I had an interesting conversation with Jim Auman - he has restored and
is flying a modified 235 airframe with a "stronger" engine (I don't remember how
strong, but he moves along right smartly).
His airplane is equipped with a MAC servo operated good-sized elevator trim
tab that did not yield enough nose-up trim authority at lower speeds
when the flaps were deployed. Using a Paul Lipps inspired mod he has
overcome that problem.
First, remember that the 235 flap actuation mechanism is a torque tube with
a console/tunnel located good-sized arm available that rotates the
tube. We didn't discuss the fwd/aft travel distance of the arm but it has
got to be several inches.
So, one end of a screen door spring is attached to the arm and the other
end to a turnbuckle which is attached to a clamp placed on the elevator
push rod. The net result is that as the flaps are lowered, spring forces
increase to add more nose up "trim" on the elevator proper. Uh, can we
call this a hybrid system and get a tax credit for it?
Jim reports that, after some experimentation in setting spring tension,
takeoff and climb does not require trim tab changes as the flaps are moved
up. Very little trim tab adjustment is used in cruise and slowing down
for approach and landing with flap deployment require no adjustment to the trim
tab since the spring "automatically" adjusts the overall elevator trim.
Additional benefits of this system are realized when the flaps are
retracted during a go-around and the aircraft does not go dramatically out of
trim (similar to the Skymaster I mentioned before). If one is flying
a 300 series with the spring driven elevator trim (whether or not the
Reichel wheel is used), the go-around from a full flap deployment requires
careful attention to the enormous change in pitch forces as the flaps are
raised. In my airplane, after applying a moderate power increase, the
flaps are retracted and the trim adjusted in steps - unwanted additional
workload during this critical maneuver.
This discussion with Jim further illuminated that the 200 and 300 series
Lancairs have a most diverse set of modifications not seen within model
types in other Lancairs, and some of these modifications greatly affect the
flying characteristics and piloting techniques of these
planes. I am sure this must provide a challenge for HPAT and LOBO
training syllabi for these models.
Scott Krueger