Low cost air speed indicator.

      Not compensated for temperature or altitude.

      Useful in the back seat of a tandem aircraft without
      a rear instrument panel.

      It is a simple water manometer 20 inches high.

      Paul Lamar


Since one is most interested in accurate airspeed when on final, would
the errors tend to cancel out changes in aircraft performance due to
temperature or altitude?

If the air was denser, the manometer/altimeter would read a higher
airspeed (correct??), so the pilot would unknowingly allow the aircraft
to fly slower to "normal" indicated airspeed.  But when the air is
denser, the aircraft will also fly slower/ground effect will increase/
etc, and the pilot should be able to make a safe "normal" landing.

Or am I thinking backwards here?

Robin B

I am not sure I understand what you are saying "changes in A/C performance".
Do you mean stall speed? I have heard of a small airline pilot in
Mexico that would stall the old twin piston engine airliner (at altitude) just before landing on a short dirt strip to make sure he landed it as slow as possible.


Paul Lamar