High Pressure

[Ironflight]

I went out to fly after work today ? the first time in about four days. Saturday was nice ? a little lunch and some formation work with Louise. Sunday was gloppy, it got cold Monday, positively frigid (for Houston) on Tuesday (and I was busy at work both days until late), so today (Wednesday) was the first day this week that was reasonable to get in a little pre-dinner Acro. As I swept through the checklist, I saw that the analog altimeter was reading about 350 ? ? a big change from our sea level altitude, but not unreasonable, so I dialed it back down. When the EFIS came up, I saw that it was reading MINUS 650? ! Oh wow ? I hadn?t bothered to check the ?thousands? needle on the analog ? what I thought was +350 was, in fact, just what the EFIS was showing ? minus 650!! As I corrected them both to field elevation, I checked the altimeter setting ? sure enough 30.63? !

When I sat in the RV-3 cockpit this evening, I noticed that the backup Winter altimeter only goes up to 30.50"??

Anybody ever recalling seeing pressures like this before? Kinda? the opposite of our summer hurricane weather?

Paul

[AltonD]

Weird weather here in south Alabama as well. Last Saturday (I think), I set the altimeter to field elevation and it was 29.57". Pretty low for winter time. Helped explain the howling winds across the runway.

[Sig600]

If I remember right, FARS prohibit flight with altimeter settings greater than 31.00"

[pauldan181]

In January of '07 there was one of those big arctic highs sitting over Minnesota and the pressure was something like 30.75. I recall the local TV weather guy commenting on record high pressures being set for some northern MN towns. It was -10 deg. F when I took off but at 5500' it was +25. The ride was smooth as glass the whole way but descending back to KFCM was like dropping into a freezer.

Paul Danclovic
Jamestown NC
RV-8A N181SB

[mburch]

Originally Posted by Sig600

If I remember right, FARS prohibit flight with altimeter settings greater than 31.00"

Good memory! That's a good one for the next FBO trivia night:

Sec. 91.144 — Temporary restriction on flight operations during abnormally high barometric pressure conditions

(a) Special flight restrictions. When any information indicates that barometric pressure on the route of flight currently exceeds or will exceed 31 inches of mercury, no person may operate an aircraft or initiate a flight contrary to the requirements established by the Administrator and published in a Notice to Airmen issued under this section.

(b) Waivers. The Administrator is authorized to waive any restriction issued under paragraph (a) of this section to permit emergency supply, transport, or medical services to be delivered to isolated communities, where the operation can be conducted with an acceptable level of safety.

mcb

[Howie]

While not an every year occurance, it is not uncommon for us to get higher
than normal pressures in the Cold parts of our winters. Usually, only in the
Interior, North West and the Slope. Check out the NOAA website and the
local TV and Newspaper sites for Anchorage, all had warning stories this past
week.

A Siberian High and greater than -40F; "high to low look out below"

H

[RV8iator]

Originally Posted by Sig600

If I remember right, FARS prohibit flight with altimeter settings greater than 31.00"

Back in the early 80's Alaska had a hugh high pressure system over it and the altimeters were 31.77 if I remember correctly. Delta cancelled all the flights, albeit at the FAA's insistence, and we were stuck there for that day. Next day the feds said we could depart daylight VMC. December in Alaska.. what were the FEDS thinking. Next day the FAA told us to set the altimeter at 31.00, hightest mechanical setting on the units, and we could use that up to 10K, then reset to 29.92 and continue.

The Captain Cook hotel had a great bar and dining room and we had a blast with all the stuck crews and passengers.

The 727's had been sitting in sub zero weather for 3 days and it took several hours to get them warmed up enough where all the gauges would read anything at all. Seems like yesterday.

Temps were something like 40 below and windy. That's one of many memories flying way up north. Different world up there.

Unusual to see that high of a baro pressure in the lower 48.

[Marc DeGirolamo]

Originally Posted by Sig600

If I remember right, FARS prohibit flight with altimeter settings greater than 31.00"

I did not realize that....learned something. Here in Canada this applies:

12.12.2 Flight Procedures
When the barometric pressure exceeds 31.00 inches of mercury, the following
procedures take effect:
(a) Altimeters of all IFR, CVFR and VFR aircraft are to be set to 31.00 inches of
mercury for enroute operations below 18 000 feet ASL. All pilots are to maintain
this setting until beyond the area affected by the extreme high pressure or until
reaching the final approach segment of an instrument approach for IFR aircraft or
the final approach for VFR aircraft. At the beginning of the final approach
segment, the current altimeter setting will be set by those aircraft capable of such
a setting. Aircraft that are unable to set altimeter settings above 31.00 inches of mercury will retain a 31.00 inches of mercury setting throughout the entire
approach. Aircraft on departure or missed approach will set 31.00 inches of
mercury prior to reaching any mandatory or fix crossing altitude, or 1 500 feet
AGL, whichever is lower.

[Sig600]

And here I thought it was because the pressure was so high it would hold your airplane to the ground.

[Lars]

Speaking of Winter altimeters, I'm looking forward to your impressions of the one you installed in the -3. I'm 95% certain I'll buy one as a backup for my panel. Some have reported fairly large (?100 foot or more) inaccuracy above 8000 feet. Not that it likely matters, but it will be interesting (to me, at least) to see how your works out.