Low wing aircraft and bubble canopy's?

[turboplanner]

It's a pity no one has found our previous discussion on this. Like switching off your computer when you forgot to save a killer speech you were writing, the second edition never seems to be as good.

 

If you look at incidents you would survive in a high wing aircraft, that puts the reasonable design task into perspective.

 

• the occupants need to be protected from being hit or crushed.
  
• the occupants need to be able to exit the aircraft when it is upside down; the nose over may not have been severe, but if a fire starts the occupants need to escape.
  

[Old Koreelah]

...I would have thought the canopy made of heavy Polycarbonate (Lexan) , shaped in a parabola, and havign the ends well anchored, would have been pretty damn strong. I know POlyCarb goes a bit milky in the sun for long periods, but.

Much as I love lexan in front of me for its impact resistance, it's soft and scratches easily, plus it develops what appear to be internal stress fractures within a couple of years. Moulding a big piece of it, and replacing it every few years would be expensive.

[spacesailor]

" Some time around the 1970s or 80s " , NOT only crumple zones ,

But a lowered speed on our roads, In the 60s and 70s many drivers did the Sydney to Brisbane, in 12 hours or less !,

Now it's 2, yes TWO Bloooodi days. ( with at least one speeding ticket ).

Have we had Less fatalities, with all our speed reduction, Toll roads and crumple zoned cars, we are still loosing far too many ( young ) people.

we are all taught to be Safe, IE drive Slower, but Not to drive faster than the Posted limit, even if it could Save Your Life.

spacesailor

[facthunter]

The different mases cannot be ignored. Crumple zones etc will absorb energy but the relative kinetic energies of the individual vehicles/objects will decide the end situation. The bigger faster vehicle will likely keep going at a reduced speed and the lighter /slower one will reverse direction thereby undergoing a larger velocity change and apply more destructive energy to an occupant than if it just hit a brick wall that didn't move. Nev

[RFguy]

It is a very very complex interaction. Far from an elastic collision of say, two ball bearings.

Nev I agree on your comments. Actually what can really hurt is that smaller vehicle goes from going forward fast to going backward fast. Hearts tear off Aortas.

 

back to the bubble canopy topic . I see some low wings have a vertical plate behind the canopy, stops a collapse. Might not stop ingress of a log. As for getting out, Tony's Cirrus had a hammer to use to get out. Hit your windscreen in the corner said the manual . Not sure if that would be easy to bust without the hammer coming back at you !

 

I would have thought the overturning moment (in a nose over event) would not be all that high, since the tail doesnt weight much . once the plane went over the nose the top of the tail would likely hit first (and knife its way into whatever was resistance) . g

[skippydiesel]

" Some time around the 1970s or 80s " , NOT only crumple zones ,

But a lowered speed on our roads, In the 60s and 70s many drivers did the Sydney to Brisbane, in 12 hours or less !,

Now it's 2, yes TWO Bloooodi days. ( with at least one speeding ticket ).

Have we had Less fatalities, with all our speed reduction, Toll roads and crumple zoned cars, we are still loosing far too many ( young ) people.

we are all taught to be Safe, IE drive Slower, but Not to drive faster than the Posted limit, even if it could Save Your Life.

spacesailor

 

The authorities like quick fixes and even better, fixes that bring in a lot of revenue. Any medico will tell you it is usually better to treat/prevent the cause of a disease, rather than than just the symptoms.

 

In this situation, death/injury by motor vehicle, it is simpler and more profitable to legislate for speed limits and their policing than it is to treat the real cause of so much carnage BAD DRIVING.

 

The latter would require mandated proper training, from a young age and policing of dangerous driving - all too hard for our dim witted leaders.

[kgwilson]

Lexan (Polycarbonate) when in good condition, that is before UV degradation & scratching is very tough & hard to break. This is not good if you need to get out in a hurry & can't open the canopy. Perspex (Acrylic) cracks easily so if you have something to hit it with you can break it to get out. Acrylic has 17 times the impact resistance of glass & Polycarbonate has 250 times the impact resistance of glass. If you end up inverted with a bubble canopy that sits on the fuselage as a bubble you will be in a lot more trouble than if there is rollover protection in the turtledeck bulkhead behind your head.

 

My canopy is perspex. It cracks easily as I found out when drilling a fixing hole in it. Luckily I was able to drill another hole & stop the crack & repaired the crack with polyester resin. There is rollover protection built in to the turtledeck behind my head. These are the 2 major control measures I have to reduce the risk in the event of a landing flip over & the risk of that happening is relatively low based on my experiences to date which includes a collapsed nose leg when initially test flying my aircraft.

[turboplanner]

The authorities like quick fixes and even better, fixes that bring in a lot of revenue. Any medico will tell you it is usually better to treat/prevent the cause of a disease, rather than than just the symptoms.

Road safety is often debated in forums like this or the letters to the editor in newspapers with single ussue fixes being very popular, but it's an incredibly complex set of factors. I was once part of a think tank run by Vicroads where we were asked to predict future requirements for atomotive and transport industries 50 years out. The auditorium held several hundred people, so it was a big one and it had a whiteboard running its full width.

I can remember one day a few people were coming up with single issue solutions, and an engineer from the Adelaide MTT which at the time were running several hundred buses stood up, walked over to the whiteboard and started laying out Australia's transport industry, and filled the full width of the whiteboard for as high as he could reach, in about 30 minutes.

He'd hardly taken a breath, but it left us all breathless, and we realised each of us were working in a minute part of that industry. I've tried to replicate that list a few time on spreadsheet but never succeeded in capturing it all.

 

The speed "fix" fits under the heading "Environment" and is simply designed to try to get all vehicles travelling as closely as possible to the same speed.

We've done the same in motor racing over the years, where these days racing is run in "Classes" where the speed is decided by the specification rules.

The reason is that drivers get less "surprises" that way, and their subconscious reactions are based on learning at just a few speeds, e.g. 40, 60, 80, 100 km/hr.

 

The latter would require mandated proper training, from a young age and policing of dangerous driving - all too hard for our dim witted leaders.

Here's a current quote from Vicroads

"All learner drivers under the age of 21 are required to complete 120 hours of supervised driving (including 20 hours at night) and record these hours in their learner log book"

(.Jul 2, 2020)

How does that compare with your requirement for the aircraft you sell?

I used to be a devotee of "Defensive driver training" where a driver with a few years experience did some intensive training to avoid accidents. That started to change when four of our top Victorian speedway drivers died in a very short period. None of the accidents was their fault, and at their skill level their car control was way above the average, yet they died on the roads. These days I'm more in favour of five year driver testing to keep their knowledge of road rules up to date and weed out bad habits.

[turboplanner]

Gull wing doors

They need to move down when you are upside down so a problem, but some other geometry might work. The main problem is, if you are in a high wing nose over you retain full door height, whereas in a bubble canopy to enter and exit you are using more that the canopy height, so even with a lightweight roll cage you will be crawling through a gap, but there should be a solution which provides that gap height.

[Old Koreelah]

...

The speed "fix" fits under the heading "Environment" and is simply designed to try to get all vehicles travelling as closely as possible to the same speed...

The reason is that drivers get less "surprises" that way, and their subconscious reactions are based on learning at just a few speeds, e.g. 40, 60, 80, 100 km/hr...

Probably the best safety rule.

 

...

These days I'm more in favour of five year driver testing to keep their knowledge of road rules up to date and weed out bad habits.

And a much more aggressive approach to weeding out those people who should never drive a car;

let's face it, there are plenty of them!

[turboplanner]

And a much more aggressive approach to weeding out those people who should never drive a car;

let's face it, there are plenty of them!

That's a pysychological problem to solve, as I mentioned the task is huge. In some cases good progress has been made.

[skippydiesel]

Turboplanner, Old Koreelah -

The problem/solution is not that complex - it is politically undesirable.

It would seem legislating for the lowest driver proficiency is preferable, to a lot of people not having driving licenses.

Face it, outside the major city centres, public transport in Au is woeful - the incompetent would have no way of getting to work/shops/etc. On this point alone we would have to ditch the market economy philosophy and provide a comprehensive, possibly cost negative/neutral, public transport system- what a wicked idea.

Our environmentally damaging (in many ways) solution is to come up with "cotton wool" fixes??? to try & keep people safe. This will always be treating the symptoms, rather than the core problem- ultimately more costly in lives & financially. but allows those in power to keep a low profile while giving the illusion of being proactive.

[spacesailor]

Your Solution,

DOESN'T leave room for illiterate folk who cannot manage in this Bureaucratic, Lawyerspeak world.

OR

Do you want Only the well educated wealthy to drive as well as the poor that cannot Afford to fly.

There,s a word for that.

The driver,s test is more book learning ( computer ) than it ever was. No qudos for being a good or a safe driver what ever.

spacesailor

Edited August 15, 2020 by spacesailor

[Old Koreelah]

Your Solution,

DOESN'T leave room for illiterate folk who cannot manage in this Bureaucratic, Lawyerspeak world.

OR

Do you want Only the well educated wealthy to drive as well as the poor that cannot Afford to fly.

There,s a word for that.

The driver,s test is more book learning ( computer ) than it ever was. No qudos for being a good or a safe driver what ever.

spacesailor

Spacey you are probably right about the trend toward written rather than practical testing;

I suspect that's mainly because it's cheaper.

In the end, improvement in self-drive, or at least machine-based crash avoidance technology may de-skill the lot of us.

[facthunter]

I remain sceptical of self drive .Autopilots, which deal with far simpler parameters, malfunction far too often. Humans are by evidence a weak link so the challenge is out there. Not taking the job seriously enough and doing other things while driving. Mental instability and drugs are obviously a factor as well. There really ARE some serious nut cases out there.. They shouldn't be allowed off their leash and we have a lot of very young ones sealing Cars and hitting high speeds they are unable to cope with skills wise. Most Netflix have hundreds of cop cars etc smashing so I guess they might consider it normal and a FUN thing to do. Even "Little" cars today have spectacular performance by yesterdays models. Nev

[turboplanner]

I remain sceptical of self drive .Autopilots, which deal with far simpler parameters, malfunction far too often. Humans are by evidence a weak link so the challenge is out there. Not taking the job seriously enough and doing other things while driving. Mental instability and drugs are obviously a factor as well. There really ARE some serious nut cases out there.. They shouldn't be allowed off their leash and we have a lot of very young ones sealing Cars and hitting high speeds they are unable to cope with skills wise. Most Netflix have hundreds of cop cars etc smashing so I guess they might consider it normal and a FUN thing to do. Even "Little" cars today have spectacular performance by yesterdays models. Nev

All true, but the Autonomous Car bubble has burst with no one having enough skill to build a foolproof algorithm. The test cars got in accidents, killed a lot of people and the industry now doesn't expecte to revisit them for several decades.

 

Even the lower level autonomy like Adaptive Cruise Control and Lane Keeping Assist require a substantial learning curve if you don't want an embarrassment.

[skippydiesel]

Your Solution,

DOESN'T leave room for illiterate folk who cannot manage in this Bureaucratic, Lawyerspeak world.

OR

Do you want Only the well educated wealthy to drive as well as the poor that cannot Afford to fly.

There,s a word for that.

The driver,s test is more book learning ( computer ) than it ever was. No qudos for being a good or a safe driver what ever.

spacesailor

 

Sorry Spacesailor if I offend but I do not see why I or the many other careful/skilful drivers should have to pay for the extraordinarily costly (in many many ways) dumbing down of driver training/standards. In my humble view, our road authorities stink!

[Paulmilo]

Gull wing doors

Gull wing still may not be able to be opened either. That said, the Liberty XL2 which has gull wing doors, also has a small hammer that comes free .... provided you buy a plane.

 

I also noted that you can access the hinges (quick release pins) from inside the aircraft with the aid of a Phillips head screw driver To remove a cover, so I suspect it may be possible to eject the whole door in some circumstances and avoid the need to hack your way out with the emergency hammer.

 

the only negative is that the fuel tank is inside the fuselage aka a Europa so i don’t think you want to spend too much time in there inverted

[turboplanner]

the only negative is that the fuel tank is inside the fuselage aka a Europa so i don’t think you want to spend too much time in there inverted

Easy fix; it's mandatory in some race cars for a breather pipe to be fitted with a bend which ensures that at no angle can fuel flow from the breather.