This is a tough trade off analysis, and a lot of it is purely
subjective; Here's my take.
Cost: the manual is far cheaper
Installation: I believe the Installation is slightly easier on the
electric but shoe horning that servo in to the elevator is not easy.
If the Gretz version is still available, it makes the electric way
easier.
weight: The electric is far lighter.
Space: The manual takes up a bit of space in the cockpit so the
electric gets the nod.
Feel: This is very subjective to say the least. For my money the
manual has a far better feel and preciseness. To add to the bargain
you can see what you got for take off or go around. Easier to set,
and quicker too. Most pilots don't like the lack of feed back from
the electric servo and its slowness. You can get various speed
changers and gain switchers. Bottom line is most pilots who have
flown with electric trim before can get accustomed to the
shortcomings. I did.
Safety: Probably the most debated issue. Surely "runaway trim" is a
possibility with the electric. It is not a possibility with the manual.
I know lots of folks will come after me for saying this, but I don't
think it is a significant problem in an RV-6A. First of all most of
the dark and stormy night horror stories are about big airplanes with
stabilizer trim. On the B-52 it was a real threat. The huge
hydraulic motors could drive the huge stabilizer very quickly to a
position far beyond you ability to overcome the pitch force with the
puny elevator. With elevator trim in the RV 6A. you do not lose
elevator effectiveness when the trim tab takes off. For example if
the trim runs away to full down (tab up) and you counter it with up
elevator, then your effective elevator power is actually more than if
the tab were elsewhere.
I have tested many times and the elevator force required to overcome
full up trim on take off is easily manageable. I don't know how fast
you can go and still control it with our using both hands but I
believe it is do able. I leave it to Kevin Horton to do this test for
us.
As for me I installed a pullable circuit breaker for the trim power
which is easily accessible. It has never been used in flight.
I went with the electric and have had several failures, all broken
wires. I replaced most of the wires with mil spec 22 ga and solved
that problem. These failures would cause me to lose trim altogether.
Basically an inconvenience in the RV-6A.
Good luck on your choice.. I like both systems, but went with the
electric and have no regrets. My little servo has 2400 hours on it
and still works. I used the matronics speed controller and ordered a
new improved one after the old one was ten years old, got rained on,
and became intermittent. When pulling it out to switch I found a
loose connection so it is still in the plane (with a rain guard) and I
have a spare if you want to make an offer. ; ).
LET THE flames begin on my rant about runaway trim. I would surely
like to hear from someone who has experienced it with an RV-6.
Denis
On Nov 18, 2009, at 10:19 , thomas sargent wrote:
> I am doing final assembly on a 6A. I've never had the trim cable
> fully installed before and am running into various problems that
> have me reconsidering things.
>
> The manual trim has the advantage that it is not electric - no
> wiring, no dependence on the electrical system. I also like the
> very positive connection from my hand to the trim tab. But, (I'm
> guessing here) the electric looks like it's a lot easier to
> install. It's probably also a lot lighter. Though, I've heard lots
> of stories about the servo's running away.
>
> Have any of you converted from manual trim to electric? Is the
> electric easier to install/live with?
>
> --
> Tom Sargent
>
>
