In the one case, the whole of the rotating mass of the engine and propeller
are turning in the same direction, while in the other case, they turn in
opposing directions, and to some extent, precession is canceled.
The argument that an affect caused by misaligned relative wind
through the prop
makes for more thrust on the right side vice the left side rings hollow,
because the big gyroscope in the front moves that force to the bottom of the
disc and makes it a nose up moment in right hand rotation, and nose down in left
hand rotation.
Same thing when the tail comes up on the Super Cub. Close to no rudder
authority, spiraling flow pushing the tail to the right, and the precession
(just during the attitude change) helping push the nose to the left.
But once the nose is up, there is no further precession, the situation is
close to that of the trigear plane, and still you have rudder dialed in. So why
has the "P" factor not vanished?
Because it's 98% spiraling flow pushing on the fin and rudder. Note that
the rudder is mounted so as to be active all of the time in countering the
spiraling flow. The amount of offset is adjusted to be ideal at cruise speeds
(so there is no trim drag).
Years ago, over New Jersey the 19 year old trainee was doing (trying to do)
stalls in climbing turns to the right in the super cub. The aerobatic rated
instructor let me try for a while with no success, it just fly's around in a
nose high spiral and won't stall. He told me to rock it a little, let the back
pressure off for a second or so, and that snap it back again.
That did work. The nose and high wing fall through smartly and recovery is
straightforward.
Then he said do some to the left.
Nose high turning left is easy at full throttle, the nose and high wing not
only went through first, they kept right on going, into an inverted spin. As was
his usual command, he yells "what are you going to do now?"
With the door and window open, I notice that my pencil is dancing on it's
point about three feet out on the wing. I have no idea, I yell back. So while we
get closer to New Jersey he explains it at length, and then recovers
crisply.
So why does it turn left so nicely when at full throttle and zero airspeed,
and so poorly to the right? Because of the "P" factor, spiral flow pushing the
tail to the right.
Lynn E. Hanover
In a message dated 12/11/2005 10:19:27 PM Eastern Standard Time,
lendich@optusnet.com.au writes:
Ed,
What you are saying reflects what I've read also - however
Tracy's experience with the difference between the 2.17 and the 2.85 suggests
that there is also the centrifugal forces of prop + rotor direction to contend
with, as Tracy required full R rudder to maintain directional control
with the 2.85, whereas with the 2.17, it wasn't anywhere near as difficult -
so I'm led to believe.
If it were just the wind from the prop corkscrewing around
the fuselage until it hit the rudder, the L and R turning props
would give a similar response in intensity. This wasn't the case, it
would seem.
George ( down under)