Transponder intall in an LS-4

[Dan Peters]

My partner and I are thinking about installing a transponder
in our LS-4. If anyone has done this in an LS-4, can
you send either a textual description or pictures of
the antenna installation?

We cannot use our tail battery (because of a repair),
and I wonder if we can put the antenna in that compartment.
I assume the encoder will fit somewhere behind the
instruments?

Thanks
Dan
N2YA, '45'

[Eric Greenwell]

Dan Peters wrote:
> We cannot use our tail battery (because of a repair),
> and I wonder if we can put the antenna in that compartment.

My Becker manual recommends no more than a 16 foot antenna cable, so I
think the tail mounting is not a good idea. It may be easy enough to
mount it inside the fuselage somewhat behind the landing gear. Have you
checked the DG site for installation notes or drawings? They do have
these for various DG gliders, and might also for LS gliders.

> I assume the encoder will fit somewhere behind the
> instruments?

Yes, the ACK 30, for example, is about the size of a small pocket novel.

--
Eric Greenwell - Washington State, USA
Change "netto" to "net" to email me directly

"Transponders in Sailplanes" on the Soaring Safety Foundation website
www.soaringsafety.org/prevention/articles.html

"A Guide to Self-launching Sailplane Operation" at www.motorglider.org

[[email protected]]

Dan Peters wrote:
> My partner and I are thinking about installing a transponder
> in our LS-4. If anyone has done this in an LS-4, can
> you send either a textual description or pictures of
> the antenna installation?

I think the tail battery compartment is a poor choice not only for the
coax length but also the difficulty of routing the coax.

I installed a transponder in my LS-4. The antenna (as you suggest) was
the hardest part. I considered a number of options, and finally settled
on the space behind the gear housing. You can reach that by pulling all
the cover plates behind the seat in the baggage compartment. It's a
little difficult to get at, but a medium-sized person can wedge their
shoulders into the baggage compartment and just reach the space behind
the grear housing box.

I got a sheet of alumium for the ground plate and attached it to the
top of the two partial bulkheads (which are rolled flat on top) in that
space with self-threading metal screws. Make a template out of
cardboard before cutting the plate -- you want the largest plate that
will fit the space. I used a bolt for the forward attachment to be sure
the ground plate didn't come loose in a hard landing and start rattling
around. I drilled a hole in the middle of the plate for the antenna and
mounted it facing down. Be sure to install the antenna in the ground
plate before mounting the ground plate in its fusilage space.

Another possible antenna location that I considered and ultimately
rejected is at the forward end of the instrument panel shield with the
antenna facing up. Antenna mounting and coax routing would be FAR
easier in this location, but I didn't like the idea of all that RF
energy toasting my tootsies. Of course that's exactly where the
transponder antenna is mounted in my new Ventus C. Oh well!

Another difficulty I had to work through was finding a place to mount
the transponder and altitude encoder in my crowded instrument panel.
The main difficulty was routing the serial cable between the two units
in such a way that it didn't interfere with the movement of the lever
arm that raises the canopy. I finally had to wire a completely new
cable that attached to the transponder at a right angle. You may be
able to avoid this.

The transponder has been in place for three years now. It tested out
with a very strong signal from the beginning and has been working
perfectly ever since. I fly close to Reno airspace, and I can't tell
you what peace of mind that baby brings me. I usually check in with
Reno Approach shortly after I get off tow. They have no trouble finding
me, and they often thank me for my trouble. Of course it's still Eyes
Out of the Cockpit.

If you need more help, feel free to email me directly.