Altimeter tolerances NZCAA
 

Looked through all the NZ rules (I'm probably just blind) but couldn't seem to find specific mentions to tolerances of the altimeter for VFR or IFR 91 or 135 operations? Is 50 ft out ok? or 75 ft? or...???
Whats the max allowable difference between two altimeters? Anyone have any idea where to actually find the answer in the rules/ac?

Cheeeeeeeeeeeeers

Part 43 Appendix D sets out the limits for altimeter accuracy during the altimeter tests - it is what is used to test in service as well.

Specifically Table 1 on page 41.

Tolerance is, for example +/- 20ft at 0. Difference between altimeters can be max 40ft as one may be -20ft and one +20ft but both must still be within +/- 20ft

I saw that but I just assumed that that was only for bench testing or something. So just to clarify if the altimeter is more than 20 ft out at sealevel compared to elevation then its unserviceable? Seems pretty conservative

Yep - but those are the tolerances - unless there is soemthing different in your flight manual, or your ops manual.

If you snag it, those are the figures a LAME will use to give it a yay or nay.

Those are far more strict than the Aus AIP tolerances.

They don't make a lot of sense from a practical point of view. Given 30'/ hPa you could easily hit or exceed the tolerances just from rounding of the QNH.

Not the best example, 20 ft at sea level.... If it is out at sea level when set to the actual QNH, you simply adjust it. If it's out at the higher levels, either throw it away and buy a new one or send it in for an expensive repair.