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3 – general i nformat i on
Note: Where the first check indicated that an altimeter is unserviceable, the
pilot is permitted to conduct a further check at another locationon
the airfield; for example, thefirst on the tarmac and the second at the
runway threshold (todetermine altimeter serviceability).
VFRALTIMETERS
With an accurateQNH set, a VFR altimeter(s) should read siteelevation to
within 100 ft (110 ft at test sites above 3300 ft) to be accepted as serviceable
by the pilot. If an aircraft fittedwith twoVFR altimeters continues to flywith
one altimeter reading 100 ft (110 ft) ormore inerror, the faulty altimetermust
be placarded unserviceable and the error noted in themaintenance release.
VFR altimeters are not permitted for aeroplane operations aboveFL200. VFR
flights operating above FL200must be equippedwith an altimeter calibrated
to IFR standards.
ACCURATEQNHANDSITEELEVATION
AQNH can be considered accurate if it is providedbyATIS, tower or an
automatic remote-reporting aerodrome sensor. Area or forecast QNHmust
not be used for the test.
Site elevationmust be derived from aerodrome survey data published by
Airservices or supplied by the aerodrome owner.
GENERAL
Heightsmeasured from aQNH or AreaQNHdatummust beexpressed in
full, e.g. 3000 ft as ‘THREE THOUSAND’ and1800 ft as’ONETHOUSAND
EIGHTHUNDRED’ adding, if necessary, ‘ON… (QNH)’.
Expressions of heightmeasured from the 1013.2HPa datummust always
include thewords ‘FLIGHT LEVEL’.
Flights cruising at or below the transition altitudemust change theArea
QNH altimeter settingwhen advised of a change byATS. Pilots of aircraft not
using radiomust use theQNH setting obtainedby setting the altimeter to
aerodrome elevation before take-off.
altimeter setting rules