Probably my explanation was not good enough. The airbrake microswitch and
the switch of the pressure transducer are in series. However with no
pressure (glider on the ground) the switch of the pressure transducer is
closed and opens reluctantly when pressure comes on (glider rolling for take
off). So this system gives a warning for airbrakes unlocked (or open) prior
to take off; it does not give an alert when flying with normal speed and
airbrakes open.
See my figure 5 of http://home.wxs.nl/~kpt9/gear.htm

Karel, NL


"Eric Greenwell" schreef in bericht
...
Todd Pattist wrote:
"K.P. Termaat" wrote:


The solution for a warning on air brakes unlocked prior to take off is
quite
easy. Use a micro switch on the air brake handle and a pressure
transducer

from a washing machine in series.

I'm confused as to why you need a pressure transducer. Just
put a microswitch on the Tost that detects the presence of
the towring, and wire that in series with the existing
sensor on the airbrakes. The airbrake sensor provides power
to both the gear sensor switch and the Tost sensor switch.
They both send power to the buzzer. If the brakes are
opened with the gear up or the ring inserted, your buzzer
goes off. Conversely, if the brakes are open and the ring
is inserted for the tow the buzzer sounds. Why wait until
you are rolling or in the air to sound the buzzer?
Todd Pattist - "WH" Ventus C
(Remove DONTSPAMME from address to email reply.)

The pressure sensor would be great for a self-launching sailplane. It
would also avoid alerting when the pilot had the spoilers open purposely
at the start of the launch, as some pilots do to avoid wing drop or
running over the towrope. An alert in those situations might not be a
bad thing, as it would test the system, and the pilot would be fully
aware that he was causing it.
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Eric Greenwell
Washington State
USA