"K.P. Termaat" wrote in message ...
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


That seems to be exactly the opposite of what would be required by
most pilots.
There is no hazard associated with having the airbrakes unlocked when
the glider is not in motion. The hazard starts when the airspeed gets
high enough for the airbrakes to suck open if not locked.

Cambridge 302 alarms at about 25kts (not sure of exact figure) if
airbakes not locked. I hear it on about half my launches with ballast
as I use airbrakes for better roll control.


Andy