Low wing hinged canopy. Dangerous!

[Sactu1]

My dad and I bought a Roko Via (low wing with forward hinged canopy) which is a great little plane- very well specced, good cruise, flys beautifully and looks great! The first comment my x-country instructor made was that it was a pretty dangerous place to be if you flipped it during a forced landing as you had no way to exit the aircraft. To be honest that wasn't something we thought about when buying the plane but is something we have thought a lot about since to the point we are considering selling and buying something else.What are people's thoughts on this? Are you comfortable flying in a plane with this configuration?

You have one of the safest aeroplanes registered with RAAus - your Ballistic Parachute Recovery System is the envy of all when flying over tiger country. Just buy one of those inexpensive perspex escape tools with the pointed metal head and a decent hand cutter and that's all you need. This is a pretty low probability scenario Andrew - just enjoy the heck out of that outstanding aeroplane of yours. I loved flying it and will catch up with you soon to give you a ride in the Glasair. Cheers, Jim.

 

 

[philipnz]

My high wing Remos has doors that can be jettisoned (or flown without). The handbook recommends ditching them before you ditch.

 

 

[Yenn]

The high wing planes I have flown usually have crack doors open as part of the emergency check list prior to landing.

 

I doub thaat the canopies of either of the low wing planes I fly would stand up to a roll over without breaking. It could still be a hard struggle to get out.

 

 

[Oscar]

Mighty difference between an acrylic canopy and a lexan canopy. An acrylic will shatter and be - once basically broken - easy to punch out shearing the attachment fixtures. A lexan canopy will take quite large amounts of deformation without shattering, and be very difficult to punch out if you can't get enough force on the edge attachment fixings.

 

 

[DWF]

How about a ballistic system to jettison the canopy?

 

Or why not go the whole hog and install an ejection seat with canopy piercing projection.

 

 

[onetrack]

This looks like a pretty good advert for good crash survivability in a high wing, light aircraft.

 

Plane crash survivors in hospital

 

 

[Oscar]

Indeed it is; it appears that it did a forward 360 roll, basically turning the fuselage into a sausage with the 'occupant cage' remaining reasonably intact and by the report, not deforming so badly that it did really life-threatening injuries.

 

Let's be realistic here. I doubt if anyone - even the best of us, and I certainly do NOT include myself even within sight of that - anticipates an overturn result from a landing, even in emergency conditions, in most cases. A ditching - yes, we'd be silly to NOT anticipate that eventuality, but overturns are usually the result of the aircraft hitting a ditch or something similar, which in most cases we can't damn well see in time to take it into consideration. Irrigation country with water supply channels is the probable exception: I've outlanded in a glider in such a field and you most certainly don't land across those. Cane fields with their clear maintenance tracks sare probably another clear message of where to point the thing, but the u/c hanging down is very likely to flip you anyway. On the upside, in a cane field you have the vertical equivalent of the 'brush' centre-strips on some highways to provide a cushion.

 

In a high-wing aircraft you can crack the doors before landing with little aerodynamic effect; for a lot of low-wing aircraft, the canopy is a lifting surface and if you crack it for enhanced exit potential you may well seriously affect the efficiency of the elevator, reducing your chance of slowing the damn thing down to minimise the kinetic energy of the crash. For a forward-hinged canopy, cracking it may also adversely affect rudder effectiveness reducing your chances of dodging the worst of the obstacles you may have to dodge, or aligning it with the waves if ditching. Cracking a rear-hinged canopy will most likely cause it to depart very suddenly, and if it hits the fin and rudder you have probably lost one control option.

 

Low-wing aircraft with doors rather than hinged canopies - e.g. Piper Pa-28s, Beech singles, Mooneys etc, have significant structural members both ahead of the door(s) and behind them. They have a 'roof' structure as well, so there is a reasonable occupant safety cage that is quite obviously not there for hinged-canopy aircraft.

 

I suggest, that this thread has bought out issues of importance in the choice of aircraft for the sort of flying one does. If you routinely fly in situations where even a forced landing is very unlikely to result in overturn, a low-wing, hinged canopy aircraft is a fairly low-risk option. If you have a BRS and are happy to use it if the apparent need happens - no problem. If you just want to hack around everywhere, including occasional transits of difficult country, then for me a high-wing aircraft offers greater secondary safety if things go pear-shaped.

 

 

[flyerme]

If we are just talking about being trapped in a low wing bubble canopy the simple way ( not pretty) would be to have a bi-fold canopy, that has a hinged seem, in centre front to back so both sides lift up ( like a lamboguini ), this was done on my supercat so if upside down the canopy still opens either side enough to crawl out... However I have no concerns flying all low wing bubble canopy in which the post refers to ( fighter planes for eg ). I feel personally if I'm conscious after a flip over , my survival, and will to live will give me everything I need to punch thru the canopy !!!!! Now that's if the canopy is still intact!!!! Having a friend up the rd ( posted on this forum about his flip over with his wife) who has flipped in a rough tall Canola paddock at lowish speed with bubble canopy, there's a good chance the canopy won't remain intact or at the very least seated..... I know a few that fly with tools such as -A tack Hammer , large screw driver , small pry bar , ect... Truth and bottom line is if you don't feel safe don't fly it.. Considering how many bubble low wingers are around happily gracing the skies (as they have done for the last 100 years) Im sure if it were a real safety problem CASA or RAA would have banned them or have you sign a waiver....

 

 

[bexrbetter]

They have a 'roof' structure as well, so there is a reasonable occupant safety cage that is quite obviously not there for hinged-canopy aircraft.

"impossible" "quite obviously"

 

Less with the "definite" statements, and more time bothering to see the number of low wings out there with roll over structures.

 

Did you stop to consider that the much higher CoG (as a land vehicle) of a high wing actually increases your chance of a forward flip.

 

Also many craft have terrible suspension dynamics that sends the front wheel forwards. Here, from 4.30 minutes, Vans raves about their front end, watch the slow mo drop test and just imagine that forward movement trying to get over a small ditch, exactly the opposite of what it should be doing and a disaster just waiting ....

 

 

 

[bexrbetter]

have a bi-fold canopy, that has a hinged seem, in centre front to back so both sides lift up

Gee, I've seen that idea somewhere before ..

 

 

 

[pmccarthy]

Have seen a tricycle RV flip over on a nice flat field. Nose wheel collapsed.

 

 

[diesel]

I fly under a canopy covering a strong wooden box.

 

It does have a good turtle deck with good head and shoulder protection.

 

I do not like big bubbles either.

 

Lots of lift lost if you lose one in flight.

 

Lots of sunburn.

 

Lots of very little around you.

 

Loss of vis is very debatable. In a turn with low wing you see all.

 

With a high wing it gets dark.

 

Fail to see how a C.150 can be safe. There is nothing in front of you that cant kill you. Lots of dead pilots.

 

Fly diesel. Petrol equals one flash and its ash.

 

Chas

 

 

[Fairoaks Flyer]

Did anyone read the ATSB final report into VH-HBB which crashed at Lismore a couple of years ago? It ended up inverted and caught on fire with both pilot and instructor being fatally injured. The Socata Trinidad had a gull wing type opening canopy, not a forward hinged one, so it shows you can be vulnerable in any configuration.

 

 

[facthunter]

I don't agree with IF you are concerned about safety aspects of certain designs you should quit flying and sit at home with a fire extinguisher.. Its very easy to wheelbarrow a tri gear if you land it too fast in a crosswind and it OFTEN ends up inverted. The fin isn't enough to guarantee room to exit either as it easily folds sideways. Let's be always able to discuss FACTS and the more information you have, the better choices you will make and improved designs will be available if they are warranted. Assuming it would have been done if it's needed is erroneous. Don't think about it and it will go away doesn't work either. Nev

 

 

[Yenn]

What are the statistics for crashes where the canopy prevented escape? I know there have been some, but don't know how many and how they compare with other types of dangers.

 

 

[onetrack]

As I understand it, there is little by way of statistics available on how the style of aircraft construction impacted on the occupants ability to exit the aircraft after a crash.

 

It makes sense on first, and casual examination, that a low wing bubble canopy aircraft will be more difficult to exit if inverted after a crash.

 

However, that conclusion can be modified greatly when the other attenuating factors - such as actual canopy design, attitude upon final crash position, and actual frame damage in each crash, is taken into account.

 

To understand what happens during and after a crash, you have to think carefully through the accident phases.

 

1. The aircraft stops very rapidly - the pilot and pax are subjected to high G-forces. These forces alone are not significant, the human has been shown to be capable of withstanding very high G-forces - if properly restrained.

 

2. The final crash position where the occupants are immediately planning to exit the wreck is important. Exiting an inverted aircraft causes immediate confusion. Everything is upside down and the brain takes time to adjust.

 

It's not the first time an aircraft occupant who ends up inverted, has been relatively un-injured in a crash - then was injured when they released their harness/seatbelt, and unexpectedly fell to the ground/aircraft roof!

 

You need to collect your thoughts and orientate yourself before taking immediate action directly after a crash. It's not helped when the person is injured, and the brain is screaming out pain messages that interfere with rational thought processes.

 

3. Injuries can often present major problems as normal functions are interfered with. It's hard to open a door or canopy with a broken arm. It's hard to move or twist out of a seat when you have back injuries.

 

4. The greatest source of injuries and the cause of fatalities in crashes (any crashes) is the body flailing round and striking sharp or solid components. Most times, it's the head that strikes instrument panels or other projections inside the cockpit.

 

This results in injury levels being increased as compared to situations where restraints stop flailing around and protective devices prevent injury (crash helmets).

 

The history of motor racing is littered with a long list of drivers who were killed by simple ejection due to lack of restraints, and head injuries caused by a lack of head protection.

 

As a result, motor racing is relatively safe today as the restraints and body protection devices are well-known and well developed.

 

There are plenty of high-speed crashes where racecar drivers have walked away - even from racecars that got airborne and inverted - very much the equivalent of an aircraft crash. Of course, racecars have strong safety cages, too.

 

So, we know today, that the severe effects of a crash result can be reduced by a good harness, by a crash helmet, and by rapidly taking stock of the situation before making rash and ill-considered moves to exit the crash scene as a matter of total urgency.

 

The problem of having a bubble canopy possibly restricting your exit can be overcome or reduced, by ensuring you are in a good position and condition after a crash and inversion, to attack the process of exiting a damaged bubble canopy.

 

 

[Oscar]

Very, very good points - all of them.

 

It should never be taken that any one design will necessarily offer better (or worse) protection in any specific situation until the actual dynamics of that situation are examined. However, it would be a whole lots more useful if there were readily-available information of the relative merits / dangers, such as they may be, of various options, that does not require one to be a de-facto structural engineer and a physicist to understand. It would ALSO be damn helpful if there was a fair bit more 'truth' in both advertising and flight reports, reviews etc. to allow people to get a better picture of what they were looking to purchase.

 

Here's an example of what I mean:

 

Ostensibly, a lexan canopy is a significant advantage over an acrylic one: I know which I'd rather be behind in case of bird strike - lexan, quite simply. I wish that a lexan windscreen was available for my Jab. I would have, with that, acrylic side windows, however. Why?

 

In an overturn event - which is quite a common occurrence for Jabs, just as for any small aircraft ( and let's be fair, Jabs end up dead ants quite frequently!) - you very likely can't get your feet out from under the panel. A nimble youngster might be able to twist and turn but basically the centre 'spine' on which the brake, trim, fuel etc. levers are housed makes it bloody near impossible for us somewhat more mobility-challenged as a result of anno domini. If you can't bring your feet to bear on the exit route, thus being able to: a) apply considerable force with your back braced against the seat, and b) being able to spread that load widely enough to really kick out a body-sized hole, your only option is your hands and arms to which they are attached.

 

Now let's look at that situation. You are upside-down, and it's pretty damn unlikely that you can reach the windscreen /canopy moulding in front - where you could perhaps brace your shoulders on the seat-back so as to exert some reasonable force, especially when still in the harness. If you undo the harness to give you better proximity to the windscreen/canopy, you are going to have to brace yourself using one arm at least, thus reducing your potential of applying force. About the only realistic option for that, resolves to punching vigorously with one hand.

 

Now, ANY windscreen /canopy that has even mild pretensions of bird-strike safety - let alone just withstanding the air pressure of flight up to VNE - is NOT going to be in the slightest fazed by someone battering it with their fist UNLESS it is already severely cracked anyway. I'd not give myself a rat's chance in a mincing machine of being able to punch out anything from an unbroken Jab. acrylic windscreen , and Lexan is one of the most popular materials for the construction of 'bullet-proof' viewing panes...

 

Acrylic will shatter with fairly minimal bending, leaving you with 'fault lines' that you can potentially use to break out growingly larger areas. You'd need to be careful to not get your hand trapped, however.

 

What do I mean - trapped? IF you manage to punch through a small broken area, but that then grabs your wrist - closing up on your wrist after your fist has penetrated the area - you are suddenly in more trouble than Ned Kelly. And here is where a broken bubble canopy is really your worst enemy. A highly-curved surface such as a bubble canopy, when penetrated from the inside, is an extremely effective 'trap' - as you try to pull your trapped hand back, it closes over it. Somewhat like a lobster-pot neck.. A relatively flat screen MAY allow you to retract your hand - painfully - through distorting the material inwards, but a bubble canopy is almost an ideal shape to just continue to tighten up around your wrist.

 

Getting back to my comment about having the side windows in my Jab. made of acrylic... even if, in an overturn, the doors (both, remember) cannot be opened enough for exit because the wings have been folded down around them (which I don''t think has ever happened in a Jab, but is certainly possible), I still have a moderate chance of being able to punch out the side window on my door by swinging my arm with all the force that an adrenaline-fuelled desire to continue to live would provide.

 

I am NOT using Jabs. as a promotion exercise here: I am using them as an example because I have all the evidence of the results of an overturn, in my own aircraft. The windscreen was broken - a bit:

 

 

The doors were completely undamaged and operable. There were some blood spots on the cockpit headliner - it looks like a result of the headset hanger tearing the nut-plate of the pilot/passenger. I know that the injuries were extremely minimal, but I'll bet someone had a nasty headache. As you can see, the nosewheel fork was quite bent. The wings have both been scrapped and the complete fin and rudder replaced. More damage was done to the fuselage by ham-fisted recovery than by the actual overturn.