Cbusbased

Ah, I'm picking up what you're laying down. The whole "...while on the ground" part went over my head. Haha

Hubble15

JNB, you are in the ballpark generally, but mistaken that torque only affects roll during power changes. Torque effect is offset by rig ... for each power setting, there can be a corresponding "no roll" airspeed (tho sadly my plane rolls a bit to the right at nearly all normal speeds). If your airplane is rigged "right", then it will exhibit little to no roll at standard power/cruise speed pairings. The best way to see this is to accelerate near Vne and pull up to the vertical. Initially, very little aileron will be required to offset the rolling tendency. As the aircraft slows, progressively more right aileron (left with a russian motor) will be required. As the aircraft nears zero airspeed, the ailerons will not have sufficient effectiveness to prevent roll and, even with full right aileron, a left roll will commence. If the aircraft was otherwise balanced, it will torque roll to the left until it pivots in the tailslide. Flown the other way, airshow guys will begin rolling left in the vertical and the left rolls will continue in the tailslide.

Hubble15

PS - only try the demo I described in an airplane certified for aerobatics

JamesNoBrakes

Sounds reasonable, but I was thinking that accelerating a rotating mass vs just swinging it at a constant speed would take a lot more force, and consequently, cause a lot more opposite force.

But yes, I agree with most of this, it kind of blows a lot of "rote" learning that pilots are taught out of the water (generally because torque and gyroscopic effects are widely misunderstood), but it's completely sound. One has to be careful as well, as there can be other effects causing the aircraft to roll, like the vertical stab/rudder, which sits a distance from the longitudinal axis, so there'll always be a little "roll" (not even getting into an advancing wingtip) when using just the rudder, unless it's a submarine with the longitudinal axis bisecting the rudder.

As far as the "on the ground" part for Cbusbased, lets go back to torque and the "opposite" reaction. Propeller travels in a circle clockwise, so the opposite reaction will be for the airplane to try and move opposite of the prop, which would be counter clockwise. On the ground though, can the airplane "roll"? Not really, the wheels are supporting it, but what it can do is try to roll the airplane left (counter clockwise) and exert more pressure on the left main. Although friction is irrespective of pressure, tires are not rigid and in real conditions it usually causes more friction effectively and that increased friction on the left main gear tries to pull the aircraft left during the takeoff run.