Engine run with top of cowl off?

[rjcthree]

I may have to go to another airport to do a prop balance. I hate the idea of removing the full cowl at a remote location. Can a prop balance be done by removing only the top cowl, and is it safe to run the engine with only the bottom cowl installed(fully)?

[Walt]

Originally Posted by rjcthree

I may have to go to another airport to do a prop balance. I hate the idea of removing the full cowl at a remote location. Can a prop balance be done by removing only the top cowl, and is it safe to run the engine with only the bottom cowl installed(fully)?

Yes and yes.
I've probably balanced more RV props than most, never had a problem leaving the bottom cowl on.

[cajunwings]

On some planes the bottom cowl can be a little floppy in the spinner area when the top cowl is removed. In those cases safety wire can be run from the cowl screw holes back to the engine to stiffen up things a bit.


Don Broussard
RV9 Rebuild in Progress
57 Pacer

[Carl Froehlich]

I would never do that. Why would you want it bouncing around, stressing the hinges and bouncing against the back of the spinner?

Carl

[kkmarshall]

I do it after every oil change to ck for a possible leak at the filter. No issues rubbing against the spinner or flopping around.

[snopercod]

[rvsxer]

Originally Posted by cajunwings

On some planes the bottom cowl can be a little floppy in the spinner area when the top cowl is removed. In those cases safety wire can be run from the cowl screw holes back to the engine to stiffen up things a bit.

That's what I do, too. Dozens of times and no problems.

[robertahegy]

Not sure, but wouldn't the loose cowl half rattling in the breeze influence the accuracy of the balance equipment? Not sure what RPMs the tests are done.

Roberta

[joe gremlin]

Originally Posted by kkmarshall

I do it after every oil change to ck for a possible leak at the filter. No issues rubbing against the spinner or flopping around.

Doing ground idle and runups with the top cowl off is one thing. Going flying with it that way it something else entirely.

On most planes, I think I'd be more inclined to try it with both the top and bottom cowl off rather than just the top. Less chance of anything bad happening that way. Of course without a plenum on the engine, I'd expect cylinder temps to be an issue regardless of whether you try it with just the top off or the entire cowl.

Really the best bet is to fly with the entire cowl in place as designed and remove it when you get there. If you're going to a maintenance shop to have the work done, then you're going someplace where fragile cowls being removed is a daily event.

[vic syracuse]

It works fine. Have done many prop balances this way. As someone mentioned, do check to make sure the bottom cowling isn't rubbing the spinner. It shouldn't happen, but these are all individually built.

Vic