QNH 1050

[A320LGW]

Current qnh at some fields in England have reached 1050. I understand this to be the limit for many aircraft altimeters. Any ideas what happens if it exceeds to 1051? Also i believe there is a regulation prohibiting ops in pressures exceeding 1049.8hpa.

[pineteam]

Hello,
I just checked in the FCOM for A320 and there is a procedure for operations at QNH above 1050. You can find it in PRO-SUP- miscellaneous: Operations at QNH Above 1050hpa.
I’m not familiar at all with this but they explained this is due to engine limitations on the nacelle and thrust reversers.
I would be interested to know more about it. =)

[champair79]

For the A320 family, it’s in the FCOM.

PRO-NOR-SUP-MISC - “Operations at QNH above 1050hPa”.

Essentially you have to check whether you’re exceeding the flight envelope of -1000’ based on STD.

Otherwise, the procedures vary slightly depending on the fit of the aircraft. The old standby altimeters have to be set to 1050 or less with some mental maths added (in 100s of feet). The ISIS fit aircraft can all be set up to 1100hPa (although you’d likely exceed the flight envelope before getting anywhere near that!).

There is a slight amendment to the way the PERF page is set up and possibly a transponder procedure to apply too.

champ