Why are TE probes so long?

D B wrote:
Why is it, then, that you can calibrate a TE probe by driving down the road
with it sticking out of the window, hooked up backwards to an airspeed
indicator (static is pressure, TE is static port) and it reads the
same as a pitot probe with a normal hook up?



In article , "tango4"
wrote:
TE is opposite to Ptot, in other words TE sucks, but nowhere near equal in
magnitude.

Ian



1. ASI has two connections: static and pitot (= total pressure = static + dynamic)

2. TE probe provides static - dynamic pressure

3. ASI measures difference between ptot (dynamic + static = total pressure) and static

4. connect TE probe to static on ASI, pitot on ASI to free air (= static pressure = ambient pressure inside your car

5. therefore ASI reads dynamic pressure (linearly proportional to airspeed below 0.3 M)

But, bear in mind that unless you hold you TE probe at least about 10 feet from you car the reading will be off quite a bit, and you should also worry about the ambient pressure inside the car. Not a good way to calibrate a TE probe. Even thought of investing in a wind tunnel?

Rgds,

Derrick.