Cowl Flap Restriction

[Newmooneyguy]

My AFM has a restriction that says not to open the cowl flaps above 120 mph.  Does anyone know what this restriction is based on?

[jetdriven]

probably flutter and stress on the cowl flaps and hinges.

[jrwilson]

What year and model is yours?  I have a 63 20C and my cowl flap restriction is 150mph, or bottom of the yellow arc.   I would think you would want them open fairly regularly over 120 mph, depending on the OAT, CHTs, oil etc...

[Newmooneyguy]

It's a 66 E model and the number might be 150 instead of 120.  I'm away now and don't have access the manual.

[takair]

My 64 has 150mph limit.  I'm pretty sure it is a structural limit.  They are fairly light weight and only have a single actuation point.  Can't imagine you would need them too much above 150mph.  CHTs are typically pretty low with the large cowl opening.

[Oscar Avalle]

One silly question, my M20C (S/N 700006) has not cowl flaps, somebody knows why, and would it be possible to install them?

[takair]

What year is your C? I'm surprised. What is in the location where the flaps would be? An opening or solid cowl? Maybe some of the guys with B models or other Cs can comment.

[Oscar Avalle]

My Mooney is 1969 model. I believe that cowl flaps could help with my CHT temperature...

[DaV8or]

Quote: oavalle

My Mooney is 1969 model. I believe that cowl flaps could help with my CHT temperature...

[Oscar Avalle]

Dave, thanks for your remarks. I just checked my cowling and discovered that that I have a hole in the engine baffle system, where the ignition coill for the uper sparks plug in cylinder 3 is.  So I would not be surprised if that actually compromises the air flow in the engine. 

[AmigOne]

I have a similar issue with #4 cylinder, 450F+ on t/o (#3 is also past 400F but no so much as #4) but at cruise it comes back below 400F but it can take a while, particularly in summertime and if I stay low, say below 3-4000ft.  After reading so many articles by Mike Bush on the subject I imagine my cylinder head disintegrating as I watch the alarm on the JPI start blinking past 450F so I want to correct this problem.  I obviously do not know about the effectiveness of cowl flaps in the M20C but in the 201 I used to own the cowl flaps were very effective, specially if you opened them fully which you almost had to do because it was hard to open them only half way.  In discussing the issue of the overheating and having checked everything else my mechanic (who said that "he was out of ideas") suggested to make the cowl flaps operational, something he had already done to another M20C in the field.  In that case he used the mechanism of a Navion so at least I am not a guinea pig and he'll do it on the basis of the prior field approval.  I also called Lasar and their response was that they a had a number of parts for the purpose of making the flaps operational and that they would call me back with a list.

[FloridaMan]

I have a '67 with the LoPresti cowling in Florida and I have yet to see any temperatures be anything but spot-on, regardless of the cowl flaps being open or closed. 

[Oscar Avalle]

I have a similar issue with #4 cylinder, 450F+ on t/o (#3 is also past 400F but no so much as #4) but at cruise it comes back below 400F but it can take a while, particularly in summertime and if I stay low, say below 3-4000ft. After reading so many articles by Mike Bush on the subject I imagine my cylinder head disintegrating as I watch the alarm on the JPI start blinking past 450F so I want to correct this problem. I obviously do not know about the effectiveness of cowl flaps in the M20C but in the 201 I used to own the cowl flaps were very effective, specially if you opened them fully which you almost had to do because it was hard to open them only half way. In discussing the issue of the overheating and having checked everything else my mechanic (who said that "he was out of ideas") suggested to make the cowl flaps operational, something he had already done to another M20C in the field. In that case he used the mechanism of a Navion so at least I am not a guinea pig and he'll do it on the basis of the prior field approval. I also called Lasar and their response was that they a had a number of parts for the purpose of making the flaps operational and that they would call me back with a list.

I have to say that since I opened the cow flaps my cht in cyl 3 went Down significantly.

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[Lood]

The limit on my F is also 150 mph. However, during my engine break-in flights, I often busted 150 mph with the cowl flaps wide open and I didn't encounter any issues. I wouldn't do that under normal circumstances though. Although my engine runs very cool, the cowl flaps on my airplane has a significant effect on the CHT's.

[mike28w]

  I know of a nitwit who occasionally forgets to close his cowl flaps when he reaches cruise (  that's me !!).   I've flown a couple of hours before with no apparent problems.  

 

   Just a fwiw, certainly not a recommendation !!     mike