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Old March 11th 07, 05:39 PM posted to rec.aviation.owning
Mark Hansen
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Posts: 420
Default Mode C is reading high....

On 03/11/07 07:49, Dico wrote:
Hello,

I've noticed during a flight the other day to Columbus that our Mode C
was reading high... by about 250 feet. The altimeter seems to be
indicating fine as on the ground, with the correct altimeter setting,
it shows the correct altitude. As well, flying the ILS, i make a habit
to check the altitude when crossing the FAF and it is correct too.

Any thoughts on what the issue is?


The transponder uses its own altitude encoder, not the plane's altimeter.

I think there's a regulation which states that the transponder must be
within 100 feet of actual pressure altitude, so you probably should have
it looked at.


Thanks,

Dico




--
Mark Hansen, PP-ASEL, Instrument Airplane
Cal Aggie Flying Farmers
Sacramento, CA