flying in snow

(Teacherjh) wrote in message ...

does your "carb heat"
just apply heated air to the regular air intake to the carb or manifold? or
is it an "alternate air source"


The former, I believe, though I'll check it out. It's an archer (we also have
a dakota, which should be similar). There is an "alternate air" lever, but
that's an alternate static source.


Technically it's both. When you use carb heat in an Archer, it
bypasses the regular intake path / air filter and sends unfiltered
warm air to the intake manifold (that would make it an "alternate air"
source). This is quite useful when your intake is blocked. I've had
to use it twice for that reason. Once because of snow buildup on the
filter and another time when I somehow sucked up a plastic supermarket
bag (commonly seen floating around in thermals here in the southwest).

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

"Rick Durden" wrote in message
m...
Lot of bad information and old wives' tales on this thread. sigh

Unfortunately, Rick is adding to that bad information.

Outside of clouds, when you are flying in snow it will not stick to
the airframe. Even heavy wet snow will not stick, so airframe icing
is not a problem.

Do NOT believe this. I have flown outside of clouds in snow and seen it
stick. As I mentioned, typically only a very light amount winds up on the
forward surfaces of the airplane, but it is absolutely false that snow
outside of clouds will not stick to the airframe.

The rest of his post (except where he revisits this point) is informative,
and does introduce a couple of points not already mentioned.

Pete

Jose,

The carburetor heat provides air from a source inside the cowling and
bypasses the air filter. It is an alternate air source for the engine
and is heated.

All the best,
Rick

(Teacherjh) wrote in message ...

does your "carb heat"
just apply heated air to the regular air intake to the carb or manifold? or
is it an "alternate air source"


The former, I believe, though I'll check it out. It's an archer (we also have
a dakota, which should be similar). There is an "alternate air" lever, but
that's an alternate static source.

Jose

On Thu, 18 Mar 2004 19:01:54 -0800, "Peter Duniho"
wrote in Message-Id:
:

"Larry Dighera" wrote in message
.. .
I only see that as an issue if you are downwind of an active volcano,
and the ambient atmosphere is dust laden. It's my understanding that
most aircraft induction systems have a spring-loaded door that admits
air in the event of an interruption of flow through the filter
element.

Huh? Many do not.

Of the 5 POHs I checked, only the Rockwell International 112A
mentioned using carb-heat as an alternate air source. Neither the
1974 Cessna Centurion, nor 1973 Cessna Cardinal RG, nor 1974 Cessna
Stationair, nor Piper Archer II, nor Bellanca Super Viking POH/Owner's
Manuals mention alternate air. Or, at least I couldn't find it.

All aircraft that I've flown DO have an alternate air
system; most of the C172-class planes I know of use carb heat as their
alternate air, not a spring-loaded door.

In the C-172S there is no carb-heat (it's injected).

My own airplane has a
spring-loaded door, but that's most likely because it's also fuel-injected,
so there's no carb heat installed.

But regardless of how the alternate air system works, it's still an issue to
be aware of. And in all cases I know of, the alternate air system means
unfiltered air. In cruise flight, not necessarily a problem, but if it also
means turning on the carb heat, it means a) you need to be aware of the
potential for the need to use carb heat, and b) you'll want to remind
yourself of the various implications of operating with the carb heat turned
on (like, need to readjust the mixture, fuel efficiency changes, maximum
power changes, that sort of thing).

You don't need to be downwind of an active volcano to care about the air
filter getting clogged.

Right. What I was attempting to imply was that at cruise altitude the
air is generally free of impurities normally filtered unless there is
a source of such impurities upwind spewing to significant heights.

Larry Dighera wrote:

Of the 5 POHs I checked, only the Rockwell International 112A
mentioned using carb-heat as an alternate air source.

My understanding from the old Jeppesen-Sandersen PP manual was that this is
standard; IOW, if your plane has carb heat, that's the alternate air source.
I would assume that most POHs would not mention something that they feel to be
obvious.

George Patterson
Battle, n; A method of untying with the teeth a political knot that would
not yield to the tongue.

"Larry Dighera" wrote in message
...
Of the 5 POHs I checked, only the Rockwell International 112A
mentioned using carb-heat as an alternate air source.

See George's post. If there's carb heat, there's usually alternate air,
even if the manual doesn't say so.

All aircraft that I've flown DO have an alternate air
system; most of the C172-class planes I know of use carb heat as their
alternate air, not a spring-loaded door.

In the C-172S there is no carb-heat (it's injected).

So? What's your point? Are you claiming the 172S has no alternate air
source?

Right. What I was attempting to imply was that at cruise altitude the
air is generally free of impurities normally filtered unless there is
a source of such impurities upwind spewing to significant heights.

I understand what you were trying to imply. But the point here is that
filtration is not the only concern with many alternate air systems, since
they combine two completely different functions (carb heat and alternate
air).

Pete

"Peter Duniho" wrote in message ...
"Rick Durden" wrote in message
m...
Lot of bad information and old wives' tales on this thread. sigh

Unfortunately, Rick is adding to that bad information.

Outside of clouds, when you are flying in snow it will not stick to
the airframe. Even heavy wet snow will not stick, so airframe icing
is not a problem.

Do NOT believe this. I have flown outside of clouds in snow and seen it
stick. As I mentioned, typically only a very light amount winds up on the
forward surfaces of the airplane, but it is absolutely false that snow
outside of clouds will not stick to the airframe.

The rest of his post (except where he revisits this point) is informative,
and does introduce a couple of points not already mentioned.

Rick has got a lot of experience. Personally, I'm not so sure I would
dismiss it easily. I'm sure you to though, and If I'd seen
differently I might look for other reasons: local temperature
differences perhaps? I'm no snow expert, but have lived in snowy
climates so I know that when snow's near the freezing point it's
wetter and sticks more readily.

-Malcolm Teas

"Malcolm Teas" wrote in message
om...
Rick has got a lot of experience.

And as I said, his post did include some useful information.

However...

Personally, I'm not so sure I would dismiss it easily.

I hope that if you had seen with your own eyes the facts that contradict his
statement, you would.

I'm sure you to though, and If I'd seen
differently I might look for other reasons: local temperature
differences perhaps?

I never said snow ALWAYS sticks to the airframe. I simply said that it can.

Rick has this problem, maybe rooted in all that experience he's supposed to
have, that he thinks he can make a single statement that applies 100% of the
time. Witness his comments about aircraft insurance as well.

I don't care how much experience a person has, it's foolish to make wild
generalizations without having the facts to back them up. Especially when
someone has already said that they have personal experience to the contrary.

Pete