Carb heat: my new policy. Any comments

Tman wrote:

Flying a lot of 152s and 172s with carb heat lately. When inbound, I've
been taught to pull the carb heat "on" downwind, hey actually use it as
a power control to slow the plane just a bit mid-field, and then more
importantly, just leave the thing on till clear of the runway and
cleaning up.

Never heard of this before.

I think I'm going to follow a new SOP. Turn the carb heat off on
mid-final.

Tha't what I've always been taught. Actually, I do it on short final.
There will come the day when you need full power for the go-around. Too
silly if you then have the carb heat on.

I was taught to push in the carb heat with my thumb while advancing the
throttle for a go-around.

"John Smith" wrote in message
...
Tman wrote:

Flying a lot of 152s and 172s with carb heat lately. When inbound, I've
been taught to pull the carb heat "on" downwind, hey actually use it as a
power control to slow the plane just a bit mid-field, and then more
importantly, just leave the thing on till clear of the runway and
cleaning up.

Never heard of this before.

I think I'm going to follow a new SOP. Turn the carb heat off on
mid-final.

Tha't what I've always been taught. Actually, I do it on short final.
There will come the day when you need full power for the go-around. Too
silly if you then have the carb heat on.

"Jon Woellhaf" wrote in message
. ..
I was taught to push in the carb heat with my thumb while advancing the
throttle for a go-around.

"John Smith" wrote in message
...
Tman wrote:

Flying a lot of 152s and 172s with carb heat lately. When inbound, I've
been taught to pull the carb heat "on" downwind, hey actually use it as
a power control to slow the plane just a bit mid-field, and then more
importantly, just leave the thing on till clear of the runway and
cleaning up.

Never heard of this before.

I think I'm going to follow a new SOP. Turn the carb heat off on
mid-final.

Tha't what I've always been taught. Actually, I do it on short final.
There will come the day when you need full power for the go-around. Too
silly if you then have the carb heat on.



Yeah, same here.

Jon Woellhaf wrote:
I was taught to push in the carb heat with my thumb while advancing the
throttle for a go-around.

That won't work so well in a Piper. You need to do one, then the other.

.... Alan
--
Alan Gerber
PP-ASEL
gerber AT panix DOT com

"John Smith" wrote in message
...
Tman wrote:


There will come the day when you need full power for the go-around. Too
silly if you then have the carb heat on.

Then again, how hard is it to shove in the carb heat knob while you advance
the throttle in a Cessna? They are right next to each other. I have always
just pushed in the carb heat handle at the same time as I advance the
throttle, not that difficult to do, even using the same hand.

Randy L.
--
Remember: Any landing that you can walk away from,
is a landing that you can be fined, sued, or prosecuted for.

"Tman" x@x wrote in message
. ..
Flying a lot of 152s and 172s with carb heat lately. When inbound, I've
been taught to pull the carb heat "on" downwind, hey actually use it as a
power control to slow the plane just a bit mid-field, and then more
importantly, just leave the thing on till clear of the runway and cleaning
up. No matter what the temp, humidity. And to have it on at all times
when the RPM is less than the green band. Kind of a preventative.

A few times I have been coming in on short final and needed a burst of
power due to a sudden downdraft, or needed to pour on a little juice cause
my approach was coming up just a bit short. Moving the throttle forward
1/4 to 1/2 inch, i.e. giving it a little juice but certainly not a go
around type of thing, often times I would get a stumble, hicuup, drop in
RPM'S for 2-3 seconds before the horses responded.

Lot of convective turb lately and that power really comes in handy at
times on mid to short final. Kind of a shocker when the engine doesn't
respond quite nicely.

This has happened on a few birds, especially on hot days. I think what's
happening is the engine is just too rich, hey I've got the mixture all the
way in, it's hot (air less dense), and it's (way) hotter with the carb
heat on ( air much less dense), all enriching the mixture, and when I put
on a little power the accelerator pump in the carb over-enriches the
engine for just a little bit; causing the stumble.

Other pilots and the A&P just tell me to pour on the power a little
slower.

I think I'm going to follow a new SOP. Turn the carb heat off on
mid-final. Reasoning: no carb, esp a warm one is going to ice up in 30
seconds, sets me up better for a go-around, and will prevent this stumble
business (I did test it out at altitude, and it prevents or at least
seriously mitigates the stumble).

thoughts?
T

What's going to happen if you actually do have carb ice which hasn't burned
off by the time you turn carb heat off? I'd much rather attempt a go around
with the carb heat initially on than attempt a go around with the lingering
effects of carb ice.

I have no idea what DA you're talking about, but what you're describing is
trying to correct a problem with the mixture by controlling it with the carb
heat. If you're landing at a high DA airport, you shouldn't have the
mixture full rich. Setting the mixture on downwind is the solution to the
problem. On a 152 or 172 you can also have your hand on the throttle with
your thumb on the carb heat. It should be a natural reaction to push both
in together or push the carb heat in first on a go around.

On Sep 7, 2:58*am, Tman x@x wrote:
Flying a lot of 152s and 172s with carb heat lately. *When inbound, I've
been taught to pull the carb heat "on" downwind, hey actually use it as
a power control to slow the plane just a bit mid-field, and then more
importantly, just leave the thing on till clear of the runway and
cleaning up. *No matter what the temp, humidity. *And to have it on at
all times when the RPM is less than the green band. *Kind of a preventative.

A few times I have been coming in on short final and needed a burst of
power due to a sudden downdraft, or needed to pour on a little juice
cause my approach was coming up just a bit short. *Moving the throttle
forward 1/4 to 1/2 inch, i.e. giving it a little juice but certainly not
a go around type of thing, often times I would get a stumble, hicuup,
drop in RPM'S for 2-3 seconds before the horses responded.

Lot of convective turb lately and that power really comes in handy at
times on mid to short final. *Kind of a shocker when the engine doesn't
respond quite nicely.

This has happened on a few birds, especially on hot days. *I think
what's happening is the engine is just too rich, hey I've got the
mixture all the way in, it's hot (air less dense), and it's (way) hotter
with the carb heat on ( air much less dense), all enriching the mixture,
and when I put on a little power the accelerator pump in the carb
over-enriches the engine for just a little bit; causing the stumble.

Other pilots and the A&P just tell me to pour on the power a little slower.

terry wrote:
On short final when sure of
making it in, we turn off carby heat so we are ready to do a quick go
around if a kangaroo hops onto the runway. But I guess you guys dont
have kangaroos. :)

We have some in the zoos, but they don't usually make it out to the
airports.

What we do have, though, is deer. I just did a go-around yesterday
because they were having dinner right at the edge of the runway.

.... Alan
--
Alan Gerber
PP-ASEL
gerber AT panix DOT com

On Sep 6, 9:58*am, Tman x@x wrote:

I think I'm going to follow a new SOP. *Turn the carb heat off on
mid-final. *Reasoning: no carb, esp a warm one is going to ice up in 30
seconds, sets me up better for a go-around, and will prevent this
stumble business (I did test it out at altitude, and it prevents or at
least seriously mitigates the stumble).

Don't put any money on that bet. I've had carbs freeze up on me during
stop-n-goes from the time it takes to kick off the heat to the time it
takes to pour on the coals. The carb can freeze in seconds.

-Robert, CFII

On Sat, 6 Sep 2008 20:54:22 -0700 (PDT), "Robert M. Gary"
wrote:

On Sep 6, 9:58*am, Tman x@x wrote:

I think I'm going to follow a new SOP. *Turn the carb heat off on
mid-final. *Reasoning: no carb, esp a warm one is going to ice up in 30
seconds, sets me up better for a go-around, and will prevent this
stumble business (I did test it out at altitude, and it prevents or at
least seriously mitigates the stumble).

Don't put any money on that bet. I've had carbs freeze up on me during
stop-n-goes from the time it takes to kick off the heat to the time it
takes to pour on the coals. The carb can freeze in seconds.

-Robert, CFII

I'm with you Bob.
I once thought I'd throttle back and poke under some mist and pop out
the other side and resume. when the power came off the revs started
dropping and dropping and dropping. I bunged on full carb heat and
then full throttle and still the revs kept dropping. out the corner of
the eye I noticed a shaft of sunlight and turned toward the hole in
the mist. about 2 seconds into the sunlight and I had full power back
again. when it happens it happens quickly.

now back to the op's description of a rev drop on opening the
throttle.
my bet is that the carb has been in service for quite a while and the
leather bucket seal on the accelerator pump is knackered. it isnt
giving the full squirt of fuel on acceleration. the other possibility
is that the little jet pipe has moved out of the centre venturi
position and the squirt isnt making it up into the inlet tubing.
far better me thinks that he doesnt wank on creating new procedures
and gets the a&p's to check the carby functioning.

Stealth Pilot