Use of Carb Heat (merged)
Why do it if it's not fun?
Joined: Jul 2001
Posts: 4,782
Likes: 12
From: Bournemouth
Good points re the difference between Continental and Lycoming.
However, does it not make sense to teach students a technique which will work for the majority of engines? I teach my students to leave the carb heat on until either going around or after landing. As already mentioned, in some aircraft doing anything else is asking for an engine failure in the right conditions. But even if your engine is not prone to carb icing, teaching it this way will enable the student to go on and fly these Continental-powered aircraft without needing to change their technique.
Discuss.....
FFF
---------------
However, does it not make sense to teach students a technique which will work for the majority of engines? I teach my students to leave the carb heat on until either going around or after landing. As already mentioned, in some aircraft doing anything else is asking for an engine failure in the right conditions. But even if your engine is not prone to carb icing, teaching it this way will enable the student to go on and fly these Continental-powered aircraft without needing to change their technique.
Discuss.....
FFF
---------------
Joined: Apr 2003
Posts: 7
Likes: 0
From: Mangakino, New Zealand
Carb heat
Fully agree with J430. Been in light aviation as an instructor for 35 years. had all sorts of carb icing including a cut at full throttle climbing out of Wellington in a 172.
Many stopped prop landings in early days because we were taught to put carb heat off at 300ft or on final.. Now it stays on until I cross the fence or after landing.
As for stalls what would you do in an emergency? Start groping for the carb heat knob instead of hitting the throttle?
To keep the FTO's happy I put the carb heat cold approaching the stall but personally go power first and get the aircraft climbing than worry about fiinding another 100rpm.
Many stopped prop landings in early days because we were taught to put carb heat off at 300ft or on final.. Now it stays on until I cross the fence or after landing.
As for stalls what would you do in an emergency? Start groping for the carb heat knob instead of hitting the throttle?
To keep the FTO's happy I put the carb heat cold approaching the stall but personally go power first and get the aircraft climbing than worry about fiinding another 100rpm.
Joined: Aug 2004
Posts: 409
Likes: 0
From: South of the border
Gday Charlie fox
there are many different models of the venerable BN2 my man, and sadly ours were not injected - for some reason that 260 horse Lyc was quite prone to a bit of ice, updraught carbs or something...
Agree with tutu and others - stall situation, get the power coming up, fly the aeroplane, then fine tune things. Prioritise.
there are many different models of the venerable BN2 my man, and sadly ours were not injected - for some reason that 260 horse Lyc was quite prone to a bit of ice, updraught carbs or something...
Agree with tutu and others - stall situation, get the power coming up, fly the aeroplane, then fine tune things. Prioritise.
The Original Whirly
Joined: Feb 1999
Aviation Qualifications: CPL
Posts: 4,327
Likes: 2
From: Belper, Derbyshire, UK
FFF,
What you say makes sense. However, while teaching it, why not point out the reasons, and the fact that different types require different treatment, and that different engines are different, and that when flying a new type you should read the POH first and go by that.
As a student, I was never told any of the above. I was told to leave the carb heat on all the way down as it happens. Later on, another instructor said I should push it in on short final. Explanations for both techniques made sense to me. What made less sense was why each egotistical instructor insisted it was done his way, that this was right, and no other way was. What made even less sense, and IMHO is downright dangerous, is that no-one mentioned that it could depend on the aircraft or engine type. I suspect they didn't even know!!!
Students aren't stupid. You can tell them to do something, while pointing out that this may not be the way they should do it now and for evermore, not matter what.
This isn't kindergarten stuff. It's basic, yes, but a lot of it is badly taught at times, and frequently misunderstood. More discussion of it can only be to the good.
What you say makes sense. However, while teaching it, why not point out the reasons, and the fact that different types require different treatment, and that different engines are different, and that when flying a new type you should read the POH first and go by that.
As a student, I was never told any of the above. I was told to leave the carb heat on all the way down as it happens. Later on, another instructor said I should push it in on short final. Explanations for both techniques made sense to me. What made less sense was why each egotistical instructor insisted it was done his way, that this was right, and no other way was. What made even less sense, and IMHO is downright dangerous, is that no-one mentioned that it could depend on the aircraft or engine type. I suspect they didn't even know!!!
Students aren't stupid. You can tell them to do something, while pointing out that this may not be the way they should do it now and for evermore, not matter what.
This isn't kindergarten stuff. It's basic, yes, but a lot of it is badly taught at times, and frequently misunderstood. More discussion of it can only be to the good.
Joined: Jan 2005
Posts: 18
Likes: 0
From: the Netherlands
Carb heat off in the before stall checklist, with carb heat on it won't give you full pwr to recover, and in the short period in which you do the stall practise you won't get ice build-up (unless you are flying a pa32-260 that builds ice within a few minutes even when its 20 degrees outside!). On short final I normally put the carb heat off at 200 feet or something, again depending on type and conditions. But it should always be off when making a go-around, especially on hot humid days!
just my 2 cents............
just my 2 cents............
Joined: Jun 2004
Posts: 125
Likes: 0
From: ENZED
Industry standard(aero club/flying school) is carb heat off at around 60kts prior to stall recovery.
On approach, should be on prior to reducing power for approach, LEAVE IT ON when on finals, untill you are CERTAIN of making the runway in a full glide situation. IE just prior to crossing the fence.
Carb heat is there to be used.
Cheers!
On approach, should be on prior to reducing power for approach, LEAVE IT ON when on finals, untill you are CERTAIN of making the runway in a full glide situation. IE just prior to crossing the fence.
Carb heat is there to be used.
Cheers!
Joined: Dec 1999
Posts: 3,077
Likes: 1
From: Oop North, UK
What made less sense was why each egotistical instructor insisted it was done his way, that this was right, and no other way was.
Joined: Mar 2002
Posts: 2,814
Likes: 0
From: Euroland
with carb heat on it won't give you full pwr to recover
Perhaps we need to remember that the recovery from the stall is made by reducing the angle of attack.......i.e. usually moving the stick forward.
Adding power is used to minimise the height loss.
Taking that in mind and the worst case scenario of a stall at low level one has to think about what actions are required after the stick is moved forward.
The most deadly stall/spin position is the old base to final turn. Usually at a height where even those that put the carb heat to cold on short final have hot air selected.
Thus the stall should be entered with the carb heat hot air on so that the student can practice all of the actions required to be completed in the worst case scenario.
Regards,
DFC
Perhaps we need to remember that the recovery from the stall is made by reducing the angle of attack.......i.e. usually moving the stick forward.
Adding power is used to minimise the height loss.
Taking that in mind and the worst case scenario of a stall at low level one has to think about what actions are required after the stick is moved forward.
The most deadly stall/spin position is the old base to final turn. Usually at a height where even those that put the carb heat to cold on short final have hot air selected.
Thus the stall should be entered with the carb heat hot air on so that the student can practice all of the actions required to be completed in the worst case scenario.
Regards,
DFC
Joined: Aug 2004
Posts: 3,557
Likes: 95
From: moon
I confess to having had the engine go silent on a 150 after lining up. Pushed the throttle in too fast. Embarrasing to have to tell the tower, but it started first try and I was more careful afterwards.
C150's will ice if you look at them wrong. Carb heat goes on just before I throttle back and reconfigure for landing. It stays on till about 300-250 feet which is when I take a decision that my approach is good enough to land. - that is if I remember it!
C150's will ice if you look at them wrong. Carb heat goes on just before I throttle back and reconfigure for landing. It stays on till about 300-250 feet which is when I take a decision that my approach is good enough to land. - that is if I remember it!
The Original Whirly
Joined: Feb 1999
Aviation Qualifications: CPL
Posts: 4,327
Likes: 2
From: Belper, Derbyshire, UK
Sunfish,
I've had something similar. I had to wait quite a while to backtrack, and suddenly the engine died. I taxied back to find out what was wrong, and got a very, very informative impromptu lecture on the differences between Continental and Lycoming engines.
After that I started leaving the carb heat on until I'd lined up. The problem with that is, sometimes I forgot to push it in. Not that it seemed to matter much in the C150 with one person; we just climbed a little more slowly, that's all. But I now have a new routine before take-off - after power checks, carb heat out, then pre-take off checks, then carb heat in. Then just give it a short blast of carb heat prior to lining up; I won't forget it, since it hasn't then been on long.
One thing's for sure; since I started flying the C150, I'm a lot more aware of RPM, how the engine sounds, and noting immediately if all just doesn't feel quite right. Which can only be to the good, of course. But I can't help wondering if the higher accident rate for the C150 over the C152 isn't due to pilots transferring from one to the other without knowing all of the above.
I confess to having had the engine go silent on a 150 after lining up. Pushed the throttle in too fast. Embarrasing to have to tell the tower, but it started first try and I was more careful afterwards.
After that I started leaving the carb heat on until I'd lined up. The problem with that is, sometimes I forgot to push it in. Not that it seemed to matter much in the C150 with one person; we just climbed a little more slowly, that's all. But I now have a new routine before take-off - after power checks, carb heat out, then pre-take off checks, then carb heat in. Then just give it a short blast of carb heat prior to lining up; I won't forget it, since it hasn't then been on long.
One thing's for sure; since I started flying the C150, I'm a lot more aware of RPM, how the engine sounds, and noting immediately if all just doesn't feel quite right. Which can only be to the good, of course. But I can't help wondering if the higher accident rate for the C150 over the C152 isn't due to pilots transferring from one to the other without knowing all of the above.
Thread Starter
Joined: Sep 2003
Posts: 307
Likes: 0
From: Not NZ anymore sadly!
The 'recommended' technique
Whats being recommended is in stall training:
Carb Heat away, then power.
In real life though, which is why we spend so much time training, my argument is that habitual 'carb heat then power' may not be best at all.
Okay at altitude prob no great probs which goes first but low on a short final, different story.
NZ is mostly a Cessna equipped country, putting 'both to the firewall' almost simulatneously is easy but in other types not so.
Hence if we train something one way, when the time really comes, faffing about to stow heat could/would become the 'automatic' priority, and in a non-Cessna that could be dangerous. Wudn't you rather you rather be pushing for some go-forward first, rather than trying to get rid of a bit of heated air in the front end?
The loss of 3 or 4 % of rpm when full power is requested with Carb Heat ON, is hardly going to be noticed for a few seconds is it?
Carb Heat away, then power.
In real life though, which is why we spend so much time training, my argument is that habitual 'carb heat then power' may not be best at all.
Okay at altitude prob no great probs which goes first but low on a short final, different story.
NZ is mostly a Cessna equipped country, putting 'both to the firewall' almost simulatneously is easy but in other types not so.
Hence if we train something one way, when the time really comes, faffing about to stow heat could/would become the 'automatic' priority, and in a non-Cessna that could be dangerous. Wudn't you rather you rather be pushing for some go-forward first, rather than trying to get rid of a bit of heated air in the front end?
The loss of 3 or 4 % of rpm when full power is requested with Carb Heat ON, is hardly going to be noticed for a few seconds is it?
Joined: Jan 2004
Posts: 43
Likes: 0
From: New Zealand
Damn Straight 1279shp
spose its the same argument of teching recovery at onset or recovery at the stall.
I think both of them are nescesary, but for a habitual process you want pilots to recognise early or recover automatically before the thing stalls.
keep ya powder dry
1M
PS. What dus it matter to you...dont you drive a turbine?
spose its the same argument of teching recovery at onset or recovery at the stall.
I think both of them are nescesary, but for a habitual process you want pilots to recognise early or recover automatically before the thing stalls.
keep ya powder dry
1M
PS. What dus it matter to you...dont you drive a turbine?
Joined: Dec 2000
Posts: 3,049
Likes: 0
From: Sydney NSW Australia
funny thing is, in my training many moons ago, i was taught to use carby heat when needed only, as constant use can increase the risk of detonation, i was taught in Piper warriors, archers and arrows. i have only ever suffered a bout of carby ice on a long descent during a nav on about a 15 deg day after fog lifting- high humidity.
I will only use carby heat without evidence of icing on long descents in raining or very humid conditions.
There has only been 1 time i have had an engine stop on mid final, i set up the approach, pulled power to idle, and the prop stopped, i was flying a Jabiru at the time. i landed normally and rolled to a stop on the taxiway, after a quick check of the essentials, fuel good, no fire etc, i restarted with some difficulty, and taxied back to the hangar, first assumptions were carby ice, and not to worry about it, but i still removed the cowl, and found that the idle position throttle stop on the carby had broken off, allowing the throttle to close completly.
I would be curious to know why different techniques are used!
I will only use carby heat without evidence of icing on long descents in raining or very humid conditions.
There has only been 1 time i have had an engine stop on mid final, i set up the approach, pulled power to idle, and the prop stopped, i was flying a Jabiru at the time. i landed normally and rolled to a stop on the taxiway, after a quick check of the essentials, fuel good, no fire etc, i restarted with some difficulty, and taxied back to the hangar, first assumptions were carby ice, and not to worry about it, but i still removed the cowl, and found that the idle position throttle stop on the carby had broken off, allowing the throttle to close completly.
I would be curious to know why different techniques are used!
Guest
Posts: n/a
Just to add a couple of things:
The current training guidance (so I'm told) is to set CH hot on downwind and then set back to cold on final. This thinking is based on the assumption that for CH to be effective, the engine must inducting (revving) to a greater degree. CH with an idling engine is not very effective (so the CAA say).
The discussion thus far seems to be centre on responding to training drills where you know when you are going to go around. The reality is that the need to go-around can be extremely sudden and unexpected. For me it is power, then drag flap, then CH cold. At the very worst I slow the rate of descent immediately.
I have never heard an engine cough and splutter because of CH, only because the power is applied too suddenly regardless of CH setting.
The current training guidance (so I'm told) is to set CH hot on downwind and then set back to cold on final. This thinking is based on the assumption that for CH to be effective, the engine must inducting (revving) to a greater degree. CH with an idling engine is not very effective (so the CAA say).
The discussion thus far seems to be centre on responding to training drills where you know when you are going to go around. The reality is that the need to go-around can be extremely sudden and unexpected. For me it is power, then drag flap, then CH cold. At the very worst I slow the rate of descent immediately.
I have never heard an engine cough and splutter because of CH, only because the power is applied too suddenly regardless of CH setting.
Joined: Apr 2005
Posts: 1,415
Likes: 9
From: Australia
In the Cessna 150/52/172 series, carb heat should be left on until after landing. During a go-around if the carb heat has been previously on during final approach (which it normally will be) the throttle should be opened to full power first, followed by carb heat to off. Makes sense, as the full throttle with carb heat on ensures that hot air dissipates any previous ice build up thus ensuring full power. Carb Ice can build up amazingly quickly with low power and carb heat cold under certain atmospheric conditions.
Read the Cessna 172 manfacturer's POH which states quite clearly: "Baulked Landing - Throttle wide open - Carburetor Heat - cold. Similarly: "After Landing - Wing flaps up - Carburetor Heat - Cold.
For a touch and go you should apply full throttle first - followed by carb heat to cold - same as for go-around procedure.
The aircraft and engine manufacturer would not recommend these procedures unless they had been thoroughly researched and in any case these procedures form part of the certification program.
My advice? You can't go wrong if you stick to the manufacturer's advice. If you think the manufacturer is wrong, then conduct your own measured trials and give the manufacturer the benefit of your expert advice. I am sure it would be greatly appreciated.
Read the Cessna 172 manfacturer's POH which states quite clearly: "Baulked Landing - Throttle wide open - Carburetor Heat - cold. Similarly: "After Landing - Wing flaps up - Carburetor Heat - Cold.
For a touch and go you should apply full throttle first - followed by carb heat to cold - same as for go-around procedure.
The aircraft and engine manufacturer would not recommend these procedures unless they had been thoroughly researched and in any case these procedures form part of the certification program.
My advice? You can't go wrong if you stick to the manufacturer's advice. If you think the manufacturer is wrong, then conduct your own measured trials and give the manufacturer the benefit of your expert advice. I am sure it would be greatly appreciated.
Joined: Oct 2000
Posts: 461
Likes: 0
From: Bristol
High Wing Drifter
I have had a near refusal of an engine to run on carb heat "on", but it was in extreme circumstances, on a a Harvard, P&W 1340 cubes, 650 odd bhp, OAT about 35deg, field 4000ft amsl.
This was at the end of a simulated forced landing, and on opening up the engine just coughed and spluttered until the carb heat went back to cold. And, no, it was not caused by too rapid throttle opening.
I have also heard of a case of an aircraft having engine cut-out on takeoff following carb icing on a long taxy out.
Moral. Most of the time everthing is OK. Just now and then you get bitten.
Regards, Dick W
I have had a near refusal of an engine to run on carb heat "on", but it was in extreme circumstances, on a a Harvard, P&W 1340 cubes, 650 odd bhp, OAT about 35deg, field 4000ft amsl.
This was at the end of a simulated forced landing, and on opening up the engine just coughed and spluttered until the carb heat went back to cold. And, no, it was not caused by too rapid throttle opening.
I have also heard of a case of an aircraft having engine cut-out on takeoff following carb icing on a long taxy out.
Moral. Most of the time everthing is OK. Just now and then you get bitten.
Regards, Dick W
Guest
Posts: n/a
I have had a near refusal of an engine to run on carb heat "on", but it was in extreme circumstances, on a a Harvard, P&W 1340 cubes, 650 odd bhp, OAT about 35deg, field 4000ft amsl.
(I jest of course) 
I have also heard of a case of an aircraft having engine cut-out on takeoff following carb icing on a long taxy out.
Moral. Most of the time everthing is OK. Just now and then you get bitten.