Emergency Egress: Improvements to the bubble canopy?

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Vigilant1

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I have a small crescent wrench for snapping a hole with progressive bites, starting at the vent and chipping out as needed. I don't think the hammer will work as well.
That's a good idea. The canopy breaker tool for the F-106 worked like that (see image below--normally painted red and kept in a set of clips on the left side of the cockpit). The breaker tool for some other military aircraft was a striking tool with a curved chipper blade, which I think would be less effective.

The F-106 model is below.

 

SVSUSteve

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This brings home the fact that a rollover structure (behind the seat or as part of the windscreen frame) is a good thing, but may not be totally effective if your harness allows the head to be up against the canopy when the plane is upside down.
A rollbar fore and aft should be part of any structure underlying a canopy.

but may not be totally effective if your harness allows the head to be up against the canopy when the plane is upside
Why would one design let alone install such a harness?

less likely to jam in a crash than a door
Two points:
1. Any data to back this up?
2. If a door is jamming in a survivable crash (<70-100 g at the floor of the cockpit), then the door needs to be redesigned.

you could even incorporate it in a (re-enforced) seat.
My concern with that would be that allowing a structural component of the seat to directly contact the ground is a good way to have the seat break loose from it's mountings thereby negating the benefit of restraints and a roll protection system. It's hard enough to keep seats where they belong with just the weight of the pilot times the deceleration forces pulling on the restraints and the floor twisting and buckling during the crash.

Why bother? If the crash is severe enough to put you upside-down, a plexiglass canopy is extremely likely to break or at least crack and in that case you can break it further by bare hand. For Lexan on the other hand it sounds like a good idea, because cutting through it would probably take at least as long as to burn 100 gallons of gasoline with you in the middle...
Excellent point.
 

Aircar

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Google 'Martin Baker MB2' for photos of the retractable roll over strut mentioned earlier.

The O-235 I had came from a Grumman Lynx that flipped on it's back on a runway and trapped the pilot upside down --the sliding canopy wouldn't and the fin crushed down .

The Victa Airtourer (production aircraft aerobatic two seats ) had a rubber bladder fuel cell directly under the seat --in a really hard landing it was likely to burst or puncture and when inverted it could leak and burn --no Cg shift from fuel use but questionable location.
 

autoreply

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A rollbar fore and aft should be part of any structure underlying a canopy.
Not necessarily, because it blocks visibility. Here in the Netherlands we long had to have barber-wire bars in gliders (because you're much more likely to land in one since they're hard to see and gliders frequently have off-site landings.)
http://www.bva-auctions.com/static/auctions/4336/lots/3-1.jpg

Horrible things and I'd rather be decapitated when landing in the wrong spot, than risking a mid-air because your visibility is so much more restricted, not to mention getting out with your parachute.
 

Hot Wings

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than risking a mid-air because your visibility is so much more restricted,

Are they really that restrictive with regard to vision? As long as the tubes are less than the distance between one's eyes there should be no blind spots at reasonable ranges?

As for egress with chute, could they not be a part of the canopy and disposed of at the same time?



Moving on and tossing out an off the wall idea for my ultralight project - gross weight 240Kg. I'm expecting a nose over to be a likely result in a botched or forced landing and am planning on a stout canopy with Lexan or PET so breaking is not an option. It will be detachable by a belted pilot from the inside.

What I've considered is a spring loaded ram that could be deployed, after the noise stops, while inverted to lift the fuselage 1/2 meter or so. The spring would need to be strong and could pose a hazard during ground operation but an inverted position sensor, (think inverse of an inertia lock in a shoulder belt) could be used. With the canopy detached and the pilot unbelted the spring would only have to lift around 75Kg, at the most.

Comments?
 

autoreply

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than risking a mid-air because your visibility is so much more restricted,

Are they really that restrictive with regard to vision? As long as the tubes are less than the distance between one's eyes there should be no blind spots at reasonable ranges?
The problem is that the extra obstruction draws attention, obscuring other airplanes. A sufficiently strong and stiff (buckling) roll-over structure in front of you will block some sight, but above all distract from moving airplanes close around the roll-over structure.
As for egress with chute, could they not be a part of the canopy and disposed of at the same time?
Yes, they are. If your canopy won't let go in flight though, you're in big trouble. A Dutch guy tried this a decade ago and got out... just.
What I've considered is a spring loaded ram that could be deployed, after the noise stops, while inverted to lift the fuselage 1/2 meter or so. The spring would need to be strong and could pose a hazard during ground operation but an inverted position sensor, (think inverse of an inertia lock in a shoulder belt) could be used. With the canopy detached and the pilot unbelted the spring would only have to lift around 75Kg, at the most.
I did similar sizing for my canopy (encloses the full fwd fuselage, slides forward). The weight of such a spring or gas strut is fairly heavy. I'd go with the jackscrew and a light motor. It also avoids the major problem of acceleration. A spring, strong enough to lift your full aircraft weight needs a massive damper to avoid shattering the whole structure.
 

Hot Wings

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I'd go with the jackscrew and a light motor. It also avoids the major problem of acceleration

I'd considered these option, and still am. Fuel containment should not be a problem. I'm not comfortable with electric power after the crash. Since I'm using a hybrid drive one of the safety features is a "G" force disconnect it would require a second source of power.

The jack screw assumes that the pilot is still physically able to do the work. There are lots of light weight options for a damper, from viscous liquid to centrifugal brakes. Pneumatic and a small orifice (susceptible to plugging) for rate control is another.

Still thinking this one out.
 

SVSUSteve

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Not necessarily, because it blocks visibility.
Horrible things and I'd rather be decapitated when landing in the wrong spot, than risking a mid-air because your visibility is so much more restricted,
The thing is that a rollbar doesn't have to be several inches in diameter and honestly, we all should be well enough versed in the inherent limitations of see and avoid that if we honestly believe a 2 inch or smaller bar is going to severely impair our ability to avoid a collision, then there's something wrong. EDIT: Wait....Hot Wings beat me to it.

What I've considered is a spring loaded ram that could be deployed, after the noise stops, while inverted to lift the fuselage 1/2 meter or so. The spring would need to be strong and could pose a hazard during ground operation but an inverted position sensor, (think inverse of an inertia lock in a shoulder belt) could be used. With the canopy detached and the pilot unbelted the spring would only have to lift around 75Kg, at the most.

Comments?
Consider for a moment whether the mechanism would work if the cockpit structure were bent severely in any given direction. That is almost a foregone conclusion with regards to ultralights because of the nature of the current approach to construction. My guess would be that your safer bet is using that weight to reinforce the structure around your seat and keep the aircraft from winding up in a position where you can't get out without mechanical assistance. That is build a cockpit that you can crawl out of even if it is inverted on the ground.

The problem is that the extra obstruction draws attention, obscuring other airplanes. A sufficiently strong and stiff (buckling) roll-over structure in front of you will block some sight, but above all distract from moving airplanes close around the roll-over structure.
You know, as opposed to those aircraft that appear stationary due to impending impact. ;)

Any actual scientific evidence to back up that cockpit structure "draws attention"?

Yes, they are. If your canopy won't let go in flight though, you're in big trouble. A Dutch guy tried this a decade ago and got out... just
Who says the frames have to be sufficiently close together to hinder egress?

Fuel containment should not be a problem.
Just out of curiosity, what are you doing with regards to that in your design?

The jack screw assumes that the pilot is still physically able to do the work.
The rule I was always taught to operate by was assume that the pilot is only able to use one hand and can't see all that well for whatever reason (smoke, darkness, blood in his eyes, etc) when designing systems related to egress and/or survival.
 

Aircar

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The Victa Airtourer was a certified aircraft and the 4 seat development Aircruiser subsequently became the RAAF basic trainer (fully aerobatic )--I am not sure where the fuel was kept in the CT4 airforce trainer --both were designed by Henry Millicer one of my old lecturers --my family owned an Airtourer for ten years . I liked it to fly in most ways inc aeros but it was a 1950s design (being fact almost exactly a scaled down Percival Provost with flat four engine --Millicer worked on the Provost shortly before coming to Australia just post war. It was designed for vertical descent survivability --much crush space under the seats and a solid overturn structure etc .

A Scottish aviation Bulldog here was doing low level aerobatics and failed to pull through at the bottom of a loop --it hit flat and skidded to a halt apparently without that much damage from a distance but the first on the spot found both occupants sitting upright, belted in but stone dead from the vertical forces -crushed spines and necks . It had insufficient crush space but a slimmer fuselage .

Autorep --My Sagitta came with the twin bars fore and aft that you refer to but I removed them and built up the 'vertical' hoop in glass roving -- it was indeed too 'crowded' with both the 'radial' canopy hoop AND the twin tubes in the front flat wrap part of the canopy --visibility in every other direction was superb including over the shoulder to the rear (a sliding bubble canopy just like the Mustang and possibly inspired by it ) --I 'lost' the original horribly wavy sliding canopy after it came loose following hitting a tiny bump on take off -winch launch - (and canopy lock over centre fouled by the rigging pin having rotated unnoticed ) --canopy stood up first after the rear roller disengaged and was able to be held (just) by the left hand until the launch completed but could not be held for a full circuit and in departing the aircraft contacted the tail and shattered (wooden frame) --the damage was visible from the cockpit and too low to jump anyway and since I already had flown it without the rear canopy was not a problem . I blew a new canopy (perfect optics ) and glass frame and cut the rigging handles short to avoid any repeat --the aircraft was burnt in it's trailer in a bushfire after I had sold it (I had specified first right of refusal to buy it back if he ever sold it )

I have flown a number of aircraft with two piece canopies (canopy bar in the usual sense) and a few ultralights with a single fore and aft --"barbed wire" stopper (SanderVeEnstra's designs) and find the hoop type an annoyance since you have to bob up and down to keep the tug 'out' of them whereas with a single fore and aft tube a little sideways movement shows clearly what is ahead --one of his aircraft was flown through a seven strand barbed wire fence -by an airline pilot - and snapped all seven without any injury to the pilot --flat wrapped Lexan canopy as well --if you severley stretch form even standard acrylic it developd crystallites --long range order that greatly toughens it --you will NOT break it by hand .(used to run a plastics molding shop .

The Dauphine helicopter canopies are made by heating a thick block of cast acrylic and progressively pulling it out into a thin sheet before drape forming and this maximizes the toughness --the medivac helicopter that lands next to me once hit a bird en route and despite blood and feathers , when cleaned off hadn't cracked it .
 

Toobuilder

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...They're relatively rare, which is imho the sole reason not every aircraft incorporates a roll-over structure...

Rollover accidents in RV's are anything but rare. Most crash scenes show the airplane inverted, and almost any off field landing is going to end up that way. The wheels are so small on the taildraggers that they flip, and the nose wheel models fare no better when the front gear leg digs in.

There is endless debate on the RV forums concerning egress after a rollover, and the general consensus is to bust through the canopy using a tool of some sort.
 

SVSUSteve

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A Scottish aviation Bulldog here was doing low level aerobatics and failed to pull through at the bottom of a loop --it hit flat and skidded to a halt apparently without that much damage from a distance but the first on the spot found both occupants sitting upright, belted in but stone dead from the vertical forces -crushed spines and necks . It had insufficient crush space but a slimmer fuselage .
That's something we encounter all too often in experimental crashes.

I have flown a number of aircraft with two piece canopies (canopy bar in the usual sense) and a few ultralights with a single fore and aft --"barbed wire" stopper (SanderVeEnstra's designs) and find the hoop type an annoyance since you have to bob up and down to keep the tug 'out' of them whereas with a single fore and aft tube a little sideways movement shows clearly what is ahead --one of his aircraft was flown through a seven strand barbed wire fence -by an airline pilot - and snapped all seven without any injury to the pilot --flat wrapped Lexan canopy as well --if you severley stretch form even standard acrylic it developd crystallites --long range order that greatly toughens it --you will NOT break it by hand .(used to run a plastics molding shop
Note to self: Pick AirCar's brain when it comes time to design the windscreen.

and the nose wheel models fare no better when the front gear leg digs in.
....and shears off. ;)
 

BBerson

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I was thinking of cutting a large frameless access window (with little clips to hold the side window in place) into the sides of my canopy (see avatar). I think I could crawl through a small side window in an emergency. Not sure how big of a hole I could cut in the canopy before a frame would be needed.

And I also wanted this side window for removing in flight also. Sort of "almost open cockpit" but without the excess drag of open cockpit.
 

bmcj

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SIDEBAR:

Speaking of egress, ejection seats with explosive charges and rockets are not really feasible on a GA planes, but what about a system that pulling the E-lever disengages the seat from the aircraft, allowing it to slide up some guide rails; the mechanism for extraction would be a simultaneous release of the canopy that angles the canopy with an upward angle of attack so that the aerodynamic forces lift the canopy and seat together out and clear of the plane?

P.S. - sorry about the run-on sentence. :gig:
 

SVSUSteve

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but what about a system that pulling the E-lever disengages the seat from the aircraft, allowing it to slide up some guide rails; the mechanism for extraction would be a simultaneous release of the canopy that angles the canopy with an upward angle of attack so that the aerodynamic forces lift the canopy and seat together out and clear of the plane?
Three major problems:
1. Getting people to actually pull the handle (read as "same problem that the BRS/CAPS has")
2. Most events leading to a crash tend to happen at low enough altitude that you're going to have little time to deploy such a system (not to mention low enough airspeed that it would be risky to try a drogue chute extrication or something similar for fear of striking the tail) let alone get the chute deployed prior to ground impact. Read as "the other problem the BRS/CAPS concept has".
3. How do you build an attachment that is easily disconnectable in that short of a time frame that is not going to be a hazard to either fatigue failure or separation in a crash landing or other event not amenable to bailing out. There's a big enough issue with GA seats not staying put in crash scenarios.
 

bmcj

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Three major problems:
1. Getting people to actually pull the handle (read as "same problem that the BRS/CAPS has")
2. Most events leading to a crash tend to happen at low enough altitude that you're going to have little time to deploy such a system (not to mention low enough airspeed that it would be risky to try a drogue chute extrication or something similar for fear of striking the tail) let alone get the chute deployed prior to ground impact. Read as "the other problem the BRS/CAPS concept has".
3. How do you build an attachment that is easily disconnectable in that short of a time frame that is not going to be a hazard to either fatigue failure or separation in a crash landing or other event not amenable to bailing out. There's a big enough issue with GA seats not staying put in crash scenarios.
Hey! I'm just the idea man. It's your job to make it work! ;)
 

SVSUSteve

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I'll give it some thought. Honestly I've always argued that there has to be a way to achieve a functional GA ejection seat but it is definitely a design challenge.
 

autoreply

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The jack screw assumes that the pilot is still physically able to do the work. There are lots of light weight options for a damper, from viscous liquid to centrifugal brakes. Pneumatic and a small orifice (susceptible to plugging) for rate control is another.

Still thinking this one out.
The (I think pneumatic) jacks glider pilots use to lift the fuselage on a wheeled cart (to put it in the trailer) might be interesting. With a few kicks (or hand movements) you can easily lift up around a thousand pounds. Pretty damage-proof too.
The thing is that a rollbar doesn't have to be several inches in diameter
An inch is enough to block sight and if I do the calculations you won't get it much smaller if you look at buckling and the dimensions of a typical experimental aircraft.
and honestly, we all should be well enough versed in the inherent limitations of see and avoid that if we honestly believe a 2 inch or smaller bar is going to severely impair our ability to avoid a collision, then there's something wrong.
I don't "believe" this. It's a fact, confirmed by both theory, tests and the experience of thousands of pilots here. Admittedly, glider pilots operate in a zillion times more crowded skies, but given the serious consequences of a midair this is an important issue.

From the car industry too, there are plenty of reports of the safety consequence small obstructions.
 

SVSUSteve

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I don't "believe" this. It's a fact, confirmed by both theory, tests and the experience of thousands of pilots here. Admittedly, glider pilots operate in a zillion times more crowded skies, but given the serious consequences of a midair this is an important issue.

From the car industry too, there are plenty of reports of the safety consequence small obstructions.
In comparison to say a full cockpit, it's only blocking a small amount of the vision of the aircraft (less than 5% most likely).

The idea of "see and avoid" generally is a very flawed one and THAT is something that has additionally been demonstrated time and again. I think it boils down more to which risk one fears most: mid-air collision or a more "traditional crash". Given the relatively low risks of mid-air collision even in crowded skies, it would make sense from an odds perspective if nothing else to worry about what is more likely. If you have a mid-air collision, then that is where being able to bail out is a concern and I was more worried by your contention that a forward place rollbar would somehow prevent this in a timely fashion.
 

bmcj

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An inch is enough to block sight and if I do the calculations you won't get it much smaller if you look at buckling and the dimensions of a typical experimental aircraft.

and honestly, we all should be well enough versed in the inherent limitations of see and avoid that if we honestly believe a 2 inch or smaller bar is going to severely impair our ability to avoid a collision, then there's something wrong.
I don't "believe" this. It's a fact, confirmed by both theory, tests and the experience of thousands of pilots here. Admittedly, glider pilots operate in a zillion times more crowded skies, but given the serious consequences of a midair this is an important issue.

From the car industry too, there are plenty of reports of the safety consequence small obstructions.
A picture is woth a thousand words...

WK cockpit.jpg
 
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