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The first thing I would check for is a leak in the pitot pressure line. Pump up the pitot and see if it holds pressure (don't forget to cover the drain hole in the pitot if it has one).
The second would be partial blockage in the pitot probe ahead of the drain hole. You could do a quick check by covering the drain hole and repeating the airspeed check with the other guys (obviously no precip!). Or just run a pipe cleaner through it from the back side.
If you cover the drain hole, use some tape that is easy to spot. I just found some gray duct tape on my pitot from the avionics shop!

Kari J. Seppanen

Flight Test Engineering Analysis

Aerodynamic Performance Group

N909RC Beech E33C

-----Original Message-----
From: Frank Gorham []
Sent: Tuesday, September 10, 2002 6:40 PM
To: IAC Acro List
Cc: Kevin & Joni
Subject: [Acro] Airspeed indicators read way low?
Just out of annual condition check.  Airspeed indicator in both cockpits (Acroduster Too) read low.  10 mph too low at pattern speed (100 reads only 90), 25 too low at flat out level.   Verified the readings with two other planes in formation.  Where to start, find and solve?  Suggestions?  Cheers,  Frank

© Dr. Günther Eichhorn
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