RV-4 canopy latch problem

[swjohnsey]

RV-4 tip over canopy. When I got it canopy latch worked fine. Canopy warning light went out. Fifty hours later I noticed that the light occasionally didn't go out. Canopy seemed to be fully latched. Later had a problem getting canopy to latch. Greasing pins seem to solve the problem. Now I have the panel in front of the cockpit off, I can see where the front pin and micro-switch for the warning light are. Everything seem to be working fine, no obstruction. Same for rear pin.

Here is the problem. With the canopy open and the canopy latch in the closed position the outside handle is parallel to the direction of flight. When I close the canopy and latch it the handle if off 20 degree or so from latched. The outside handle is indexed to the shaft with a through bolt so it can't be off.

I think the culprit might be the middle pin on the roll bar. Help!

[Scott Hersha]

I?m trying to understand your situation. If the handle doesn?t make it back to parallel in the closed/locked position, it sounds like the canopy latch system and pins are not fully seated. What has me confused is what you say about the middle pin on the roll bar. I have no ?pins? on my roll bar. In fact, the roll bat has nothing to do with the canopy other than providing an anchor for the lanyard holding the canopy in the fully open position.

If you cant be assured that the canopy is fully latched, with both pins fully seated, be very careful about flying it like that. A canopy becoming unlatched, and leaving the scene very quickly, is not a pleasant experience. This has happened and you can read about here on this website. When you get this sorted out, consider the secondary latch system that Vans has for the RV4. Less than 20 bucks. Prevents inadvertent opening of the RV4 canopy in flight.

[fixnflyguy]

Pictures may help..there are a ton of -4's with "different than plans" latch systems. If yours is per plans, and has the $15.00 VANs safety latch also, your canopy will have two levels of latching. I also have a micro-switch for a warning light that I installed at the forward latch pin hole, and it takes only about .015" travel off of the lock position to illuminate the light. The mechanism itself that the handle attaches to has the stop built in that regulates the handle angle, and the mid-position pin at the roll bar you mention would have to be an added component for a canopy taxi position,in which there are many homebrewed variations for. A friend had a very clever one that was actuated by the standard canopy lock system, but controlled a separate pin mounted on the canopy cross brace and engaged it into the roll bar when the canopy was about 2" open. There is another thread going on discussing canopy latch variations and there is a picture posted of my "standard" per plans latch with the safety lock that was posted by a friend (I cant post pictures), you may use as a comparison.

[gmcjetpilot]

Originally Posted by swjohnsey

RV-4 tip over canopy. When I got it canopy latch worked fine. Canopy warning light went out. Fifty hours later I noticed that the light occasionally didn't go out. Canopy seemed to be fully latched. Later had a problem getting canopy to latch. Greasing pins seem to solve the problem. Now I have the panel in front of the cockpit off, I can see where the front pin and micro-switch for the warning light are. Everything seem to be working fine, no obstruction. Same for rear pin.

Here is the problem. With the canopy open and the canopy latch in the closed position the outside handle is parallel to the direction of flight. When I close the canopy and latch it the handle if off 20 degree or so from latched. The outside handle is indexed to the shaft with a through bolt so it can't be off.

I think the culprit might be the middle pin on the roll bar. Help!

There is no standard canopy closed light on a RV-4 as part of the kit. It was a builder add on. None of the two place RV's or most General Aviation planes I have flown have door/canopy closed lights. It is obvious the RV-4 canopy is closed and latched w/o a light.

One guess, the issue is with the switch or circuit that the light is attached. Do you know if micro switch closes circuit to ground or positive? You may have a bad switch or short to ground. If you removed this light (and circuit) you will be like most RV-4's.

I don't understand your last comment, but it does not seem relevant:
When I close the canopy and latch it the handle if off 20 degree or so from latched. The outside handle is indexed to the shaft with a through bolt so it can't be off.

Second guess is possible for canopy to be latched with pins fully engaged or backed out slightly and still be very secure. When the light comes on do you push on handle to close position to see if light extinguishes?

[FinnFlyer]

A visual inspection should show you want is preventing you from turning the handle the last 20 degrees to horizontal.

In my RV-4, what stops the handle from turning further are the nuts on the screws that goes through the nylon block through which the 3/8" steel tube goes through from out side handle to inside handle.

Obviously something in rear or front of the alum tubes where they go through the rear bulkhead or instrument panel would also stop it.

Have you inspected the holes in the nylon blocks behind the rear bulkhead and in front if the instrument panel? I could imagine that they could have worn to create a rim halfway through the block. Or perhaps the blocks have somehow moved and the tubes only go through the bulkhead or instrument panel. If you can't see it, remove one block at a time and see if it makes a difference.

Finn

[swjohnsey]

I discovered that the "taxi" latch at the middle on the roll bar is non-standard. There is an addition pin designed to keep the canopy cracked open and the pin engages an additional hole when fully closed. I think that is the problem.

Seems the builder of this airplane once took off with the canopy open and he and his girl friend held it closed by hand for quite a while, hence the warning light.