Primarily for general aviation discussion, but other aviation topics are also welcome.
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By Flying_john
#1838225
Ask your LAE or Inspector to bring his pitot static test set to the airfield and check altimeters and transponders to a known good calibrated piece of equipment and make sure you have an external static source unaffected by turbulent airflows.
By rainbow462
#1838227
Thanks for the replies

I'm observing the FL from the transponder screen. Also when I check back FR24 it matches what I saw in flight. Finally using getyourwings software and a polotaware base station I can it is receiving the ADBS signal and the altitude is significantly out e.g. -600'

I'm assuming the TRT800H has a built in encoder.
The static port at the back is not connected to the altimeter/external port and is just is open in the back of the dashboard
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By Jonzarno
#1838249
I’m not sure that the conversion is always infallibly accurate.

I have repeatedly, but not on every flight, had a problem when flying the ILS into one particular airport in Germany (only there and nowhere else!) of ATC telling me that I am 200 feet below my actual altitude based on my mode S read out.

I stress that this does not happen in any other sector, and I have confirmed that my transponder encoder is properly calibrated and both my altimeters show that I am at my assigned altitude. It has happened often enough on the sector for me to point this out to controllers each time it happens.
#1838256
rainbow462 wrote:Thanks for the replies

I'm observing the FL from the transponder screen. Also when I check back FR24 it matches what I saw in flight. Finally using getyourwings software and a polotaware base station I can it is receiving the ADBS signal and the altitude is significantly out e.g. -600'

I'm assuming the TRT800H has a built in encoder.
The static port at the back is not connected to the altimeter/external port and is just is open in the back of the dashboard


It will not work properly unless plumbed to the same static pressure as the altimeter.

I would suggest you get the system checked over and sorted properly before it gets you into trouble.

On a similar note, there are likely a bunch of the new crop of carry-on EC devices with similar cockpit static/ altimeter static pressure discrepancies.
By PeteM
#1838310
I've been down this route recently.

Transponder and altimeter disagree.

Wander around the hangar and discover that my altimeter disagrees by about 3-5 millibars (although a lot more for one!).

Nice new altimeter. Transponder still disagrees - although by somewhat less! Check all the static lines, renew a couple of bits of brittle plastic tubing - still not quite right - recalibrate blind encoder. Bit shocked that without the external static, the altitude error is over 300ft!

All agree! (well generally the digitalisation does mean they are not quite 'in step'). But the surprise was this all happened over less than a year - surprisingly quickly for instruments to drift.

(and yes the LAA do not work to ICAO tolerances) which started this whole business off after a new radio!)