Carb heat...again!
Joined: Apr 2002
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From: Strya
In the Tomahawk, the POH clearly states that in the approach carb heat should only be used if there is an indication of icing. (which can be checked for on downwind and then the control left well alone) It also states that full throttle operation eg go around with carb heat on can cause detonation (the tomahawk has no accelerator pump).
Yet still instructors tell students to apply carb heat on base in a Tomahawk....
What I'm trying to say is, if an instructor says "there is only one way etc etc" and it's different to the POH, then be somewhat sceptical about where they got this and other facts from. Many cr@p myths are perpetuated by bad instructors and beleived by students.
Don't be afraid to question why? Or best of all..
Read the POH!
Yet still instructors tell students to apply carb heat on base in a Tomahawk....
What I'm trying to say is, if an instructor says "there is only one way etc etc" and it's different to the POH, then be somewhat sceptical about where they got this and other facts from. Many cr@p myths are perpetuated by bad instructors and beleived by students.
Don't be afraid to question why? Or best of all..
Read the POH!
Joined: Aug 2001
Posts: 306
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From: UK Work: London. Home: East Anglia
didn't the RAF permanently wire-lock the carb-heat on all their Chipmunks to hot?
They did... but on the Chipmunk it's not really "hot, it's more like "warm" - all that happens is that the engine starts breathing warm(-ish) air from within the cowling rather than the chillier stuff outside. So the power loss is much less significant. It's still a loss though, but the RAF operated its Chippies from HUGE long airfields, so didn't really need the power.
With the carb heat being less effective it takes a lot longer to clear any ice.
Similar set-up on the Yak-52 where the external air scoop retracts into the cowling for warm air. The Yak is more prone to carb-ice on the ground than in the air, but I got a touch of it the other day, in a spinning exercise, so it's still possible.
Joined: Dec 2000
Posts: 166
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From: UK
Similar set-up on the Yak-52 where the external air scoop retracts into the cowling for warm air. The Yak is more prone to carb-ice on the ground than in the air, but I got a touch of it the other day, in a spinning exercise, so it's still possible.
The Russian flight manual only states that "at temperatures of +10c or more the carb heat may be left out", whatever that means. That tends to suggest at less than +10c carb heat should be left hot. Apparently some Yak 50's did not have a carb heat flap at all, the mechanics took them off!
Whatever the answer I have picked up icing whilst taxying at temps of +5c or less, but never in flight so long as you have a power setting above 'economy cruise'
As the carb intake temp should remain between +10 and +45 the lever seems to be more use as a carb cooler on summer days and a carb heater in winter
Joined: Aug 2001
Posts: 306
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From: UK Work: London. Home: East Anglia
We have a long running debate in our group regarding the Yak 52 carb heat (or not). Can you operate yours in flight? We have to back off the speed to about 170kph before we can move the lever !
I know what you mean, it is not easy to go from cool to warm with any kind of speed on. 170kph seems a sensible limit for trying.
And the whole engineering of the thing is less-than-perfect, especially that hinge at the back.
I too have used it only infrequently in flight, and have not had a lot of trouble hitherto. But I shall be using it more in future. Never had carb icing at steady power of 60%/6 or above, but a couple of months ago I landed somewhere just as it was starting to drizzle, and at the end of the landing roll found I couldn't open the throttle to taxi off the grass runway! (as you know that's a pretty infallible sign of carb icing on a Yak). Fortunately I had a few knots on and was slightly downhill so able to clear the runway while I whacked it into warm air for a couple of minutes - problem solved. And then the other day I had a sticky throttle coming out of a spin recovery. It gave me a little bit of throttle, enough to maintain level flight at 170kph and 82%, but didn't want to go forward past that and I was keen not to use excessive force and risk bending the linkage. So again I put it into warm air, looked at fields (but was at 6000 feet so loads of options) and two minutes later exercised the throttle gently and all back to normal. Again, it was an absolutely classic carb icing day, prop throwing offf contrails at run-up, little wispy patches of vapour visible at all levels.
I've decided next time I'm doing stalls or spins I'll put it into warm air for the last thousand feet of the climb and the clearing turns, and leave it there until I restore normal cruise or high-power aeros.
Joined: Dec 2000
Posts: 166
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From: UK
Lowtimer,
(...and not wishing to hijack this thread into a Yak debate)
Very novel how carb ice on the Yak actually affects throttle lever travel rather than the more common choking the carb on Western engines.
Strangest incident I had was whilst extended taxying from one side of the airfield to the other. The RPM kept creeping up and up and up despite the throttle being fully shut. By the time it got to 60% the brakes were getting a trifle warm and my right hand knackered. I was about to cut the switches and roll to a halt when I decided to try the carb heat. A bit of a fiddle as the right hand was in fulltime use on the brakes so the left hand had to cross over for the lever. within 10 seconds the RPM fell back to normal then the engine spluttered as it swallowed the water !
(...and not wishing to hijack this thread into a Yak debate)
Very novel how carb ice on the Yak actually affects throttle lever travel rather than the more common choking the carb on Western engines.
Strangest incident I had was whilst extended taxying from one side of the airfield to the other. The RPM kept creeping up and up and up despite the throttle being fully shut. By the time it got to 60% the brakes were getting a trifle warm and my right hand knackered. I was about to cut the switches and roll to a halt when I decided to try the carb heat. A bit of a fiddle as the right hand was in fulltime use on the brakes so the left hand had to cross over for the lever. within 10 seconds the RPM fell back to normal then the engine spluttered as it swallowed the water !
Joined: Aug 2002
Posts: 205
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From: northants
Satco "The Russian flight manual only states that "at temperatures of +10c or more the carb heat may be left out", whatever that means. That tends to suggest at less than +10c carb heat should be left hot."
The manual also states "Hot when outside temp is below +10C, otherwise colc, or in-between position according to outside temp".
Also " If carb icing is experienced during the descent, the throttle may become jammed. In this case, close the gills to maximise heat, ensure carb heat hot is selected, and gently try to move the throttle back and forth until the ice is broken and the throttle moves. It may be necessary to continue to make small throttle movements to prevent further jamming if icing conditions are very bad"
Lowtimer, do you not apply carb heat in a Cessna when closing the throttle for spins/landing, so why should the Yak be different.
If you experience carb icing on the ground, it will happen when airborne.
The manual also states "Hot when outside temp is below +10C, otherwise colc, or in-between position according to outside temp".
Also " If carb icing is experienced during the descent, the throttle may become jammed. In this case, close the gills to maximise heat, ensure carb heat hot is selected, and gently try to move the throttle back and forth until the ice is broken and the throttle moves. It may be necessary to continue to make small throttle movements to prevent further jamming if icing conditions are very bad"
Lowtimer, do you not apply carb heat in a Cessna when closing the throttle for spins/landing, so why should the Yak be different.
If you experience carb icing on the ground, it will happen when airborne.
