converting inches to mb

[Sam Rutherford]

Does anyone know of a slide-rule/whizz wheel out there for this?

Something that both does the calculation, and leaves a reminder of the 'other' setting - but not calculator and scrap of paper?!

Thanks, Sam.

[Chilli Monster]

Any good IFR Flight Guide (Jeppesen, AERAD En-Route Supplement, RAF Flight Information Handbook) will have conversion tables.

Failing that - learn a few of them, interpolate between those using 1mb = 0.03 ins. Easy ones to remember:

1013.2 = 29.92 (So 1013 = 29.91)
1016 = 30.00
1024 = 30.24

[BEagle]

To convert inches of mercury to millibars, multiply the inches value by 33.8637526

To convert millibars to inches of mercury, multiply the millibar value by 0.0295301

Simplify it as you wish.

[Sam Rutherford]

I am hoping for a system which you turn/spin/slide which both does the calculation and leaves an immediate record of the mb you are supposed to be flying. This would mean not having to write down every single change separately.

Ie (please ignore the figures, for illustration only):

ATC give you 1013, you convert to 29.92 and put it in altimeter.
A little later, when you make a call, if you read the inches off (they're pretty small), and then calculate back, the chances are you'll tell 1012 or 1014 to ATC, with them then having to correct you.

Over months or years (but perhaps even hours) this would get really tedious!

An mb altimeter is on the list, but it's not a cost-free change!

Sam.

[Lasiorhinus]

Print this out, laminate it, and attach the strip of paper to the dashboard, next to your altimeter.

990 29.23
991 29.26
992 29.29
993 29.32
994 29.35
995 29.38
996 29.41
997 29.44
998 29.47
999 29.5
1000 29.53
1001 29.56
1002 29.59
1003 29.62
1004 29.65
1005 29.68
1006 29.71
1007 29.74
1008 29.77
1009 29.8
1010 29.83
1011 29.85
1012 29.88
1013 29.91
1014 29.94
1015 29.97
1016 30
1017 30.03
1018 30.06
1019 30.09
1020 30.12
1021 30.15
1022 30.18
1023 30.21
1024 30.24
1025 30.27
1026 30.3
1027 30.33
1028 30.36
1029 30.39
1030 30.42
1031 30.45
1032 30.48
1033 30.5
1034 30.53
1035 30.56

[Sam Rutherford]

...I can do that (and perhaps put one of those sliding 'windows' you get on freebie calendars on it). I was looking if something to do this already existed (slide rule type).

Otherwise I'm still having to write/note/mark something every time - and then delete that note afterwards.

Sam.

[Chilli Monster]

Sam

I fly an Aztec which has the same problem. I suggest you take my first comment (get a set of conversion tables) and using those a) convert the pressure to set on the subscale; and b) REMEMBER what pressure in mbs you're on should you need feel the need to say it to ATC.

Bear in mind the latter isn't necessary as ATC don't want to know what pressure you're on, as they're going to give you a pressure to fly on anyway (and which you will readback when given - even my short term memory copes with that). The only time you volunteer a pressure is when you've got it from an ATIS and you check in with ATIS code and QNH - which you will have in millibars anyway.

[Fright Level]

I'm still having to write/note/mark something every time - and then delete that note afterwards.

Isn't that what a plog is for? Mine is covered in notes & numbers after even a short VFR flight.