I cannot remember having such a string of high pressure systems over western Europe for such a long time either, particularly at this season.
at my home base: EDFM Mannheim/City METAR EDFM 280850Z VRB02KT 9999 SCT029 00/00 Q1045=
Just checked my kneeboard notes from yesterday, Farnborough gave me Q1045 at around 1100. Most everywhere else it was Q1044 throughout southern England all day. I took off from Southend at -FL008!
It’s the first time I’ve been unable to validate the altimeter reads +300ft for +10hPa as the subscale doesn’t go up to 1054!
validate the altimeter reads +300ft for +10hPa
What on earth is that supposed to achieve? Are you checking if somebody sneaked into the instrument overnight and changed the gear ratio between the knob and the dial? Or are you trying to find missing teeth in these little cogs, so it doesn’t catch you out when adjusting the instrument later (in which case, exercising it through the expected QNH range and 1013 would be more sensible)?
Or are there really failure modes in an altimeter that this check will find?
I was taught about this test in some IR theory, but don’t remember where or when.
I think it is just supposed to check that changing the QNH by 10 changes the altitude readout by 300 or so. I have no idea whether this is a plausible failure mode of the mechanism but it would not surprise me if it was… consider the extreme case of the knob being totally disconnected internally but still driving the subscale (and the “pilot” adjusting it not noticing the needle is not going around ).
Probably written by the same kind of instructor that insists on doing the VOR needle deflection checks (you know the ones – tune a VOR, center the needle, and then turn the OBS to -10 / -5 / +5 / + 10 / +180 and check the needle moves appropriately) on an EHSI, just because that’s the way it is done on the old analogue displays he grew up with.
I have no idea whether this is a plausible failure mode of the mechanism but it would not surprise me if it was… consider the extreme case of the knob being totally disconnected internally but still driving the subscale (and the “pilot” adjusting it not noticing the needle is not going around ).
It would be some kind of a big coincidence if in that case the altimeter would still show the correct airfield elevation… The only altimeter test I have ever heard of (or performed or taught) was to either check that the airfield elevation is shown when QNH is selected and that mutliple altimeters do not differ by more than the allowed tolerance.
I have been taught the +- 10hPa check by several instructors over the years and it was expected in the IR test. Never considered what failure mode would be flagged by that check. Will discuss with my old IR instructor next time paths cross, as he was always urging to drop unnecessary checks but never called me on that one.
Might be more relevant in the rental sector, perhaps?
Of course, +- 10 from QNH is probably a pretty realistic differential for any flight I’m likely to undertake, so it is exercising the likely range of use (1013 aside).
Never heard of that. Seems to be yet one more if those UK instructor/examiner fetishes.