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<< Lancair Builders' Mail List >>
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In a message dated 7/31/2001 9:18:23 PM Pacific Daylight Time,
lancair.list@olsusa.com writes:
<< Do you have anything else connected to the gear up circuit ? >>
This brings to mind Tim Ong's excellent landing lights. These babies are
clamped to the landing gear leg and should not be on while the gear is in the
wells. Consequently, Tim has designed a circuit with relays and whatnot
intended to keep power off the lights while the gear microswitches are open.
I have not studied Tim's circuit, nor anyone else's circuits which depend on
the state of the landing gear (a two-speed elevator trim circuit comes to
mind as it was discussed in this forum years ago). I'm not saying that Tim's
or the other circuits can gererate a sneak circuit of the type Sven alludes
to. However, it's more "stuff" hanging off the gear circuit, which I wanted
to avoid.
I replaced my SPDT gear down switch with a DPDT switch (from Pacific Coast
Avionics, I think). I use one pole for the gear up-down circuit in the usual
manner. I use the other pole to interrupt power to the landing lights. This
replaces the relay in Tim's circuit. They are two completely isolated
circuits, except for the fact that they share different halves of the same
switch. (Oh, yes. There's a separate "landing light on-off" switch in
series with the landing gear switch -- the landing gear switch simply ensures
that the lights are not on while the gear switch is in the UP position)
If I were so inclined, maybe I could leave the landing lights switched on and
wait for the glowing wings to indicate that the gear switch was DOWN but the
gear was still in the wells....or put a plexiglass plug in the wing skin
(like the BD-5 fuel gauges) and if the plug is glowing, the gear's up....but
I won't.
- Rob Wolf
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LML website: http://www.olsusa.com/mkaye/maillist.html
LML Builders' Bookstore: http://www.buildersbooks.com/lancair
Please send your photos and drawings to marvkaye@olsusa.com.
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