I have the answer, as quoted by my good buddy, Slats Retract:
"Hi Shane,
you are a good observer. You noticed the yoke mouvement when selecting the flaps. It has something to do with screw-drive actuators
(called aileron deflection actuators or ADAs) which drive the ailerons down for take off. Boeing wrote a technical note explaining the sudden kick in the yoke."
And the complete explanation:
"2 DEFLECTED AILERONS FOR TAKEOFF
The Deflected Ailerons are part of the A1 Performance Improvement
Package, (PIP) and will deflect the ailerons approximately 11 degrees in
order to improve takeoff performance. Small 28 VDC screw-drive actuators
(called aileron deflection actuators or ADAs) are installed in the control
linkages leading to each aileron hydraulic actuator, and are activated by a
switch in the flap handle transducer when in the 6.5 to 31.5 degree Takeoff
Flap range. When the ADAs are energized, they extend and apply a
mechanical input to extend the aileron hydraulic actuators. The inboard
ailerons will deflect to 11.5°, the outboard ailerons to 15°. The aileron
deflection is removed when the flaps are retracted after takeoff, and the
system cannot be energized again until after the aircraft has cycled through
a landing; they are never deflected for any other phase of flight.
Since the introduction of the Deflected Aileron System, two anomalies have
appeared which are explained below. While these anomalies do not impact
the safe operation of the aircraft, they may cause concern to the flight
crews. Crews should be briefed as explained below:
2.1 MOMENTARY CONTROL WHEEL DEFLECTION
When the Deflected Aileron System is active and the aircraft is also
equipped with the Roll Control Wheel Steering (RCWS) option, there will be
a momentary control wheel deflection of approximately 12 degrees for 1
second when the ailerons initially deflect or retract after takeoff. This
deflection is normal, and an explanation of this phenomena is provided
below:
When the RCWS (or Autopilot) is active, one of the inboard ailerons (the left
aileron for RCWS 1, the right for RCWS 2) is controlled by the Flight Control
Computer (FCC) electronically. In this mode, the engaged aileron actuator
will not accept mechanical inputs, and deflection must occur electronically
through the FCC. The FCC attempts to accomplish this deflection at the
same rate that the ADA is trying to deflect the aileron mechanically. In
actual practice, however, due to small lags in the aileron response to the
FCC commands, the aileron is usually moving a little slower than the ADAdirected
movement. The ADA then backdrives the control wheel slightly
until the aileron catches up; this causes the aforementioned momentary
aileron pulse.
The characteristic explained above is normal, and actually provides a
positive, tactile indication that the ailerons have deflected. Typically, if
RCWS 1 is active, the control wheel will move counterclockwise when
lowering the ailerons and clockwise when raising them. If RCWS 2 is active,
the opposite will be true.
MD-11 Bulletin Flight Control Systems
27 January 2005 page 6
This same phenomena will also occur when the Autopilot is engaged while
the flaps (and ailerons) are retracting after takeoff. The effect on autopilot
control is negligible, and will usually not be noticed by the crew unless they
are specifically looking for it."
Thanks Slats Retract for the complete answer and everyone else who contributed! I hope PMDG models this in their upcoming MD-11 software for FS2004.
