I’ve just found myself in yet another debate about whether carb heat should always be applied while landing. This time it started because a new TB9 owner experienced engine sputtering and a subsequent quitting of the engine on final in very hot temperatures. I was trained to always apply carb heat on final, even in the hot and humid climate I flew in during my early years. The TB10 manual says to apply as needed, and I’ve heard conflicting advice from flight instructors over the years. I suspect those instructors are simply parroting what they were taught. Can anyone point me to an authoritative source on the topic?
I can only say that I was taught to apply carb heat on reducing power to land regardless of temperature – usually downwind as opposed to final. Though I have had one instructor say “not required above 25degC” I am unhappy with this idea as to me its all about moisture content of the air, not temperature. The debate I have had with others is whether to move carb heat to cold on final at 2-300ft or only when advancing the throttle for T&G or Go-around / having landed and on roll – out. The deciding factor seeming to be down to aeroplane/engine type.
Regards, SD..
skydriller wrote:
The debate I have had with others is whether to move carb heat to cold on final at 2-300ft or only when advancing the throttle for T&G or Go-around / having landed and on roll – out.
It seems exceedingly unlikely that you would get any noticeable amount of carburettor icing in the 20 seconds or so remaining to touchdown when you pass 200-300 ft. On the other hand if you do need to do a go-around/balked landing, you don’t need one more thing to think about. I always turn off carb heat on short final, which is at about 200 ft. (When making an instrument approach, I turn off carb heat at about 200 ft about the DA.)
For the same reason you put the prop on fine pitch on final.
As per the POH
In the Cessna 150 the POH says carb heat cold after landing or on a baulked approach.
If your landing on a dew laiden grass runway and you go carb heat cold at the widely taught 200 feet sooner or later the engine will stop.
Bathman wrote:
If your landing on a dew laiden grass runway and you go carb heat cold at the widely taught 200 feet sooner or later the engine will stop.
Sooner or later, no doubt, but if it happens after landing, there’s no safety issue, is there? It could be embarrassing of course.
I have only ever applied carb heat if the conditions required it. Both the planes i have owned had carb air temperature indicators, so I knew if I needed (or didn’t) need it. Otherwise, I do not apply carb heat without an indication it is needed.
To my knowledge setting full power with carbheat ON may lead, depending on OAT / density altitude, to detonation, i set carbheat always to OFF in short final.
Once again I agree with @Skydriller. I hope this doesn’t become a habit🙂
I was reading an old Info PIlote the other day at the club and it was about the high percentage of accidents and hard landings due to expected carb icing.
This was the compounded when doing touch and goes which carb icing was expected to have formed during the approach and landing and had not cleared when the carb heat was returned to cold and full power applied, ending in an EFATO.
The answer to that is, get a carb heat gauge and see what happens. You might be surprised.
I was taught to apply carb heat on reducing power to descend, and to close it after landing. That was at Inverness EGPE on a C152. It was not required when checked out on a C150 at Grand Junction KGJT in July – west of the Rockies.
Later I changed to closing it at 2 -300’ on our Jodel DR1050, with O200, – until after landing at Broadford , Skye, the engine almost stopped when I opened the throttle to turn and backtrack, If it had been a go-around, it could have been a disaster.
The FAA state carb ice cannot occur above 25C. The Canadian CAA disagree, and say with mogas it can occur at any temp. I now start the take-off roll with carb heat on if carb ice is likely, closing it as I reach full power. I also do this when below carb ice temp with a wet deiced runway.
I’ve has several power losses and engine stoppages, but always with enough runway to land or stop. All in the Jodel with O200 and Mogas, none with Avgas and O200 in the Bolkow Junior. But frequent stoppages in both immediately after starting a cold engine. Assumed to be carb ice as carb had frost on the outside in cases where it was quickly looked at.
