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Dual Altimeters

This may be a dumb question, but why are two altimeters required in Europe vs only one in say the US, Australia, Canada etc? Or are they actually required? Presumably it is perfectly legitimate to fly an N-registered aircraft in Europe with only one altimeter....

I thought maybe it is an IFR requirement, but even basic (certified) VFR machines seem to have them

EGPD / OMDW / YPJT, United Kingdom

I'm pretty sure this is only an IFR requirement - my TB10 POH says it is certified for VFR with one altimeter, but needs two for IFR.

Having 2 is nice - you can set one to STD pressure and the other to a suitable QNH for terrain avoidance.


AFAICS, most (but not all) european countries require dual altimeters for IFR. And yes, this one is a registry thing (not airspace) so don't need dual altimeters to legally fly across Europe if your countries registry does not require it.

I never really understood the point of dual altimeters for redundancy purposes, because both altimeters are usually connected to a single static system. An altimeter is such a simple instrument, I think it is almost impossible for the instrument (not the static system!) to fail. But agreed, if your altimeter fails in widespread low IFR, that can be a problem.

I guess the authorities in the USA, Canada, etc. did not consider the very remote possibility of a failing altimeter significant enough. European authorities do not tend to have such a pragmatic approach.

Mainz (EDFZ), Germany

According to FSAV (Minimum equipment for flights in german airspace) two independent altimeters are required only for RSVM airspace. So there has to be a second static system for the second altimeter, when you want to use german RSVM airspace.

For other countries, I don't know.

fly safe!

Aufwind GmbH
EKPB, Germany

I recall reading a piece by someone I know who is very good at reading the EASA regs, that the number of altimeters, and also the number of 8.33 radios, is as per the requirements of the airspace being overflown.

Or, of course, as per the requirements of the State of Registry, if these are stricter.

Two altimeters is the norm on IFR aircraft. Also some pilots prefer to set one to QNH or 1013 (according to the current clearance etc) and leave the other on QNH.

Shoreham EGKA, United Kingdom

Two altimeters is the norm on IFR aircraft

In Europe, but this is not universal will struggle to find two altimeters on a light aircraft in the US....even IFR....just as it seems you will struggle to find any aircraft in Europe which does not have two altimeters...VFR or IFR

My question relates to whether it would be necessary to add a second altimeter to an aircraft imported from the US which is to remain on the US registry?

EGPD / OMDW / YPJT, United Kingdom

My question relates to whether it would be necessary to add a second altimeter to an aircraft imported from the US which is to remain on the US registry?

For Germany, yes, but only if you want to fly IFR and use RSVM-Airspace. So that depends a bit on the exact type of a/c.

But if you import an aircraft from the US, I guess, you'd have to buy an altimeter anyway, because of the inHg pressure scale in the US. So you may just deplace the old one and have it set to 29.92 if you like.

"N1234AB, descent 2000 ft, QNH 1009"

"Äh ... can you give me that in inches?

"N123AB, roger, descent 24000 inches, QNH 1009"


Aufwind GmbH
EKPB, Germany

Honstetly, flying IFR I would not feel comfortable without a second altimeter (at work, we have three with three independent and independently heated static sources!). I consider this as kind of life insurance. Separation in vertical direction is only 1000ft. And on ILS approaches I will go down as low as 200ft in solid IMC. A second altimeter (always set to the same reference pressure as the first one, otherwise it would be totally useless) gives me the peace of mind to operate in crowded airspaces and in close proximity to the ground.

EDDS - Stuttgart


presuming that RVSM is not a factor for you, the answer is no. Lots of smaller N-reg. Aircraft in Europe flying IFR with just one altimeter. On the other hand, an old used altimeter will cost you almost nothing.

Mainz (EDFZ), Germany

I fly an N reg aircraft, which still has just one altimeter. In the UK I presume I am flying on my JAR license because I am in the UK airspace and that has more privileged attached to it (i.e. the IMC Rating). If I fly in IMC (not necessarily following IFR rules, but VFR rules), is this legal with one altimeter? Would it make any differenc if I was flying IFR rules?

If I fly outside of the UK in my N reg then I presume I am flying on my FAA license which has no additional privileges so regardless of my one altimeter, I have to stay VFR anyhow (well until the Enroute Instrument Rating comes into effect).

Am I right, am I wrong?


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