Carb Heat on Dirt

[MSP Aviation]

Hi all,

I did my first flight on a 172 this summer in Utah. Our final landing was on the airport's dirt/dust strip. Just before landing, the instructor had me cut off the carb heat so the air would be coming from the filter, not the unfiltered heated air. (this was an early 172 modified with a 180hp engine, i'm not sure if the intake is the same on other airframes, i've only flown this 172 once). this was to prolong the life of the engine. do you guys do this when landing on not-well-prepared dirt/dust/sand with your aircraft? just felt like sharing, and curious as to your opinions.

MSP

[Airbus38]

Hi there,

In a lot of aircraft, the Carb Heat is closed prior to landing as a matter of routine. I guess the reasons are twofold -

1) If the air is unfiltered with the C/Ht hot, the increased chance of something entering the engine nearer the ground.
2) In case of a sudden need to 'go around' or recover from the incipient stall near the ground ensuring full power is instantaneously available. Equally applicable if doing T+G landings, selecting C/Ht cold is one less thing to do on the ground roll.

A38

[QDMQDMQDM]

I think mostly a good idea to close carb heat just before landing for these two reasons. Don't always remember though!

[MSP Aviation]

nice to hear it's a common practice, i've always switched it off on the landing roll during T/Gs, but so far all my training's been done out of KISP, which has 737 service, (and the nice facilities that come with said service) and not much debris to worry about!

[Spodman]

I pull off the carbie heat at 300' (PA28), but have made a deal with myself to LEAVE IT ALONE if I notice in the flare. Have done one go-around with the heat on and didn't react to the low performance (shame...)

[Whirlybird]

As we've discussed on other threads on this subject, whether or not it's safe to put off the carb heat on final depends on the aircraft type, and you need to read the POH. From my own experience, DON'T do it on a C150; or you are quite likely to get carb ice before you land!

[rustle]

Originally Posted by Whirlybird

As we've discussed on other threads on this subject, whether or not it's safe to put off the carb heat on final depends on the aircraft type, and you need to read the POH. From my own experience, DON'T do it on a C150; or you are quite likely to get carb ice before you land!

At least as important as any POH (or bulletin board) recommendation in relation to carb heat is an understanding of ambient conditions (temp & humidity) and the likelihood of carb ice, combined with your actual experience of carb ice during enroute FREDA checks and/or (in the case of circuit bashing) during your downwind check of carb heat on that day and in those conditions.

[IO540]

I read somewhere that flying around with carb heat ON significantly reduces engine life, due to ingestion of abrasive dirt. This is even if done at altitude.

It makes sense if you do regular oil analysis. There is a lot of silicon in the oil, which comes from soil ingestion. This isn't doing the engine any good. It's what emery paper is made of.

[172driver]

Originally Posted by rustle

At least as important as any POH (or bulletin board) recommendation in relation to carb heat is an understanding of ambient conditions (temp & humidity) and the likelihood of carb ice, combined with your actual experience of carb ice during enroute FREDA checks and/or (in the case of circuit bashing) during your downwind check of carb heat on that day and in those conditions.

rustle, exactly. I personally only use it if and when required and definitley have it 'off' for a landing (although I admit to sometimes forgetting that), for the two reasons mentioned above: power avail for a GA and dirt ingestion.

[gasax]

If its really dusty then carb heat off in most aircraft is the preferred method. Interestingly with a Gipsy the handbook recommends 'warm air' - because it causes the air to turn abruptly through 90 odd degrees and provides a level of filtering.

But in this country there are few places where this stuff is really needed - farm strips during a very dry harvest, beaches on the dry stuff. Otherwise dust ingestion is going to take much longer to kill an engine than anything else will.

[Whirlybird]

At least as important as any POH (or bulletin board) recommendation in relation to carb heat is an understanding of ambient conditions (temp & humidity) and the likelihood of carb ice, combined with your actual experience of carb ice during enroute FREDA checks and/or (in the case of circuit bashing) during your downwind check of carb heat on that day and in those conditions.

Exactly. And I've yet to have a flight in this country in a C150 where you don't have some indication of carb ice.

[the dean]

Originally Posted by Whirlybird

As we've discussed on other threads on this subject, whether or not it's safe to put off the carb heat on final depends on the aircraft type, and you need to read the POH. From my own experience, DON'T do it on a C150; or you are quite likely to get carb ice before you land!

i agree with whirly...

in those few seconds just at the wrong time you can get ice..

leave it on until you are on the ground...and if you have to do a go round then just get used to having to put it off..AFTER NOT BEFORE full power has been applied...

i would prefer the little dust it might ingest while still moving on the runway to finish the landing roll ( and i am not suggesting taxying with it on ) to putting if off at 300 feet and then finding having to do a go round that the engine coughs or worse...

which is worse ...the possibility of a little light dust ingestion or the almost certainty of some ice even on ( and more likely then indeed ) your average summers day ( depending on your latitude and location that is...)

the dean.