Escape hatch?

[sfGnome]

On the (many) occasions when I'm daydreaming, thoughts often turn to planes I'd like to build. I like some of the low wing types, but I'm concerned about the lack of exit options should it flip (such as in Rocketdriver's sad KR2 accident). Question is, would it be possible to build in a removable floor panel?

 

First and foremost, would it affect the fuselage's structural integrity? In a monocoque body, the skin takes a lot of the stress, so it may not be acceptable on some types (eg Morgan?).

 

Secondly, how would you latch it in such a way that it could be opened when needed by either pilot or passenger, but couldn't be accidentally kicked open by a restless passenger (I've had the between-the-legs throttle on an older Jab knocked that way). I guess if it were hinged at the front and latched at the rear then an accidental opening would give you a helluva fright, but nothing worse.

 

So, is it;

 

a) one of those simple ideas that leave you wondering why it hasn't been thought of before (not very likely ),

 

b) one of those dumb ideas that's long been discarded as totally impractical (and if so, why), or

 

c) already in use in a/c where it's a valid option?

 

 

[rgmwa]

I'm building an RV-12 at the moment, and there's no way you could put a sizeable hatch in the floor without causing major structural problems - even if you could find a practical location for it. ie, centre, passenger or pilot side?, in front of the seats or behind them in the baggage compartment?, etc. Also if it was anywhere near the centreline, it would almost certainly foul control cables, fuel lines etc. And even if you could find somewhere for it, you may not be able to open it if the flip caused the airframe to distort. You might have a better chance with an aircraft that used welded frame construction, but if it's monocoque and smaller that a B17 or a Mosquito, I don't think you could do it. Much better to land right side up! :thumb_down:

 

 

[facthunter]

it's seriously one of the reasons why I lean strongly towards a high wing. It's not difficult to end up inverted on the ground. Perhaps consider a good roll bar instead. With all the controls and the need for strength in the middle of an aircraft, I can't see how you could have an alternative exit through the floor. Nev

 

 

[Guest Maj Millard]

It's always smart to have a good strong roll-over bar in a low winger . Additionally in aircraft like the Rvs etc, it's very wise to also have a small axe handy to fracture and smash out the perspex canopy if you have to. It's amazing just how fast one's survival instinct kicks in when your on your back with fuel dripping on you !....................Maj...

 

 

[sfGnome]

It's always smart to have a good strong roll-over bar in a low winger . Additionally in aircraft like the Rvs etc, it's very wise to also have a small axe handy to fracture and smash out the perspex canopy if you have to. It's amazing just how fast one's survival instinct kicks in when your on your back with fuel dripping on you !....................Maj...

Yep, I guess a small axe is easier to install than a hatch. All I'd have to do then is work out how to stop the beloved from wielding it in my direction when I hit the bumpy stuff...

:hittinghead:

 

 

[Guest Jake.f]

I wonder if there would be any market for a small device that through some magic of materials science could cut or fracture perspex easily with minimal power such as muscle power and batteries.....

 

 

[kgwilson]

The Sierra I am building has a rollover cage built in to the rear bulkhead just behind the pilots head. It is 40mm x 40mm x 5mm aluminium angle in an inverted V from the main longeron to the centre line. There is a smaller one at the rear just in front of the elevator spar. This plus a good tomahawk axe in an easy to reach position. A hatch is entirely impractical in my opinion.

 

 

[Spin]

"You mean something like this: http://www.spservices.co.uk/item/EMI_EMIWindscreenCenterPunch_76_0_24_0.html"

 

You're going to suffer serious disappointment if you try and use something like that to get out through perspex - the material is too soft and you'll just push a little dent into it.

 

 

[Guest Jake.f]

Something like that, although it would work for perspex... probably doesn't even exist because perspex is too soft and flexible rather than hard and brittle like glass

 

 

[Gnarly Gnu]

Yep, I guess a small axe is easier to install than a hatch.

You might get away with a small gnome-sized axe but CASA won't allow you to carry weapons remember. On the other hand perhaps there is grounds to claim the shotgun and axe are to facilitate rapid exit in a crash situation.

 

A roll cage is good but remember to pad it for the protection of your noggin. Several pilots have died from head injuries in aircraft accidents where the aircraft was intact and still in quite good shape.

 

 

[turboplanner]

Yes I think you'd really need a Gnu sized axe.

 

Better to get an engineer to design in a roll bar well clear of the head arc with reasonable shoulder harness tension.

 

I would be thinking full tube rather than angle, but it's surprising what shapes produce strength in conjunction with existing structure, and this is important because you can't afford the weight of a car type roll cage.

 

Canopy destruction is a worthwhile subject to discuss here, because if you're upside down, wielding any weapon effectively is problematical - if you drop it, it may be out of reach, there may be a huge urgency due to fire, and if it is holding the aircraft off the ground you don't want to make it collapse.

 

 

[facthunter]

In reality, ( if things are bad like fuel leaking) you may not have the time. If it doesn't burn you have a different situation, but you can't be sure. Might be better to consider doing the fuel system right with a racing car type tank and a small fire extinguishing system plumbed in. The Ryan STM has a pylon just in front of the cockpit for ground clearance. Nev

 

 

[Gnarly Gnu]

Yes I think you'd really need a Gnu sized axe.

Pah, cantcha see the horn in my pic?

 

 

[Guest Maj Millard]

Believe me, when you want out, you want out now !....especially after an 'incident' when the adrenalin is pumping. Do what ever you need to, to make that possible. A good roll over structure is a good start so that you are still capabable of getting out, but you do need to get through that 1/4" thick capopy if it's between you, and freedom. I'm sure the carrage of a small axe would not upset the authorities in a private use aircraft , if you really explain to them what it is really for..................................................................................Maj...

 

 

[turboplanner]

Yes, you might as well carry a box of matches and blow the friggin' thing off BR.

 

Another issue is the unfamiliar gravity forces when you are upside down. Apart from the fact that a lot of people are inured when the pull the pin without thinking of the drop, you can always move as freely.

 

I put a tractor up on its tail once. I was protected by a roll bar and the 3PL implement, but couldn't push the clutch in to stop the wheels turning because I coulnd't use the downward force of my body weight. As I pushed with my leg, I slid backwards, so I had to pull the shutoff lever.

 

Wielding an axe etc when upside down my not be easy in some AC.

 

 

[Wayne T Mathews]

Believe me, when you want out, you want out now !....I'm sure the carrage of a small axe would not upset the authorities in a private use aircraft , if you really explain to them what it is really for..................................................................................Maj...

Many years ago I read somewhere that if Keith Anderson had had a hatchet with him in the Kookaburra, he'd have been able to clear the scrub and get airborne again. I don't know where that was written, or even if it's true, but it doesn't matter. It's the excuse I use to carry a small hatchet behind the seat of my Cub. I've never used the hatchet to clear scrub, or break perspex, but it makes a great hammer and prybar for pounding in my tiedown stakes and then levering them out next day.

 

 

[sfGnome]

A small butane torch would sort the Perspex quickly and with little effort but obviously no good if there is a risk of fire and who'd want to carry one of those in the cockpit.

Of course, if it was NASA then they'd fit explosive bolts... :big_grin:

Seriously, you can never cater for every circumstance, but if you can at least cater for some of the more common ones (and sadly, flipping doesn't appear to be totally uncommon), then all the better. So, apart from wielding an axe, is there a better way to make perspex break when you want it to and not when you don't (like, when you're flying).

 

 

[turboplanner]

Separating it into two aspects:

 

(a) being crushed in a flip

 

(b) getting our with a Canopy which opens upwards, or slides, or with gull wing doors.

 

(a) seems feasible to build a hoop or king pole.

 

(b) a wider frame space further back in the fuselage?

 

Maybe someone could specify an aircraft where a .dwg or .pdf drawing is available with frame dimensions

 

 

[Guernsey]

The Sierra I am building has a rollover cage built in to the rear bulkhead just behind the pilots head. It is 40mm x 40mm x 5mm aluminium angle in an inverted V from the main longeron to the centre line. There is a smaller one at the rear just in front of the elevator spar. This plus a good tomahawk axe in an easy to reach position. A hatch is entirely impractical in my opinion.

Hi Kevin, when we were at Tarree I asked Gary Morgan what would happen if we were inverted and he said that the canopy would break itself.

If you take a string line from the top of the bulkhead just behing the pilot and run it down to the nose, you will notice that it passes through the top of the protruding canopy so that if you were inverted with the nose and the bulkhead on the ground, the canopy would have to break.

 

Whilst it is of course possible to invert a low wing aircraft in an accident, they tend not to go over as easily as a high wing because of the lower centre of gravity

 

I guess we shall just have to go back to bi-planes.:thumb_up:

 

Alan

 

 

[Wayne T Mathews]

Of course, if it was NASA then they'd fit explosive bolts... :big_grin:....So, apart from wielding an axe, is there a better way to make perspex break when you want it to and not when you don't (like, when you're flying).

Nope.

 

 

[turboplanner]

Get a high wing or a full structure low wing with side door (like a Cherokee) would probably be the last word unless someone comes up with some lateral thinking.

 

 

[Guest rocketdriver]

Having been thre, done that, a couple of comments. .. bit long, so my apologies ...

 

1. In my KR2 the canopy fractured as mentioned above.

 

2. Built in to the rear of the canopy was a rudimentary roll over bar which had looked sufficient before the accident. however it fractured too.

 

3. Luckily .... I had replaced some useless foam panel fill at the cockpit rear with a semicircle of 3mm non a/c ply to seal off the rear of the fuselage. (it looked better especially varnished ....). This remained 100% intact and transferred the overturned load into the fuse structure just behind the seat. however, in doing so it applied a load in an area not properly supported so a longeron and the side panel ply fractured under the combined load of the vertical and the additional load of pilot weight applied sideways as the a/c rolled slightly whilst upside down so that one wing tip was on the ground. (as far as I can see, it went over straight, stabbed the fin into the soft ground , then settled the left wing tip onto the ground.

 

4. My mate's straps were not properly tightened. ("well, I didn't think we were going to have an accident"!), so he ended up sort of sideways in the cockpit, his legs on my side of the cockpit. However he had enough freedom to kick and shove his way out of the canopy, and perhaps thats where he got his cut on the forehead.

 

5. My straps were tight and I ended up with my head jammed into the soil, bum on the seat (I think), chin forced onto my chest and with my left arm jammed by my side by my body weight I think. I felt unable to move and was concerned that I should continue to be able to breathe, as I had heard of people suffocating whilst otherwise unuinjured in an overturn accident ...... Can't remember why I didn't use my right hand on the harness ..... I remember it felt as if it was also jammed in place but I can't think by what that would have been ....

 

6. As soon as the tail was lifted, I was able to free my arm, get to the harness catch and after some fiddleing, unlatch it and wriggle out of the pax side of the cockpit.

 

Some thoughts .....

 

1. Any roll over structure (vital IMHO) MUST be properly supported at the fuselage by an appropriate triangulation to spread the load into the airframe.

 

2. Roll over structure MUST support the a/c so that, resting upside down, there is clearance between the crew's head and the ground. (it might need to be higher than you think, depending on the fuselage, empennage and cowling profiles and where the pilot sits relative to the CoG

 

3. The roll over structure needs to have a pad or similar at the top to spread the inverted a/c weight into possibly soft ground.

 

4. The roll over structure would ideally be behind (or in front of) the crew positions sufficiently that it does not impede egress when upside down.

 

5. If you want an escape hatch, then perhaps a largish panel cut into the canopy , perhaps 500 mm front to rear and running from side to side of the canopy, supported by the canopy base structure and and secured by (soft wire) safety wired pins might be an idea. Then, in a worst case, you have an emergency hatch that does not compromise the a/c structure and that, could perhaps also be operated from outside in emergency .....

 

Cheers

 

RD

 

 

[turboplanner]

4. My mate's straps were not properly tightened.

5. My straps were tight and I ended up with my head jammed into the soil, bum on the seat (I think), chin forced onto my chest and with my left arm jammed by my side by my body weight I think. I felt unable to move and was concerned that I should continue to be able to breathe, as I had heard of people suffocating whilst otherwise unuinjured in an overturn accident ...... Can't remember why I didn't use my right hand on the harness ..... I remember it felt as if it was also jammed in place but I can't think by what that would have been ....

 

6. As soon as the tail was lifted, I was able to free my arm, get to the harness catch and after some fiddleing, unlatch it and wriggle out of the pax side of the cockpit.

 

1. Any roll over structure (vital IMHO) MUST be properly supported at the fuselage by an appropriate triangulation to spread the load into the airframe.

 

5. If you want an escape hatch, then perhaps a largish panel cut into the canopy , perhaps 500 mm front to rear and running from side to side of the canopy, supported by the canopy base structure and and secured by (soft wire) safety wired pins might be an idea. Then, in a worst case, you have an emergency hatch that does not compromise the a/c structure and that, could perhaps also be operated from outside in emergency

Some very good points from Rocketdriver coming from practical experience.

 

4. The body is a bit like a thick skinned balloon full of water, it distorts to an amazing degree during deceleration, and will slide out of a loose harness. In this case the passenger was departing the scene, and if the accident had been more prolonged could easily have impeded the pilot, or knocked him unconscious.

 

5. This is a very realistic report on what really happens in an end for end, whether in an aircraft or car. You are in shock, so it's hard to think, and this is where pre-training so your actions are sub-conscious is SO important. Survival instinct always kicks in but in some people faster than others.

 

You can see how it would be hard to remember where the axe was and where you needed to hit it. In RD's case he was trapped, probably by his body weight, which is a whole new sensation upside down. Even the harness behaves differently upside down. I use Simpson harness which operates in a shear action foir just this type of escape.

 

6. In this case there was help. Even if you were solo five minutes out into the training area, you could be in this position with no one to lift the tail.

 

1. RD's comment is quite true, and in this flop over, just the plywood almost did the job, but there are other scenarios where the aircraft is slapped down with more than 1g, and this could be catching the wheels on a fence, ditching into the water, or ripping a wing off, starting a rotating motion which pulls the wingless side into the dirt.

 

Bear in mind what you want to triangulate to protect - you and the passenger - and that the resulting rigid section doesn't have a sharp transition into the rest of the more flexible frame which could cause a cracking point in normal flight.

 

Nascar, and Drag Race cars have the triangulated section incorporating the driver's seat, so when it all goes wrong, he goes with the seat, and the heavy bits are crushed or fall off, so you can absorb some of the weight increase by deleting external seats, and incorporating seat structure into the basic design.

 

Second 5. RD is onto something here which would suit some of the deathtrap bubble tops. Needs a little more work to come up with fasteners, but it has good potential.

 

 

[kgwilson]

This is the triangulated rollover built in to the rear bulkhead of the Sierra I am building. It is supported by the longerons and parcel shelf with the turtledeck helping with rigidity. There is a similar structure at the rear just in front of the elevator spar to help keep the rear of the turtledeck from collapsing if the vertical stabiliser steel fin post gives way. Given the high strength of the Sierra frame I think that while not perfect this should be adequate in a basic flip over.

 

 

 

[Guest rocketdriver]

This is the triangulated rollover built in to the rear bulkhead of the Sierra I am building. It is supported by the longerons and parcel shelf with the turtledeck helping with rigidity. There is a similar structure at the rear just in front of the elevator spar to help keep the rear of the turtledeck from collapsing if the vertical stabiliser steel fin post gives way. Given the high strength of the Sierra frame I think that while not perfect this should be adequate in a basic flip over.[ATTACH]15158[/ATTACH]

Just a comment, but the base of the triangle appears to join the fuse longeron with nothing to transmit and spread the load into the rest of the airframe. This is likely to lead to the longeron bending on impact, so reducing the clearance the protects the occupants. If it were me, I would want to trangulate the areas under the roll bar so that the forces are distributed into the rest of the airframe .........

cheers

 

RD