A question about propeller torque during takeoffs

Discussion in 'Other Mechanical Systems Tech.' started by _viper_, Jan 12, 2009.

  1. _viper_

    _viper_ New Member

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    Hello!

    I'm new on the forum and hopefully I picked up the right discussion board.

    As the title says I'm looking for a information about propeller driven airplanes and their behave on the takeoff run. Does the pilot apply diffrential braking when the throttle is being pushed fully open? Or how much pilots normally used rudder during takeoffs? As fas as I know the propeller torque is major problem in high power piston engine aircrafts, like WW2 eras fighter planes(P-51, Spit, Fw-190, Bf-109)

    Another question is about tri gear planes, a good example for a warbird could be a P-39 or for a civil plane an ordinary Cessna. An effect called P-factor doesn't exist on takeoff rolls in these planes but are the still some propeller torque wich pushes the left main gear towards ground. How does the pilot cope with this? does he apply differential braking on his/her right foot?

    Thanks and take care!
     
  2. drgondog

    drgondog Well-Known Member

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    same but less than the big birds. A prop that rotates clockwise as seen from cockpit, tends to torque the fuselage 'counter clockwise' . For opposite rotation - opposite effect.

    Only ailerons and rudder can create the aerodynamic forces necessary to keep the airplane centered on the runway - and only when enough ground speed is generated to make any aero surface effective. A pilot will use both to counteract torque and keep the bird centered.

    Personally I never used brakes once I made the active and started take off roll, and for big iron you always feed in throttle smoothly - never abruptly anywhere near a runway or close to ground and slow speed. The latter is a sure fire technique to exterminate the rich but stupid pilot that steps up from a Bonanza to a Mustang
     
  3. Colin1

    Colin1 Active Member

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    Which would you say was the worst?
    I know the Spitfire Mk 21's ground-handling got pretty nasty
     
  4. FLYBOYJ

    FLYBOYJ "THE GREAT GAZOO"
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    The Corsair was really nasty as well.

    Also consider that aircraft with a nose wheel are better behaved. Tail draggers, even small GA aircraft could humble the best pilots, especially if you throw a cross wind into the factor.

    Agree Bill - never go on the brakes during take off roll unless you plan to abort or in the case of a tail dragger, wish to know what it's like to have a prop strike.
     
  5. renrich

    renrich Active Member

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    For the Corsair, six degress right rudder trim and six degrees right aileron down on takeoff.
     
  6. drgondog

    drgondog Well-Known Member

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    For the 51 it was also six degrees rrt and 'feel' on ailerons. When I got the tail up everything was focused on horizon and every input from me was putting 'my level wing picture' on the horizon...

    Agree 100% w/Joe's more thorough description.. nose over for hard brake, ground loop for asymetrical pressure. I never had to abort a takeoff so never experienced the nose over - but have seen a few.

    I heard a great story from one of my former naval aviator friends who flew two tours on AD's (w/Navy Cross).. all about swapping ships with an A4 wing for takeoff and touch and go's after a hard night of drinking. One day to study the manual.

    A4 drivers were extremely lucky to not commit suicide when strapped into the AD and running throttle up during takeoff (believe the AD was 12 degrees and sloooooooooowwwwwww on the throttle run up).. believe both wing commanders may have been assigned to fly brooms on halloween after that.

    The first two ADs went careening off the left side of Kaneohe runway. Rest stood down before serious damage.

    Pretty funny story by Marshall Knox - guess you had to be there to truly enjoy the mayhem.
    '
     
  7. _viper_

    _viper_ New Member

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    Many thanks for your answers 8)

    Still I do have one or two questions. How important is to lock the tailwheel during take off and landing? I also remember reading that in some planes the tail wheel could be locked by helding back the stick.

    I would assume that during takeoff roll the stick (taildraggers) is held back untill the airspeed has increased :?:
     
  8. HoHun

    HoHun Active Member

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    Hi Viper,

    >I also remember reading that in some planes the tail wheel could be locked by helding back the stick.

    I believe that was the North American Aviation way of doing things. From the P-51 AAF Training Manual:

    "In ordinary taxiing, keep the stick in neutral or slightly aft of neutral. This locks the tailwheel and makes it steerable 6° right or left with the rudder.

    To make sharp turns or go around corners, unlock the tailshweel by pushing the stick full forward. In this position the tailwheel is full swiveling."

    So it's "full forward to unlock", not "fully back to lock". I think the latter might be difficult to control.

    Except for the P-51, the AT-6 seems to have had the same system at least in some of its countless variants. I found one cockpit photograph of an AT-6 showing a label: "Move stick forward to unlock tail wheel", but that might not have been the most frequent variant.

    You can find an AT-6 (or rather Harvard) manual here on this board, but it's in Dutch, and while I managed to make sense of most of its contents, the interesting bits on the tail wheel mechanism eluded me ...

    http://www.ww2aircraft.net/forum/other-mechanical-systems-tech/harvard-iib-5728.html

    Regards,

    Henning (HoHun)
     
  9. renrich

    renrich Active Member

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    Saw a video of a modern day pilot flying a Sopwith Camel on UTube. This Camel had the 160 HP Gnome rotary engine. The prop is attached to the engine and the prop and engine whirl around together. The engine does not have a throttle so engine speed is controlled by the magneto with only a few speeds, mainly off or on. Kind of like revving the engine in a car. With the Camel on the ground the engine was going from full off to full on and the whole airplane was trying to rotate around the engine and prop. You have to see it to believe it.
     
  10. drgondog

    drgondog Well-Known Member

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    That is correct for the only variants I flew. IIRC the tailwheel locked in straight position and stayed that way on retraction.
     
  11. MikeGazdik

    MikeGazdik Member

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    I have nothing to offer. I just find it amazing that we are talking to people that have (or do) fly some of these planes. I have touched a very few of these planes, and could feel the history. That fact that some have taken them into the air..... unreal. I feel lucky to be on the same website!
     
  12. Marcel

    Marcel Well-Known Member

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    Translation:
    The rest is about the fact that it can't make a huge angle as it can be detached from the rudder.
     

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  13. _viper_

    _viper_ New Member

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    Niice, thanks for the translation! The thing is that I can only speak and write English, Finnish and some Swedish.

    By the way does anyone know how much the prop torque and gyroscopic action affects in twin - or four engined planes (like DC-3, DeHavilland Mosquito, A-26, B-17, B-29) I managed to find a list of counter-rotating propeller planes Counter-rotating propellers - Wikipedia, the free encyclopedia which eliminates the whole issue.
     
  14. FLYBOYJ

    FLYBOYJ "THE GREAT GAZOO"
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    Twins will be a little different unless you loose an engine on takeoff, then you have all kinds of problems to deal with. 4 engine aircraft were different and more forgiving but twins will kill you very quickly if you maintain proficiency, and the same hold true in today's world with GA twins.
     
  15. _viper_

    _viper_ New Member

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    So you do mean that a normal twin of four engined prop plane behaves like a norman single engined plane? Sorry I had to make sure. The Wikipedia says about P-38 Lightning that :

    "Another issue with the P-38 arose from its unique design feature of outwardly rotating counter-rotating propellers. Losing one of two engines in any twin engine non-centerline thrust aircraft on takeoff creates sudden drag, yawing the nose toward the dead engine and rolling the wingtip down on the side of the dead engine. Normal training in flying twin-engine aircraft when losing an engine on takeoff would be to push the remaining engine to full throttle; if a pilot did that in the P-38, regardless of which engine had failed, the resulting engine torque and p-factor force produced a sudden uncontrollable yawing roll and the aircraft would flip over and slam into the ground. Eventually, procedures were taught to allow a pilot to deal with the situation by reducing power on the running engine, feathering the prop on the dead engine, and then increasing power gradually until the aircraft was in stable flight. Single-engine takeoffs were possible, though not with a maximum combat load."

    drgondog wrote that P-51 Mustang required aileron and rudder trim on takeoff. But as far as I've seen Spitfire pictures there are no aileron trim at all? Obviously it would require a lot of extra work to keep the Spit still. Or maybe I've been too blind to notice the trim in the aileron :oops:
     
  16. drgondog

    drgondog Well-Known Member

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    Look closely - there is no possible way the Spit could remotely run straight with foot off rudder pedals, and when reaching enough airspeed to lift the tail exert no roll control - you must have aileron control and rudder input with those big engines.

    The P-38 acts no differently than other twins when you lose an engine.

    The 'Live' wing has both thrust and lift...(more lift than dead wing). As Joe pointed out the live wing wants to roll the airplane to the dead side, and the live engine wants to yaw the airplane to the dead side.

    Think of the forces which lead to a snap roll. Bad thingy on take off.

    I have never flown a very powerful twin like the P-38 but even a Baron or a 410 require care when you lose one at low speed...

    I believe Joe once noted that the great thing about twin engines is that they will carry you all the way to the crash site when you lose one.
     
  17. FLYBOYJ

    FLYBOYJ "THE GREAT GAZOO"
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    A twin doesn't, a four engine aircraft like a B-17, you have a lot less to worry about.
     
  18. FLYBOYJ

    FLYBOYJ "THE GREAT GAZOO"
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    YEP!
     
  19. _viper_

    _viper_ New Member

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    Yes exactly what I thought. For example the Wooden Wonder aka. Mosquito needs proper rudder input that it wont be all over the place :?:
     
  20. FLYBOYJ

    FLYBOYJ "THE GREAT GAZOO"
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    Exactly - during the application of power and during the takeoff roll the pilot is "dancing" on the rudders, applying little inputs to keep the aircraft straight. At one point slight forward yoke or stick is applied to get the tail up and to keep the aircraft in a straight and level attitude. Once that is happening you have rudder effectiveness and all directional control is thru the rudder. After a few more seconds airspeed comes up to rotation speed and the aircraft will fly - then go to Vx or Vy.
     
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