Hi Folks,
N135TD tends to oscillate slowly in altitude when the stick is left free.
This is most noticeable when the Navaid autopilot is on, since there is a
natural tendency to keep the airplane level, without really noticing it,
when the pilot's hand is on the stick. Typical parameters are speed
variation +/-5 KIAS, altitude +/-50 feet, VSI +/-300 fpm, and a total cycle
time of about 1 minute.
The only significant play in the pitch control system comes from the
(normal) loose fit of the hinge pins in the antiservo/trim tabs. There is
no deadband in the pitch control during flight, and the response to stick
inputs is quite positive. Though we haven't measured stick force gradient,
it feels very reasonable, with a solid push or pull required for a change in
pitch attitude.
The only deviation we can see from the specifications is the width of the
Flettner strips. By the time we got done filling and finishing over them,
they measure about 3/4" to 7/8" wide from the trailing edge, to the point
where they disappear into the tab surface. The manual specifies 1/2"
maximum. Thickness at the trailing edge is 3/8", which is the maximum
recommended. If we need to make the slope to the trailing edge more abrupt,
we will grind them down appropriately. I would just hate to tear up the
nice painted surface, only to find that it made no difference! Anyone with
experience or some solid theory on this?
Dave DeFord
N135TD
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