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Runaway trim

 
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dean.psiropoulos(at)veriz
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PostPosted: Fri Nov 09, 2007 12:59 am    Post subject: Runaway trim Reply with quote

Frank is correct:

The folks at the Portland RVators did some testing on the runaway trim issue
and confirmed this. While full up or down trim is difficult to counter-act
when the aircraft is flying at high speed, simply throttling back and
slowing down restores sufficient control authority to the pilot that a safe
landing can be made.

One thing I have not heard mentioned is elevator trim twitchiness in the RV
aircraft. I had heard some folks mention that there is too much (electric)
trim twitchiness at high speed and, trim does not respond fast enough when
the aircraft is flying slow in the pattern. So....I purchased a trim
control module from F-1 Rocket Boy to solve this (perceived) problem. I
have a micro switch that opens when the flaps are down to send a signal to
the trim control module to change the trim motor speed. One of the design
features of this unit is that it has a runaway trim sensing feature built
in. If the trim button is held for more than 5 seconds (ie. a trim wire
shorted to ground), the trim control module assumes a runaway condition and
shuts off the trim motor. Cycling power returns the unit to normal
operating condition.

Does anyone on the list use one of these trim control modules? Is it worth
the time and effort I had to put into wiring it into my system (the price
was reasonable)? And lastly, has it been reliable and does it always work
as advertised? Since the airplane hasn't flown yet I'd like to know what to
expect. Thanks.
Dean
RV-6A N197DM
Functional (electron) checkout in progress.
Quote:
__________________________ Original Message________________________________

Subject: RE: TRIM Disconnect Switch
From: "Hinde, Frank George (Corvallis)" <frank.hinde(at)hp.com>>

And if you have a fast airplane like an RV or Glassair and the stick
forces get too high then simply slow down.

I certainly would not bother with another switch.


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frank.hinde(at)hp.com
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PostPosted: Sat Nov 10, 2007 1:46 am    Post subject: Runaway trim Reply with quote

On my RV7 its just not that big of a deal, sure at speed you barely
touch the trim switch to adjust but honestly its not hard to trim it
out.

Frank
RV7a IO360

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