Cold weather ops

[Happy Dog]

Many GA a/c are restricted to operations above a certain temperature. In my
case (Zlin 242L) the restriction is -20C at sea level and goes down to -40 C
(or F) at 9000 feet. But, the POH doesn't say why. Anybody know?

moo

[Rosspilot]

>Many GA a/c are restricted to operations above a certain temperature. In my
>case (Zlin 242L) the restriction is -20C at sea level and goes down to -40 C
>(or F) at 9000 feet. But, the POH doesn't say why. Anybody know?
>

Yes. Any colder than that and you freeze your ass off, moving the CG too far
forward and out of the operating envelope.
<G>


www.Rosspilot.com

[Mike Rapoport]

It could be all kinds of things. My airplane has high and low start
restrictions and an absolute temperature limit. The start restrictions are
based on the possibility/probablility of a hot start and the absolute
temperature limit is based on the fuel gelling.

Mike
MU-2


"Happy Dog" > wrote in message
. ..
> Many GA a/c are restricted to operations above a certain temperature. In
my
> case (Zlin 242L) the restriction is -20C at sea level and goes down to -40
C
> (or F) at 9000 feet. But, the POH doesn't say why. Anybody know?
>
> moo
>
>

[Steve Chalfin]

"Happy Dog" > wrote in message >...
> Many GA a/c are restricted to operations above a certain temperature. In my
> case (Zlin 242L) the restriction is -20C at sea level and goes down to -40 C
> (or F) at 9000 feet. But, the POH doesn't say why. Anybody know?
>
> moo

A recent thread on the Diamond Owners Website addressed the -20 degree
C limitation for the Diamond Star. According to Diamond, this is due
to temperature limitations on the avionics.

Steve

[Happy Dog]

"Steve Chalfin" > wrote in message
> > Many GA a/c are restricted to operations above a certain temperature.
In my
> > case (Zlin 242L) the restriction is -20C at sea level and goes down
to -40 C
> > (or F) at 9000 feet. But, the POH doesn't say why. Anybody know?
>
> A recent thread on the Diamond Owners Website addressed the -20 degree
> C limitation for the Diamond Star. According to Diamond, this is due
> to temperature limitations on the avionics.

Yeah. I've heard this. But why the change with altitude?

moo

[Dylan Smith]

In article >, Happy Dog wrote:
>> A recent thread on the Diamond Owners Website addressed the -20 degree
>> C limitation for the Diamond Star. According to Diamond, this is due
>> to temperature limitations on the avionics.
>
> Yeah. I've heard this. But why the change with altitude?

At a rough guess, because at sea level you're likely to be just starting
out so everything's cold at that point. At 9000' you're flying, the
engine's hot, and you can provide enough heat to prevent the avionics
from going out of spec until a colder temperature.

--
Dylan Smith, Castletown, Isle of Man
Flying: http://www.dylansmith.net
Frontier Elite Universe: http://www.alioth.net
"Maintain thine airspeed, lest the ground come up and smite thee"

[Doug]

Deice fluid freezes if the temp gets low enough (below about -40 but
check this). Flaps wont come up due to being frozen etc.

"Mike Rapoport" > wrote in message .net>...
> It could be all kinds of things. My airplane has high and low start
> restrictions and an absolute temperature limit. The start restrictions are
> based on the possibility/probablility of a hot start and the absolute
> temperature limit is based on the fuel gelling.
>
> Mike
> MU-2
>
>
> "Happy Dog" > wrote in message
> . ..
> > Many GA a/c are restricted to operations above a certain temperature. In
> my
> > case (Zlin 242L) the restriction is -20C at sea level and goes down to -40
> C
> > (or F) at 9000 feet. But, the POH doesn't say why. Anybody know?
> >
> > moo
> >
> >

[G.R. Patterson III]

Dylan Smith wrote:
>
> At 9000' you're flying, the
> engine's hot, and you can provide enough heat to prevent the avionics
> from going out of spec until a colder temperature.

There are airports higher than that in the States, so I doubt that's the reason.

George Patterson
Love, n.: A form of temporary insanity afflicting the young. It is curable
either by marriage or by removal of the afflicted from the circumstances
under which he incurred the condition. It is sometimes fatal, but more
often to the physician than to the patient.

[Malcolm Teas]

(Steve Chalfin) wrote in message >...
> "Happy Dog" > wrote in message >...
> > Many GA a/c are restricted to operations above a certain temperature. In my
> > case (Zlin 242L) the restriction is -20C at sea level and goes down to -40 C
> > (or F) at 9000 feet. But, the POH doesn't say why. Anybody know?
> >
>
> A recent thread on the Diamond Owners Website addressed the -20 degree
> C limitation for the Diamond Star. According to Diamond, this is due
> to temperature limitations on the avionics.

Think about density altitude. At -20 C and sea level, the density alt
is just under -10000 feet according to the my trust E6B. At -40 C and
9000 feet pressure alt, the density alt is -10000 feet.

Looks like a limitation on the range of adjustment that can be made.

In the AIM, there's also a limitation on adjustment for your
altimeters due to low pressure. If you can't adjust your altimeter
correctly, you can't fly. I think this happens in Alaska very
occasionally.

-Malcolm Teas

[Robert Moore]

(Malcolm Teas) wrote

> Think about density altitude. At -20 C and sea level, the density alt
> is just under -10000 feet according to the my trust E6B. At -40 C and
> 9000 feet pressure alt, the density alt is -10000 feet.


Better get a new E6B. :-)

Bob Moore

[Peter Duniho]

"Robert Moore" > wrote in message
. 6...
> (Malcolm Teas) wrote
>
> > Think about density altitude. At -20 C and sea level, the density alt
> > is just under -10000 feet according to the my trust E6B. At -40 C and
> > 9000 feet pressure alt, the density alt is -10000 feet.
>
>
> Better get a new E6B. :-)

He got the wrong numbers, but it IS true that the density altitude winds up
about the same for both calculations (around -5000'). So maybe the answer
IS something that has to do with density altitude.

I think it's more likely a limitation on the engine (to keep MP within
limits), rather than some altimeter thing. But it seems logical that
density altitude is the problem, in this particular example (that may or may
not apply to other aircraft, of course).

Pete

[John Galban]

(Malcolm Teas) wrote in message >...
> (Steve Chalfin) wrote in message >...
> At -40 C and
> 9000 feet pressure alt, the density alt is -10000 feet.

Huh? I show it as around 4,100 ft.

John Galban=====>N4BQ (PA28-180)

[Andrew Sarangan]

"Peter Duniho" > wrote in message >...
> "Robert Moore" > wrote in message
> . 6...
> > (Malcolm Teas) wrote
> >
> > > Think about density altitude. At -20 C and sea level, the density alt
> > > is just under -10000 feet according to the my trust E6B. At -40 C and
> > > 9000 feet pressure alt, the density alt is -10000 feet.
> >
> >
> > Better get a new E6B. :-)
>
> He got the wrong numbers, but it IS true that the density altitude winds up
> about the same for both calculations (around -5000'). So maybe the answer
> IS something that has to do with density altitude.
>
> I think it's more likely a limitation on the engine (to keep MP within
> limits), rather than some altimeter thing. But it seems logical that
> density altitude is the problem, in this particular example (that may or may
> not apply to other aircraft, of course).
>
> Pete

I suspect it is related to the maximum power output from the engine
(not MP, because that is not related to density altitude). Engine
power increases roughly 2% per 1000' decrease in density altitude. At
-5000' you will be developing 110% of the rated horsepower. That is a
nice round number, and could very well be the reason for the
limitation.

[Malcolm Teas]

"Peter Duniho" > wrote in message >...
> "Robert Moore" > wrote in message
> . 6...
> > (Malcolm Teas) wrote
> >
> > > Think about density altitude. At -20 C and sea level, the density alt
> > > is just under -10000 feet according to the my trust E6B. At -40 C and
> > > 9000 feet pressure alt, the density alt is -10000 feet.
> >
> >
> > Better get a new E6B. :-)

Or, perhaps, remember how to do density alt. calculations. Yep, I
messed up there.

> He got the wrong numbers, but it IS true that the density altitude winds up
> about the same for both calculations (around -5000'). So maybe the answer
> IS something that has to do with density altitude.

Well I get a density alt of about -5000 for sea level and -20 C, and
5000 for 9000 foot press. alt and -40 C. This is with my revised E6B.
<grin> So, 4000 to 5000 less than the pressure altitude at least.

-Malcolm Teas