FaroeFlyer
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What Are Cowl Flaps?

Thu Sep 01, 2005 12:55 pm

Can anyone give me an explaination, please?
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HAWK21M
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RE: What Are Cowl Flaps?

Thu Sep 01, 2005 1:12 pm


Usually Cowl flaps are doors that are located on the bottom of the cowling, located either inside or outside. They are in this location because that is usually the end of the path for the cooling air flow. These doors are opened and closed by the pilot from the cockpit.
Usually they are manual and are operated by a lever or a knob. In some cases they are electric and are opened and closed by a switch.

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regds
MEL
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LeanOfPeak
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RE: What Are Cowl Flaps?

Thu Sep 01, 2005 1:45 pm

Most reciprocating aircraft engines are air-cooled. At low speed, there's not as much airflow as there is at cruise (As should be obvious). As such, when operating at low speed and/or an extremely high power setting, opening the cowl flaps allows additional cooling for the engine. But in an established cruise with a higher volume of air available, the cowl flaps can be closed to eliminate excess cooling (And the drag associated with it).
 
FaroeFlyer
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RE: What Are Cowl Flaps?

Thu Sep 01, 2005 4:00 pm

Very good explaination. Thank you both very much
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Pilawt
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RE: What Are Cowl Flaps?

Sat Sep 03, 2005 7:46 am

On large radial engines the cowl flaps often completely encircle the engine nacelle, as shown below:

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Photo © Lawrence Feir
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Photo © Jeffrey P. Jacobs



-- Pilawt
 
SWISSER
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RE: What Are Cowl Flaps?

Thu Sep 15, 2005 3:43 am

Even Concorde had such a system, but they where called rampers!
they provided more air for the engine at high speeds and altitude!
What time is top of descent?
 
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HAWK21M
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RE: What Are Cowl Flaps?

Thu Sep 15, 2005 3:48 am

Quoting SWISSER (Reply 5):
rampers

Why the Name.
Any Pics.
regds
MEL
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SlamClick
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RE: What Are Cowl Flaps?

Thu Sep 15, 2005 4:27 am

There was another cooling system for big recips, called augmentor tubes. The Convair 440 and the Martin 404 were rather similar airplanes as seen below:

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Photo © Art Brett
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Photo © Jeffrey S. DeVore


The Martin on the right has cowl flaps running almost the full perimeter of the cowling and you can see the big exhaust stacks on the lower outboard side.

The Convair on the left had augmentor tubes which ran the length of the engine nacelle, all the way to the trailing edge. The intake for these tubes was at the firewall just behind the engine and the exhaust stacks ended at the mouth of these tubes. At high power settings the increased exhaust pressure would draw the air out of the inside of the cowling by venturi effect. The more power you pulled the better the system worked. I have to believe it was lower drag than the big old barndoor cowl flaps.
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vc10
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RE: What Are Cowl Flaps?

Thu Sep 15, 2005 7:56 am

Swisser,
Sorry no such thing as rampers on Concorde

Intake Ramps --Yes-- these reduced intake air speed when aircraft speed above Mach 1.3

Secondary Air doors --yes-- these introduced powerplant cooling air when aircraft speed above 220 kts [closed for take off ]

But there was nothing on the aircraft like adjustable cowl flaps

little vc10
 
SWISSER
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RE: What Are Cowl Flaps?

Fri Sep 16, 2005 10:11 am

Quoting Vc10 (Reply 8):
Swisser,
Sorry no such thing as rampers on Concorde

Intake Ramps --Yes-- these reduced intake air speed when aircraft speed above Mach 1.3

Secondary Air doors --yes-- these introduced powerplant cooling air when aircraft speed above 220 kts [closed for take off ]

But there was nothing on the aircraft like adjustable cowl flaps

little vc10

Yes off course Peter,
if you go more technical on the complete Concorde system it is indeed different on the fuction of the prop cowl flap, just as you said!

But basically it has quite the same function like a cowl flap on a prop aircraft, it reduces the airflow and produces more air density for the engine.

I cannot say it is the same system, better said the same science family, to correct my previous post!

I think that was really a marvelous piece of engineering and what really made Concorde "the" Concorde!
What time is top of descent?
 
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Jetlagged
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RE: What Are Cowl Flaps?

Fri Sep 16, 2005 1:59 pm

Quoting SWISSER (Reply 9):
But basically it has quite the same function like a cowl flap on a prop aircraft, it reduces the airflow and produces more air density for the engine.

Supersonic intake ramps and radial engine cowl flaps are totally unrelated. Intake ramps don't reduce airflow. They reduce air intake velocity by changing intake area and directing shock waves. Air mass flow remains the same.

Cowl flaps control the airflow past the engine cylinders for cooling purposes.
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SWISSER
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RE: What Are Cowl Flaps?

Sat Sep 17, 2005 5:39 am

Quoting Jetlagged (Reply 10):
Supersonic intake ramps and radial engine cowl flaps are totally unrelated. Intake ramps don't reduce airflow. They reduce air intake velocity by changing intake area and directing shock waves. Air mass flow remains the same.

Cowl flaps control the airflow past the engine cylinders for cooling purposes.



Quoting SWISSER (Reply 9):
I cannot say it is the same system, better said the same science family, to correct my previous post!
What time is top of descent?
 
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Jetlagged
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RE: What Are Cowl Flaps?

Sat Sep 17, 2005 8:06 am

Quoting SWISSER (Reply 9):
I cannot say it is the same system, better said the same science family, to correct my previous post!

Depends how widely you define "science family" I suppose.
The glass isn't half empty, or half full, it's twice as big as it needs to be.

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