Phil,
I don't have an MT, so can't say I can repeat this scenario (I have a 2-bladed Hartzell and don't normally carry power during the rollout)...just had some thoughts (that the smarter-than-me aerodynamicists here can vet
).
When you chop the power, perhaps you're cutting out (or just decreasing) any remaining torque, P-factor and slipstream effects that the prop may be generating, so cumulatively I could see some right-turning tendency coming from that; and if it takes place as you're beginning to feel the effects of decreasing rudder effectiveness as you slow, perhaps the turning tendency becomes even more marked, and it takes more left rudder to correct it.
Not sure about braking effect from the prop, though I'm not sayin' it aint so...just seems like at the low power settings you're talking about, the prop is likely already at the pitch stop, so the blade pitch probably isn't changing when you chop that last little bit of power, you're just decreasing the thrust vector from the prop (and since a bit more is coming from the downward moving blades on the right side, the effect is the right turn...that leads me back to the thoughts in the paragraph above).
One other question would be whether the tail is on the ground when the power is chopped and the turn occurs, and (please don't take this wrong) I'm interested in why you're keeping the power on after touchdown. I was taught to bring the power to idle at or before touchdown, then (on a wheel landing) to let the tail down smoothly, then get the stick in my gut for better controllability and more effective braking. Not bashing your technique, it could be a very valid technique that I'm not familiar with...just thinking that there is a lot going on with changing power settings and changing rudder effectiveness with the tail wheel off the ground (if it is still up).
Just some thoughts, and it'll be interesting to hear what the guys with mucho TW experience say, and whether there's a difference between 2 and 3 blades, or MT vs. Hartzell.
Cheers,
Bob
