K model cowl flaps

[DonMuncy]

Is the effort necessary to close the cowl flaps (K model) dependent on the adjustment of the closed position of the flaps. My hangar elf may have adjusted mine open a little more than necessary when in the closed position. They open and close easily on the ground, and are easy to open in flight, but are very difficult to close when flying.

[Oscar Avalle]

14 hours ago, DonMuncy said:

Is the effort necessary to close the cowl flaps (K model) dependent on the adjustment of the closed position of the flaps. My hangar elf may have adjusted mine open a little more than necessary when in the closed position. They open and close easily on the ground, and are easy to open in flight, but are very difficult to close when flying.

Don, interesting I have the same problem... I can not close my cowl flaps in flight. I was wondering if somebody could help us shed a light on what is going on. In my case given my high CHTs I did not bother too much about it.

[milotron]

15 hours ago, DonMuncy said:

Is the effort necessary to close the cowl flaps (K model) dependent on the adjustment of the closed position of the flaps. My hangar elf may have adjusted mine open a little more than necessary when in the closed position. They open and close easily on the ground, and are easy to open in flight, but are very difficult to close when flying.

My K has the 252 mod and has had a vernier style knob installed for control of the cowl flaps. It is possible to close them at cruise but literally requires two hands to push it in, otherwise many turns of the knob will easily close it.  There is an awful lot of windforce trying to hold that flap open, so not surprised by the high amount of effort required.  

When trying to open in flight, if you push the center release on the vernier while the flaps are closed the knob tries to shoot out of the panel due to this pressure. I can see why they went to electric cowl flap control on the later versions.  

 

[CaptRJM]

Mine are hard to close in flight too, but not what I'd call very difficult.  It just takes firm pressure.  If you put any side pressure on the knob, it will become extremely difficult, almost impossible to close the cowl flaps.  I have never even thought to using 2 hands as mentioned.  I do know one individual who bent the shaft by not pushing the knob straight.

We have adjusted my cowl flaps to be open about 1.5", when measured at the rear.  This provides a fair amount of airflow over the cylinders thereby reducing temps.

[DonMuncy]

Mine are adjusted about 1 inch open. I don't have the Vernier set-up; just a push-pull knob. Maybe someone will jump in with more knowledge to help us.

[milotron]

I'll have a look tomorrow as to how much it opens, but it is at least 1.5".  They are completely shut in the closed position.

[LANCECASPER]

3 hours ago, milotron said:

My K has the 252 mod and has had a vernier style knob installed for control of the cowl flaps. It is possible to close them at cruise but literally requires two hands to push it in, otherwise many turns of the knob will easily close it.  There is an awful lot of windforce trying to hold that flap open, so not surprised by the high amount of effort required.  

When trying to open in flight, if you push the center release on the vernier while the flaps are closed the knob tries to shoot out of the panel due to this pressure. I can see why they went to electric cowl flap control on the later versions.  

 

The 252 and Encore had electric cowl flaps which work great when they work. When they don't it can be a challenge.

 

[N231BN]

They should be easier to close the longer you make the adjustment(more open). The 231 needs additional exit area for airflow, if you adjust them to close all the way the top cowl bulges up due to the pressure.

I have been thinking of getting a field approval to add louvers in an area similar to a Bonanza or C182.

[ArtVandelay]

I never realized the J and K cowl flaps were so different, Js close no problem

[N231BN]

Is the effort necessary to close the cowl flaps (K model) dependent on the adjustment of the closed position of the flaps. My hangar elf may have adjusted mine open a little more than necessary when in the closed position. They open and close easily on the ground, and are easy to open in flight, but are very difficult to close when flying.

Are you referring to going from trail to closed or from open to trail?

There is a little bracket that keeps the arm from going too far over center in the open position. If that gets bent they will be hard to move to the trail position. There will be more pressure on the arm if you lengthen the adjustment as that makes the flaps open more as well.

[N231BN]

I never realized the J and K cowl flaps were so different, Js close no problem

The cowl flaps are longer on the K. Very similar system though.

[DonMuncy]

4 hours ago, milotron said:

I'll have a look tomorrow as to how much it opens, but it is at least 1.5".  They are completely shut in the closed position.

I may not have been clear. In the closed position, mine are open about an inch.

[jerryg324]

I'm struggling thru the painful trial and error adjustment and rigging process...  I found a set of the factory mod cowl flaps and just completed the installation...  Other than the new hing arrangement the only difference is they are 2 inches           Shorter than the original cowl flaps...  The key in the adjustment is the length of the push pull cable end not the adjustment of the cowl flap links...  Mine are opening and closing in flight at all air speeds now with very little pressure...  Originally they were very hard to open and close in flight and after installing the new cowl flaps they would not close in flight no matter how I had the links adjusted...  Today I got it right !!!!   They open and close smoothly and now I can run in trial without significant lose of speed...  Getting the alignment of the scissor linkage and proper travel is rather complicated...

[DonMuncy]

Wow, you have my admiration. It doesn't seem to be possible to describe it any better than you have, so I guess my elf will just have to start the trial and error process. Was there any way you could tell (on the ground) you were doing it right, or did you have to fly it to test it.

[jerryg324]

After removing the cowling I could get a good look at the linkage and see how it needed to cross over center at the open and closed position then it was just a  matter of adjusting the cable end and firewall attach point to get full travel on the scissor links...  Adjusting the cowl flaps are nothing after that...   Be very cautious of the scissor link orientation they only clear each other and function correctly in one arrangement that includes the orientation of the small pins and the cable rod end...  If I pull my cowling any time soon I'll get some pics for you...  The whole system is very confusing...  It worked perfect first test flight...

[DonMuncy]

Thanks, I appreciate the help.

[Yooper Rocketman]

My last trip back from Florida (last Saturday), my cowl flaps would not close when leveling out in cruise.  I have been noticing the flaps were opening a bit farther, but until this issue never looked into it (and yes, they were getting progressively more difficult to close).  I pulled my cowl and found the scissors linkage had "gone over center".  Long story short, the mechanical stop, an Adel clamp on the motor mount, had been progressively slipping and turning on the motor mount, allowing the flaps to move a bit farther open on every hard pull opening them.  Once I fully adjusted everything, I can pull them open with two fingers and they close with much less resistance than before.  You ARE overcoming the tension on the two springs on closing, so there will be more effort to close than open.  But as Jerry pointed out, the key is proper adjustment AND proper STOP adjustment.

Tom

[DonMuncy]

Thanks, good information.

[milotron]

So...after two trips the airport, radio drama and eventually a pleasant flight....

 

My cowl flaps are 4.25" when in the fully open position. Seems excessive compared to the others noted here. Perhaps I have a rigging issue.

[Pritch]

I am still new to my 84K but the cowl flaps are a little hard to push closed.  However it appears that if I have them in trail when I land and am taxiing and go to open fully, the are already fully opened.  Is this an automatic thing?

Pritch

 

[DonMuncy]

I don't claim to be an expert, but my impression is that when you put them "in trail", they are free to move wherever they want to (dictated by gravity and aerodynamic forces.) Thus, when you land and slow to taxi speeds, they will drop completely open.

[jerryg324]

Don is correct the cowl flaps only have two hard positions "open" and "closed" both held by an over center of the linkage...  The in trail position is on available in flight due to the airflow thru the cowling actually holding them partially open at a point where the pressures are balanced...  The most common problem with the hard closure is the small tab being bent which keeps the over center links from going to far in the full open position...   It's easy to see next to the exhaust...

[Pritch]

Thank you Don and Jerry, lots to learn over my ole 63C (plus not flying for 13 yrs) but I am getting it.  I do know that I have to replace one of the piano hinges on one cowl flap that was noted in my PPI done by the very competent and fair Lasar.

Pritch

[N231BN]

Deleted, already answered...

Edited June 29, 2016 by N231BN

[jrwilson]

On ‎6‎/‎27‎/‎2016 at 4:54 PM, DonMuncy said:

I don't claim to be an expert, but my impression is that when you put them "in trail", they are free to move wherever they want to (dictated by gravity and aerodynamic forces.) Thus, when you land and slow to taxi speeds, they will drop completely open.

My 84K has the three positions (Full open, trail, closed), but in "Trail," they don't open completely on the ground when the aerodynamic forces aren't pushing them, they stay in trail (1/3 open)...