Date: Mon, 21 Sep 1998 12:19:37 -0400
From: Lynda Frantz <LFrantz@compuserve.com>
Subject: Flap relays
Sender: Lynda Frantz <LFrantz@compuserve.com>
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A few comments on the 320/360 electric flap system and in particular the
system where the push link passes through the aft spar.  

First it is critical that the limit switches always work perfect.  An over
extension of the flaps could bend the push link and result in asymetrical
flaps.  This is a bad thing.  Although aysemitrical flap problems have been
rare on the Lancair there have been two reported incidents  which resulted
in crashes.  Fortunately both occured in ground effect and the pilots
walked away without a scratch.  It is imperative that the push link not
bind in the aft spar hole.  This too could cuase a bending moment on the
link causing it to fail resulting in asymetrical flaps.

Now back to the electrics of the flaps mentioned in Dan Schaefer's post.  
I eliminated the flap relays totally and replaced them with two small but
electrically big diodes.  I also  got rid of the magnetic position sensors
which I did not trust and their associated heavy cover etc.  The circuit is
simple and uses two diodes rated at 6 amps continuous and 50V, two standard
microswitches used as the travel limit switches and one double pole 3
position flap switch is all that is required.  The nice thing about the
circuit is that it retains the braking feature by putting a short across
the flap motor when the flap switch is moved to the OFF/Brake position
forcing the flaps to stop rather than coast.  I figure I saved about one
pound with this installation.

The big inductive loads as mentioned in Dan Schaefer's previous post are
infact real.  The braking feature which puts a short across the motor prior
to it coasting to a stop produces perhaps hundreds of amps briefly.   I got
them at a surplus store for $.10 each.  Digikey stocks similar diodes.  To
be safe I would use diodes rated even higher than mine.

I was reluctant to put this aproach out because it is rather crude and any
change to the flap system is critical.   But  it has worked perfect so far
on both my and George Stevenson's Lancair 320's for the past three years. 
I'll try to get Lynda to find room in the Dec/Jan  Lancair Network News for
this circuit too.

Jim Frantz
Lancair Network News