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ACRO E-mail Archive Thread: [Acro] RE: Airspeed indicators read way low?

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ACRO E-mail Archive Thread: [Acro] RE: Airspeed indicators read way low?


Thread: [Acro] RE: Airspeed indicators read way low?

Message: [Acro] RE: Airspeed indicators read way low?

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From: "Seppanen, Kari J" <kari.j.seppanen at>

Date: Wed, 11 Sep 2002 02:26:46 UTC


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

kari.j.seppanen at

N909RC Beech E33C

-----Original Message-----
From: Frank Gorham [mailto:frankgorham at]
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,
Attachement 1: part2.html


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