Kelvin,
The switch is a pressure switch. With the relative wind nearly straight on
the air into the tube is under suction. The switch is assembled to the ho
se to the leading edge using its pressure side. The switch is normally ope
n so with suction on the tube, the light is off at low angles.
At about 14 degrees angle of attack the switch is now under pressure from t
he ram air. The switch is normally open and at about 3 inches of water ish
, the switch will close and allow current to flow to the light/horn.
Once you land, and the speed diminishes, the pressure drops and the switch
opens and the horn goes off.
Not rocket science.
See photo below:
Regards,
Bud Yerly[cid:image001.png@01D2F05D.21C06F50]
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s 10
From: Kelvin Weston<mailto:kelv@kdweston.biz>
Sent: Tuesday, June 20, 2017 5:03 PM
Subject: Europa-List: Re: Stall Warner - switch problems
Hi Bud and all
Now I am really confused. I have fitted the Europa stall warning mod and sw
itch but not yet used in anger.
How is this switch designed to work?
Is it normally closed and held open by pressure above a certain speed.
Or is it normally open and is closed by low pressure (vacuum), like a conve
ntional Cessna stall warner, caused by the angle of the wing.
The mod leaflet suggests it is operated by vacuum, but your description of
it being on until above a certain speed suggests the first option.
The switch has a hose connection to both sides of what I assume is a diaphr
agm, so it is easy to connect incorrectly.
If it is normally closed then does that result in the buzzer operating cont
inually on the ground until above the stall speed?
I think that would eventually get to be a bit of a pain, especially during
long holds on the ground.
--------
Regards
Kelv Weston
Kit 497
kelv@kdweston.biz
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