On Jun 15, 9:42 pm, Le Chaud Lapin wrote:
On Jun 15, 3:30 pm, wrote:
Adding electronic controls to something like a trim tab on a
lightplane is one of those "better" ideas that has no basis in
reality. It adds complexity, which adds failure points and cost and
weight, none of which are welcome.

I hear a lot of mechanics say this about cars. I think there should
be a qualification made thos these types of statments...

A good example of an "improved" system in lightplanes was the
electric flaps in 150s and 172s. The old system involved a lever and
some cables. The lever was pulled up to 10, 20, 30 or 40 degrees, so
the lever was the flap position indicator and the cables were the only
other weight involved. The effort to pull the lever up was a point of
complaint with some feeble pilots.
The electric flap system has a gearmotor driving a jackscrew,
microswitches on the jackscrew nut sleeve to limit its travel, a DPDT
momentary switch on the panel, a special wirewound potentiometer in
the wing to follow the bellcrank to drive a flap position indicator on
the panel, and cables and pulleys from the right wing (where the motor
is) to the left wing to drive the left flap.
So now we have the same cables and pulleys (although a little less
of them), a switch that fails regularly (the springs that center it
break), and cable bundle whose connectors at the wing roots and flap
motor assemble get wet and corrode), microswitches that get oil in
them off the jackscrew threads (meaning that sometimes the flaps won't
come down, or worse, that they won't retract on a go-around), a five-
pound motor and jackscrew (which lowers useful load), a special
potentiometer that wears out and costs more than $500 from Cessna and
isn't available anywhere else (bought one a few years ago), a flap
position indicator that costs $475 (bought one last year), and the
loss of the option of raising the flaps right at touchdown to get max
weight on the wheels for braking on short strips, which annoyed no end
a lot of the bush guys who relied on that feature. At least Cessna
left things alone in the 180 and 185, airplane flown by real pilots
who didn't mind pulling a lever.
You can decide if this was an "improvement." Lots of owners who
have had to have this system fixed don't think so.

Dan