December 2005 — Vol. 22, No. 12 - RC Soaring - RCSoaring.com

two channels, one of them elevator,
which stops one from adjusting left
surfaces independently from right
surfaces.
Similarly, pilots with very basic radios
won’t have endpoint adjustments.
The danger, and an explanation
with a partial prevention:
So, WARNING: If you don't have a
radio with “endpoint” (or “travel”)
adjustments (which are actually rate
adjustments), check your servos for
similar throw before you stick them in
your wings.
Elevon servos of mismatched response
could make a flying wing roll upon
elevator input. Flaperon, flap, or
spoileron servos of unequal response
can make a standard planform roll, just
when one is close to the ground, trying
to land. (Bad.)
Sherman continued: “You’re probably
more likely to get servos that don’t
match out of different batches. They
order a load of components from Korea
or wherever, and the components are
probably tested to be within tolerances
of each other. But the next batch of
components may be from a different
supplier. So who knows whether they
match the first set.”
Philip’s servo test stand. The servo to be tested is hooked up to a receiver and actuated
through the transmitter function. The protractor attachment gives a direct reading of servo
throw. This test bench allows matching of servos or use of transmitter endpoint adjustments
to artificially match them before they’re in an airplane.
Note: Yoda is not necessary, but his presence does add a certain ambience to the proceedings.
36 R/C Soaring Digest