How does a cowl flap work

Pilots of America. Cowl flaps: Never used them before. My understanding - opened up, they allow more airflow over the engine for cooling. Are they normally operated on a simple procedure like open during taxi, open during takeoff and climb, closed during cruise?

Or is it more complicated than that? Matthew , Jul 1, Ideally, you look at CHT to determine when to open them. But it often ends up being just like you describe except they should also be closed for descent and landing, and open for go-around. MAKG1 , Jul 1, Read the POH of the appropriate airplane. You may find some occasional differences, but generally: open on startup, taxi, takeoff and climb.

Close in cruise assuming temps come down and stabilize. Keep closed until landing then open once clear of runway. Fearless Tower , Jul 1, Sounds like it's a simple enough concept.

I can understand things better when I know the "why" behind it. I might be riding along in a soon and wanted to understand the usage. This may be further modulated using the mixture control in some cases.

RotorDude , Jul 1, Joined: Apr 8, Messages: 31, Joined: Jun 11, Messages: 13, Location: My own special place. Display name: Canis Non Grata. Dang, not much to add to either Matthew's already basically good grasp of the matter nor Ron's very well written explanation. I know. About the only thing I would add as additional explanation for Matthew's benefit is that if you are wondering why have them closed during descent and landing, one big reason is to help prevent shock cooling.

They are basically an additional powerplant management control. You probably started with two, throttle and mixture then later added a third, prop. Now you have a fourth, cowl flaps. Fun stuff! SkyDog58 , Jul 1, Do non HP engines just not generate enough power to require them for extra cooling?

It seems I have only heard of them in connection with old planes, are they peculiar to radial engines? They are flaps or doors on the engine cowling that open up in order to provide increased cooling airflow for the engine. They look like this when open. The disadvantage is that the open flaps also increase drag. So on airplanes equipped with cowl flaps, they are generally opened for low-speed, high-power situations such as takeoff. This is the harshest operational regime for the engine since it is at its highest power and relatively low cooling airflow due to low airspeed.

They are then closed either reaching cruise or reaching a point where the airplane can transition to a lower-power, higher-speed climb profile. They're not specific to radial engines, but do tend to be more common in older aircraft there are exceptions though. Newer airplane and engine designs are more likely to have sufficient inherent cooling airflow to not require cowl flaps.

The photo above comes from AVweb, which also has a nice article explaining more about the function and usage of cowl flaps. Cowl flaps are used for engine cooling and you'll find them on many high performance piston aircraft. They are particularly useful during climbout when you are at a high power setting and slow ish airspeed.

Opening the cowl flaps allows more airflow across the engine but produces some drag. They are typically mounted on the bottom of the engine cowling. Sign up to join this community. The cooling lip works most of the time with lower-horsepower engines. In general, cowl flaps should be an all-or-nothing exercise: Keep them fully open, or fully closed, as appropriate.

An exception is when cruising a turbocharged engine at high altitude, where cooling airflow is thin but cooling drag is still a speed drain if the cowl flaps are fully open. Cowl-flap use is critical but easy, and following a few simple steps can save you a lot of unnecessary expense. C hecklists: Follow the appropriate ones — before, during and after flight.

O pen your cowl flaps for start-up, taxi, run-up, and for taxi-in after your clear the runway. W atch cylinder and oil temperatures and close the cowl flaps as you level the aircraft into cruise flight. L eave the cowl flaps closed for descent and landing, open them again as you tax to parking, and close and plug them if possible when you hangar or tie down.

Proper cowl-flap use is an exercise in pilot procedure and temperature control. Follow your checklists, but do not be afraid to deviate from them if your engine temperatures begin to get too hot or cold. But along with good-condition engine baffles and proper fuel flow set-up, correct cowl flap use is vital to getting the best life out of your engine. Fly safe, and have fun!

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