Simviation Forums

Hi, I am very new to the whole world of FS. I do not mean to appear thick, but can anyone please explain to me what cowl flaps are, what do they do, and how do you use them during flights. i.e. what sort of settings are used during take off, cruise and descent etc. I would be very grateful for any help.

Ive been simming for ages and even i dont know
Can anyone help

JImbo

To put it simply, they are to control the temperature of the engine by adjusting the airflow over the cylinders.

Open the Cowl flaps for take-off.
Watch the engine temperature gauge in the cruise and adjust the cowl flaps as necessary to maintain a safe cylinder temperature.
Close the cowl flaps prior to closing the throttle for a landing to prevent "Shock cooling" the engine...VERY IMPORTANT!
Watch the Exhaust Gas, and Cylinder Head temperatures all the time...!
(The use of the control is similar to using the Carb Heat knob on the panel)

Cheers...!

Paul.

Most enclosed radial engines are fitted with cowl flaps or blinds.

Cheers Foz, got you know.

Jimbo

Hi Mr. Foz. Many many thanks for your help. I guessed they were important, but couldn't figure out how. Once again, many thanks.

SO all these years you've been opening and closing them at the wrong time?

Glad I'm not your mechanic..

Another thing about cowl flaps is that when taxiing, they should be open... even though your throttle settings are low when on the ground, there's not so much air flowing over the engine. Generally, you'll start the engine with cowl flaps closed, so the temp. will quickly come up to normal, then open them once the engine's warmed up. In extreme cold, you might leave them shut. Depends on the engine, etc.

Cowl flaps are quite useful things.

How they work:
Imagine a house. On the upwind side you open a window and let a breeze in. This is like a closed cowl flap condition. Now you walk to the other end of the house and open the door. Now you have a forceful breeze rushing through the openings. This is the open cowl flap condition. (Try this sometime, it's pretty cool)

How you use them: (real-life info used, aircraft in example is a PA-31 Navajo (twin, 310HPx2 turbocharged, 175 knots))

On startup they are closed and stay that way until right before departure (to get the temps up, it takes a while). On climb they are open all the way to keep the temps down.

Once at cruise they are closed as temps permit, sometimes cracked open a little to add a little cooling.

On descent they stay closed, because we start reducing power well before the descent and there is no danger of shock-cooling.

On approach they stay closed unless you're fast or high. The cowl flaps on the Navajo are about 1 - 1.25 square feet total, so if you open them they're like speed brakes. You lose about 10-15 knots at cruise if they're left open.

Once on the ground they're open all the way, and stay that way until engine start the next time.


Here's a picture of the cowl flaps on the Navajo. They're the large doors hanging 2/3 of the way back the engine cowling, on the bottom: http://community.webshots.com/photo/237 ... 8407NXnnev

For a smaller plane example, see the two door-looking things hanging down off each side of the cowling here:

http://community.webshots.com/photo/237 ... 6281GZRpwY

These pictures are 2400x1800 so you can zoom in and see some great detail.

EDIT: fixed links

The photos also have a "forbidden" message in their place.

(The use of the control is similar to using the Carb Heat knob on the panel)

Mmm. Not exactly. *leans against desk and opens textbook*

Carb heat introduces warmer air into the throat of the carberator, which prevents or removes ice from the carb. Ice will form there at just about any outside temperature. This is because of Boyle's law, stating that at a constant temperature the volume of a confined ideal gas varies inversely with its pressure. So when the air gets to the lower pressure area of the carb throat, the temperature also decreases which can form ice. Also with the reduced temps water vapor condenses out, which further increases the chances of carb ice.

So, carb heat is turned on when within a certain outside temperature range, at low power settings, and when in freezing precip (obviously).

I don't know if it actually affects the aircraft in FS2004, but you're supposed to open them up while you're climbing, and close them while cruising or decending like everyone else said.

I found this article which explains it very well. http://stoenworks.com/Tutorials/Cowl%20Flaps%20&%20Engine%20C.html

BTW, the default setting for opening the cowl flaps is Ctrl + Shift+ V and closing them is Ctrl + Shift + C...  :)