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Somebody on the list once gave a formula or a conversion method to take
airspeed and convert it into units of pressure.
Due to my gear up landing I want to fit a pressure switch in the pitot line.
I need to know how to convert airspeed into pressure units in order to buy
the correct switch. Electronics catalogs have adjustable pressure switches
at under $20.
The "dynamic pressure" measured by a pitot tube, relative to the static port,
is:
Q = 0.5 * rho * V^2
Where rho is the density of air, and V is the forward speed.
In reasonable units (approximating 200 kts at sea level),
Q = 0.5 * 1.225 kg/m^3 * 100 m/sec = 6125 Pa
in screwy american units, that's 0.888 psi.
If you want the gear warning to come on below say 80 kias (~40 m/sec),
then Q = 980 Pa = 0.142 psi.
- bob mackey
flying a 235
building a 320
103MD -at- pure-flight.com
[use this email address - the one at the top is spam bait]
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