Cowl Flaps

Well, hell, I feel cheated now.

I just went and checked the Cardinal POH, and guess what?

I was taught wrong.

You're supposed to leave 'em closed until you're on the ground when you descend. And you can even close 'em in a normal climb.

Damn.
 
Foxcow said:
Newer Arrows don't.
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they have louvers in the bottom of the cowling





Each plane is different in performance (closed/open) but generally you will see some performance increase with them closed even if it doesnt show up on the ASI.

There are many options and theories on operation of cowl flaps. pretty much use the POH and adjust (within limits) for temps and such
 
Foxcow said:
Newer Arrows don't.
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A lot of Piper singles don't. Comanches don't (at least the 180 and 250 HP models, don't know about the 400). Same for Mooneys. I think they are much more common in Cessnas than in some other piston GA makes.
 
tonyw said:
Well, hell, I feel cheated now.

I just went and checked the Cardinal POH, and guess what?

I was taught wrong.

You're supposed to leave 'em closed until you're on the ground when you descend. And you can even close 'em in a normal climb.
Click to expand...
I'm surprised that you were taught wrong. This isn't one of those "do because something says do it" situations.

The purpose is engine temperature management. Open increases airflow over the engine. Closed decreases airflow over the engine.

So,

when engine power is low and the engine will cool, you...

when engine power is high and the engine will heat up, you...

on a hot day you'd...

on a cold day you'd...

during cruise flight you'd...

The only one that's not necessarily intuitive is ground taxi, which has been mentioned.
 
MidlifeFlyer said:
I'm surprised that you were taught wrong. This isn't one of those "do because something says do it" situations.
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Me too. The guy who taught me this knew his stuff, and was the guy who was responsible for maintaining the Cardinal!

Ah, well. Live and learn, eh?

I think -- and this is just a guess -- that the reason he said to open the cowl flaps on descent was just in case I had to go around. It kind of makes sense. When you're going around, fussing with the flaps, the gear, etc, the last thing you need is one more thing to deal with (the cowl flaps). But then, if you're going around, and don't get to the cowl flaps for a few seconds, it's not going to kill the engine, either. Who knows?

But like I said, live and learn.
 
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