by reducing them to the same datum. The actual PFD altitude for the first check was 20 feet while the standby was 100 feet, for example. This is in fact outside tolerance for the altimeter system, according to the FRM
While I don't fly the 744, the Australian AIP requires altimeters in
any IFR aircraft to agree within 70 feet. I don't know the specific tolerance for the 744, so I said
if they were out of tolerance, they should have been written up. It was you who suggested that they were.
The comment about the altimeters reading the same
regardless of whether or not one is corrected for temperature applies because the aerodrome QNH
has been corrected for temperature up to the airfield elevation.
If you are sitting at the airport, and you have the airfield QNH set, then all altimeters have to read within tolerance
regardless of whether or not one is corrected for temperature!