Canopy blown open on takeoff: Analysis and repair inquiry pair.

So there I was, with my 5 year old in the back seat, barreling down the runway on a takeoff roll when suddenly I was back to open cockpit flying. I got the -4 settled down.

Some Background:
I am not the original builder of this aircraft, most of my work has been on a wood & fabric bird. I am going to need help identifying the parts and assembling a bill of materials for the repair. I am also not the owner of this aircraft, the owner is not the builder either. The owner has the plans and logs, and fortunately does not seem to be interested in drawing blood.

The Damage:
There is a "rib" like structure to which attaches a scissor-like hinge mechanism which holds the canopy when it is open. As the canopy opened in takeoff propwash, the scissor extended all the way and yanked on a cantilevered bolt which went through the rib-like crossing structure. This structure had flanges on top and bottom, but unfortunatly these flanges are not continuous across across the pit, being interrupted in the center, where the structure bent. The rib structure pulled the rivets out of the right hand canopy skin and puckered the skin on the left.

How I think this might have happened:
This canopy has a safety latch. The spring pushing forward on this latch appears to have gotten stuck on the side (flat), rather than the back (edge) of the latch which aparently caused it to jam backward and not close. Second, After this incident and surveying the damage with the owner, he got in and closed the canopy. The scissor mechanism and bent cross-structure take a little pushing to close the canopy, but with him in the airpane, and the lever in the closed position, I observed that the front rod engaged, but the back rod did not, leaving the back end of the canopy opened enough for me to slip my fingers in. This might have happened to me on that flight, with a half secured canopy twisting and allowing the front rod to pull out.

Now for the repair questions:
Does someone know the name, and perhaps part numbers that I am talking about? Do you know offhand what size rivets I will need to make the repair? With the rivets on the right pulled out, I don't think I want to re-use the same holes. I'd probably be better off massaging the skins flat and filling in the holes and making new ones. Bondo I suppose. It appears the original structure was welded to a tube that runs around the canopy. I may need to tig that, which means I'll need to drill out the rivets holding the polycarb canopy in place, fix the weld, then replace the rivets.

I think I'll change the washer on the saftey latch

Needless to say, I'll be religiously checking the engagement on the front AND back rods in the future.

Vans will be available after the weekend. Am I on the right track here? Any advice appreciated.

Welcome to VAF!

Andrew, welcome to VAF-------sorry about the canopy damage

Wow. Glad no one was hurt. Sorry this happened. I'm sure you will get good recommendations on repairs posted here on VAF. Pictures will help.

Wow! That sucks but luckily you weren't in flight!

If you don't mind me asking (I hope this doesn't sound like arm chair quarterbacking cause it isn't) - did you check the canopy right before takeoff? Did it seem closed?

This is the #1 scariest thing for me flying an airplane with a canopy. If it comes off in flight, chances are you will be hurt (at least) and you will most likely lose your headset as well, leaving you unable to talk to the rear seat passenger (who will be terrified).

I used to tell new students in the Pitts that if the canopy came off and they couldn't talk to me and the aircraft seemed not under control - don't wait.... jump.

Glad you're OK....

There are quite a few builders and flyers in the SLC area so you should be able to connect with one of them. I have kids and grandkids in Murray so we are down quite often too.

Best of luck getting your plane back into flying condition. PM me for contact info.

Andrew, a good resource for now and your future is to order the RV-4 CD from Vans. It will help you understand the original construction and give you the "lingo" to describe things with other RV-4 builder/owners.

http://vansaircraft.com/cgi-bin/store.cgi?ident=1417309934-78-660&browse=new&product=cd_plans

It sounds like you are talking about the center rib in the canopy. It comes in one piece but a lot of builders cut it in the center to get the gap in the canopy right. On the two I have cut, I built a gusset with flanges top and bottom that got riveted to the rib to reinforce it. I can send you part numbers tomorrow for the rib. As I recall, an426-3-? Rivets are used to rivet the canter rib to the canopy. You might be able to reuse the holes with the next size larger rivets , an426-4-?.

I think you are right on the money with the split rib. It makes sense why that was done, although I never did like that this build had no flanges on the gusset, so it was weakest right where it was loaded. If I recall, there are three layers to to rib. Thanks for getting me the part numbers and thanks to those suggesting the CD.

I'll get some photos in the next day or so. I think this experience would be instructive to others who happen upon the thread.

Concerning whether the canopy was locked, I can't be certain. I would think that I would notice if it wasn't. There was some scraping on the end of the forward rod consistent with it being forced open. I think I'll be painting the ends of the rods red so that they will show red if not completely engaged, again, religiously checking the front and rear on runup.

Hard to say exactly what you need to do without seeing the damage. I omitted the canopy latch from my build, mainly because I needed a deeper latch than Vans supplied. I use a piece of cord rather than a metal scissor action keeper to prevent the canopy going too far. No problems there. The big thing is to check canopy closed before take off and pulling the lever back I can see and feel the front and rear being pulled down as the pins slide in.
Section 9 of the builders manual and drgs 41, 42 are what you need.
I could possibly copy them and try to post them here or email them.
[email protected]

My Canopy repair for the same experance

Been there , Done that. I hope this thread will help in the repair of your canopy
http://www.vansairforce.com/community/showthread.php?t=101313&highlight=canopy

Warning light

It wont help you fix it, but when you do, install a warning light..I put a microswitch at the forward end of the latching pin. Even a hair from full lock it is big and bright. I mounted the light just above the throttle on left side of panel. Too many bad stories about unlocked canopies. Some folks have even installed horns.

I'm also paranoid about the canopy on takeoff and seem to have a similar set up to Bill.

The warning light is a GREAT idea. Aside from takeoff, I even had it light up in-flight once on a really bumpy day telling me to check the canopy handle to make sure it was secure. I also checked the entire canopy locking mechanism after that flight and all was good. If the handle drifts up about 3 or 4 millimeters the light will come on.

Here are two pictures of the set up in my -4. Big credit to Doug Weiler for taking the time to put this in!

You'll notice in the first picture that the canopy latch handle looks closed but isn't closed all the way. You can see the red light on the panel above the throttle (next to the engine monitor) that is on whenever the canopy latch isn't completely down and secure.

Note the lever position and the red light at the end of the pushrod.



The second picture is what it looks like when everything is good to go, locked and secure.

Note the lever position and NO red light at the end of the pushrod.



It's part of my pre-flight and landing checklists. It was VERY noticeable in-flight on that bumpy day that it came on.