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How low can you set your altimeter pressure...?

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How low can you set your altimeter pressure...?

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Old 13th Dec 2011, 17:22
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How low can you set your altimeter pressure...?

The pressure here is currently 950mb. In the days of pre-digital cockpits most altimeters had a physical limit on how low the pressure could be set.

Is it an issue with the current generation of aircraft?

Last edited by Biggus; 13th Dec 2011 at 17:39.
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Old 13th Dec 2011, 17:31
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Some time in the early eighties at Aberdeen we flew on the regional QNH because nobody could wind down to QFE.
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Old 13th Dec 2011, 19:03
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Smile In my years as a Nav Inst Fitter

I seem to remember that the limitation on Barometric Altimeters was in the region of 28in to 31in on yank kit or 950mb to 1050mb on our good old British stuff don't know about glass cockpit but it was all to do with the amount you could flex or compress the pressure bit inside the altimeter.
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Old 13th Dec 2011, 20:16
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I beleive the new Met Office barometers (digital) are caliberated down to at least 890 hPa.
 
Old 13th Dec 2011, 20:43
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Just who is Hector Pascal, and why are we letting a Frenchman run the weather?
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Old 13th Dec 2011, 20:48
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Particularly since he rudely muscled in and put Millie Barr out of business.
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Old 13th Dec 2011, 20:49
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The QFE at KAF is regularly in the 890 region - well below the limit of my old altimeter
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Old 13th Dec 2011, 20:50
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Particularly since he rudely muscled in and put Millie Barr out of business.
I don't think that he even tried to negotiate!
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Old 13th Dec 2011, 20:50
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Just who is Hector Pascal
Apparently he's a black and white coloured Irish greyhound and is very good at forecasting the weather. On good flying days he can be found scratching to get out of the crewroom. On days where the weather is looking a bit iffy, he's generally found slumped by the door staring out of the window. And on days where it's really bad, he can usually be found sitting by the beer fridge barking at it.
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Old 13th Dec 2011, 20:53
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Puts me in mind of the Bungling Baron's pet whippet.
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Old 13th Dec 2011, 20:56
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Surely the point is moot. If the pressure in the uk is 950 I thought your biggest issue was keeping the doors on the hangar much less worrying how to work out how high you are.
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Old 13th Dec 2011, 20:56
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Dusting off the brain cells, wasn't QNE used once the pressure fell off the bottom of the dial? Seem to recall it was 940 or 945mb. St. Mawgan recorded 948 during the Oct 87 storm.
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Old 13th Dec 2011, 21:13
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Physical limit

Biggus

In the days of pre-digital cockpits most altimeters had a physical limit on how low the pressure could be set.
In search of the physical limit i turned down the Smith KAA 1803 from year 1968 klick on my desk. I stopped 5.000 feet below sealevel at about 750 mbar, as my fingers turned sore.

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Old 13th Dec 2011, 22:33
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Airbooses go down to 745mb and up to 1050/1100mb depending on MSN/type
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Old 14th Dec 2011, 01:46
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Airbooses go down to 745mb and up to 1050/1100mb depending on MSN/type
Ditto with most Boeings I have flown, but for a while we had some 737s that would only go down to 950mb. That occasionally became an issue.
Lowest I have set personally is 932mb (the center of the low pressure system was estimated at 928mb), highest 1047mb, at the same airport.
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Old 14th Dec 2011, 08:23
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One of the reasons why civil airfields use QNH instead of the more logical QFE is to ensure common settings at all terrain altitudes.
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Old 14th Dec 2011, 09:29
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I don't know why but back in the days of the CAA ATPL exams before all this fangled euro thingy, one of the exam questions was the range of an altimeter's setting on the mb scale and the answer was 950-1050. Thanks PPSC you may be gone but you engrained some pretty useless stuff in my memory...... if only I could remember to read the wind of the ND when selecting flap 1 these days..............
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Old 14th Dec 2011, 10:51
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About a Dachshund...oh sorry wrong question!
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Old 14th Dec 2011, 11:40
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I think it's just a trans-gender issue! You never see Hector or Millie in the same place. If you ask me, I think they're the same ........person
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Old 14th Dec 2011, 14:09
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On the C130J the main (HUD) altimeter goes down to 951mb & the standby all the way down to 745mb.
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