A very high pressure settled in Pacific NW:

KPSC 020453Z 31006KT 6SM BR BKN007 BKN075 M07/M08 A3066 RMK AO2
SLP389 T10671078

That's the highest that I've ever remember seeing.

I always thought that the NW seems to have larger pressure swings
(probably more so in Alaska). We can go from 2960 to 3060 in about two
days.

BTW, FAR 91.144 restricts flight operations when barometric pressure
exceeds 31 inch mercury. Any idea why? (note this restriction applies
to VFR traffic a well).


M wrote:
> A very high pressure settled in Pacific NW:
>
> KPSC 020453Z 31006KT 6SM BR BKN007 BKN075 M07/M08 A3066 RMK AO2
> SLP389 T10671078
>
> That's the highest that I've ever remember seeing.
>
> I always thought that the NW seems to have larger pressure swings
> (probably more so in Alaska). We can go from 2960 to 3060 in about two
> days.

"M" > wrote in message
ps.com...
>
> BTW, FAR 91.144 restricts flight operations when barometric pressure
> exceeds 31 inch mercury. Any idea why? (note this restriction applies
> to VFR traffic a well).
>
>
The Kollsman Window is only required to have a range of 28.00 to 31.00
inches Hg. So if barometric pressure is outside that range, you cannot
accurately set most altimeters.

John Severyn
@KLVK

I don't believe VFR flight requires accurate altimeter adjustable for
barometric pressure. 91.205 only requires such altimeter for IFR
operations.


J. Severyn wrote:
> "M" > wrote in message
> ps.com...
> >
> > BTW, FAR 91.144 restricts flight operations when barometric pressure
> > exceeds 31 inch mercury. Any idea why? (note this restriction applies
> > to VFR traffic a well).
> >
> >
> The Kollsman Window is only required to have a range of 28.00 to 31.00
> inches Hg. So if barometric pressure is outside that range, you cannot
> accurately set most altimeters.
>
> John Severyn
> @KLVK

I don't believe VFR flight requires accurate altimeter adjustable for
barometric pressure. 91.205 only requires such altimeter for IFR
operations.


J. Severyn wrote:
> "M" > wrote in message
> ps.com...
> >
> > BTW, FAR 91.144 restricts flight operations when barometric pressure
> > exceeds 31 inch mercury. Any idea why? (note this restriction applies
> > to VFR traffic a well).
> >
> >
> The Kollsman Window is only required to have a range of 28.00 to 31.00
> inches Hg. So if barometric pressure is outside that range, you cannot
> accurately set most altimeters.
>
> John Severyn
> @KLVK

Correct. But you still are required to follow the NOTAM in extremely high
or low barometric pressure conditions. If you read FAR91.144 quoted here:

"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."

In other words, it says "Read the NOTAM" or "Get a Waiver". Normally the
NOTAM will restrict operation at certain altitudes so that safe altitude
separation can be maintained in spite of the inability to correctly enter
the barometric pressure.

John Severyn
@KLVK


"M" > wrote in message
oups.com...
>I don't believe VFR flight requires accurate altimeter adjustable for
> barometric pressure. 91.205 only requires such altimeter for IFR
> operations.
>
>
> J. Severyn wrote:
>> "M" > wrote in message
>> ps.com...
>> >
>> > BTW, FAR 91.144 restricts flight operations when barometric pressure
>> > exceeds 31 inch mercury. Any idea why? (note this restriction applies
>> > to VFR traffic a well).
>> >
>> >
>> The Kollsman Window is only required to have a range of 28.00 to 31.00
>> inches Hg. So if barometric pressure is outside that range, you cannot
>> accurately set most altimeters.
>>
>> John Severyn
>> @KLVK
>

"M" > wrote in message
oups.com...
>I don't believe VFR flight requires accurate altimeter adjustable for
> barometric pressure. 91.205 only requires such altimeter for IFR
> operations.
>

AIM 7-2-2 might answer your question about high and low barometric
pressures.
John Severyn
@KLVK

That is the highest pressure you can set on the Kollsman
window.



"M" > wrote in message
ps.com...
|
| BTW, FAR 91.144 restricts flight operations when
barometric pressure
| exceeds 31 inch mercury. Any idea why? (note this
restriction applies
| to VFR traffic a well).
|
|
| M wrote:
| > A very high pressure settled in Pacific NW:
| >
| > KPSC 020453Z 31006KT 6SM BR BKN007 BKN075 M07/M08 A3066
RMK AO2
| > SLP389 T10671078
| >
| > That's the highest that I've ever remember seeing.
| >
| > I always thought that the NW seems to have larger
pressure swings
| > (probably more so in Alaska). We can go from 2960 to
3060 in about two
| > days.
|

Heck,,, get out and go flying. The wings love the thick air and the
motor really LOVES it too.

M wrote:
> A very high pressure settled in Pacific NW:
>
> KPSC 020453Z 31006KT 6SM BR BKN007 BKN075 M07/M08 A3066 RMK AO2
> SLP389 T10671078
>
> That's the highest that I've ever remember seeing.
>
> I always thought that the NW seems to have larger pressure swings
> (probably more so in Alaska). We can go from 2960 to 3060 in about two
> days.

M wrote:
> BTW, FAR 91.144 restricts flight operations when barometric pressure
> exceeds 31 inch mercury. Any idea why? (note this restriction applies
> to VFR traffic a well).

The "why" is that the altimeter setting range on most altimeters doesn't
go past 31.00". Does anyone have an example of a NOTAM under 91.144?
(how restrictive is it).

The rules that apply in Canada are a bit more explicit: >
http://www.tc.gc.ca/CivilAviation/publications/tp14371/RAC/12-1.htm#12-12

Basically it says
- for enroute, set the altimeter to 31"
- for IFR approaches, set the altimeter to the actual altimeter setting
if able, otherwise set it to 31" and adjust the altitude minima (add
100' and 1/4 SM per 0.1" above 31.00")
- aerodromes which cannot report the actual altimeter setting are
restricted to VFR.
-"For aircraft operating VFR, no additional restrictions apply; however,
extra diligence in flight planning and in operating in these conditions
is essential. "

And it may not be a perfect solution, but GPS altitude
readout may be independent of baro altitude.



"Fred G. Black" > wrote in message
...
|M wrote:
| > BTW, FAR 91.144 restricts flight operations when
barometric pressure
| > exceeds 31 inch mercury. Any idea why? (note this
restriction applies
| > to VFR traffic a well).
|
| The "why" is that the altimeter setting range on most
altimeters doesn't
| go past 31.00". Does anyone have an example of a NOTAM
under 91.144?
| (how restrictive is it).
|
| The rules that apply in Canada are a bit more explicit: >
|
http://www.tc.gc.ca/CivilAviation/publications/tp14371/RAC/12-1.htm#12-12
|
| Basically it says
| - for enroute, set the altimeter to 31"
| - for IFR approaches, set the altimeter to the actual
altimeter setting
| if able, otherwise set it to 31" and adjust the altitude
minima (add
| 100' and 1/4 SM per 0.1" above 31.00")
| - aerodromes which cannot report the actual altimeter
setting are
| restricted to VFR.
| -"For aircraft operating VFR, no additional restrictions
apply; however,
| extra diligence in flight planning and in operating in
these conditions
| is essential. "

wrote:
> Heck,,, get out and go flying. The wings love the thick air and the
> motor really LOVES it too.

The engine will produce more power with denser air, but
atomization of the fuel suffers in the cold and consumption can go up.
Condensation in the engine is much more pronounced in the cold, too,
and corrosion starts to set in if the thing isn't run until the oil's
hot enough to get rid of it. Here in Alberta the engine simply won't
get hot at -25°C; it'll barely get warm, and we've had some hassles
with corroded cylinders on the coldest engines.

Dan

Using carh heat on the ground, with a carb temp gauge can
improve extreme cold weather performance. And the use of
baffles on oil coolers and cylinders is very important.



> wrote in message
ups.com...

wrote:
> Heck,,, get out and go flying. The wings love the thick
> air and the
> motor really LOVES it too.

The engine will produce more power with denser air,
but
atomization of the fuel suffers in the cold and consumption
can go up.
Condensation in the engine is much more pronounced in the
cold, too,
and corrosion starts to set in if the thing isn't run until
the oil's
hot enough to get rid of it. Here in Alberta the engine
simply won't
get hot at -25°C; it'll barely get warm, and we've had some
hassles
with corroded cylinders on the coldest engines.

Dan

Jim Macklin wrote:

> Using carh heat on the ground,

In cruise flight carb heat should be set to give a carb temp of approx
45-50F.

At the coldest place in the carb. It depends where the
probe is installed. If in the throat, then you might want
to see 100° F, if at the throttle plate /venturi, then just
solidly above freezing.


"Newps" > wrote in message
. ..
|
|
| Jim Macklin wrote:
|
| > Using carh heat on the ground,
|
| In cruise flight carb heat should be set to give a carb
temp of approx
| 45-50F.

"M" > wrote in message
ups.com...
>
> A very high pressure settled in Pacific NW:
>
> KPSC 020453Z 31006KT 6SM BR BKN007 BKN075 M07/M08 A3066 RMK AO2
> SLP389 T10671078
>
> That's the highest that I've ever remember seeing.
>
> I always thought that the NW seems to have larger pressure swings
> (probably more so in Alaska). We can go from 2960 to 3060 in about two
> days.
>

Actually got out and practiced in the pattern a little bit today with my
instructor, but since he isn't allowed to instruct in our clubs planes, we
were splitting time (we did my primary instruction through a different
club).

Altimeter setting when we started up at Renton Municipal (KRNT) was "30.64",
and remember sitting there thinking, "hmmm... I wonder if it goes that
high???" During our second trip around the pattern, they updated the ATIS
and it dropped a little bit to "30.62"

Fog was being stubborn to burn off today, as we were going to go at 10am,
but Renton was fogged in and it didn't go away until about noon, and as we
were in the patter could see there still a good deal of fog to the south.

Have to say it was nice to get out today, as it was the first time in 6
weeks that I had flown, and thought I might be kind of rusty being a sort of
low time pilot, but all of my landings were great and the base to final
turns were all pretty much right on the glide slope and on the centerline,
with the exception of the second, which I overshot the base-final turn, but
I just continued a nice coordinated turn and didn't try to rush it as I had
plenty of room to get lined up and fix the problem.

Jim Macklin wrote:
> That is the highest pressure you can set on the Kollsman
> window.
>
>

I can hardly see how it should affect VFR flights. Additionally if the
pressure is higher than 31 inch mercury and the altimeter is set to
3100, the true altitude would be higher than what's indicated by the
altimeter. For VFR flights this would almost never introduce any
problems. (Even for IFR terrain separation this allows a bigger margin
for terrain clearance).

The only problem I could think of is the mode C requirement for
altitude above 10,000 MSL, if someone flying without a mode C x-ponder,
set their altimeter to 3100, on day with pressure higher than 31"
mercury, and flying right near 10,000 feet indicated on their altimeter
:-)

"M" > wrote in message
oups.com...
> Jim Macklin wrote:
>> That is the highest pressure you can set on the Kollsman
>> window.
>>
>>
>
> I can hardly see how it should affect VFR flights. Additionally if the
> pressure is higher than 31 inch mercury and the altimeter is set to
> 3100, the true altitude would be higher than what's indicated by the
> altimeter. For VFR flights this would almost never introduce any
> problems. (Even for IFR terrain separation this allows a bigger margin
> for terrain clearance).
>
> The only problem I could think of is the mode C requirement for
> altitude above 10,000 MSL, if someone flying without a mode C x-ponder,
> set their altimeter to 3100, on day with pressure higher than 31"
> mercury, and flying right near 10,000 feet indicated on their altimeter
> :-)
>

I thought the Mode C transponder reports Pressure Altitude and is basically
fixed at 29.92?

"M" > wrote in message
oups.com...
>>
>>
>
> I can hardly see how it should affect VFR flights.

Well pattern altitudes might be one problem. How about easterly/westerly
odd/even +500 altitudes?

John Severyn
@KLVK

So everybody fly their pattern 100 ft higher than normal. Big deal.

As long as everyone all max out their Kollsman's window at 3100 in the
same vacinity, even/odd +500 altitude would be just fine. You still
have the same vertical separation. Plus, VFR is see and avoid.
even/odd +500 altitude doesn't really do much separation when someone
flying magnetic course 001 converge with someone flying course magnetic
179, all legally at odd+500 VFR altitude and only 2 degree off from a
head-on.


J. Severyn wrote:
> "M" > wrote in message
> oups.com...
> >>
> >>
> >
> > I can hardly see how it should affect VFR flights.
>
> Well pattern altitudes might be one problem. How about easterly/westerly
> odd/even +500 altitudes?
>
> John Severyn
> @KLVK

ATC computer converts the pressure altitude with local altimeter
setting. If ATC knows everyone is using 3100 as their altimeter setting
(can be by regulation in high pressure >31" situation, such as in
Canada), the computer can do similar converson, so the IFR separation
would not be unaffected.

Wade Hasbrouck wrote:

>
> I thought the Mode C transponder reports Pressure Altitude and is basically
> fixed at 29.92?

J. Severyn wrote:
> "M" > wrote in message
> oups.com...
>
>>>
>>I can hardly see how it should affect VFR flights.
>
>
> Well pattern altitudes might be one problem. How about easterly/westerly
> odd/even +500 altitudes?

So you're a couple hundred feet off, that's no big deal. As for pattern
altitudes I always use 1000 agl, plus or minus depending on how I round
the field elevation.

M wrote:

> ATC computer converts the pressure altitude with local altimeter
> setting. If ATC knows everyone is using 3100 as their altimeter setting
> (can be by regulation in high pressure >31" situation, such as in
> Canada), the computer can do similar converson, so the IFR separation
> would not be unaffected.

If the pressure gets above the limit IFR flight would not be allowed,
simple as that. That happened 10 or 15 years ago in Alaska. Very rare.

">
> A very high pressure settled in Pacific NW:
>
> KPSC 020453Z 31006KT 6SM BR BKN007 BKN075 M07/M08 A3066 RMK AO2
> SLP389 T10671078
>
> That's the highest that I've ever remember seeing.
>

Yeah with terrible smog to go along with it. Once you get to 1-1.5K and look
down it's almost like a fog bank it's so dense.
We're getting as bad as Los Angeles :-(

Cheers:

Paul
N1431A
1S0

You are flying VFR at 17,500 MSL with an altimeter setting of 30.66. You
pick up an IFR clearance and are given FL190. You begin a slow climb. As
soon as you pass 18,000 MSL you set your altimeter to 29.92. It now reads
17,300 so you set it back to 30.66. It now reads 18,000, so you set it back
to 29.92. I now reads 17,300 ...

Conclusion: It's impossible to get above 18,000 MSL if the altimeter setting
is 30.66.