REFLECTOR: TAS calibration?

[Geoff Gerhardt]

Guys,

Flying today I realized that my ground speed seems to be always greater
than my TAS.  I figured at least some of the time it should be less (i.e.
into a headwind).  But it always seemed to be greater.  So, today, I flew
in a box, E, W, N, S and recorded my TAS and GS.  My TAS was constant at
159ktas on each leg, and my GS (GPS) was 185, 179, 171, 175 for the W, N,
E, S legs.  If I add all those up and divide by four, I get 177.5kts, yet
my TAS registered 158ktas.  Am I missing something?  Is my airspeed
indicator reading too low?

Thanks.

Geoff
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