Originally Posted by
Paul Cantrell
Ascend Charlie says:
Just a nit - not all fins are canted (I don't think the R22 is, the R44 & 66 are). You can kind of tell by how an R22 flies at cruise - still needs a fair bit of left pedal compared to a 206.
Also, some (like Enstrom) don't really have much fin at all.
The original question asked about why the left yaw, and I agree that what people have been mentioning are the biggest factors, but nobody mentioned transmission drag, which is typically what's yawing your nose left during the flare of an autorotation. The friction inside the gearbox tends to want to drag the nose, but is typically being countered by torque, fin, and pedal. But during unpowered flight, and especially when you wind the RPM up, the drag is sufficient to be noticed, although not a huge effect (if there's any crosswind it'll typically hide any transmission drag effects).
One of the big differences between a touchdown auto and an actual engine failure is the nose swing as you cushion. When performing a touchdown auto (training maneuver) the engine is at idle and tends to counter that left yaw as you cushion the landing. With an actual engine failure you notice that you need some right pedal as the rpm comes down when you cushion. (my experience with turbine engines, recips...been too long ago to remember)