Mitty opined

Gents,

Though this is not strictly an IFR question, I am pretty sure that you have
opinions that I would like to get.

Subject is Lycoming O-360 engines. I have flown behind a number of them in
Pipers and the POH instruction on carb heat is always "as required."
Specifically there is no requirement for carb heat on the landing checklist.
This makes sense to me as the intake charge is routed through the oil pan cum
intake manifold and, with the throttle nearly closed hence low flow
velocity, should get adequately warmed up. At least that is my rationale
for why the POH does not call for heat.

I am about to get checked out in a Civil Air Patrol 172 that has an STC'd
O-360 installed in place of the original Lycoming O-320. The 172 POH wants
carb heat on approach. This makes no sense to me. If I have to do a go
around it is just one more workload item/one more thing to forget and, from
my Piper experience, it does not appear to be necessary. My guess, without
benefit of any actual facts, is that this POH requirement comes from
Cessna's Continental roots and has no engineering justification. So it
seems wise to ignore it.

Comments? (Please, let's not go to the FARS with this question. That is not
my interest.)

I flys a 172 with an O-360 engine and d not use carb heat on approach, I have
never had a problem, on approach.

The 2 times that I have had carb ice problems have been in cruise and high
humidity. Go figure.


-ash
Cthulhu in 2005!
Why wait for nature?