"Cub Driver" wrote in message
...
On Sun, 07 Nov 2004 05:09:36 GMT, "Dudley Henriques"
wrote:

"why does the banking of wings by
the use of ailerons not just roll an aircraft but also produces a turn

He wants to know why his pilot can't simply do rolls around the
plane's longitudinal axis.

Perhaps it would help to know what inputs are necessary to make such a
roll? If you are rolling to your left, do you apply right rudder?

A slow roll is extremely difficult to visualize with verbal
interpretation only.
The best way to describe what you are asking..say a slow roll to the
left is to first understand that a slow roll isn't exactly a roll dead
on the longitudinal axis as the axis relates to a "level" roll. The
visualization of a slow roll to the left can be made by envisioning a
reverse capital letter D, which naturally isn't in my little bag of
computer symbols, so a roll to the right is much easier to visualize. So
to the right, you can envision a capital letter D.
The reason for the D shape is because to do the roll properly, you will
have to pass through exact inverted at the airplane's level flight
inverted attitude to keep altitude in check during the roll. The
tightness of the D shape will depend on the wing design of the airplane
you're flying. A symmetrical wing on a Pitts, or an Extra for example
will be a much tighter D than say a Citabria with a high lift cambered
wing.
Anyway, the vertical line of the D represents the raising of the nose
during the first half of the roll until right past the full inverted
position. At that point, the nose must again be lowered to a normal
level flight attitude, and this is represented by the curve on the D
returning the airplane back to upright level flight attitude.
The roll can be done with inside rudder at roll initiation or without
insider rudder. When flying airshow demonstrations, I seldom used inside
rudder with inside aileron when initiating a slow roll. Reason for this
is that adverse yaw will pull the nose outside, which if caught exactly
right, will result in your going straight to the required top rudder you
need to carry you through knife edge at the right spot on the roll axis,
and if it's a point roll, you don't have to change feet at the first
point, but to do this requires a fairly fast roll rate, so it's aircraft
specific. In the P51 for example, the roll rate isn't fast enough to use
the adverse yaw generated so that it negates the normal inside rudder
you need to counter that adverse yaw, which in turn means you enter with
aileron and insider rudder, and immediately go to top rudder as soon as
a positive coordinated roll entry has been accomplished.
Back to the Pitts, entering into the first knife edge, you have steady
inside aileron and have blended in enough positive pitch with elevator
to climb the vertical D line nose high for the inverted level
transition.You hold top rudder through knife edge and then start
blending in whatever forward stick you need to pint the nose at level
inverted. You're also blending off the top rudder at this point at a
rate that will neutralize it passing through inverted. Stick at this
point is forward and in the corner for aileron and elevator blending.
Passing through inverted, you switch to opposite side top rudder and
reverse the procedure, blending in past the second knife edge, as you
come back down the backside of the D curve whatever back pressure you
need to return the nose to normal level flight attitude.
What I've just described is much better learned in actual flight, where
a slow roll can be done by rote, then understood
afterwards...........and in far less words to boot :-)
Dudley Henriques
International Fighter Pilots Fellowship
for email; take out the trash