Canopy pin retention block modification?

My first attempt at bolting the plastic canopy pin block was a complete failure. The instructions basically say: close the canopy, and drill 2 holes through the rear seatback bulkhead and the block. Unfortunately, while the block sits flush against the aft side of the bulkhead with the canopy open, I didn't realize that when the pin is engaged and pushing forward on the block, the angle of the pin tilts the block so that it is no longer sits flush on the bulkhead. I discovered this as I was working on drilling out the aft side of the block to accept the nuts; which are supposed to be "pressed in" to the block. The holes that I had drilled while sitting inside the cockpit, were not perpendicular to the face of the block. Additionally, my skill level and tool set are not complete enough to drill this borings so that they are precisely concentrical to the existing screw holes.

Soooo…my question is…has anyone replaced this complex attachment procedure by simply tapping the block and driving in two screws without the counter-bored/pressed-in nuts? The block's material reminds me of the stuff inside locknuts, and when I screwed in an AN-509 screw to test my theory, it seemed plenty secure.

I'm trying to visualize the forces that this block will be subjected to. Mostly, UP, I think.
So if I can position the block tight inside the bulklhead's flange, it seems that the aluminum structure would be carrying this load, and the screws' job is to merely hold it in position.
Thoughts? Advice? Admonitions?

Thanks in advance for your feedback.

Hallooo...

So, I'm assuming that I have a bent pin, and no one else had to deal with this issue.

Forget the mod..how did you countersink the nuts?

Anyone have any suggestions on how to go about boring the holes for the "pressed in" nuts? What tool/bit should I be looking for?
Thanks,

AAflyer said:

Anyone have any suggestions on how to go about boring the holes for the "pressed in" nuts? What tool/bit should I be looking for?
Thanks,

Click to expand...

After drilling the holes for the screws with a standard bit, I used a straight flute reamer of approx the size of the nuts to "grind" out the plastic for the nuts. Made them a bit undersized and pressed in the nuts. Worked out ok.

Not sure about your earlier alignment issue. It was hard to make work I remember that part, but I just fit it in place and maybe opened up the entrance of the hole for the pin a touch so it would align as it closed. In the end my pin does not go all the way in the block when the canopy is closed. But it's in enough to secure it. (I think this is because when I tighten down the screws it pulled the block forward a bit from the fully engaged location I had it in).

In the end, do what it takes to line up the holes and secure the block.

What I did

I did not use the bolts. I just installed a couple of large screws. Their only purpose is to hold the block in place while the canopy is open and to allow the pin to pull out during opening. The canopy pins the block when closed so I too the easy way.

Getting canopy snug...

Andy,
Your statement about the pin not fully seating?.doesn't this prevent the tailend of your canopy from seating snugly against the fuselage? This is exactly what I'm worried about; that if I bolt a block that is slightly mis-aligned, then the pin will jam before it's fully inserted.

AAflyer said:

Andy,
Your statement about the pin not fully seating?.doesn't this prevent the tailend of your canopy from seating snugly against the fuselage? This is exactly what I'm worried about; that if I bolt a block that is slightly mis-aligned, then the pin will jam before it's fully inserted.

Click to expand...

No, it's more an issue of the hole in the block is deeper than it needed to be in my case. With the canopy in the closed position with the rear down properly there was a gap between the end of the pin and the forward face of the bulkhead. Maybe it's related to my fit up front against the roll bar. In my case I have a wider gap than some I've seen. Doesn't really matter as it's all covered by the fiberglass strip anyways.

I think your angles should work out fine in the end. Lots of them have been made with these parts somehow!