I've been recently training guys on a couple of Luscombes (and a others) and an unusual trend has crept in regarding the operation of Carb heat prior to t/o and on the app to land. This is pertinent to the Continental in particular.
In these cases carb heat has been applied (pulled?) whilst taxying and right up to the point of departure, in one instance for over 4 minutes! that's a lot of unfiltered air! I'm sure most of the Luscombe chaps apply carb heat mainly during power checks and (strongly recommended in high medium to high risk conditions) just prior to applying full power to get airborne.
In the other cases, carb heat is being applied correctly when below 2000 rpm, say on base but then removed (pushed in?) a long way out on finals - more of a Warrior habit (Lycomings ). Our beautiful Continental is now purring along at around 1500 rpm on finals with a good chance of collecting that nasty ice once again.
in one case the time between pushing the carb heat in (removing it) and landing was over a minute and a half - long enough to make your heart miss a beat should you want to go around.I'm not saying the old girl will stop but, on demand, she may well take valuable seconds to
recover and to the uninitiated, this could lead to feeling of a potential engine failure at the very least. I's no big deal if you leave the carb heat out right up to landing. If it's a touch and go, then that's the point to remove the carb heat , or, at the very least remove the application on very short finals, although in testing conditions this is messy and distracting. If carb heat is left out,(applied) over the touch and go/ go around, again, it's not the end of the world either. About 2 HP. Sort strips could be a problem though.
All is good with my colleagues now, and my primary objective is providing guidance and safe operation of these old girls ( the Luscombe!), ensuring Luscombes are preserved (along with their pilots) that bit longer!
Just thought I'd mention it as I'm sure the vast majority of luscombe pilots operate the carb heat system correctly.
Sadly, Autumn is not far away..
carb ice is sneaking up..
Happy flying all.