What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Modification for assured tilt-up canopy jettison-

Hartstoc

Well Known Member
I’ve just launched into an aerobatic training program in my tilt-up RV-7A. After shelling out big bucks for the required parachutes, I began to wonder if the gas springs on my tilt-up could thwart or complicate an actual attempted bailout following a structural failure or mid-air collision. The thought of the potential injuries that could result from a flailing canopy still attached by gas springs to an aircraft tumbling out of control is disconcerting. I started a thread on this subject a while back, and a link to that is at the bottom of this post.

There are only three conditions during which the gas springs and their retainers are not subject to about 20# of compressive force: when the open canopy is struck by a gust of wind from behind, when the hapless pilot backs the airplane with open canopy into a partially closed hangar door, and when the canopy is jettisoned during flight.

Considering this, I elected to modify the excessively-sturdy 5/16” diameter anchoring bolts to include the breakaway feature described below. The trick was to keep them strong enough withstand the ocassional gust of wind from behind, but weaken them enough to break when subjected to an in-flight canopy jettison event. Photos with descripive captions of the modification I decided upon can be found here (9/23 edit: after the “ruthlessly helpful” suggestions and admonitions Appearing later in this thread, I concluded that I also needed to cut slots allowing the canopy hinges to depart directly upward during canopy jettison ;-). Photos and captions of this process have been added here as well.

https://public.fotki.com/Hartstoc/canopy-release/?view=roll#1

Yes- this IS a purely intuitive modification that probably should be subjected to some calibrated destructive bench-testing to make sure it will behave as desired. Sometimes it just makes sense to trust ones intuition, so I’ll leave the bench-testing to others. Fortunately, the consequences of a fatigue failure of one of these bolts would not amount to more than an inconvenience, and I’ll report back if that ever happens. So far it is working fine. I hope we all have adopted the policy of never walking away from an RV with an open tilt-up. I’m especially attentive to that now!

Buy the way, I did try out the idea of simply removing the gas springs for aerobatics, but the challenge of getting in and out of the plane with a parachute strapped on your back while managing the unsupported canopy led me to promply discard this option.

Here is the link to my earlier thread on the topic. It also poses the question of whether it makes sense to just leave those expensive parachutes in the hangar when not doing aerobatics:

http://www.vansairforce.com/community/showthread.php?t=162107&highlight=Canopy+jettison
 
Last edited:
Re: walking away with canopy open

I do it all the time. There's a doo-hickey that attaches to the lift strut and snaps into position when the strut extends far enough. Once in position it prevents the canopy from closing until it's manually pulled out of the locked position.

Having mistakenly trusted a set of slowly failing lift struts before, I wouldn't be without it.

The only way an idiot like me can defeat this idiot-proof device is by not assuring the canopy has opened far enough for the lock to snap into position before letting go.

On the jettison subject, I'm assuming you've slotted the forward deck skin over the hinge arms so they can come clear when the jettison handle is pulled. I removed my jettison T-handle when I realized the canopy would never jettison from a closed position without these special rainwater ingress slots cut. :rolleyes:
 
Buy the way, I did try out the idea of simply removing the gas springs for aerobatics, but the challenge of getting in and out of the plane with a parachute strapped on your back while managing the unsupported canopy led me to promply discard this option.

The very early RV-6's used a prop rod instead of struts. You could remove the struts and resort to a prop rod.

I do it all the time. There's a doo-hickey that attaches to the lift strut and snaps into position when the strut extends far enough. Once in position it prevents the canopy from closing until it's manually pulled out of the locked position.

A length of 3/8" fuel hose slit to allow it to be slipped over the strut rod accomplishes the same thing.

And yes, bad form to walk away from a non-secured tip-up canopy--only takes one strong gust of wind or an inattentive pilot to ruin your day. :)
 
The very early RV-6's used a prop rod instead of struts. You could remove the struts and resort to a prop rod.

And yes, bad form to walk away from a non-secured tip-up canopy--only takes one strong gust of wind or an inattentive pilot to ruin your day. :)

I recommend the original "Prop-Rod" solution. I never liked the struts.
And yes, you must have the slots cut above hinges. Cover the slots with 3-M tape and they will never be noticed.
 
I recommend the original "Prop-Rod" solution. I never liked the struts.
And yes, you must have the slots cut above hinges. Cover the slots with 3-M tape and they will never be noticed.

Thanks for the idea- If my breakaway bolts ever give me problems, I?ll resort to the prop-rod idea, but it is kind of nice having the gas struts. Working on the slots now. - Otis
 
I wonder if you could reduce diameter at the small end of the taper so the ball would pop off easier?
-
2dahl76.png
 
I wonder if you could reduce diameter at the small end of the taper so the ball would pop off easier?
-
2dahl76.png

Or machine some out of delrin. It might be easier to just chuck that up in a lathe and drill a hole through the center to weaken it. You would have to play around with the diameter.
 
Here's a thought... If the struts are attached, and the canopy is trying to exit up and back, the struts should help raise the front of the canopy into the slipstream (and perhaps over your head) as it passes.

If I were really worried about them *not* letting go, when boarding for an aerobatic flight I would get in, then disconnect the fuselage end of the strut before closing the canopy. Then I could close the canopy and disconnect the upper end. Stow struts securely out of the way, and bob's your uncle.
 
I wonder if you could reduce diameter at the small end of the taper so the ball would pop off easier?
-
2dahl76.png

I did consider this, but was concerned that flexing during normal operation could lead to random failures. The method I devised of weakening the bolt shafts is subject to very little flexing, if any, during normal ops because of the pre-stressed assembly and positive loading from the “strong” side from the gas springs. Also, the longer lever arm between the ball and weakened point on the bolt will amplify the shock load that will break to bolt.
 
Last edited:
On the jettison subject, I'm assuming you've slotted the forward deck skin over the hinge arms so they can come clear when the jettison handle is pulled. I removed my jettison T-handle when I realized the canopy would never jettison from a closed position without these special rainwater ingress slots cut. :rolleyes:

I?m still pondering this important comment, and I may yet cut these slots. For now, after studying the various posts on taking off with an unlatched canopy, or having a canopy inadvertantly unlatch in flight, I concluded that changing the bailout proceedure might make the slots unnecessary, especially if there are two people on board to help with canopy jettison.

If I did have the slots, my proceedure would be: 1- remove headsets. 2- check that center latch is engaged and leave it that way. 3- disengage primary latch. 4- pull jettison T- handle. This would hopefully make a pivot point put of the center latch, which would hopefully cause the canopy to do a clean back-flip as it departs.

In the absence of slots, my aerobatic instructor and I decided on this procedure instead: 1- remove headsets 2- disengage center latch. 3- disengage primary canopy latch while stabilizing canopy sides with the palms all free hands on board. The canopy should partially open and find an aerodynamic neutral point, but allow enough space for the it to slide aft and free the hinges when you: 4- pull the T-handle. For now, this is the proceedure that my instructor and I verbalize prior to boarding the aircraft before each flight. We also verbalize steps 5-7, 5- disengage seat belts. 6- Get your butt out of and away from the aircraft. 7- Visually identify the parachute D-handle, engage it with the thumbs of both hands if able, and push it briskly away from your chest with both hands. Having visualized your way through these proceedures just prior to each possible need to execute on them could save your life.

Of course, all bets are off if the aircraft is tumbling wildly out of control, which may be a fairly likely Scenario. In that case , there is just one item: Quickly find a way to jettison the canopy or open it sufficiently to fight your way out. You will at least have substantial motivation on your side! - Otis
 
With no slots, there might be a good possibility of the aft of the canopy floating upwards as the 'unlatched' folks have reported. Then what happens? The canopy may come straight back at you and hit you in the face.

The way Van originally designed it with the slots would seem to say the canopy would lift up at the front and do a back flip over the top, keeping it somewhat away from the occupants.

I'm sure Van considered the options in the initial design. :)
 
I?m still pondering this important comment, and I may yet cut these slots. For now, after studying the various posts on taking off with an unlatched canopy, or having a canopy inadvertantly unlatch in flight, I concluded that changing the bailout proceedure might make the slots unnecessary, especially if there are two people on board to help with canopy jettison.

The newest design from Van's (the RV-14) has slots to allow for jettison of the canopy. I assure you that because of the trouble they cause in designing a fully sealed fwd canopy, etc., they would have been left off if not considered necessary.

This is experimental aircraft after all so if incorporating brainstormed design and modifications makes you feel better when wearing your parachute..... have at it, but if you plan to fly aerobatics with others, your eyeball engineering (in my opinion) would likely be putting them in jeopardy if you ever do have to get out.
There are many others that thought they were smarter than Van's (and at times they have been) but this is not something to be second guessing Van's about, without even doing any testing to prove it is viable.
 
With no slots, there might be a good possibility of the aft of the canopy floating upwards as the 'unlatched' folks have reported. Then what happens? The canopy may come straight back at you and hit you in the face.

The way Van originally designed it with the slots would seem to say the canopy would lift up at the front and do a back flip over the top, keeping it somewhat away from the occupants.

I'm sure Van considered the options in the initial design. :)

Well, given that the original design had slots and no gas springs, and virtually all tilt-ups now have gas springs and no slots, we are all in new territory. I?ve certainly considered the possibility of being injured by the canopy, and I?m concerned about it. There is a good chance that I?ll end up adding the slots to my plane. Until I do, as far as I can see, the exit strategy I described is the best availble. I?m not expecting to jump out of my airplane, but I?m pro-actively considering the possibility. I wonder if that can be said of the thousands of aerobatic hours that have been enjoyed in RV?s with unmodified gas springs and no slots by others dutifully wearing the required parachutes?

I guess one additional step should be added to my current bailout proceedures- explore the possiblity of exiting through the unlatched but still attached canopy. Depending upon the condition of the aircraft, that just might work.

This is all intended as a discussion of the problem. I?m not yet suggesting that I have arrived at a reliable solution, but the great value of this forums is being able to include the thoughts of others such as you in the process.- Otis
 
The newest design from Van's (the RV-14) has slots to allow for jettison of the canopy. I assure you that because of the trouble they cause in designing a fully sealed fwd canopy, etc., they would have been left off if not considered necessary.

This is experimental aircraft after all so if incorporating brainstormed design and modifications makes you feel better when wearing your parachute..... have at it, but if you plan to fly aerobatics with others, your eyeball engineering (in my opinion) would likely be putting them in jeopardy if you ever do have to get out.
There are many others that thought they were smarter than Van's (and at times they have been) but this is not something to be second guessing Van's about, without even doing any testing to prove it is viable.

Thank you for this, your points are well taken. I?d add that where the realm of bailouts from homebuilts is concerned, the term ?eyeball engineering? can pretty much be applied to all designs, even Van?s. The military has the rescources to stage meaningful testing and the horsepower to tote a quarter ton of ejection technology, but we don?t.

I think most of the points I made in the post just prior to this one apply here as well. I can?t imagine anyone smarter than Van- least of all me! This is about discussing an uncomfortable topic, hoping to incorporate the thoughts of all. I?m now seeing slots in the future for my 7A, but once they are there, I have pretty high confidence in my breakaway bolt solution. It is interesting that the RV-14 includes a work-around for the gas spring issue. - Otis
 
...if you plan to fly aerobatics with others, your eyeball engineering (in my opinion) would likely be putting them in jeopardy if you ever do have to get out.

That was my thought exactly on reading this thread. Eyeball engineering is just that: nothing but a guess and not worth betting one's life (certainly not mine) and that of one's passenger. Whenever I see an "improvement" offered by a builder, my first thought is always show me the math. If that can't be done, it's not worth my time. Others, of course, may feel differently.

As to those who do feel differently, consider this: while we all have the legal right to do as we will in experimental aviation, simply having the right to make a choice doesn't render any choice made safe, sane, or intellectually defensible. We each decide precisely where to draw that line, but at least accept that there is a line - and thoroughly examine every proposed deviation from plans (even our own ideas) critically and with complete dispassion prior to making a decision.
 
I think most on here are vastly underestimating how difficult getting out of a out of control aircraft will be. The violent motions, lack of proper restraints and canopy configuration will make it nearly imposssible and to date I have not heard of a successful bailout from a Vans side by side airframe.
If you are going to add anything to a RV to improve your odds of getting out it would be a ratcheting 5 point aerobatic restraint system. This might require beefing up attach points.
G
 
I think most on here are vastly underestimating how difficult getting out of a out of control aircraft will be. The violent motions, lack of proper restraints and canopy configuration will make it nearly imposssible and to date I have not heard of a successful bailout from a Vans side by side airframe.
If you are going to add anything to a RV to improve your odds of getting out it would be a ratcheting 5 point aerobatic restraint system. This might require beefing up attach points.
G

THANKS to all for your “ruthlessly helpful” suggestions. After a bit of thought, I came up with a way of cutting hinge slots without even removing the canopy. Photos with captions of this process have been added to the same album showing the gass spring mods(in which I have very high confidence.):

https://public.fotki.com/Hartstoc/canopy-release/?view=roll

Now I’m back to the safer bailout drill:
1- Remove headsets.
2- Check center latch to verify that it is fully engaged.
3- Release main canopy latch.
4- Jettison canopy.
5- Release seat harness.
6- Exit aircraft.
7- Visually identify D-ring- insert both thumbs if possible and push away from chest.

I do plan one additional mod, out of concern that cables attached to glare-shield mounted devices like GPS antennae might impede a clean exit of the canopy. I will cut a large hole in the glare shield and install a mount below this to support such devices, then stretch a piece of black fabric over the hole. The devices will remain with the aircraft when the canopy is jettisoned.- Otis
 
Last edited:
I like it if you are concerned about canopy jettison. Maybe a frangible hinge cover like the RV14 aftermarket? It has enough strength to hold itself and be water tight but easily broken with a push. The thin tabs on the nut retainer shear to release the canopy. It has been tested on the ground but not in flight. The nut retainer is installed by rotating 90 deg to lock in place using a simple supplied tool. If you remove the canopy for service, remove the nut retainers or you will shear them. a couple extra nut retainers are supplied in case you forget or want to test. they can be painted but spray them with a sealer firstly to prevent acetone from reaching the plastic. as an alternative, spray them with a UV enamel clear, such as rust-oleum.

42b789_8baf518269dd4ab5b16e700770114f7d~mv2.jpg


42b789_7a3f64b26e99440699056d5fe83dd075~mv2.png
 
Last edited:
Well, given that the original design had slots and no gas springs, and virtually all tilt-ups now have gas springs and no slots, we are all in new territory.
There are other reasons for the change, though. The original -6 tip-up had arms that came straight back from the hinge points to the canopy frame. The slots were necessary to allow the canopy to open.

The design was changed at some point to have hook-shaped arms so the canopy could open without requiring slots in the fuselage. The hooks make ejection more questionable as they prevent the canopy from coming straight out and back... You now have to raise the back of the canopy far enough that the hooks can clear the panel.

Although i've removed and installed my canopy frame a couple of times, I don't recall how far the rear has to be raised to slide it back. Maybe I should try that.
 
There are other reasons for the change, though. The original -6 tip-up had arms that came straight back from the hinge points to the canopy frame. The slots were necessary to allow the canopy to open.

This was only in VERY early kits.

The design was changed at some point to have hook-shaped arms so the canopy could open without requiring slots in the fuselage. The hooks make ejection more questionable as they prevent the canopy from coming straight out and back... You now have to raise the back of the canopy far enough that the hooks can clear the panel.

This change came around 1990 or 1991. My kit was amoung the first to have the "hook shape" hinges. The slots were still required to facilitate canopy jettison.

Although i've removed and installed my canopy frame a couple of times, I don't recall how far the rear has to be raised to slide it back. Maybe I should try that.

See above notes. Just researched builder log. Canopy hinge change to the "hook" style was early to mid 1991.
 
Last edited:
See above notes. Just researched builder log. Canopy hinge change to the "hook" style was early to mid 1991.

Drawing #52 (Drawn 12-89) for the -6 was changed (R2) in 6-92 with the note -

CHANGED TO "GOOSE NECK" HINGE AND ADDED SECTION DD
 
Drawing #52 (Drawn 12-89) for the -6 was changed (R2) in 6-92 with the note -

CHANGED TO "GOOSE NECK" HINGE AND ADDED SECTION DD

Yeah, They weren't real quick with plans revisions back then.
My log shows: "8/18/91..Fitted forward canopy frame with new goose neck hinges. Trimmed canopy side rails & rear canopy bulkhead."
 
Yeah, They weren't real quick with plans revisions back then.
My log shows: "8/18/91..Fitted forward canopy frame with new goose neck hinges. Trimmed canopy side rails & rear canopy bulkhead."

Yes... The early -6 plans tended to be more of a guideline than actual plans...:D
 
If you get air under that canopy, those struts don't stand a chance. The canopy will pull them right off, even at slow speeds. That canopy is a LOT of sail area.

I wish I had saved my old struts to prove this once and for all.

If you have the slits cut and release it, it will be gone.

Also, you can push up on the rear of the canopy and you will have the strength to get out. The challenge is, what will you hang up on, on the way out.

Those of you that do acro, do you practice egress? Do you have your passengers practice egress? Have you verified they have their parachutes on and tightened correctly?

Do you make sure you and your passengers have tightened the harnesses correctly? (Sub strap first, lap belt second, and shoulder straps last! Most people do the shoulder straps first, which is a big no-no!)
 
If you get air under that canopy, those struts don't stand a chance. The canopy will pull them right off, even at slow speeds. That canopy is a LOT of sail area.

I wish I had saved my old struts to prove this once and for all.

If you have the slits cut and release it, it will be gone.

Also, you can push up on the rear of the canopy and you will have the strength to get out. The challenge is, what will you hang up on, on the way out.

Those of you that do acro, do you practice egress? Do you have your passengers practice egress? Have you verified they have their parachutes on and tightened correctly?

Do you make sure you and your passengers have tightened the harnesses correctly? (Sub strap first, lap belt second, and shoulder straps last! Most people do the shoulder straps first, which is a big no-no!)

I believe that what you say here is true if the the aircraft is still moving forward at high velocity such that a great deal of lift is acting on the canopy, but I?m concerned that the struts could be a problem if the aircraft is tumbling or gyrating wildly. Obviously, you are in unexplored territory if that happens anyway, but I think I have weakened the bolts to the point that they would probably break with virtually any canopy release scenario. If not, I?d be making every effort to position myself to kick the canopy off if I had to, and I?m sure the bolts would break then. There are no guarantees of anything where bailing out is concerned- you can only do your best to tilt the odds in your favor.

And yes, shoulder straps should not be particularly tight, only the lap belt. Having everyone properly buckled in and active verbal rehersing of bailout proceedures before each and every flight is crucial. Otis
 
Back
Top