RV-4 Safety canopy latch

Hey RV4 veterans,
I am working on the canopy right now and am having trouble understanding why the safety latch is needed. I'm talking about the steel hook that penetrates throught a slot cut in the cockpit rail. It releases at the same time as the tubes dissengage so what is the benefit? At high speed does the canopy bow upward, shake, rattle, distort? The tube system seems pretty secure. At fly-ins I see lots of RV4's that don't have them installed (most). Am I missing something? The directions say that "several RV4 owners have experienced canopy blowoffs during flight." Did this happen because the locking lever was accidentally activated? In which case, the safety latch would not help at all since it would also be disengaged. Thanks for helping me to turn the lights on in this dark room I'm standing in.

Brian Vickers, Bainbridge Island, WA
1959 C-172 owner/driver while aircraft building rolls along
Used O-320 and wood prop planned - and darn thankful just for that!!!

Like you I couldn't understand either. I have to push the canopy release lever WAY forward to disengage the pins that hold the canopy closed. An accidental bump in flight isn't going to accidentally open the canopy. However, I put it on 'cause Van said to. For what it's worth.

I had the same issue/concern, and then a bright light went off at Oshkosh one year.....

For those not using push/pull controls, Van's installation of the quadrant is in the upper rail, just a few inches from the canapy release. I believe that in the event of an emergency go around, the possiblity of pushing the wrong or too many levers could be interesting

My quadrant is located low, so I haven't entirely decided whether I'll install the safety latch: there's no reason for my hand to be anywhere near the canopy release under normal or unusual situations.

Canopy Safety Latch

Openning at speed will cause the canopy to depart the aircraft potentially causing damage. I never liked the tip-over canopy latch on my RV-3 and the -4 system is almost identical.

Here's why:

1 - It's a single throw lever, which means one action can open the canopy.
2 - When the canopy is open, the pins stick out, should the canopy close on it's own (wind, or stupid lineman) the pins scrape the fuselage.
3 - I dont like having an external knob out in the breeze. Just astetics.

I have two potential designs. One is a dual-lever locking latch that seperates the aft/fore pins into two levers. When the canopy is secured, the levers align a hole for a ball-lock pin to secure them in place. My second design is a rotating tube with cam on either end. The cam mates to a pin in the fore/aft of the cockpit area. The cam-action would really suck the canopy in nicely and allow for better gap-seals that compess. When the tube was rotated closed a tab would drop to secure the works.

Whatever I decide, I'll post when I'm done.

-Bruce

Never had one on my RV-4

Brian Vickers said:

Hey RV4 veterans,
I am working on the canopy right now and am having trouble understanding why the safety latch is needed. I'm talking about the steel hook that penetrates throught a slot cut in the cockpit rail. It releases at the same time as the tubes dissengage so what is the benefit? At high speed does the canopy bow upward, shake, rattle, distort? The tube system seems pretty secure. At fly-ins I see lots of RV4's that don't have them installed (most). Am I missing something? The directions say that "several RV4 owners have experienced canopy blowoffs during flight." Did this happen because the locking lever was accidentally activated? In which case, the safety latch would not help at all since it would also be disengaged. Thanks for helping me to turn the lights on in this dark room I'm standing in.

Brian Vickers, Bainbridge Island, WA
1959 C-172 owner/driver while aircraft building rolls along
Used O-320 and wood prop planned - and darn thankful just for that!!!

Click to expand...

Flew my RV-4 for years and years with out any safety and never installed one or lost my canopy. You are not missing anything. Personally I figured If I could not tell the difference between the Yellow knob for the canopy and he Black/Red/Blue knobs, 10 inches above, I deserved to have my canopy blow off.

A safety pin or latch is a great idea. I guess I never put it on because it is a extra step to secure the canopy. Van's optional secondary latch is not a bad idea. I had bought the safety latch kit but never installed it, but you are right there is many good reasons to install a safety.

The down side I could think of is if you need to get out by someones help from the outside. If there is a safety pin they may not be able to open the canopy. That's a remote scenario but I guess its possible.

Bottom line is it's UP to YOU. I had modified mine so full forward on the yellow canopy knob was engaged. It was part of my pre-takeoff checklist. My Pins where custom made of titanium and had a large engagement overlap. In flight the pressures on the handle to open it would have required a deliberate force and long throw on the handle, so I was not too worried. I kept some wrap around safety glasses in a side pocket by the way, in case I ever went without a canopy and had no eye protection or it blew off. I am pretty sure you can fly with out the canopy but its not easy.

A friend, a few hangars away has a Giles 202. He failed to latch the canopy and started his take-off run. The canopy blew off the airplane and damaged the fuselage and tail feathers to the tune of more than $5000. He now has a flashing LED on his panel when the master switch in on and the canopy is not latched.

With a moment of distraction this kind of thing can happen to any of us.

Bob Severns

The thing I don't understand about the canopy latch is that the safety latch disengages before the canopy pins do.

Latch Key Kids...

Brian,
I looked at the canopy lock on the RV4 way back when I built mine the same way, like the RCA dog...I decided to go with the pins but design a hold-back/ canopy taxi position pin to prevent the canopy from departing inflight should I inadvertently push the latch handle forward (mine locks aft, unlocks fwd). I haven't had any problems so far in 1400 hours! The canopy is stable and doesn't shake or vibrate at high speed and takes quite a bit of movement on the handle to unlock. I completely ignored the hook and left it off.
My latch is pictured below, works as a hold open on the ground, (through a hole in canopy bulkhead) canopy hold back inflight (aft over top of canopy bulkhead). Works good, has lasted a long time...

Rob Ray

PS: My Harmon Rocket has the exact same latch setup sans hook (it's an RV4 setup cause' the HR2 IS an RV4...)and I have seen 260 MPH several times and the canopy is still attached.

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