Emergency Egress: Improvements to the bubble canopy?

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Hot Wings

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That is build a cockpit that you can crawl out of even if it is inverted on the ground.

That would be ideal but it's just not possible. Forget standard ultralight tube and rag construction, think more along the lines of a conventional glider pod. That is also why I don't envision a ram mechanism being bent beyond the point of being functional.

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

The tank will be tucked well inside the fuselage structure in a very reinforced area not likely to be breached. There is nothing near that can puncture it and I'll probably use a dry break fitting at the tank just to be sure. I've got room for a standard off the shelf 5 gallon fuel cell and can't build one for the same cost in materials and time. Fuel tanks built into the structure of a composite fuselage look appealing at first glance, but between the problem of sealing against leaks and leakage from crash damage, I'm looking for a better way.
 

Aircar

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Loved the photo of the Spaceship one "view" bmcj --given that the people who sign up for a ride @ $200 000 plus are doing it "for the view,stupid" (Burt) they seem to have a problem Houston. Did you notice the emergency evacuation provision for Mike Melville?--the exit is through the nose cone -FORWARD into the airstream ......it's in the you tube "towards a black sky" series ( I think that's the right title) and shows Burt showing Mike how to 'limbo' out the front end --Mike doesn't look completely convinced .
 

SVSUSteve

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The tank will be tucked well inside the fuselage structure in a very reinforced area not likely to be breached. There is nothing near that can puncture it and I'll probably use a dry break fitting at the tank just to be sure. I've got room for a standard off the shelf 5 gallon fuel cell and can't build one for the same cost in materials and time. Fuel tanks built into the structure of a composite fuselage look appealing at first glance, but between the problem of sealing against leaks and leakage from crash damage, I'm looking for a better way.
I'm designing to keep the fuel tanks out of the fuselage for my aircraft. They are going to be in the wings and design to be crash-resistant to exceed the US Army standards. It will be more expensive in cost and effort but especially for the larger of the two designs, it will probably be much lighter.

That would be ideal but it's just not possible. Forget standard ultralight tube and rag construction, think more along the lines of a conventional glider pod. That is also why I don't envision a ram mechanism being bent beyond the point of being functional.
The issue I would see would not be the ram mechanism being bent but rather the issue of the path of it being obstructed. This is actually an issue with energy absorbing seats and other mechanisms that require a clear path to function as designed. The other concern I would have is for it inadvertently being triggered in a crash sequence.

Did you notice the emergency evacuation provision for Mike Melville?--the exit is through the nose cone -FORWARD into the airstream
A similar technique was used in some of the early X-planes (as in the Edwards supersonic test beds) if I remember correctly. I wouldn't be entirely convinced either.
 

Vigilant1

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I'm designing to keep the fuel tanks out of the fuselage for my aircraft. They are going to be in the wings and design to be crash-resistant to exceed the US Army standards.
Farther off topic: I'll probably go with fuel in wing stubs rather than a fuselage tank, as I think it is likely safer, but I can envision cases where I'd be better off with fuel in the fuselage. For example, during a landing in the trees it will be very difficult to prevent a branch from penetrating deep into the wing, whereas it might be a bit easier to prevent a breach of a more compact fuel cell somewhere deeper in the fuselage. I'm also considering Explosafe or similar material, but I'm not sure it'll be worth the time/cost/weight/trouble. It seems effective in preventing explosions of fuel tanks, and as a side benefit also reduces sloshing and helps assure electrostatic grounding, but my main concern is fuel leakage/ignition from a compromised tank.

Mark W.
 

SVSUSteve

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but I can envision cases where I'd be better off with fuel in the fuselage. For example, during a landing in the trees it will be very difficult to prevent a branch from penetrating deep into the wing, whereas it might be a bit easier to prevent a breach of a more compact fuel cell somewhere deeper in the fuselage.
Then you design the wing to either shear or to withstand the impact in such a way the tank is protected. I have a way of doing this but I'm working on developing it so we can use it in my design. If it works as I hope, I will share the information with you.
 

autoreply

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Information on its tolerance against alcohol should be available from most industrial tank manufacturer.
No. My girlfriend is in charge of the alcohol tolerances and nobody else. At least, that's what she told me :gig:

On a serious note, my concern with ethanol is in my composite structure. Fuel in a composite tank is well documented and proven, but the recent addition of more and more ethanol worries me. In a separate composite tank (or bladder, race cell or welded tank) I still wouldn't be bothered (you simply replace it), but my tanks are integral and weakening major bulkheads and wing skins gets my nerves.

Massive thread drift by the way.
 

Vigilant1

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Any clue whether those are available in larger sizes (20-ish gallons)? Similar considerations as you and I'm a bit afraid of the ethanol and it's impact on the bulkhead it will be sloshing against. (welded tanks are an option too..)
Yes, there are more here.
 

JimCovington

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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:
The Zvezda SKS-94 does this with a little explosive cartridge assist - considerably less than a standard ejection seat. I've seen them called "extraction" seats. You want the push; there are some situations where you can't count on the canopy to pull you out.

http://www.aafo.com/racing/tech/seats/part2c.htm
 

Dana

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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.
Not convinced of the value of such a system but the mechanics of it is close to my day job where almost everything is moved by pneumatic cylinders... a pneumatic cylinder or cylinders operated by a small gas bottle, it doesn't take much for a one shot operation, and a simple flow control (orifice) to control the extension speed. It could even do double duty... for example a small hand pump for relatively low pressure to lift the canopy and keep it open for normal use, or blow it open with the emergency bottle at a high enough pressure to lift the entire fuselage when inverted. Of course you'd need that roll bar at the attachment point...

Re fuel cells, these guys make all kinds of custom bladder tanks.

-Dana

Chaste: why virgins run.
 

wsimpso1

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OK, gotta get into this conversation.

A big fraction of powered planes finish emergency landings on their back. It is just a consequence of sticking little tires in soft ground, and usually happens after the airplane has almost stopped. I know one lady who did a nice job of setting a powerless Cherokee on a plowed field, 66' of main tire trenches, and 3' of nose gear dig-in. The airplane hung on its nose for a bit before it finally fell onto its back. I have heard the tale a bunch of times, and that noseover is what I am designing for. The Cherokee was exited by pushing the door open and crawling out...

SpaceShipOne's nose egress hatch was to be used in an unrecoverable spin, and that was clear in the Discovery Channel video. Thinking about that, I would expect that just about any airframe or controllability issue would have that ship rotating with the nose being "out". There are little to zero dynamic airloads on the nose in a spin - indicated airspeed goes away... And you don't limbo out, you slack the shoulder belts, fold at the waist, release the nose cone, then release the lap belt and out you go. Centrifugal forces do the work. Actually having a quick way out on a double hull pressurized space craft is doing something.

Next, the whole Fuel-in-the-cockpit thing has been talked to death elsewhere. Please...

The Long EZ rollover structures were designed for nose-over, as are most other of this type. In the case of an airplane being put onto pavement upside-down at near flight speeds, well, I do not believe you have seriously looked at what that would take to be sturdy. Something like the roll cages used in various serious circle track cars would be needed, and then it would be trying to come out of the rest of the structure. In these race cars, the cage is the frame... In a big Ag plane you might be able to carry the weight.

My solution is a gullwing door set. The bows at the front and back of the door blend into a roof section, it is beefy and designed to hold the twice the weight of the airplane. The doors will come off by pulling a handle, which pulls hinge pins with cables. That facilitates in-flight jettison as well as release after landing. I am thinking about one of the little tab and slot engagements at the back edge like the glider guys have to make sure that it rotates out and away. If you are upside down, the whole thing would have to be shoved laterally, but it looks like it will work.

If I somehow land on the roof at stall speed, I still expect that the windshield will give up, then the leading edge of the roof will dig in, and it will come apart. But this last mode is a fairly rare one, and I am not going to design for it.

Billski
 

Vigilant1

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My solution is a gullwing door set. The bows at the front and back of the door blend into a roof section, it is beefy and designed to hold the twice the weight of the airplane. The doors will come off by pulling a handle, which pulls hinge pins with cables. That facilitates in-flight jettison as well as release after landing. I am thinking about one of the little tab and slot engagements at the back edge like the glider guys have to make sure that it rotates out and away. If you are upside down, the whole thing would have to be shoved laterally, but it looks like it will work.
Billski
This is about what I've been thinking of. The central bar provides a fairly robust "cage" overhead, good bracing of the forward canopy bow against rearward forces, and unless the aircraft ends up on it's roof with weight on both doors simultaneously (seems unlikely), you'd have a way out. It will weigh a bit more than a bubble canopy, and the increased area requiring sealing against wind/rain is a bit of a downside.

Mark
 
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autoreply

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Thanks for the link Dana!

@ Billski, did you consider hinging your gull-wing doors at the aft door post? Wouldn't that make both opening them when upside-down and in-flight getting out a lot easier?
 

addaon

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Any clue whether those are available in larger sizes (20-ish gallons)? Similar considerations as you and I'm a bit afraid of the ethanol and it's impact on the bulkhead it will be sloshing against. (welded tanks are an option too..)
It looks like up to 16 gallons is readily available. Bunch of options, too; two shapes (this is the one more likely to fit in a wing), two colors, with or without baffling foam.
 

TFF

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I dont know if this has been noted here. On the biplaneforum.com a similar discussion is on over there. One pilot, who had the experience of flipping, had opened his canopy for his egress during his emergency landing, and when the plane flipped it slammed shut as it went over. he said he would have drown if he had gone into the ditch next to where he was if he went in. A lock open would be good to prevent this.
 

SVSUSteve

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A big fraction of powered planes finish emergency landings on their back. It is just a consequence of sticking little tires in soft ground, and usually happens after the airplane has almost stopped. I know one lady who did a nice job of setting a powerless Cherokee on a plowed field, 66' of main tire trenches, and 3' of nose gear dig-in. The airplane hung on its nose for a bit before it finally fell onto its back. I have heard the tale a bunch of times, and that noseover is what I am designing for. The Cherokee was exited by pushing the door open and crawling out...
I would also like to point out that it's a risk even in a wheels up landing in a retractable, especially if the skin at the bottom of the engine cowling is breached (not at all uncommon) and the bottom of the firewall is either vertical or, even worse, canted forward. It acts like the blade on a plow and not only can lead to a

If I somehow land on the roof at stall speed, I still expect that the windshield will give up, then the leading edge of the roof will dig in, and it will come apart. But this last mode is a fairly rare one, and I am not going to design for it.
My solution is a gullwing door set. The bows at the front and back of the door blend into a roof section, it is beefy and designed to hold the twice the weight of the airplane.
You might think again. That's not at all uncommon especially in spin/stall accidents or where the aircraft gets too low, hangs their wing tip up on a tree and then hits the ground. Guess what is one of the common ways people in cabin style aircraft crashes wind up with their brains outside their skulls in what (with a little better design) would be a survivable crash?

One problem with the "twice the weight of the airplane" approach: a lot of the crashes that are survivable involve an impact of three g or greater. There are a couple of ways of minimizing this issue.
1. Stronger frame (our designs-both the LSA and the larger one currently on the drawing board- use a factor of at least 4-5 G as a design point); also remember to factor in not only the vertical impact but the simultaneous longitudinal loading since you seldom see these in isolation during crashes.
2. Keeping as much weight forward (off the rollcage if the aircraft does invert) and as low on the aircraft as possible (which minimizes the chance of a rollover or initial collapse in an upright impact)

The Long EZ rollover structures were designed for nose-over, as are most other of this type. In the case of an airplane being put onto pavement upside-down at near flight speeds, well, I do not believe you have seriously looked at what that would take to be sturdy. Something like the roll cages used in various serious circle track cars would be needed, and then it would be trying to come out of the rest of the structure. In these race cars, the cage is the frame... In a big Ag plane you might be able to carry the weight.
Then you just design it that way. It's easily doable and basing designs on race cars and ag aircraft is a much better option than looking backwards at aircraft designs that are often mediocre at best and accepting that as a status quo.

Wouldn't that make both opening them when upside-down and in-flight getting out a lot easier?
Given the frequency of people failing to properly latch their doors, I would wonder if the risk of the added drag from a door popping open in flight would be worth the potential benefit of a much less likely crash.
 

BBerson

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I dont know if this has been noted here. On the biplaneforum.com a similar discussion is on over there. One pilot, who had the experience of flipping, had opened his canopy for his egress during his emergency landing, and when the plane flipped it slammed shut as it went over. he said he would have drown if he had gone into the ditch next to where he was if he went in. A lock open would be good to prevent this.
Emergency window panels that break free inward, could help here.
 

wsimpso1

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I did not want to hinge the doors from the back - I want to be able to taxi with the doors open and then be able to close them for flight. Suicide doors won't really allow that. I am skeptical that my doors would stay on if opened at my cruise speed, but if they did stay put, that would complicate emergency egress, whether in flight or on the ground. I am putting in pullable pins and a handle to make sure that they are out of the way in case I need out.

Let's try to keep this all in perspective... First off, this thread is about Emergency Egress, so all of this talk about impact protection is thread drift. Interesting drift, but still off topic. So, THREAD DRIFT ON.

We are talking about building an airplane here. The airplane's empty weight can not be be more than about 60% of its gross weight, or it will have nearly zero utility and awful performance. So everything about it becomes a compromise. Including how much structure you put around the people.

No flight vehicle can be designed to be survivable in all foreseeable crashes. Even paragliders. The reason is simple - We are way outside of human scale on energy. To survive, we must suck up the energy while keeping from crushing the soft pink critters in the seats.

Human beings are not very tough. Have one step off of a platform 12' up and probability of a death is pretty large. Lots of other data exists indicating g's and g rates for the human head and forces on the spine, and so on. The biggest statistic we need is that if we keep an upright crash (measured at the seats) to 19g, keep the cabin in one big piece, keep the seat and seat belts attached throughout, and don't impale the humans with something, they will probably live through the event. Doing all of this from a significant sink rate into a hard landing with your weight spread out over the chair and everything working right is an accomplishment. SUSVsteve would have us tossing in a higher sink rate and upside down, rolling and yawing from a tree strike. You now have more vertical velocity to suck up with a less desirable structural load path, far more concentrated loads on the human (harness instead of whole seat plus harness), and much higher likelihood of head strikes, and it just flew right past human survivability.

I challenge anyone to design a steel tube roll cage (nice ductile zone behaviour) to suck up a whole airplane moving 40 feet per second inverted and stay below 19 g. Oh, it can be done, but wait until you face up to the real world with it. IF you could keep it at 19 g through out the vertical arrest, it will require 1.3 feet of crush space. That is 15 inches of free room between your head position (flail, seat belt extension and looseness, seat deformation, etc) and the ceiling. Large parts of the load curve will be at lower g, so even more travel will actually be required. You would need more like 2-4 feet of free room. Maybe that is not so bad, you might be able to stand up inside your bird. Not even in NASCAR... and in NASCAR, they learned that you need to prevent the inverted events. They do that by having a couple lift spoilers that open based upon simple aeroforces if the car gets sideways or backwards. The cars stay upright way better now.

If we want to build our airplanes for the most likely events, we design it to stand an engine out emergency landing on a flat (if not level) chunk of ground from its engine out sink rate and stall speed. This means reasonably low landing speeds to keep the kinetic energy down and min sink rates that are fairly reasonable too. We also design it to have benign stall behaviour so that stall spin events are easily avoided. Do those two things, and the airplane is likely to land fairly slow, upright and under control. Even a landing in a forest under those conditions is likely to be survivable.

Want to make the interior and seating like a NASCAR racer, with 3' of otherwise unused headroom, and well, it might be safe, but if you can get it to fly, it might be an awful airplane that no one will want to fly. Your airplane, you go for it.

Mine has a cabin that will stay together at 19 g, Confor foam seats and wide aerobatic harnesses to keep the forces on the humans down. It also has plenty of static stability, benign stall foils, reasonable stall and sink rate so that it is easily possible to do a survivable landing under engine out conditions. And if, as it slows down after reaching the mud, it digs in and ends up on its back, the roof and tail will stand the blow so that we can release belts and doors and crawl out.

Billski
 
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