The International Cessna^® 170 Association

Well, I admit I'm not absolutely certain, but the way I read it... no one may fly unless certain requirements are established by the Administrator and published in a Notam. So if the pressure is that high.... lacking that NOTAM which describes the requirements that must be met.... then no one may fly.

Thanks, George. Very strange wording for a reg -- kind of begs for clarification, as if there were some unstated assumption behind it that I don't know about.

At any rate, it'll be a cold day in Bemidji before I ever have to worry about it, and if it happens, I'll probably be at home huddled by the fire rather than out there committing aviation!

Thanks for pointing this out, though -- I love weird facts that I might never have to actually, you know, use!

John

Dawson City/YT

METAR CYDA 142000Z 00000KT 20SM SCT055 BKN120 OVC240 M33/M34 A3101 RMK SC3AC1CSO SLP570=

Wow! That "M33/M34" part is what I'm talking about! I'm a wuss. When it's like that here, my airport friends and I will meet for breakfast and then go huddle in someone's heated hanger, work on an airplane project or hangar-fly. Airports here get awfully quiet in that kind of cold.

From http://answers.noaa.gov/noaa.answers/co ... p?kbid=544:

The North American record for high pressure was set in 1989. At 2000 GMT on
31 January 1989, an anticyclone of historic proportions brought a "sea-level
equivalent" pressure of 31.85 in (1078.4 mb) to Northway, on the Alaska
Highway in the east central part of Alaska. When pressures occur in this range,
many commercial aircraft are grounded because their altimeters aren't designed
for such high settings.

I was there in 1989 when the barometric pressure was above 31.00"Hg over much of Alaska. If my memory is correct, daylight, VMC-only flights were all that was permitted by the FAA. It was severe clear at the time. Our jets were Part 91 and were allowed to fly normal flights. Some airline flights were cancelled because they would not/could not fly under VFR for whatever reason.

It was also not a problem for the piston engine fleet either as it was just too cold for anyone to fly.