Cherokee Carb Heat.

Is this just a technique or proper procedure?

All the Piper POH's I've seen say only use carb heat if you suspect
carb icing.

In a previous article, pamaway (Hobbes1157) said:
Hi there. I've got a question about the carb heat in a Cherokee. I was told
that you only need to apply it for a short while (5 seconds) while on downwind

I'd make it 10 seconds myself. I once got a big power loss taking off
because I'd only done the carb heat check for 5 seconds in the run-up.
I was a solo student at the time, and having what I considered an
"inflight emergency" (even if it was solved by the second item on the
power loss checklist) was enough to give me the shakes for a while.

to make sure the carb is clear of ice. She (CFI) said that Pipers don't need it
all the time as Cessnas do. Is this just a technique or proper procedure?
Comments appreciated.

The POH recommends occassional checks - I try and do it every 15-20
minutes in conditions conducive to icing. The difference in the
procedures between Piper and Cessna are that the carbs in the Pipers are
placed so that they get warmed by the engine better, so it's not as big a
problem.


--
Paul Tomblin , not speaking for anybody
"The thing you don't check is the thing that will kill you."
-- Rick Grant (quoting RCAF pilot training)

Plus: Hey Jay is this a family event at Oshkosh you're planning? I've got
my
non-flying family driving with me up to OSH and would like to meet some
other
local and non-local friendly folks!

As a matter of procedure we don't use carb heat in the pattern at all in
Pipers. In fact, in nine years of flying 140s thru 235s, I've only used
carb heat "for real" once. (Of course, I don't fly IFR...)

As for the Oshkosh get together being a "family event", well, my two
children (ages 9 and 12) will be there, so I guess we'd better keep our
clothes on for the most part!

If you're gonna stop by, it would be good to sign the roster (see the post
"Oshkosh Get Together Roster -- Sign in, please!") so we all have some idea
of who's who... (By the way, did you see the invite at Green Castle?)
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

Actually, I got in a situation in a cherokee (a 1980 Dakota) where the engine
was icing up and quitting just on the taxiway. By the time I got to the runup,
the engine just died. Happened a few times, had the thing looked at, the
conclusion was carb ice. On the ground, no less.

Jose

(for Email, make the obvious changes in my address)

I just scanned my Warrior II POH for this. It says to use carb heat if you
suspect icing (anywhere, but particularly in descents with low throttle
settings), and advises on how to check for the presence if icing. There's
also an optional carb ice detection system available for my model. Unlike
the Grumman AA1-C I fly, however, the descent checklist in the Piper says
"CARB HEAT ON (if needed)" instead of an unqualified "CARB HEAT ON".

I seem to remember hearing something about the location of the carburator
intake under the hood in the Cherokee -- it gets pre-warmed air or something
like that, and that's why it's not as likely to happen.

There's a decent article out there about this, if you're interested:
http://www.avweb.com/news/columns/182189-1.html.

Happy Landings!


"Hobbes1157" wrote in message
...
Hi there. I've got a question about the carb heat in a Cherokee. I was
told
that you only need to apply it for a short while (5 seconds) while on
downwind
to make sure the carb is clear of ice. She (CFI) said that Pipers don't
need it
all the time as Cessnas do. Is this just a technique or proper procedure?
Comments appreciated.
Plus: Hey Jay is this a family event at Oshkosh you're planning? I've got
my
non-flying family driving with me up to OSH and would like to meet some
other
local and non-local friendly folks!

Thanks,
Nolan

PPSEL, INST, commerial student
IA24 (green castle)

Teacherjh wrote:

Actually, I got in a situation in a cherokee (a 1980 Dakota) where the engine
was icing up and quitting just on the taxiway. By the time I got to the runup,
the engine just died. Happened a few times, had the thing looked at, the
conclusion was carb ice. On the ground, no less.

The main reason you don't need to habitually use carb heat with a Lycoming
is the fact that they run the induction tubes through the oil sump. When
the engine is warm, the hot oil tends to keep the carb warm. The situation
you describe (cold engine, near-closed throttle plate) would be perfect for
formation of carb ice if the humidity were high.

George Patterson
The optimist feels that we live in the best of all possible worlds. The
pessimist is afraid that he's correct.
James Branch Cavel

(Paul Tomblin) wrote in message ...
The difference in the
procedures between Piper and Cessna are that the carbs in the Pipers are
placed so that they get warmed by the engine better, so it's not as big a
problem.

And it really only applies to early models of Cessna 172s.
Beginning in the '68 model year, the 172 used the same Lycoming
engines as Piper, with the carb mounted on the oil pan. For some
reason (probably liability), Cessna chose to keep their "always use
carb heat" instructions, even though the Lycoming engine is far less
susceptable to carb ice.

Looking at the big picture, it really doesn't matter much which
procedure you use. If you use carb heat for landing, you just have to
remember to shut it off if you go around or after you land.

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

pamaway (Hobbes1157) wrote in message ...
Hi there. I've got a question about the carb heat in a Cherokee. I was told
that you only need to apply it for a short while (5 seconds) while on downwind
to make sure the carb is clear of ice. She (CFI) said that Pipers don't need it
all the time as Cessnas do. Is this just a technique or proper procedure?
Comments appreciated.
Plus: Hey Jay is this a family event at Oshkosh you're planning? I've got my
non-flying family driving with me up to OSH and would like to meet some other
local and non-local friendly folks!

Thanks,
Nolan

PPSEL, INST, commerial student
IA24 (green castle)

Nolan
For the lesser experienced pilots in particular, the use of carb heat
can save you some anxious moments without unduly affecting the engine
performance in the pattern. Of course you'll notice the loss of
performance if you forget to turn carb heat OFF if you elect to make a
take-off or go-around. Even then it isn't life threatening unless
really adverse conditions exist.
A little trick that I learned back in the early 50's, and pass on to
all who don't know of it, is using the PRIMER to keep the engine
running if it shuts down for carb ice. The primer injects fuel
directly into the intake manifold bypassing the carburetor and can
keep the engine running intermittently and in many cases generate
enough heat for the carb heat to become effective again. I've used
this technique a few times in aircraft to get home. In Pipers (PA25
Pawnee while crop dusting) and Cessnas (C-172 and 177).
Ol Shy & Bashful

(Rocky) writes:

A little trick that I learned back in the early 50's, and pass on to
all who don't know of it, is using the PRIMER to keep the engine
running if it shuts down for carb ice. The primer injects fuel
directly into the intake manifold bypassing the carburetor and can
keep the engine running intermittently and in many cases generate
enough heat for the carb heat to become effective again. I've used
this technique a few times in aircraft to get home. In Pipers (PA25
Pawnee while crop dusting) and Cessnas (C-172 and 177).
Ol Shy & Bashful

That's a brilliant suggestion -- I'm assuming that you leave carb heat
on, so that there's still an air supply into the cylinders.


All the best,


David

--
David Megginson, , http://www.megginson.com/

(Rocky) wrote in message . com...
snip
A little trick that I learned back in the early 50's, and pass on to
all who don't know of it, is using the PRIMER to keep the engine
running if it shuts down for carb ice. The primer injects fuel
directly into the intake manifold bypassing the carburetor and can
keep the engine running intermittently and in many cases generate
enough heat for the carb heat to become effective again. I've used
this technique a few times in aircraft to get home. In Pipers (PA25
Pawnee while crop dusting) and Cessnas (C-172 and 177).
Ol Shy & Bashful

I've heard this before, but haven't yet found anyone who can explain
how that would work. The development of carb ice causes the engine
to run rough/die because the ice is blocking air from entering the
carb. This generally results in a very rich mixture. How does adding
even more fuel via the primer help the engine to run??

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