Compressor Stall you fail again. If the QNH at 0200 is 1010 and the QNH at 0500 is 1011, then by linear interpretation as per the AIP, the QNH at 0330 is 1010.5. Do you use 1010 or 1011 and can you provide a reference that justifies your answer, being aware that your previous assertion was incorrect. And yes it is academic but academic is what is required when doing exams. In real life, it makes no discernible difference.