[Flyin'Dutch']

Is there a reason why fully opening the throttle shouldn't also set the carb heat to cold via some sort of mechanical linkage?

Certification?

[Morten]

Err... if you do have carb icing you would want carb heat applied whilst you are also applying full power !?

Morten

[pullup]

"Time to flare....cold air"

[Gertie]

Is there a reason why fully opening the throttle shouldn't also set the carb heat to cold via some sort of mechanical linkage?

In my case that's exactly what happens - the mechanical linkage is the one between my thumb and the rest of my hand.

(Provided I remember, on the rare occasions I'm flying a non-injected aircraft, that I am actually flying a non-injected aircraft - that's the hard bit.)

[flyingeeza]

Carb heat left on with full power applied is a bad habit, and the engine doesn't like it much either.
But do not try it at DA of 8000' with the OAT around 38degC. As it is you can barely climb with two notches of flap in a loaded Cherokee 140 in those conditions, so carb heat cold on short final is indeed a very good habit to get into.

[Paul_Sengupta]

Where on earth are you going to find a DA of 8000ft in this country? If you get that, the airport is probably on fire.

But yes, agree. I had to thermal soar a PA28 back up to altitude in warm and sunny Florida once after the carb heat cable broke with the carb heat "on" from a PFL. With full flap it was still descending. With two stages it was still descending. With one stage it barely held level. With no flap I got a very gently climb until I got into a thermal over the trees when I spiralled in that to get back up to altitude. I was a few hundred feet MSL at the time, but probably with a DA of about 2000ft.

[Rob L]

Carb heat left on with full power applied is a bad habit, and the engine doesn't like it much either.
But do not try it at DA of 8000' with the OAT around 38degC. As it is you can barely climb with two notches of flap in a loaded Cherokee 140 in those conditions, so carb heat cold on short final is indeed a very good habit to get into.

Your picture quotes Lycoming, flyingeeza. Your words state "bad habit" inter alia, but have you ever flown behind a small Continental?

I mean no harm, but your post suggests tarring all engines with the same brush.
Rob

[flyingeeza]

Carb heat left on with full power applied is a bad habit, and the engine doesn't like it much either.
But do not try it at DA of 8000' with the OAT around 38degC. As it is you can barely climb with two notches of flap in a loaded Cherokee 140 in those conditions, so carb heat cold on short final is indeed a very good habit to get into.

Your picture quotes Lycoming, flyingeeza. Your words state "bad habit" inter alia, but have you ever flown behind a small Continental?

I mean no harm, but your post suggests tarring all engines with the same brush.
Rob

Only going on what all of my instructors have been teaching me since 1979. The aircraft down in the Channel was indeed Lycoming powered so that's the subject engine here. And it's the habit I'm on about. Why leave the carb heat on once you're over the numbers??
And yes, I have spent many happy hours flying C150/152 including about 50 hours in the one in the photo below...a carb ice prang on a sunny warm afternoon! (not my prang)

[flyingeeza]

My feet...in my QuicksilverMX1

[Paul_Sengupta]

150 = Continental, 152 = Lycoming.

[GAFlyer4Fun]

Getting this thread back on track...

...
Incidentally, once the engine has actually stopped it's too late to apply carb heat, surely. Mine at least relies on intake air being drawn over a (rapidly cooling) heat exchanger and through the carb. If the engine's not turning there is no air being drawn through. Never mind wriggling the throttle - you need to be cranking the engine on the starter or diving!

Have you considered how high to cruise to have a sporting chance of being able to re-start an engine in a dive? I think there is a reason why during PPL training we are taught to set up a glide and not a dive. (Guessing it is something to do with typical GA cruising altitudes not being high enough).

[Gertie]

(Guessing it is something to do with typical GA cruising altitudes not being high enough).

What is "high enough"? - I'm typically around 6,000' (weather and airspace permitting) but only because I CBA to spend the time getting higher. From there you've got minutes and miles if the engine stops.

[matthew_w100]

Getting this thread back on track...
Have you considered how high to cruise to have a sporting chance of being able to re-start an engine in a dive? I think there is a reason why during PPL training we are taught to set up a glide and not a dive. (Guessing it is something to do with typical GA cruising altitudes not being high enough).

I think you've misunderstood. I wasn't advocating diving - and certainly not to restart the engine (though we do so to restart when our engine stops at the top of a loop...) I was pointing out you need the engine to be turning for the carb heat to do anything useful. I remember saying this to my FI many decades ago as he was suggesting the first thing he'd do on engine failure, before even setting up a glide, would be to put carb heat on. He agreed but said that in the event of a real failure he'd be cranking the engine on the starter all the way down to the ground. This does not appear to be part of the standard PPL drill.

But when our engine does stop in (negative g) in a loop it only takes a couple of hundred feet to start it again

[Morten]

From what I read, few engine failures actually lead to a stationary prop. Carb ice in particular should not lead to the prop stopping. As long as the engine is turning, it will try to suck air in. As long as it is sucking air in, making it suck in warm air (and the engine compartment will stay warm for a while even if there's no fire in the hole) should alleviate carb icing.

Morten

[alexbrett2]

He agreed but said that in the event of a real failure he'd be cranking the engine on the starter all the way down to the ground. This does not appear to be part of the standard PPL drill.

I'm guessing this actually means repeated attempts to start rather than continuously, as I'd imagine the latter runs the risk of burning out the starter and/or flattening the battery quite early, which if it is e.g. a carb ice problem which melts itself as you get lower, but you then can no longer try and start the thing, would be quite bad?