transponders 91.217, and 91.413

91.413 specify a 24 month check even if used for VFR only for the
transponder to report accurate altitude

AIM 7-2-3, check altimeter against know field elevation and baro setting, if
difference is greater than +/- 75ft from the known elevation. The altimeter
accuracy is suspect and should be reported to a repair station for
evaluation and correction.

The altimeter and transponder must be checked every 24 months for operations
in IFR. (91.411)

That is the only VFR "check" of the altimeter that I have found tonight. But
if the altitude or altitude reporting function (blind encoder) reports
altitude to the transponder, it must be checked every 24 months. If you
don't have a transponder, and you never fly IFR, if the baro setting
displays within 75ft of field elevation. It's "good to go".

BT

"Eric Greenwell" wrote in message
...
BTIZ wrote:
it better be... if the transponder is installed..
BT

"Stefan" wrote in message
...

BTIZ wrote:


you do.. you listen to the local ATIS or ASOS or AWOS or check with FSS
or ATC on freq and find out what they are using in the local area

I've yet to see a glider with an accurately calibrated altimeter.

When I had my biennial check on my transponder, there was no check of the
altimeter. They did adjust the encoder to read the current pressure
altitude. I know there are strict requirements for encoder and altimeter
accuracy for IFR flight, which requires testing the encoder and altimeter
up to the altitude they will be used in. Is there some regulation
requiring an aircraft with a transponder used in VFR flight to also have
an altimeter calibration? I don't think Mode C is required, so perhaps the
regulation, if there is one, applies only if an encoder is installed?



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Eric Greenwell
Washington State
USA