Mk V Altimeter adjustment

I am in the process of deciding whether to create an adjustable animated altimeter dial for my FSX F2B. The Bristol used a Zenith Mk V.

I am unsure as to how the adjustment functioned in these early aircraft. I gather the altimeter dial itself rotates. What was it adjusted to.... height of the starting airfield.... barometric pressure? FSX and FS9 altimeters adjust to barometric settings.

Any assistance would be greatly appreciated.

[FlyXwire]

Originally Posted by robby88

I gather the altimeter dial itself rotates. What was it adjusted to.... height of the starting airfield.... barometric pressure?

Hi Rob,

The Mark V altimeter is an aneroid barometer, that responds to atmospheric air pressure, and the instrument was calibrated to reference standard barometric pressure from mean sea level. The height indicator is always adjusted to zero at the airfield GL before flight.

[Taz]

robby88- There have been two types of altimeter settings used for decades, QFE and QNH. QFE assumes field elevation is zero and would obviously only be used by nations where their airfields are very close to sea level (read UK). So without a local barometric pressure setting you could set the altimeter to zero before take-off and be close when you landed a couple of hours later. If you landed somewhere else, no problem if you had a radio and could get the local QFE setting. FlyXwire's drawing shows the disadvantage if you use QFE and cannot update it because of no radio. For QNH with no radio, you would set the actual field elevation before take-off and be good anywhere you flew (unless a large change in barometric pressure occurred or you flew a long distance). QNH was used by nations with a large difference in field elevations and with field elevations way above sea level, such as the USA. The UK stubbornly held on to QFE until at least the early eighties when I first flew F-111Fs there. By then most airfields would give you either a QNH or QFE altimeter setting as requested. Do not know if they still use QFE in the UK or not.

Taz
Terry Phillips

Thanks Dave & Taz