K Cowl Flap Correct Rigging

[jetdriven]

Sorry guys, I'm data driven here, and airplanes have true airspeed right there in the cockpit, but I have to see this to believe it.  Otherwise, it's science or data by consensus and there's too much of that going on.  Yes, air spilling out the front is drag and drag through the cooling fins and out the bottom is drag also.. Now whichever is more or less than the other can be verified and flown out.

Our plane right now is flying the  air race classic.. There was quite a show when we handicapped at 190.5 mph at 6000 feet which is about 8 miles an hour faster than any other 4cyl Mooney in the history of the ARC.  This goes back to 1965 and there is 97 airplane handicaps on that list. And about 14 MPH faster than the MSE thats in the race with it as well. And it does 196 or 197 at sea level. The book levels are bullshit, but actually if you correct for nonstandard temperature, this plane will make those numbers. But we didn't get there by believing hangar stories.. For example, thanks to a good friend of mine @bluehighwayflyer, he noticed the Acclaim type S has no flap hinge covers, and neither does ours. Its faster. Spent 200 bucks to find that out.  Spent a lot more to find out that a lot of the stuff doesn't work at all and that stuff you think works works in the opposite. Its still got metal belly plates and square wingtips, too.

Unless you're Jesus Christ or George Strait, bring data please.

[Fly Boomer]

37 minutes ago, jetdriven said:

Unless you're Jesus Christ or George Strait, bring data please.

Short list.  

[LANCECASPER]

1 hour ago, jetdriven said:

Sorry guys, I'm data driven here, and airplanes have true airspeed right there in the cockpit, but I have to see this to believe it.  Otherwise, it's science or data by consensus and there's too much of that going on.  Yes, air spilling out the front is drag and drag through the cooling fins and out the bottom is drag also.. Now whichever is more or less than the other can be verified and flown out.

Our plane right now is flying the  air race classic.. There was quite a show when we handicapped at 190.5 mph at 6000 feet which is about 8 miles an hour faster than any other 4cyl Mooney in the history of the ARC.  This goes back to 1965 and there is 97 airplane handicaps on that list. And about 14 MPH faster than the MSE thats in the race with it as well. And it does 196 or 197 at sea level. The book levels are bullshit, but actually if you correct for nonstandard temperature, this plane will make those numbers. But we didn't get there by believing hangar stories.. For example, thanks to a good friend of mine @bluehighwayflyer, he noticed the Acclaim type S has no flap hinge covers, and neither does ours. Its faster. Spent 200 bucks to find that out.  Spent a lot more to find out that a lot of the stuff doesn't work at all and that stuff you think works works in the opposite. Its still got metal belly plates and square wingtips, too.

Unless you're Jesus Christ or George Strait, bring data please.

George Strait used to be my next door neighbor back in the 90’s. Does that count . . lol?

When Bob Kromer, the test pilot for the 252 talks about the cowl flap being open 1” and the cruise speed increasing, he also mentions how the cowl flap (not flaps like on the 231) on the 252 is a lot more efficient and creates less drag.

If it’s data you want, get in touch with Bob Kromer. He mostly likely still has all of it. He can walk you through it. https://www.linkedin.com/in/bob-kromer-45048326

[jetdriven]

It should be easy for @Pinecone to verify this. He's got some fancy radios now and at least in a couple places that shows TAS.  Plus a brand new cowl flap motor for free courtesy of www.flyrpm.com

[kortopates]

1 hour ago, jetdriven said:

Sorry guys, I'm data driven here, and airplanes have true airspeed right there in the cockpit, but I have to see this to believe it.  Otherwise, it's science or data by consensus and there's too much of that going on.  Yes, air spilling out the front is drag and drag through the cooling fins and out the bottom is drag also.. Now whichever is more or less than the other can be verified and flown out.

Our plane right now is flying the  air race classic.. There was quite a show when we handicapped at 190.5 mph at 6000 feet which is about 8 miles an hour faster than any other 4cyl Mooney in the history of the ARC.  This goes back to 1965 and there is 97 airplane handicaps on that list. And about 14 MPH faster than the MSE thats in the race with it as well. And it does 196 or 197 at sea level. The book levels are bullshit, but actually if you correct for nonstandard temperature, this plane will make those numbers. But we didn't get there by believing hangar stories.. For example, thanks to a good friend of mine @bluehighwayflyer, he noticed the Acclaim type S has no flap hinge covers, and neither does ours. Its faster. Spent 200 bucks to find that out.  Spent a lot more to find out that a lot of the stuff doesn't work at all and that stuff you think works works in the opposite. Its still got metal belly plates and square wingtips, too.

Unless you're Jesus Christ or George Strait, bring data please.

First apologies to @PeteMc for miss remembering that the service manual was not corrected. 

But here's the scoop, this was figured out by the Continental engineer that worked the 231 Engine installation for Mooney on site at Mooney. I learned about it when I was taking Continental's A&P maintenance class at Fairhope nearly 2 decades ago so I've forgotten exactly if he said 1" or 1.5" but I've posted this multiple times here over the years and these days enough people have heard this now that I'll just let someone reply - but its being questioned....

After the initial installation was done they were trying to address some reported cooling complaints so they were testing various things. So they learned closing the cowl flaps all the way was really reducing cooling. But they were surprised to discover why, which was because it was causing enough back pressure at the air inlets preventing air from flowing through. The bigger surprise is that it was also disrupting airflow over the prop enough that when eliminated they got something like a 10 kt increase in airspeed (which is probably a bit of an exaggeration). But the point is they weren't expecting the back pressure and resulting turbulence at the air inlets was as disruptive to air flow as they found. There just wasn't enough outflow at the bottom of the cowling to with cowl flaps closed to create the low pressure area below engine to allow the air to move freely through the inlets and down the engine cyl fins into the low pressure area without the cowl flaps open some amount. The 252 doesn't have this issue since even with the large single cowl flap closed both sides of the lower cowling have enough open area to allow air to flow freely through from the top high pressure area and down to the low pressure exit. 

Edited June 19 by kortopates

[Pinecone]

11 hours ago, jetdriven said:

It should be easy for @Pinecone to verify this. He's got some fancy radios now and at least in a couple places that shows TAS.  Plus a brand new cowl flap motor for free courtesy of www.flyrpm.com

I can check this out in the next few weeks.

But I figure Bob Kromer did this testing, with an instrumented aircraft back in the 252 testing.

The real answer would be a variable inlet to control the amount of air coming in, and keeping the excess out.  And maintaining smooth flow around the cowling.

[jetdriven]

I mean, what is optimal is optimal, but they should've at least put that in the service manual so that you can rig

the aircraft properly for what it wants not just what looks right or what you think is right or what looks right on older planes.

[EricJ]

5 hours ago, jetdriven said:

I mean, what is optimal is optimal, but they should've at least put that in the service manual so that you can rig

the aircraft properly for what it wants not just what looks right or what you think is right or what looks right on older planes.

Sometimes field experience reveals things that weren't anticipated during development.    It's not an unusual thing, and it's often useful to benefit from field experience.   The certification process doesn't generally allow the benefit of the field experience to go back into the documentation without disturbing the existing certification, so it's expected that that would rarely happen.

 

[jetdriven]

Respectfully, I disagree.. Yes, we understand how machines work better as time goes on that's why we revise manuals. To incorporate what we learned about these things as they accumulate service in the field. There's no certification  infringement for saying you should bring the flaps in an partially open instead of fully closed position, it's actually within the usable range of what was there before, and you can issue a service letter that  advises owners and operators.

They always wanna say well you have recertify the device if you do this and that's rarely the case. This doesn't even mean the definition of a major alteration, or an alteration at all really.  You know Lycoming ran an engine for 100 hours with the roller camshaft and tappets. And then they had a couple of test airplanes. They flew 100 hours or more as well. And then they sent them out ... They had revise the parts catalog to show the new stuff. If that's not a major change, what was. I think more than likely, it's the fact that these airplanes are already been sold and although you can get better performance out of it, they kind of don't care. They have to get involved if safety as it stake, but not for optimal performance.

[EricJ]

38 minutes ago, jetdriven said:

They have to get involved if safety as it stake, but not for optimal performance.

Yup, so there's little motivation to spend the time to update a document, especially if changing the document might have any undesirable consequences.

I don't really disagree with anything you said, but if there's no motivation to make a document change, and/or even a slight reason not to, it's not likely to happen.   So it is sometimes beneficial to take note of the field experience and benefits it might provide.   Sometimes "best practices" are outside of what the manuals say, and sometimes the FAA even cites that.