Boilermonkey

Cowl Flaps Closure M20C

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Boilermonkey    15

The cowl flaps on our M20C don't close flush with the body of the airframe.  They are not hitting anything, it actually looks like the linkages are adjusted intentionally for this.  

Is this common?   Are they meant to close flush?  Or are they intentionally left open a bit for airflow?

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carusoam    4,005

It depends...

Early in the C timeline cowl flaps were adjustable.

At the end of the timeline, the flaps were set and not adjustable.

With cowl closures, and other aerodynamic mods combined with the plane's personal OAT profile... Being set about an inch or two open seems to be the way...

More attention to the health of the doghouse for cracks, holes and seals will probably result in better CHTs...

To get a better idea of the future of the C timeline... look up David's cowling mod  that has better air flow in its design...

The old dog house came before the time when aerodynamics was applied to everything...

From my hours as a C owner... not a mechanic.

Best regards,

-a-

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orionflt    343

They should be flush when closed and if I remember correctly 3/4 in open. I actually have Mike a bit more but I will look up the exact specs when I get home. 

Brian

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RLCarter    406
1 minute ago, Raptor05121 said:

I'm curious why the M20C and M20D are different

They do seem to be all over the board 

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philipneeper    62
7 hours ago, carusoam said:

It depends...

Early in the C timeline cowl flaps were adjustable.

At the end of the timeline, the flaps were set and not adjustable.

With cowl closures, and other aerodynamic mods combined with the plane's personal OAT profile... Being set about an inch or two open seems to be the way...

More attention to the health of the doghouse for cracks, holes and seals will probably result in better CHTs...

To get a better idea of the future of the C timeline... look up David's cowling mod  that has better air flow in its design...

The old dog house came before the time when aerodynamics was applied to everything...

From my hours as a C owner... not a mechanic.

Best regards,

-a-

Mine are fixed, non adjustable

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Raptor05121    957
1 hour ago, RLCarter said:

No spec for closed, only open

Interesting, only 2" when open? My cowls open to...a lot of inches. Way more than 2!

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daver328    1,368
8 hours ago, Boilermonkey said:

The cowl flaps on our M20C don't close flush with the body of the airframe.  OURS DONT CLOSE FLUSH EITHER

They are not hitting anything, it actually looks like the linkages are adjusted intentionally for this.  YUP - THEY ARE!

Is this common?   YES

Are they meant to close flush?  NO

Or are they intentionally left open a bit for airflow? YES

Bob Kroemer (Mooney test pilot) in his classes the past two Mooney Summits has mentioned leaving them open about an inch and a half (1-1/2") during cruise ... Ever since I heard that - that's what I do! 

Ours ARE adjustable. 

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Sabremech    1,018
1 hour ago, daver328 said:

Bob Kroemer (Mooney test pilot) in his classes the past two Mooney Summits has mentioned leaving them open about an inch and a half (1-1/2") during cruise ... Ever since I heard that - that's what I do! 

Ours ARE adjustable. 

I have mine adjusted as Bob Kroemer suggested. 

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carusoam    4,005

For the adjustable flaps...

Also check how the cowl flap controls are connected to the engine mount.

1) My C's were connected with some hardware that was not very solid.

2) oil drops and dirt seemed to be part of the system.

3) some parts would slide when they were not supposed to.

4) some parts were stuck when they were supposed to slide.

5) I used Bob Kromer's advice and set them open and compared to a newer M20C with fixed flaps. I used Bob Kromer's written advice (often), printed in the MAPA magazine...

6) This all seemed OK, but there was no engine monitor to show how good this was working.  Just a sole CHT and single EGT to work with.

PP thoughts and old memories...

Best regards,

-a-

 

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