Cowl Flaps

[clamman]

Could someone explain what these actually do and the proper way to use them? I've tried playing with them and I see no difference one way or the other.

[Tim_A]

Cowl flaps are small doors on the bottom of the cowling. Their purpose is to increase air flow over the engine, and thereby improve cooling. They are primarily opened for high power low speed operations, e.g. take off and climb, when the engine generates lots of excess heat. You should see a reduction in cylinder and oil temperatures when they are open.

http://www.avweb.com/news/leadingedge/leading_edge_21_remember_your_cowl_flaps_198546-1.html

[lnuss]

For some additional information, you can also see this FSwiki page (http://www.flightsim.com/fswiki/index.php/What_are_cowl_flaps%3F).

[tatest]

The purpose of cowl flaps is to control airflow for engine cooling.

A side effect of cowl flaps is that open, they increase drag, and should thus slow the aircraft.

Whether or not you notice either of these effects, depends on the model you are using. The simulator models both cooling and drag for use of cowl flaps on air-cooled engines, but the effects may not be there in every model built for the simulator.

There have been some real world cooling system designs, such that a particular setting of cowl flaps (or openings on radiator ductwork) actually add an increment of thrust. AFAIK, the simulator does not support this effect.

You will see, in some models, cowl flap eye candy, pieces that move with cowl flap setting. This is something separate from the cooling and thrust effects, you can have cooling and drag effects and no eye candy, and you can have eye candy with no effects.

So if you don't notice anything, the effects may not be modeled, or they may be too subtle for you, unless you are taking detailed notes on all control inputs and performance outputs, over time.

[ReggieF5421]

I find that cowl flaps become more important on aircraft with more, higher horsepower piston engines.

In addition to whether or not the behavior and drag is modeled into the aircraft being used, I've also found that the level of realism settings will also effect the cowl flaps behavior

The default DC-3 is one aircraft where the cowl flaps can create problems with overheating and reduced power.