View Full Version : Altimeter Accuracy

LD Max
3rd Dec 2006, 15:26
For a commercial flight, I understand that the accuracy of the altimeter should be verified during the pre-flight checks on the ground to within +50 and -75 feet.

Where do these figures come from, i.e. is it JAR, CAA, ICAO or what?

A direct reference would be helpful.


3rd Dec 2006, 16:33
Probably JAR-OPS 1

Had a quick look but couldn't find it.#
Try a search on the CAA web site

LD Max
4th Dec 2006, 11:10
Thanks for looking, but done that. Spent about 3 hours googling for it too, before trying here...

I'd be interested to know how the figures were calculated also...

4th Dec 2006, 11:32
It may be to do with RVSM, rvsm (http://www.ecacnav.com/downloads/TGL6rev1.pdf)

4th Dec 2006, 11:56
From my recollection the right seat altimeter compared with left seat altimeter shall be within 50' and each shall be within 75' of ground elevation, at PRE-START. For RVSM max diff is 200' in RVSM airspace IE above FL290.

4th Dec 2006, 13:12
LD Max, I went through the same evolution a few years back. All I found in documentary form was in PANS-OPS, as follows:

“A serviceable altimeter will indicate the height
of the altimeter in relation to the QFE reference point
within a tolerance of +/- 20m or 60 ft for altimeters
with a test range of 0-30K ft”
PANS-OPS Vol 1 Pt VI, Ch2 para"

I looked in JARs but discovered that the limits were in JTSOs (Joint Technical Standards Orders), but that JTSOs hadn't actually been written yet! So I felt free to rewrite our SOP according to ICAO.

There are other standards in there for altimeters with a greater range also.

LD Max
4th Dec 2006, 18:17
Thanks Guys.

Flight Detent
5th Dec 2006, 09:27
'LD Max' -

for me, it's in the B737NG FCOM, Volume I, under Limitations.

Cheers, FD :E

5th Dec 2006, 10:43
'LD Max' -
for me, it's in the B737NG FCOM, Volume I, under Limitations.
Cheers, FD :E

Ohw nice, so for an A320 or a B747 it is not applicable.:mad:

5th Dec 2006, 14:49
for altimeters rangeing from 0-30000 it should be 60'. And with a range from 0-50000 it should be 80'.


5th Dec 2006, 17:38
It has to do with RVSM,and it's a predeparture check that you have to do.At cruising level the difference must be less than 200'.