# The torque roll



## Milosh (Oct 22, 2009)

Can someone explain why an airplane torque roll is, please.


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## Shortround6 (Oct 22, 2009)

If, say the propeller rotates to the right, it is the tendency of the airplane to rotate (roll) to the left when the throttle is opened.


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## Messy1 (Oct 22, 2009)

It's the forces of the engine and propeller being transferred to the body of the plane.


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## vanir (Oct 22, 2009)

Answers above correct. The torque of the motor is working on a body of mass, the crankshaft, the conrods, the prop, the body of the plane wants to rotate in the other direction because of Newton's law (equal and opposite reaction).

With inline engines some of the torque is transmitted torsionally along a long crankshaft, so it spreads out over a greater area. This is why radial engines produce sharper torque rolls, because the torque from the motor is being transmitted onto a small cranksaft and is felt more suddenly and dramatically by the airframe.


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## Shortround6 (Oct 22, 2009)

Also radial engines are usually bigger, more displacement= more torque, more torque=more reaction


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## Wiking (Oct 25, 2009)

Shortround6 said:


> Also radial engines are usually bigger, more displacement= more torque, more torque=more reaction



The descriptions are good. Modern US aviation terminology calls it torque reaction, but 'Torque Roll' works well. 

Some examples to illustrate the concept: 

- An aircraft mechanic friend was witness to a F4U Corsair accident in which the pilot applied too much throttle too early in his take-off, still low (perhaps in ground effect) and the force of torque overcame the aerodynamic capabilities of the wings, rolled the plane inverted and it crashed on the runway.

- In flight a pilot could take advantage of torque roll, since the plane would roll faster in one direction than the other. If the pilot knew an attacker's aircraft had an opposite-spin prop, he'd roll in the direction of best advantage. I have heard this being the case primarily in WW1 when even some engines rotated with the prop. (Rotary engine vs Radial).


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## Guns'n'Props (Oct 27, 2009)

Wiking said:


> - In flight a pilot could take advantage of torque roll, since the plane would roll faster in one direction than the other. If the pilot knew an attacker's aircraft had an opposite-spin prop, he'd roll in the direction of best advantage. I have heard this being the case primarily in WW1 when even some engines rotated with the prop. (Rotary engine vs Radial).



Yep The Sopwith Camel was the classic case. It was easier and faster to turn 270 degrees than go directly left if I remember correctly. Still a great fighter for WW1.


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## Carboncrank (Feb 10, 2019)

vanir said:


> Answers above correct. The torque of the motor is working on a body of mass, the crankshaft, the conrods, the prop, the body of the plane wants to rotate in the other direction because of Newton's law (equal and opposite reaction).
> 
> With inline engines some of the torque is transmitted torsionally along a long crankshaft, so it spreads out over a greater area. This is why radial engines produce sharper torque rolls because the torque from the motor is being transmitted onto a small crankshaft and is felt more suddenly and dramatically by the airframe.



I'm trying to see how the length of the crankshaft could have anything to do with it at all. When torque is applied the thing that is the source of the torque needs something to push against in order for motion to happen. Equal and opposite. All that matters is the amount of torque, not over the length of what's creating it. With a long crankshaft or a short crankshaft with the same amount of torque being applied either system is applying the same Force. If the mass of the object the torque is pushing against to create the motion is the same it doesn't matter whether it's applied over one foot or 20 ft the amount of opposite force would be the same.


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