation clockwise the resultant torque is oposit (counterclockwise).
4 Turning Forces
Torque- on the ground relates to a left turning force.
Torque-in the air relates to a rolling motion.
P-factor-is only present in a nose up pitch attitude, that changes the angle of attack on the right side prop disk and relates in a yaw to the left in a clockwise rotating prop.
Prop Slipstream- is a left turning force.
Gyroscopic procession-is a left turning force in a tailwheeled airplane, in a tricycle gear airplane it is a right turning force.
This is because when you pitch the nose down the gyro effect is a resultant force which applied 90 degrees later in the prop rotation, relating to a left turning force. The nose gear airplane, when the nose pitches up the resultant force is applied also 90 degrees in the prop rotation which translates into a right turning force.
As for the drill if you pulled the trigger fast the drill will torque dramatically. If you pulled the trigger slowly you will feal little or no torque. So torque is not a constant. Same as in an airplane.
This tread was my attempt to point out that the AH planes show different trim settings in the cockpit from one another.
Also Auto-takeoff should reflect that some right rudder trim is needed, some up elevator trim is needed. Also in auto climb the elevator trim should not be in the full up position, but should reflect about 2 degrees up and have some remaining elevator trim left.
If I tookoff in an airplane and advanced power slowly and use rudder to maintain directional control and elevator this should be all the control input I would need except for crosswind takeoffs. If I abruptly applied power I would need full right rudder and brake, aileron probably full and still end up in a bad ground loop situation.
Straiga
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I'll try and find this site I ran across when AH2 first came out in regards to how a Spitfire handles on take off and what is needed to ensure a safe take off.
IIRC it said that you needed to slowly walk the throttles up, input some right roll and input some right rudder. The right roll was to help counter act the tendency of the left wing to dip due to torque from the motor. The nose would have a tendency to want to come right then back to the left as the power was increased. Obviously to counter this you'd use right rudder.
All this was written by a pilot who owns and flies Spitfires. I thought that the original ground modeling of the Spitfire was correct. Sometime in the beta the ground handling was changed. Reason I thought it was correct is I couldn't take off at all until I found the writeup from this pilot. The second I used what he had said I was off the deck with no issues at all. Then HTC changed something in the next beta that didn't require me to use this anymore.
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Cobra
I cant see using aileron upon the first power application in a Spit or ME-109. When the landing gear is close to the center of gravity there nothing to stop the roll effect, not even aileron because at zero airspeed there is no airflow across the ailerons to counter the roll. Rudder and elevator are the only effective control surfaces at this speed because they sit in the prop wash and having a constant airflow acrossed the control surfaces.
About 40- 50 is average speed for the airlerons to become effective. Some may be less some may be more depends on the mass of weight the ailerons have to move.
But I can see using ailerons on takeoff in a Spit or 109 after having effective ailerons to keep from dragging a wing tip, due to the narrow gear carriage.
When the landing gear are far apart like a P-47, P-51 the torque rolls the plane on to the left main landing gear, and compresses the oleo strut, this produces friction from the tire on the runway and pulls the airplane to the left (Yaw), just like a brake would work. At the time of lift off the torque is still present but not that pronounced, but is something that the rudder cant handle.
Remember after you takeoff when you use right aileron you get yaw to the left, so there for you will need more rudder to maintain a straight out climb. Then P-Factor comes in to play, this will also require more rudder.
Straiga
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Jeff Ethell (http://www.airspacemag.com/asm/web/special/ethell/pirep2.html)
Lining up for take-off is intimidating with that Rolls-Royce engine sticking way out in front. There is no sense in thinking too much about it. Throttle up slowly to prevent a lurch to the right (if in a Griffon Spit where the propeller turns the opposite direction from American aircraft)...left foot moves forward almost in concert with the left hand to keep the nose straight. Monster torque shoves the right wing down rapidly, very much like the P-40, until full left aileron and full (give or take a minuscule amount) left rudder is held. The Rolls is a wounded dragon bellowing horrendously.
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Let me try that again...
I was talking about two different types of torque in my previous post. The statement:
Originally posted by stantond:
So, like pulling g's in a drag racer or when turning an aircraft, dynamic torque is a transient effect. The torque seen and talked about related to horsepower is a transient effect when you are trying to stop or slow down an engines rotation by applying a load. That deceleration in rotation generates torque.
was confusing. The acceleration due to turning an aircraft is caused by centripetal acceleration and is not transient. The torque generated when applying a load while the engine is at a constant rpm is due to the force created by adding more current for an electric motor or more fuel/air in a gas engine. I agree with everything HiTech stated.
Basically (and I must use some math here) torque is the cross product of a force vector times a radial distance vector.
T= r x F
This torque can be static, for a static force F. This torque can be constant, for a periodic, but not time varying force F. This torque can be transient, or what I call a dynamic torque for a dynamic force F.
An example of a static force is from a torque wrench. An example of a constant periodic force occurs in an electric motor, or gas engine at constant speed. An example of a transient force occurs when changing the speed of an electric motor, such as during motor startup or when an engine changes rpm.
I was trying to show, by using an electric hand drill, the dynamic torque effect. This effect only occurs during a rapid speed change, such as starting an electric motor or rapidly revving an engine. A rotational acceleration must occur for this dynamic torque to exist. That is because the dynamic force F only occurs when a there is a rotational acceleration. This purely rotational dynamic torque can be put in terms of inertia and rotational acceleration.
It is this dynamic torque effect which causes a ground loop if the engine has enough inertia and is revved quickly. This dynamic torque effect will also roll an aircraft at slow speeds when quickly changing rpm’s, provided the engine has enough inertial. In both cases, the propeller speed is constant.
Hope this makes what I was talking about clearer.
Regards,
Malta
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Stantond: One of us is still missing somthing.
The torque is beeing generated by the motor in either eletric or combustion motor. This torque is either acclerating the motor or used up by the prop to produce thrust. In either case for a given throttle setting the torque relative to the airframe remains the same.
Im some how missing somthing if your saying the accleration is causing more torque than the motor can generate.
HiTech
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QUOTE] Originally posted by HiTech
The torque is being generated by the motor in either electric or combustion motor. This torque is either accelerating the motor or used up by the prop to produce thrust. In either case for a given throttle setting the torque relative to the airframe remains the same.
[/QUOTE]
What I am saying is the torque relative to the airframe does *not* remain the same when accelerating the motor compared to the torque on the airframe when the prop produces thrust. The dynamic torque due to inertial acceleration is directly transferred to the airframe when accelerating the motor. There is a time needed after increasing the throttle for the motor to speed up. That time is when dynamic torque occurs.
Dynamic torque comes from the overall torque budget which means torque to the propeller will be reduced until the motor stops accelerating. When the motor reaches the intended speed, dynamic torque goes away, and all torque from the motor is provided to the propeller.
The throttle has to be moved before dynamic torque will occur. Changing the throttle has the effect of creating dynamic torque which is transferred directly to the airframe. In differential terms, a gradual throttle (s) increase (small ds/dt) produces a small dynamic torque and an abrupt large throttle increase (large ds/dt) produces a maximum dynamic torque.
Regards,
Malta
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Dynamic torque comes from the overall torque budget which means torque to the propeller will be reduced until the motor stops accelerating. When the motor reaches the intended speed, dynamic torque goes away, and all torque from the motor is provided to the propeller.
I 100% agree with this, but how is the total torque to the airframe changed when the total torque budget remains constant as you just stated? Because torque to the prop is taken by the airframe just as the dynamic torque is.
Also had another thought, are you basing this on knowledge of cars? If so the difference would be when at steady speed engine torque on a car is pitch, and torque is roll when engine is accelerating. Hence is different than an airplane where both are always roll.
Or am I missing somthing similar to a gear ratio change on the torque?
HiTech
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HiTech,
This may take a while to accept but the propeller and rotating gears in the gearbox induce no torque on the airframe at constant speed. Torque from the engine rotates the propeller, which as you know produces thrust. As I understand, this thrust is asymmetrical and produces an external rotational force or 'torque' which is induced on the aircraft wings. This 'torque' is due to airflow (I called it propwash) and not propeller rotation.
The torque from the engine to the propeller is not offset by a torque on the airframe through the engine. Ideally, no torque would be transferred from the engine crankshaft, propeller, or rotating gears through the engine block to the airframe. Friction and engine vibration produce a small torque.
In an attempt to describe this for a constant speed engine.... the pistons move due to combustion forces which are converted to a rotational motion through a crankshaft. The engine is designed to keep these forces on the crankshaft balanced. The motion of these pistons and the rotation of a crankshaft place no torque on the airframe because of symmetry and the forces are balanced. Bolting on a gearbox does not add some path for torque to get into the airframe. Similary, putting a propeller on the gearbox offers no path either. This same concept applies to propellers on a ship or submarine and big fan drives used in closed circuit wind tunnels.
Regards,
Malta
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Sorry stantond the prop drag must exatly = the torque produced by the engine or it would be accelerating.
Why do you think helicoptors have tail rotors.
Every action requires a = and oposit reaction.
HiTech
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Yes, my bad. Torque due to propeller drag was not considered, good point. All propeller drag torque will be transferred directly through the engine to the airframe. I got hung up on inertial (dynamic) torque.
Helicopters need a tail rotor to balance out the rotor's airfoil drag torque. Changing a helicopter rotor’s speed also causes torque. However, the rotor airfoil drag causes all the torque at a constant rotor speed.
Newton’s laws certainly apply in both cases.
The torque output by an engine is equal to the amount of load, provided the load torque does not exceed the engine torque output limit. In other words, an engine will only put out the amount of torque needed to balance the torque budget. If there is insufficient engine torque to do that, I don't believe the engine will be able to speed up quickly so that dynamic torque can occur.
My understanding of the constant speed variable prop pitch mechanism is that the angle of attack of the propeller, and its corresponding thrust and drag, change based on the available torque. At takeoff, a maximum torque provides a coresponding maximum thrust, angle of attack, and prop drag. The engine torque output is equal or greater than the torque required to rotate the prop at its constant speed. A reduction in throttle position keeps the prop speed constant but reduces the angle of attack, thrust, and prop drag. The more torque available, the greater the angle of attack for more thrust.
From what I have read, most, if not all WW2 fighters had more torque than required at takeoff. This allowed rapid engine speed changes with resulting ground loops and torque induced rolls at low airspeeds. I originally thought this was probably due to inertial dynamic torque. But, a rapid propeller pitch change when the throttle is quickly moved at low airspeed might produce a more severe torque, due to a rapid change in propeller drag torque.
Regards,
Malta
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Constant speed props work conceptualy with torque, but acctualy just work off rpm, advance throttle /more torque/ prop speeds up slightly , valve opens,pitch increases/ prop changes back to original rpm.
HiTech
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Originally posted by Straiga
I wish you guys could fly the real P-51D, I have, and my experiences flying it is what im telling you about.
Straiga
I know some guys in the P-51 community. What's the tail number or nose art on your Dad's airplane?
I may have some pictures of it if he does airshows.
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Punt for Straiga