Message-ID: <006901bf617e$8cdb0240$2331143f@oemcomputer>
Reply-To: "dfs" <dfs@gateway.net>
From: "dfs" <dfs@gateway.net>
To: "Lancair List" <lancair.list@olsusa.com>
Subject: Navaid
Date: Mon, 17 Jan 2000 22:37:52 -0800
Mime-Version: 1.0

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To Jim Olson's request about Navaid autopilots.

Hi Jim, I've got a Navaid installed in N235SP with the VOR and GPS connected
to the "Track" position of the selector switch. The signal out of the CDI
and GPS (DC, about +/- 150 millivolts max deflection, I think) are routed
thru a selector switch so I can track either at the flip of a switch. Did
some experimenting at my old home-base, Torrance, Ca and found the Navais
would track down the Localizer better than I did.

One thing that was a bit disconcerting was the unit's tendency to track up
to a mile off the actual planned ground path. Seems,with a unit as
un-sophisticated as this, your aileron trim settings will affect how far
from the desired path you will settle down. It's not much of a big deal, you
just have to know what's going on.

I found that at least a wing leveler was imperative on any cross-country
trip where I needed to consult a chart or airport data book. Without it, I'd
spend no longer than 20 seconds with my eyes down on the map or book and
when I looked up the damned horizon would be over at maybe 30 or so degrees!
With the Navaid on "wing leveler", once carefully trimmed in pitch, I could
check the charts or data book at my leisure and upon looking up, things
would look pretty much as I left them. (Before all you guys out there get on
my case about flying with my eyes inside the cockhouse, sometimes you just
have to look at a chart or data book - helps when you need to know what
frequency to dial up to get ATIS or call the tower).

I mounted the servo under the passenger seat about 8 - 10 inches behind the
rear of the main spar (the only place I had room) and had an extension shaft
made that extened forward to the spar web, where I mounted a bearing for the
forward end. the shaft had an arm welded to it to drive the aileron
push-rod. The push-rod went straight thru the same hole used by the main
aileron push-rod and connected, in a straight line, by the way, to the
aileron mid push-rod coupler. This way, I didn't have to worry about the
fore and aft translational movement of the stick.

When all is said and done, I'm quite pleased with the unit. Just be sure to
install the diode that freezes the unit during transmitter keying or you
will get an unsettling "Twitch" in roll when you hit the "Transmit" button.

No altitude hold on a unit like this, of course, but for a small Lancair,
who needs it?

Dan Schaefer

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