Bill,
Here is one:
I believe it has NC and NO contacts so it could be used as both an air
driven squat switch and as a gear warning device at certain fixed
speeds.
Others have used an adjustable washing machine water level switch although
I'm not sure how it would be plumbed.
Mcmaster-Carr also has some inexpensive pressure differential switches
(pitot/static):
Remember that low airspeed = low pressure differential.
|
|
Pressure in Units |
| IAS mph |
Knots |
"H2O |
"Hg |
PSI |
|
|
|
|
|
| 40 |
34.8 |
0.79 |
0.06 |
0.028 |
| 50 |
43.4 |
1.23 |
0.09 |
0.044 |
| 60 |
52.1 |
1.77 |
0.13 |
0.064 |
| 70 |
60.8 |
2.41 |
0.18 |
0.087 |
| 80 |
69.5 |
3.15 |
0.23 |
0.114 |
| 90 |
78.2 |
4.00 |
0.29 |
0.144 |
| 100 |
86.9 |
4.94 |
0.36 |
0.178 |
I am sure there are circuit board suitable differential pressure sensors
used in AOA systems and in certain air/data computers.
Here is one:
The now discontinued Rocky Mountain Instrument's micro-encoder has a
speed that could be set for annunciating a gear warning.
Advanced Systems AOA also has a gear warning mode.
Good Luck
Scott Krueger
In a message dated 1/16/2010 7:29:17 A.M. Central Standard Time,
bill_kennedy_3@hotmail.com writes:
I'm
going to build the gear not down warning system suggested by Randy Stuart in
an earlier email. I thought Aircraft Spruce had a airspeed sensing switch, but
I couldn't find it in their catalog. Can any of you help me find a source for
the pressure switch?
I've never had a close call with the gear in three
plus thousand hours of retractable time, but I've always been a little uneasy
with no warning system in my LNC2. I had hoped that I could talk Blue Mountain
Avionics into building a warning system into their EFIS, but that didn't work
out. Randy's system looks great to me and I'm eager to try it. I've attached
Randy's drawing just in case others might want to revisit the
idea.
Thanks -- Bill Kennedy
=
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