What are cowl flaps?

"Jon Kraus" wrote in message newsBm%g.17816

5 or 10 knots? What are they freakn' barn doors or something? :-) Sure
your not fibbing?

Sometimes cowl flaps can really disrupt airflow. On the DC3, the cowl flaps
have 3 positions: open, closed, and trail (controlled, btw, by a pair of
round valve handles that look for all the world like they were borrowed from
a steam locomotive). Open,they really stick out all around the cowling, and
in trail, they are pretty much closed, but will stay open a bit as needed.
Cowl flaps are an item on the pretake-off check. If you try to take off
with them in "open", it will set up a hell of a buffet.

"John Gaquin" wrote in message
. ..

"Jon Kraus" wrote in message newsBm%g.17816

5 or 10 knots? What are they freakn' barn doors or something? :-) Sure
your not fibbing?

Sometimes cowl flaps can really disrupt airflow. On the DC3, the cowl
flaps have 3 positions: open, closed, and trail (controlled, btw, by a
pair of round valve handles that look for all the world like they were
borrowed from a steam locomotive). Open,they really stick out all around
the cowling, and in trail, they are pretty much closed, but will stay open
a bit as needed. Cowl flaps are an item on the pretake-off check. If you
try to take off with them in "open", it will set up a hell of a buffet.

You wouldn't believe the drag on a P47 Thunderbolt with the cowls open.
Don't know about the D models, but on the N, you can easily use them as a
speed brake :-)) Also, taxiing with them open just about totally blinds you
in front of the airplane....not that the visibility is all that great in
front with them closed :-))
Dudley Henriques

Some airplanes WILL NOT FLY with cowl flaps fully open. In the 50's there
was a Boeing Stratocruiser that took off from Boeing Field, Seattle. They
forgot to close the cowl flaps from ground to climb and ended up ditching
straight ahead in Elliot Bay, where the plane rests today.

http://www.ovi.ch/b377/articles/lady/

Karl



"John Gaquin" wrote in message
. ..

"Jon Kraus" wrote in message newsBm%g.17816

5 or 10 knots? What are they freakn' barn doors or something? :-) Sure
your not fibbing?

Sometimes cowl flaps can really disrupt airflow. On the DC3, the cowl
flaps have 3 positions: open, closed, and trail (controlled, btw, by a
pair of round valve handles that look for all the world like they were
borrowed from a steam locomotive). Open,they really stick out all around
the cowling, and in trail, they are pretty much closed, but will stay open
a bit as needed. Cowl flaps are an item on the pretake-off check. If you
try to take off with them in "open", it will set up a hell of a buffet.

For a minute I thought you were talking about the one that was ditched in
Elliot Bay in 2002, which was because they ran out of gas... They
relied/trusted the fuel gauges and didn't check the tanks, whi.ch were wrong
and they didn't have very much fuel. They later on fished that one out of
Elliot Bay and restored it, again.

But, I read the posting and sawa "In the 50's..." :-)

Sadly, there are lots of planes at the bottom of Elliot Bay and Lake
Washington.

"karl gruber" wrote in message
...
Some airplanes WILL NOT FLY with cowl flaps fully open. In the 50's there
was a Boeing Stratocruiser that took off from Boeing Field, Seattle. They
forgot to close the cowl flaps from ground to climb and ended up ditching
straight ahead in Elliot Bay, where the plane rests today.

http://www.ovi.ch/b377/articles/lady/

Karl



"John Gaquin" wrote in message
. ..

"Jon Kraus" wrote in message newsBm%g.17816

5 or 10 knots? What are they freakn' barn doors or something? :-) Sure
your not fibbing?

Sometimes cowl flaps can really disrupt airflow. On the DC3, the cowl
flaps have 3 positions: open, closed, and trail (controlled, btw, by a
pair of round valve handles that look for all the world like they were
borrowed from a steam locomotive). Open,they really stick out all around
the cowling, and in trail, they are pretty much closed, but will stay
open a bit as needed. Cowl flaps are an item on the pretake-off check.
If you try to take off with them in "open", it will set up a hell of a
buffet.

karl gruber writes:

Some airplanes WILL NOT FLY with cowl flaps fully open. In the 50's there
was a Boeing Stratocruiser that took off from Boeing Field, Seattle. They
forgot to close the cowl flaps from ground to climb and ended up ditching
straight ahead in Elliot Bay, where the plane rests today.

The obvious question here is: Why would the cowl flaps open that far
if the plane wouldn't fly with them in that position? Unless it were
strictly for keeping the engine cool on the ground, I suppose (?).

--
Transpose mxsmanic and gmail to reach me by e-mail.

But he has a Navion... I thought it would be similar to my Mooney...

John Gaquin wrote:

Sometimes cowl flaps can really disrupt airflow. On the DC3, the cowl flaps
have 3 positions: open, closed, and trail (controlled, btw, by a pair of
round valve handles that look for all the world like they were borrowed from
a steam locomotive). Open,they really stick out all around the cowling, and
in trail, they are pretty much closed, but will stay open a bit as needed.
Cowl flaps are an item on the pretake-off check. If you try to take off
with them in "open", it will set up a hell of a buffet.

Jon Kraus wrote:
But he has a Navion... I thought it would be similar to my Mooney...

They are pretty large doors, maybe 6x10" and the main cooling
intake is a few square feet. Closing them pretty much seals
up the cowl, only a little air escapes around the exhaust pipes.

They absolutely cause a 10knot difference in performance in a Skymaster
P337.
And if I recall they caused about 7 knots degradation in my 73 F33a Bo

Jon Kraus wrote:
5 or 10 knots? What are they freakn' barn doors or something? :-)
Sure your not fibbing?



Ron Natalie wrote:

In my plane, I can get another five to ten knots when
I close them.

On 26 Oct 2006 15:05:08 -0700, "swag" wrote:

They absolutely cause a 10knot difference in performance in a Skymaster
P337.
And if I recall they caused about 7 knots degradation in my 73 F33a Bo

In my old Deb which has a number of speed mods and big engine they are
good for at least 10 knots.

Jon Kraus wrote:
5 or 10 knots? What are they freakn' barn doors or something? :-)
Sure your not fibbing?

It's not the flaps creating the drag. It's the air the let in around
the engine and out the bottom that adds the extra "cooling" drag.




Ron Natalie wrote:

In my plane, I can get another five to ten knots when
I close them.
Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

Roger (K8RI) wrote:
On 26 Oct 2006 15:05:08 -0700, "swag" wrote:

They absolutely cause a 10knot difference in performance in a Skymaster
P337.
And if I recall they caused about 7 knots degradation in my 73 F33a Bo

In my old Deb which has a number of speed mods and big engine they are
good for at least 10 knots.

Jon Kraus wrote:
5 or 10 knots? What are they freakn' barn doors or something? :-)
Sure your not fibbing?

It's not the flaps creating the drag. It's the air the let in around
the engine and out the bottom that adds the extra "cooling" drag.


The air that goes into the cowling for cooling is air that isn't
used for thrust anymore, and when there's less thrust there's less
speed. With the cowl flaps closed, most of the air can't get into the
cowl openings and goes around instead, contributing to thrust.
There were some airplanes with well-designed cooling systems that
were able to recapture the lost thrust through the heating and
expansion of the cooling air. There was a discussion on one of these
groups several years ago about it. I think the P-51 was one of them.
The light airplanes we fly have cooling systems that are crude by
comparison.

Dan