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Aircraft accidents AIrcraft to blame?

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Aircraft accidents AIrcraft to blame?

Old 11th Feb 2009, 18:49
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Aircraft accidents AIrcraft to blame?

This year has started off in a bad way with a number of fatal and tragic accidents culminating in the latest one which is extra awful as it appears to have involved young people.

Many of our light aircraft are 20 30 40+ years old. Yes we have advanced in leaps and bounds with avionic advancements.

With a car the development has involved deformable structures, engines that go below the passenger compartment and airbags. In racing cars fuel cells which dont catch fire.

The engine on an aircraft is held by a few alloy tubes and there is nothing to stop the mass of engine metal joining you in a headon.

What more can be done to protect pilots from pilots. Cirrus must be commended for their work on ballistic shute recovery systems and vertical impact seats plus airbags.

What can we safely do with older aircraft to make them safer to their occupants if anything or is it all down to pilot training?

Another very sad day.

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Old 11th Feb 2009, 19:16
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I think that if you have a wing or elevator come off, there is nothing that can be done - short of a BRS chute - because the descent is at about -3000 to -20000fpm i.e. 30 to 200kt VS which is going to be fatal. And you will get the 30kt end of this range only if the wreckage is spinning down.

For lower energy impacts, the huge trend towards ultralight/sports machines makes it much harder to provide any protection because those things are so flimsy. I know their supporters say they are tested to +6g or whatever and I am sure that is strictly correct but it is obvious when looking at one that there is little or no impact protection and there cannot be much within the weight limits. The only safety comes from their substantially lower stall (landing) speeds.

Today's sad accident looks like yet another very low level midair - the UK gets on average one a year. The best protection is to fly as high as possible and certainly above about 2000ft.
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Old 11th Feb 2009, 20:13
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Not necessarily the case ... ?! LOL

YouTube - Full Scale Wing falls off

AJ
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Old 11th Feb 2009, 20:25
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That one is a fake. Done to death all over the internet
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Old 11th Feb 2009, 21:04
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IO540, the +6g rating relates to normal flying conditions. Modern aircraft have very good impact ratings. The Diamond DA40 offers protection to 1000g acceleration, as I believe does the DA42.

The Grob is a relatively modern aircraft.

As with everything in aviation, it is a trade off. It's easy to add extra protection to a car, where weight affects only acceleration and fuel efficiency. With an aircraft, every extra kilo of weight added profoundly affects the flying characteristics. This is why aviation is usually at the cutting edge of materials technology. Modern aircraft materials are so far removed from what was in use 20 years ago as to be a completely different beast.

So yes, I would say that modern aircraft are FAR safer than those made a few years ago.

Of course, due to the high cost of buying and maintaining an aircraft, in comparison to that of a car, aircraft will tend to remain in service for longer. Of course, with an aircraft, very sensibly, most of the effort goes into ensuring that the accident doesn't happen in the first place, as a light aircraft accident, no matter what protection you have, is unlikely to be survivable. Therefore all the design and statutory effort goes towards preventing crashes in the first place, by having very high standards of maintenance, and by providing thorough training and regular assessment of the pilots.

It is unfortunate that we have experienced several fatal general aviation accidents in the past few months, but the numbers are still incredibly low on comparison to the number of flights, and flight hours, and anything else you choose to look at.
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Old 11th Feb 2009, 21:28
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1000g acceleration, as I believe does the DA42.
Uh........no
The cockpit area of the DA-40 and the DA-42 has been rated to 26 G impact resistance. One of the reasons as to why the seats are not adjustable.
Here is an interesting video of the " AMSAFE" airbag seatbelt system:

YouTube - Diamond DA40 AmSafe L
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Old 11th Feb 2009, 22:20
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The airbag video was interesting but I noted there was no engine or forward crash visible just a bag deployment.

A twin is far safer in a head on collision than a single.

The biggest killer in a single is the fact that there is little to restrain the massive block of the engine from coming back through the firewall into the cockpit.

In a modern car the engine is directed down away from the passenger area. Not so in a light aircraft.

For that reason the airbag while a great addition is not going to help much against a few hundred pounds of solid metal joining you in the cockpit at 30 mph plus.

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Old 12th Feb 2009, 09:09
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Some data on midairs: from here we have

Following a previous mid-air collision, a CAA working group reviewed the recent history of mid-air collisions between recreational aircraft. The review determined that UK-registered aircraft had been involved in a total of 30 mid-air collisions in the period 1995 to 2004, resulting in 27 fatalities from 14 fatal accidents. Thus, collisions averaged three per year, and roughly half of the collisions involve at least one fatality.
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Old 12th Feb 2009, 09:29
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More of a case to retrofit ballistic shute systems to aircraft which are suitable and for current manufacturers like Diamond to follow Cirrus?

Airbag technology could also be looked at not just for collision protection but maybe also for water ditching?

If an aircraft was a car it would never be licenced

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Old 12th Feb 2009, 09:50
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If it was as easy to get in an aircraft and fly it as it is to get in a car and drive it, then I would agree that the crah safety standards should be the same. However, in the aircraft industry, the efforts are concentrated on prevention rather. This is why anything involved undergoes rigorous testing and regular inspections. This is as true for the pilots as it is for the aircraft. Our training and preparation is far removed from the amount of training a car driver gets. And we are under constant checking and verification.

Also, aircraft undergo rigorous checking and testing, as do the great guys who maintain them.

I don't think the weight penalty of impact protection systems, and the financial penalty in terms of getting a new system trialled and approved, and the on cost, would prove to be worthwhile.

The number of people killed is, still, extremely small. And whilst every death that can be averted is obviously a worthwhile goal, as with all things in aviation it comes down to the trade off.

Someone in another thread said today "nothing that is worthwhile can ever be 100% safe". Whilst I can see this is no comfort to anyone who has lost friends and/or family, the tota numbers killed are so vanishingly small that I think we have the approach just right.
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Old 12th Feb 2009, 10:25
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I don't think the weight penalty of impact protection systems, and the financial penalty in terms of getting a new system trialled and approved, and the on cost, would prove to be worthwhile.
Crash protection is not really about weight. Take Formula 1. The cars became faster lighter and the crash protection amazing with modern formula 1 technology.

Cirrus are dipping their toes in the right direction I would like other manufacturers to follow suit and to make aircraft which protect pilots from themselves.

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Old 12th Feb 2009, 12:31
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In formula One you have, effectively, a "money no object" situation. In the aviation environment, the cost is very definitely an object.
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Old 12th Feb 2009, 13:50
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There is little to compare an aircraft with a car, its like apples and oranges. The risk in a car is much higher with other cars going the opposite way just a few feet away and if you stray off track by more than a few feet and you will crash into a barrier or building.

The problem with ballistic chutes and airbags is the risk of accidental activation.

The only real use I can see for a ballistic chute is mid air or structural failure. Both are very rare occurences that probably would compromise the airframe to a point where it wouldn't withstand the forces generated by the chute deployment.

Likewise airbags, if it was faces hitting control yokes that was killing pilots I would agree, but I think you will find it is general impact forces and fire that is the big threat.
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Old 12th Feb 2009, 17:07
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For that reason the airbag while a great addition is not going to help much against a few hundred pounds of solid metal joining you in the cockpit at 30 mph plus.
That all depends on the impact obviously, an airbag can only do so much.
So if that is a fair argument is open for debate.
Is surely helped in this accident:

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Old 12th Feb 2009, 19:11
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The biggest killer in a single is the fact that there is little to restrain the massive block of the engine from coming back through the firewall into the cockpit.
Interesting. What data is the assessment based on? Since another prevalent school of thought suggests the engine in a single protects the occupants, due to the far stronger nose structure that is necessarily in place to support the engine during normal operations. In a twin the nose is a light and flimsy aluminium or plastic design with no protective ability whatsoever.

There should be ample data from crash investigations, and studies of that data, to suggest what the main causes of injury in light aircraft crashes are. From the data, it should be fairly straightforward to conclude what the most effective improvements would be.

So in discussions like this one, where is that data?

On the other hand, if light aircraft (passive) crash safety were mainly a sales pitch, the lack of supporting data would be understandable...

Regarding the comparison with formula 1, vertical impact speed is generally not a problem in formula 1 crashes. Reducing vertical impact forces, thus lowering the risk of crippling or fatal spinal compression injuries, is a large part of what modern increased crash safety aviation seats (in light aircraft!) are about. That is why we can't put our knees on the seats anymore, or put stuff underneath them...

Passive crash safety would be the last thing I'd be looking for in selecting an aircraft.
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Old 12th Feb 2009, 20:26
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I think bjornhall is on the right track. I've had a close look at at least 8 serious crashes of light aircraft. Not one of them has had the 'great big lump of engine' infringe on the passenger cabin by very much.

In not one of these incidents was the airframe so distorted that the pilot and passengers could not escape. Two of these incidents were at very high speed and were simply not survivable, deccelerating from 150 kts oddd in the space of a couple of feet does horrible things - but the airframe whilst pretty bent did not compress much and we could easily access the interior.

I would certainly agree that some airfrqames are more likely to have crashes. Either due to the type of flying the airframe does - or foibles in their handling.

Modern airframes do protect the occupants rather better but the nut behind the wheel is a much bigger influence on accident rates and accident types.
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Old 12th Feb 2009, 20:51
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Interesting.....
Take a look at the pawnee for an example of a strong cage around the pilot. I have seen one broken one where the largest single item was the cockpit area. Not exactly a recent type.
As to retrofitting airbags and parachutes, I don't think it would be feasible, any more than retrofitting an airbag in my MGB. If I choose to drive old cars and fly old aircraft surely that is up to me to decide what level of risk I am prepared to accept, an old a/c with superb short field qualities and sodall avionics, which has been flying for longer than I have been on this earth, or state of the art glass. Please let us keep some choice, not one size fits all and the nannies will keep us safe
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Old 12th Feb 2009, 21:02
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I tent to agree. The State has no business in dictating the attitude to risk of an individual.

The risk to unrelated 3rd party casualties is negligible.

There is a bit of a grey area however when it comes to passengers. What expectation of safety should they have? Tricky one...

As regards midairs, I do think Mode C should be mandatory in all cases unless technically infeasible (no electrical system). Then, the remaining pilots could make a reasonable choice on whether to spend money on some form of TCAS. Currently it is largely a waste of money. Mandatory Mode C would also help ATC in the hundreds of serious CAS busts that occur every year.
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Old 12th Feb 2009, 21:31
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There is a bit of a grey area however when it comes to passengers. What expectation of safety should they have? Tricky one...
Yes, I see your point. I do tell them that the aircraft is 56 years old, and I do give them a safety briefing, but actually I don't think I am putting them at more risk than in a more modern aircraft. If it is that dangerous how did it get to be that old?
As for mode C, eliminating the requirement for those a/c without an electrical system would actually remove a surprising number of potential paints. Gliders, which are rather hard to see, rely on battery power for their radios and varios. So do hot air balloons but they are pretty hard to avoid seeing even if they tend not to paint on primary radar.

Actually, I do have an electrical system, but as I have got bugger all to look at inside I tend to keep my head out of the cockpit (and I have a rear view mirror, just as well as everyone keeps overtaking me) Also the passenger gets to help with the lookout, having even less to see inside, once they get bored with the back of my head.

Someone said in another thread that we shouldn't try to solve people problems with widgets. I tend to agree.
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Old 12th Feb 2009, 22:14
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The only real use I can see for a ballistic chute is mid air or structural failure. Both are very rare occurences that probably would compromise the airframe to a point where it wouldn't withstand the forces generated by the chute deployment.
Loss of power over inhospitable terrain at night or in IFR would be another good reason to deploy the chute. Going down in the mountains in poor visibility is almost guaranteed to kill occupants. If I found myself in that situation and had the BRS option I'd go for it.

The chutes work best when the aircraft is in stablized flight at speeds within the normal flight envelope. After a midair or a structural failure stabilized attitude is unlikely, and airspeed might be a problem as well.
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