NG Altimeter tape ramping

[Jambo Buana]

On several occasions now I have witnessed the ALT tape wind down at an alarming rate by 1 or 2000 feet. It happens very quickly then seems to rectify itself. Has anyone seen this on this or other types, and do you know if it was 'fixed' and if so what was the actual problem?

Could this ramping down of the altimeter cause false EGPWS alerts?

[Shaka Zulu]

i've seen it happen before, went from 41000' to 0' and back. attributed it to a mobile phone in the aircraft going off. asr'd it and fcr'd it but no follow up as of yet.
rgds
SZ

[Wings Of Fury]

Wouldn't have been the Captains mobile would it?!:=

[BackPacker]

Speculating here. The aircraft is parked on the ramp and depending on the wind direction, the wind may actually blow directly into the static port instead of sideways along it. 1000' or 2000' of altitude only requires 33-66 mbar of pressure differential.

Not an airliner specialist, but I seem to recall that the LHS and RHS have different static ports, each on their own side of the aircraft. If so, a gust of wind from, say the right side of the plane would increase the pressure on the right side, thus forcing the AI to show a higher pressure = lower altitude for a few seconds, while the LHS would have a lower pressure = higher altitude.

Jambo, would that be consistent with your observation?

(Still does not explain a 41.000' excursion as reported by SZ tough.)