Buckled flap handle

[Pat Fagan]

I was on base leg for landing the other day with 3 notches of flap on when the flaps retracted on their own and the handle banged loudly to the floor. I have had that happen a few other times before with 3 notches if I don't get the pin fully seated in the flap quadrant. It's annoying, but no big deal. This time however when I tried to use the flaps the button stuck in the tube rendering the lock pin useless. I went to fix it today and discovered the problem was the flap handle a bent slightly immediately aft of the slot for the quadrant. The bent handle is what caused the inner tube to bind when I pushed the button in. What I find very surprising though is that the handle bent downward, not up like you might expect. After all, any bending moment is applied against the air loads when deploying the flaps so it seems logical that if the tube where to bend ( not very likely with that wall thickness over such a short distance ) it would bend upward. Perhaps it was a cumulative load from having happened before but still, there isn't anything for the handle to bang against on the way down and there certainly isn't any mass at the end of the handle. I straightened the tube ( and it took a heck a lot of beating with a plastic mallet ) and tapped out the buckle then sleeved the handle to stiffen it. FYI

[Zzz]

Thanks for the report, Pat.

Yours is using the 3/4" tubing? Do you have the doublers welded on around the notch? It's hard to tell with the tiny image.

I've been planning on building a new flap handle to replace my quickbuild one, extending the handle 4", as well as bumping up the tube diameter to 7/8". It's not exactly a priority though since my machine isn't completed.

Sure would be curious to know why yours failed where it did.

[jaredyates]

I also wonder Pat, was this the revised handle, and can we put your story in the newsletter?

[Pat Fagan]

The handle is the original design, 3/4" .049 tube. The doublers end just aft of the slot. I sleeved it with a 7/8" tube that was notched to fit around the doublers which made it a snug enough fit that I could try it out on the plane before welding it on. Now I think I'll just leave it as is, unwelded. I'll attach a larger picture. Jared you can use this for the newsletter. I was going to ask you about that anyway. Do you still have the article about finding my neighbors truck? It didn't make it in the last issue. We're off for a cruise today so might not have internet access for a week.

[jaredyates]

Yes Pat, I ran out of space in the last one but plan to use it in this one.

[Battson]

I was on base leg for landing the other day with 3 notches of flap on when the flaps retracted on their own and the handle banged loudly to the floor. I have had that happen a few other times before with 3 notches if I don't get the pin fully seated in the flap quadrant.

An aside, the plans leave insufficent clearance to let those two parts engage properly, which causes a problem like you describe. I've posted a seperate thread (link below) about how to adjust the flap handle to prevent that happening.
http://bearhawkforums.com/forum/safe...t-interference

I note the newer plans call for a doubler in that area, so I bet you're not the first person to experience such a problem.

[John Bickham]

Since a picture is worth a thousand words.....
This is a picture of the doubler specified in the plans that Battson referred to.


Flap lever parts (1).JPG

[Pat Fagan]

I don't recall ever hearing about the doubler mod for the flap handle. That certainly would have solved the problem. Still seems counterintuitive that it would bend in the direction it did.

[DRLPatrol]

Could it have bent down from inertia when it "banged loudly to the floor"?

Doug

[Battson]

I don't get it either - cannot imagine why is would bend that way. I even did a basic force vector and bending moment analysis, cannot work it out.

[Bdflies]

Is it possible that a passenger used the flap handle as a "hand hold", applying weight as they shifted into / out of the seat?

Bill

[Pat Fagan]

No, I doubt someone shoved down on the handle getting in or out. It's just not convenient for that. Apparently the speed with which the flaps self retract is sufficient to impose those loads, especially over time.

[John Bickham]

My curiousity got the best of me. The doubler at the slot was recommended in January 2006 Enginnering Change Notice.
I hadn't noticed that Eric has put in an "E-mail notice" option for new safety updates on his Mybearhawk.com site!! Really thanks too much Eric. I need all the help I can get. Subscribing now.

[John Bickham]

Oopsies, after going through the subscription service, looks like Jared had his tech hand in this. Thanks too much to you too, Jared.