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Cowl Inlet Screws, how many & how?

TX7A

TX7A

Well Known Member
Drawing calls for three #8 screws/nutplates for top-bottom cowl attach on inboard side of each inlet. I have a couple of concerns: I hear stories about the lack of ease in removing these screws to remove the top cowl. Putting three nutplates in the required space looks pretty tight but doable.
Right now I am considering using three mini floating nutplates each side.
Has anyone installed just two evenly spaced screws here?
Has anyone used camlocs here? If so how many per side?
Any gotchas?

Thanks for any tips on this.
 
Sam,
I have had good success with just 2 screws per side. I usually use # 10 screws, and have actually flown inadvertently without those screws installed( all the way to Vne) without any adverse effects!
 
I struggled to see how to get 3 on each side given the space available, and 3 seemed overkill. I installed 2 #8s evenly with floating nutplates. I'm not an engineer, but based on learning throughout the build, 2 on each side appears plenty adequate. I am confident in the 4 total and haven't thought about it since. No issues so far...8 hours into phase 1.
 
If you go with the spacing on the plans, you will have to do something like this with the nutplates.
IMG_3742-M.jpg
 
Are you folks trying to fit all three nutplates in a line with the rivet ears ??

Like this - - -

Try putting the nutplates on a 45* angle as to the rivet ears

Like this / / /

Much easier to the spacing closer.
 
I installed all three but generally only use the forward two, at least during my first couple hundred hours when the top cowl comes off relatively frequently. That aft one is a bit of a pain to remove unless you use a mini socket.
 
Installed all three use all three have no problem

The title says it all but you are thinking ahead so you are obviously a thoughtful builder. I also have a screw in the outboard side of the cooling air inlets and I mount a 0.016 aluminum cover that wraps around the front of the cowl covering the cowl separation gap and and secured with one screw in the upper cowl half and one screw in the lower cowl half which takes the front end separation loads off of the hinges. A stubby #2 phillips screw driver works fine for installing and removing the screws. This is not a remove and reinstall before flight item, it's more like an oil change interval.

Bob Axsom
 
I'm liking the idea of two #10's as John suggested. Still on the fence though.

Bob,
The area you mention on the OB side of inlets has concerned me as well. Seems like a good place for a "pressure leak". Good idea you have about the cover. I was thinking about building-up a composite lip of sorts on the inside of the lower cowl. We'll see.


Thanks for the replies!
 
Two #8 fixed nutplates

I have close to 200 hours with only two flat head #8 screws with fixed nutplates per side. I use tinnerman washers under the head to distribute the load and protect the paint. No issues what so ever. Would do it again.

Caution-Make sure you space the pattern so that the aft most screw/nutplate doesn't come near the starter ring gear.
 
Pmerems said:
Caution-Make sure you space the pattern so that the aft most screw/nutplate doesn't come near the starter ring gear.
Click to expand...

I installed 3 nutplates each side but the rear ones were just too close to the ring gear for comfort. I removed them and have flown 530 hours with just the two on each side.

Fin
9A
 
TX7A said:
Has anyone installed just two evenly spaced screws here?
Click to expand...

I plead guilty on this one, having used 2 #8 countersunk screws on each side.

I've got 6 years and 930 hrs. on my configuration and don't have plans to change, but, of course, you need to do what's right and what you're confortable with.
 
alcladrv said:
I plead guilty on this one, having used 2 #8 screws on each side.
Click to expand...

Me too. I floxed an aluminum plate between the cowl and nutplates. One nutplate is fixed and one is floating. I use truss head screws. Just like new @ 150hrs.
 
I used 2 no 10 screws but added an aluminum backing plate on the nut plates. Insurance? I was told my Ed McGowen of the Griffin, Ga builder assistance that used to be there that many builders used only one #10 screw per side.
Smilin' Jack
 
I'm only chiming in because no one has answered the camloc question. I was going to attempt this but was not comfortable with the clearance for the camloc body. Especially near the ring gear. I ended up with three nutplates, no problem. I ran a tap partially through the nutplates to make it easier to start them straight and I typically use a short driver to better fit into the cowl opening with my big hands. It has been a preflight check for me (look into the opening for bird's nests or other foreign objects and, oh yeah, check the screws) but I have never seen them be anything less than snugged when I go to remove them. And I, too, have left them out for a flight without seeing any adverse effects (other than to my peace of mind when I discovered the oversight).
 
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