# Is an aileron roll easier, opposite the rotation of the propeller?

We all know helicopters have tail rotors because they would spin out of control thanks to Newton's third law.

That got me thinking, would a single propeller plane have an easier time doing an aileron roll opposite the rotation of the propeller? And do light aircraft require any special tricks like having one wing longer than the other or the ailerons being tilted in the rest position?

• A failing tail rotor is a recoverable failure in a helicopter given the right conditions. Commented Feb 5, 2019 at 19:05
• Yes. In the US, props spin clockwise from the pilots point of view, so rolling left is easier than rolling right. No tricks on the wings. Ailerons might have small trim tabs that are adjusted for straight & level flight. Commented Feb 5, 2019 at 19:07
• Some aircraft do have an offset thrust line to counter propeller turning effects. Commented Feb 5, 2019 at 19:24
• I question the answers presented here. When the engineers design the aircraft, they take into consideration the effect of the rotating propeller. If they didn't the pilot would have to constantly provide offsetting flight control inputs to keep the wings level (to prevent a roll). So the amount of aileron required (and the resultant lateral trim forces) should be the same for rolls in either direction. Commented Oct 17, 2022 at 17:14
• Another technique used on some aircraft is to mount the wings at slightly different angles (of incidence)) to compensate. Aircraft so modified would require identical trim forces to generate rolls in either direction. Commented Oct 17, 2022 at 17:19

## 2 Answers

Yes: Rolling one direction easier than the other, as you mentioned, newton's laws are at work here.

Special Tricks? Also Yes. There are several design strategies to deal with asymmetries of thrust from propellers. Bear in mind that these thrust asymmetries are not always at work, so any design feature is a trade off. The propeller must be running, angle of attack is a factor, etc. I have heard of asymmetrical wing incidence used, but more often a slight offset of a tail-plane, such as the vertical stabilizer is used.

• I question the answer presented here. As mentioned, when engineers design the aircraft, they take into consideration the effect of the rotating propeller. If they didn't, the pilot would have to constantly provide offsetting flight control inputs to keep the wings level, depending on other factors such as AOOA, power setting etc. So the amount of aileron required (and the resultant lateral trim forces) should be the same for rolls in either direction. Commented Oct 17, 2022 at 17:15
• @CharlesBretana because prop torque is variable with rpm and pitch, it would be very difficult to develop a passive system to cover all bases. This is why rudder must be applied in high power/slower flight situations. Generally, it is easier to roll one way than the other with a single engine. (PS way safer to use the rudder). Commented Oct 18, 2022 at 0:06
• @Robert, Yes, I understand that, but obviously, if designers make an adjustment to compensate for a part of the effect generated by prop torque, then isn't it indeterminate (at any specific rpm, AOA, and pitch attitude) as to what direction would be easier to roll? Isn't it clear that at one end of the rpm/AOA spectrum it will be easier to roll in the direction opposite from the direction that would be easiest at the other end of the spectrum? Commented Oct 18, 2022 at 22:30
• ... and rudder is only effective at higher AOA, where adverse yaw exists. It is not slower (airspeed), that matters. Rudder at low AOA, at any airspeed, only generates a sideslip. Secondly, High power settings cause P-Factor yaw because of AOA, (the angle between the plane of the prop and the relative airstream), The other yaw-inducing effect is from the corkscrew (helical) shape of the prop wash hitting the vertical stabilizer. But this yaw (sideslip) only induces a roll when at significant AOA. Commented Oct 18, 2022 at 22:43
• @CharlesBretana I'm unclear on which part of the answer you are questioning. Is it whether the roll is easier in one direction vs. the other, or about the compensation in the design? Commented Oct 24, 2022 at 18:31

Yes. Even more yes when the engine also has a lot of rotating mass, as with the Sopwith Camel. "The torque effect of the engine also meant that the aircraft rolled much more readily to the right than the left and this could lead to a spin. Many novice Camel pilots were killed when they turned right soon after take-off." https://www.warhistoryonline.com/world-war-i/the-killer-camel-sopwith-camel.html