I saw a similar system to this in an RV4 which I flew in this Summer. It
used light springs attached to a small lever on the back of the control
column near the floor. The springs went to either side of the cockpit (the
seating in an RV4 is tandem), and the pilot could easily move the lever left
or right and it would either tension the left spring or right spring and so
provide a bias force to the stick. As in your system, it had a negligeable
effect on the stick forces and had been fitted after the aircraft had been
completed. Seemed a very elegant and simple solution and the springs could
be easily unhooked from the lever to completely disengage the system if
required. I seem to remember hearing that some Long-Ezes also used a
similar system to this.
Now, has anyone tried to get such a scheme through the PFA? Do you think it
would be acceptable to them?
David Cripps
GBWJH (007)
-----Original Message-----
From: owner-europa@aztec.houxou.com
Subject: Re: Roll trim?
<< Has any one install a mechanism in the fuselage underneath the cockpit
module in the manner of a screw or lever adjustment connected directly to
the stick to preload aileron trim through the control linkages in the
fuselage, springs etc?
>>
I have in mind a very simple (crude?) roll trim mechanism which I expect to
add over the winter. I will fit a small fiberglass bracket near the bottom
rear of the stick (secured by the retention bolt) to hold an automatic cleat
of the type used on small sailboats; this cleat is just a pair of spring
loaded jaws which serve as a one direction stop on a line passing through
the
jaws. The line may easily be popped out of the jaws to release the line and
then re-inserted - this allows loosening the line.
A short piece of bungee cord with a loop on one end will be used as the
spring. The loop will be placed over either of two bolts whose heads
protrude
3/4 inch from the front of the outer sections of the thigh rest (one bolt on
either side), at the level of the bracket affixed to the stick; the other
end
of the bungee will pass through the automatic cleat. By pulling the bungee
through the cleat one will increase the aileron trim force, having first
placed the loop over the bolt on the appropriate side for the trim direction
needed.
The spring force needed for aileron trim is relatively small and rough
experiments show that this setup will provide sufficient trim in my plane
whose trim is neutral without tabs installed. A slight left roll occurs
apparently due to assymetrical loading from pilot weight; leaning toward the
center of the cockpit counters the observed roll.
This method allows adding the trim system as an afterthought (important in
my
case). This trim system is inexpensive, light, easily and quickly
disconnected if it malfunctions (unlikely in such a simple system), and
easily adjusted in flight by simply pulling on the bungee. The trim force
applied is easily over powered by the pilot; indeed, the applied trim is not
noticable through the stick in flight. The drawback is that it won't level
the wings automatically or track a course as the Navaid will.
John N44EU
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