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Hersham Boy
2nd Jun 2003, 16:49
I was just reading the very sad thread about the accident at Coventry and it got me thinking that that isn't the first time I've read about serious accidents either happening or being narrowly averted due to some sort of failure of this type.

This concerns me...

The pilot is expected to check their a/c over before flying and that should make the spotting of a jammed control, for example, likely (along with full & free checks pre-t/o, of course), but spotting a likely folding wing is going to be more difficult (assuming there aren't visible gaps in airframe etc.).

Surely there's a reason why a/c need to be checked, serviced and overhauled as often as they do?! I think there are enough things to think about in flying - worrying over a wing dropping off all the time could just be enough to take the fun out of this!

Who is responsible for the structural safety of an a/c at the end of the day - an engineer or the pilot in command? And if the latter (pilot is ALWAYS responsible for safety of any passengers, right?), then how can we be certain of structural integrity if the a/c is not owned by us but by a club or group, for example?

And am I being over-reactive about this or is it a more widespread concern?

I hasten to add this is not intended to be or to provoke an 'engineer-bashing' thread

Hersh

IO540-C4D5D
2nd Jun 2003, 17:05
You HAVE to trust the last engineer who looked at it. The usual pre-flight checks will only pick up obvious things, or obvious cases of malicious damage.

Most engineers are very good. On any airfield, the "monkeys" (if any) will be well known so if you are in charge of maintaining a plane, ask around first.

With club planes flown by many others, perhaps you have the extra assurance that if it is dodgy, somebody else is likely to get killed first!

Having said this, structural failures / control problems are extremely rare. If they weren't then I would never fly because something like that is a virtually certain death.

Mike Cross
2nd Jun 2003, 17:10
Statutory Instrument 2000 No. 1562
The Air Navigation Order 2000

Pre-flight action by commander of aircraft
43 The commander of an aircraft registered in the United Kingdom shall reasonably satisfy himself before the aircraft takes off:

....
(c) that the aircraft is in every way fit for the intended flight, and that where a certificate of maintenance review is required by article 10(1) of this Order to be in force, it is in force and will not cease to be in force during the intended flight;

Note the use of the word "reasonably".

Mike

Shaggy Sheep Driver
2nd Jun 2003, 21:21
I think you just have to ask yourself 'how often does this happen?' I personally know of only one such incident, and that was casued by 2 pilots aerobatting a non-aerobatic aircraft. They paid the ultimate price.

There have been lots of incidences of structural failure after loss of control in IMC or very severe turbulence, but structural failures (this weekend's tragedy apart, where we don't yet know the cause) where the aeroplane has not exceeded its design limts are (AFAIK) just about non existant.

Anyone know of any?

SSD

Aerobatic Flyer
2nd Jun 2003, 21:36
Yes. Failure of the main wing spar in a Robin DR400 in 1997. The weather was calm, the aircraft was flown well within its limits, and there was no evidence of previous damage. Four people died.

It was blamed on poor manufacturing quality.

Evo
2nd Jun 2003, 21:46
For what it's worth, and I don't have the exact quote to hand, Pilot recently ran an article on Robins and mentioned the DR400 accident in France. IIRC, the magazine said that the assumption was that the aeroplane had been involved in an unreported incident earlier in it's life where it was overstressed or involved in a ground collision.

Aerobatic Flyer
2nd Jun 2003, 22:02
The BEA (French AAIB) said it was "very unlikely" that the failure was due to any previous damage.

There was a lot of muddying of the waters after this accident. Initially the pilot was blamed for having performed aerobatics during the accident flight. This was later discounted by eye witnesses, and by the radar trace.

It would suit everyone for the explanation to be pilot error or previous damage, as the alternative is worrying. Since the accident report was published, all DR400's have had their operating category downgraded from U to N, and have to undergo an inspection of the spar.

It has to be kept in proportion, though. One failure, in many hundreds of thousands hours operation - including plenty where the aircraft must have been overloaded or overstessed.

Dude~
2nd Jun 2003, 23:36
Does anyone know what happened to the Arrow at Thruxton a couple of years ago. Didn't its wing fold in day VFR straight and level? That was scary as I was due to be checked out on that.

Also, doesn't the CAP10B have a history of wing spar failiures following particularly aggressive yet legal aeros?

Aerobatic Flyer
2nd Jun 2003, 23:52
The Cap 10B has had some spar failures, but generally caused by overstressing either on the accident flight or a previous flight.

The one I fly has a recording G meter, and club-imposed limits of +4.5 and -3g. Woe betide anyone who exceeds them! In France, parachutes are mandatory for aeros. Despite the monitoring and low G limits, I'm not sure I'd be happy to aerobat the Cap without one.

Dude~
3rd Jun 2003, 00:12
Indeed, I know a CAP10B part owner in France, who, having reached a certain age, has completely stopped flying his CAP due to the aggressive flying by his co-owners. I used to go up with them and one guy, an ex Jaguar pilot used to load on 5 or 6g very sharply, at low level, thus rendering our parchutes virtually useless should the wing have folded. I remember one time spinning quite low, the engine quit (when we took off the low fuel lights were on), so he dived vertically at 180kts (near Vne?) pumping the throttle and the prop just turned enought to restart. Then he pulled out over the field very low and very very fast. I have to admit it was fun at the time, but I wouldn't do it again although that has more to do with the aircraft than the pilot, who happened to be exceptionally skilled. We once did 8 landings 0.3 by doing light bulb shaped 180 turn backs at about 80 ft at each end of the runway (nill wind of course).

Good old remote French airfield, no authorities, no rules, no radio and virtually no witnessess!

Sorry babbling on like that...!

skydriller
3rd Jun 2003, 03:20
Aerobatic Flyer,

Our Aeroclub has a DR400-140B and Ive seen the Notice from the DGAC regarding the accident etc, but it isnt much of a report on the accident itself, just mentions it as the reason for the need to get the spar checked and refrain from certain manouvers etc...and of course the guys at the club have about ten different versions of the events cause.... muddying waters...
Do you happen to know if the Accident report is available online anywhere – preferably in english as though my french has improved no end since being here it isnt perfect by anyones standards!!

Regards, SD..

Aerobatic Flyer
3rd Jun 2003, 05:10
skydriller

The accident report is available on-line in French here. (http://www.bea-fr.org/docspa/1997/f-qf970622/htm/f-qf970622.htm)

I don't know if there is an english translation, so... here's my translation of a few bits:

Hypotheses
Overstressing....... "this hypothesis is improbable".
Failure due to previous damage...... "not very probable".
A slight precision here... the overstressing hypothesis is "improbable", while the failure due to previous damage is "très peu probable" in the original French. That's not as strong as "improbable". A good lawyer could be gainfully employed arguing about it. In fact, many probably are....
The hypothesis that failure followed a progressive weakening of the main wing spar is the most probable.

Cause of the accident

The accident was caused by the failure in flight of the right wing.
The gluing and assembly defects found are the determining cause of this failure, through weakening and accelerated ageing of the structures concerned, which lowered their resistance to authorised load factors.

The DR400 is the mainstay of French flying club fleets. A lot of influential people argued against any blame being approtioned to the aircraft, and the arguments are not over yet. But, as I said, it has to be kept in proportion. I still fly DR400's quite happily, and would always choose one in preference to a PA28 - despite the latter's stronger wings!

PPRuNe Radar
3rd Jun 2003, 05:14
There was an accident many years back (Robin I think) where the pilot had hit a haystack on landing. Everything looked fine but the spar had been fractured and it failed structurally on the next flight.

Probably in the old AAIB bulletins somewhere.

In fact ... here it is .....


G-DELS accident report (http://www.aaib.dft.gov.uk/bulletin/dec96/gdels.htm)

andrewc
3rd Jun 2003, 07:07
This sort of failure mode, either catastrophic physical collapse
or loss of key control surfaces does happen and is a significant
contributor to fatal accidents in light aircraft.

I fly a Cirrus which incorporates a BRS whole-body parachute
system which gives the pilot an extra option for survival in
what would otherwise be fatal incidents...

These are now becoming available for retrofitting to most
light-single GA aircraft...check them out!

-- Andrew

englishal
3rd Jun 2003, 07:27
I think there are many light aircraft pilots who would be happy to have a ballistic parachute fitted to their aircraft. I would, at least it gives you an option if the wings do fall off.

You wouldn't dream of crossing the channel on a ferry with no lifeboats....

Cheers
EA
:D

Hersham Boy
3rd Jun 2003, 16:37
Looks like I'll be avoiding the DR400, then!

If nothing else, this kind of thing goes to show how much more important it is to speak up as a group or club flyer if you think you've had a heavy landing/minor taxiing collision than to try and avoid the embarrasment.

skydriller
3rd Jun 2003, 18:27
Aerobatic Flyer,

Thanks for that, much appreciated.:ok:

Hersham boy,

All I can say is, if you get the chance to fly in a Robin, grab it! Your view of the DR400 would definitely change if you have flown one. In comparison to a PA28 or Cessna, well, there is no comparison as the robin is IM Humble opinion much more fun & enjoyable to fly. I learnt to fly in C152s & PA28s in the UK and switched to Robins (unavoidable!) when I came to France.

Regards, SD..

CRX
4th Jun 2003, 20:42
On a similar vein, does anyone know of any cases of structural failure of a Tipsy Nipper? I regularly aerobat one, sticking to within its limits (+4g on a permit/No inverted system therefore no negative). I gather the wing is immensely strong.
I have read the 'Tipsy Nipper Story' book and it mentions quite a few fatals, but I believe all due either to mishandling/bad luck after engine failure or low-level aeros. I can't find any mention of structural failure.
Any more info would be appreciated.

CRX

Hairyplane
4th Jun 2003, 20:48
THe DR400 is a fabulous aircraft with over 10 million flying hours to its credit.

There s great controversy surrounding the in-flight break up in France.

According to Guy Pellisier of Robin - lovely bloke - whilst they did find evidence of inadequate adhesive contact area in the examination of the wreckage, the structure was still deemd to exceed its design parameters.

It is a difficult inspection that requires an opening cut into the box spar, ironically risking weakening the structure a lot more than any insufficent adhesion that they have found thus far.

They have found more aircraft - either side of the accident machine - that were bonded less than adequately by modern methods/ increased inspections etc.

However, still none have been found that fail to meet the design parameters.

This is an unfortunate incident that has dealt Robin (Apex) a real blow - some say unfairly.

I dont speak for Robin, I may have got the story wrong. However, My DR400 Regent - a Jan 01 model (fully featured in Todays Pilot July 01) - continues to give me and my passengers enormous pleasure.

If you want a pleasant surprise - step out of your spammer and give one a go.

Check out the numbers too - huge range, impressive speed (on fixed gear/ prop), great lifting capabilities and all out of a farm strip if necessary.


If you are in the Midlands, or want to travel, are genuinely in the market for a brand new plane and want to talk to a totally satisfied customer as opposed to a salesman - I'll take you for a ride.

All the best

HP

Aerobatic Flyer
4th Jun 2003, 21:17
If you want a pleasant surprise - step out of your spammer and give one a go.
I'll second that. I rent a 160hp model, which will cruise at 130kts at altitude, is fun to fly, easy to land, and has great visibility. Knocks spots of a PA28.

It's not all that good on short strips, though. Perhaps with a different prop it would be better, but initial acceleration and climb is a bit slow.

gasax
5th Jun 2003, 00:34
===========================================
This sort of failure mode, either catastrophic physical collapse
or loss of key control surfaces does happen and is a significant
contributor to fatal accidents in light aircraft.
===========================================

Well Andrewc, you're right it does happen, but you're wrong in stating that it is a significant contributor to fatal accidents.

Structural failure is virtually the least common cause of fatal accidents.

Start with all the pilot caused varieties, continued flight into IFR, landing and takeoff incidents, mechanical (i.e. engine failure, running out of fuel etc, etc.). And then you get to structural failure - so long as you have already captured pilot error over-stressing the airframe due to un-approved aerobatics, loss of control, dis-orientation.

There is no doubt the ballistic parachute gives a great sense of safey - but it will never significantly reduce the fatal accident rate.

John Farley
5th Jun 2003, 02:31
Hersham Boy

As it happens I was at Coventry, watched the Ryan take-off, but looked away left just before the accident. Starting in 1951 I have watched 10 aircraft crash at airshows. Nine were classic pilot pigs and one you could argue about.

But in the context of your post (and NOT this very sad accident) I would like to raise the issue of walk around checks as I think they are not always done properly.

My experience of watching many pilots do such checks leads me to feel they are often a token ritual banging, thumping waggling set of actions, rather than a serious inspection of the aeroplane. Just one example will serve to illustrate the point I am making, namely what we can do to check an aileron.

At the very least we want to carefully stand in front of it, then using two hands, gently and with feeling, move it over its full range of travel while concentrating on assessing whether there is any lack of smoothness in the friction forces or small noise that might indicate something rubbing. Is there a nice smooth stop at full deflection both ways? Has the surface any abnormal end play? A quick grab and waggle as you pass by will not tell you these things. Depending on the type, what can you see of the condition of the hinges and wire locking of any associated bolts? What about evidence of lubrication or corrosion? Is the bonding wire in place? If there are bolts holding on a mass balance are they properly locked? If there are drain holes in the surface are they clear? What about backlash in the circuit (if you have a passenger or crew member ask them to hold the other one central while you carefully, again with feeling, try and detect free play on your side) I could go on but I am sure you get my point.

Of course if you have done several flights that day, your inspection can be much reduced. But not before the first flight. It is your neck, so do what you reasonably can to look after it.

What I like to see is a pilot who from different angles includes standing still and LOOKING at the aircraft. Really studying it.

Sorry I don't mean to rant

John

Hersham Boy
5th Jun 2003, 18:15
OK - I'll promise to try a DR400 :) This many users can't be wrong!

I understand your point, John - early on in my training I was caught out leaving the oil filler cover unlatched on a C152 because it was freezing cold and I was in a bit of a hurry to get warm. It flipped open in flight. As it sits edge-on to the airflow no harm was done but I felt like a right plank and learned to slow-down and be more thorough!

But my concern is not so much with my checking of the a/c but whether I would actually be able to spot, say, the fractured spar that was the result of the Robin striking the hay bale in the AAIB report earlier in the thread. It is pure conjecture, of course, but perhaps that pilot made a thorough check of the a/c following the incident and satisfied himself it was undamaged?

It's a rhetorical question, of course. There's no way you could spot a fractured spar (or similar) on a walkround and I understand the statistics for this kind of incident are very low. It's just this kind of possibility, however remote, that would keep me flying tank-like spamcans!

I must be getting risk-averse in my old age :(

Hersh

Mike Cross
5th Jun 2003, 19:06
People are also unaware of the amount of damage that can be caused to a spamcan by a seemingly minor scrape.

Noth that the pilot of this PA28 (http://www.aaib.dft.gov.uk/bulletin/jul98/gbrjv.htm) elected to fly it, unaware that he had damaged the wing spar attachments.

The wing is inherently strong and forms a long lever. If you apply pressure to one end of it, spread over an area, you are just as likely to cause serious and invisible damage to the root attachments with little or no visible surface damage at the point of impact if it is made of metal as if it is made of wood.

In the case of the PA28 above he hit a post. Localised pressure meant that surface damage was visible. If it had been something soft like a hay bale he would have caused just as much damage to the spar attachments but less visible surface damage because the pressure would have been applied over a larger area.


Mike

Lowtimer
5th Jun 2003, 19:12
Hersh -

There's no way you could spot a fractured spar (or similar) on a walkround

I don't know about that. I'll admit to the possibility that some forms of internal damage may leave no external sign, but there are quite a few ways such damage might reveal itself, albeit subtle. I have always made a practice of carrying out JF's advice about standing back and looking at the aeroplane from a reasonable distance, from different angles. Does the dihedral look right? From square on the nose, does the tailplane make a right angle with the fin? Do the tips of the tailplane tappear to touch the visual surface of the wings in the right place? Is there any unusual washout or washin? Closer in, perhaps using reflections off the skin, are there any signs of stress such as faint wrinkles running diagonally across metal or fabric panels? Are there any rivets or stiches which are starting to pull or come loose? If you push up carefully on the wing tip, does the wing take up the strain evenly, and are there any sounds you wouldn't expect? Do the doors and removable access panels fit in the same way they always have, or is there a bit of a struggle to get latches / fasteners home? Are hinges rubbing or binding? On biplanes of course you also have the condition and tensions of the rigging wires to look at.All these could be clues to something having changed inside the structure.

Genghis the Engineer
5th Jun 2003, 20:03
I'm with JF - much can be seen on a pre-flight, and much of it regularly isn't. I recall a while ago somebody flying an aircraft to me for an air test, insisting on doing my own pre-flight despite his having just landed it and finding a dozen or so serious faults.

Having said that, are pilots properly trained to see these faults? I had an interesting conversation with Whirlybird recently where she recounted being taught during her AHI course how to do an A-check, but was taught it by a LAME, not a pilot. That may arguably be a practice that should be spread.

And yes, before now I've flown somewhere for a meeting, walked back to my aircraft with another Engineer before departing, who has idly pointed out faults on my own aircraft that I'd missed on my pre-flight. Embarrassing but good sport. I know of a club where finding a fault on somebody else's private aircraft earns you a pint - it's in the club rules, and the standard of aircraft there is sparkling !

G

Hersham Boy
5th Jun 2003, 22:04
I'm well-willing to have an engineer (or other well-informed personage) show me a proper A Check (correct terminology?)

Genghis - I don't think you're East Surrey? Anyone who's local to EGKR who is willing to show the ropes would be welcomed with a smile and (a) subsequent pint(s). :D

Feel free to post or PM! Cheers to any and all willing to help :)

Hersh

Genghis the Engineer
5th Jun 2003, 22:52
'Fraid not, but in this context I think you want a LAME familiar with / rated on the type, rather than a more academic gingerbeer like m'self. I know the types I fly and work on on-principle and out of self preservation, but I'm not licensed in that context.

I think the correct terminology is actually "Check A", but many people call it a DI (Daily Inspection).

G

Aerobatic Flyer
5th Jun 2003, 23:37
What I like to see is a pilot who from different angles includes standing still and LOOKING at the aircraft. Really studying it.

And checking that things which should be symeteric are.

I learnt this by not following the above advice, before flying a Slingsby T67. I gave the undercarriage a cursory inspection, and it looked normal on both sides. However, it wasn't. The right side was damaged by an earlier heavy landing, which could be clearly seen when looking at both sides from a distance.

Fortunately the damage was so severe that the aeroplane pulled to one side when taxying, so I abandoned the trip before takeoff. It turned out that the wing had been badly damaged as well, but this was not visible externally.

If I had flown, there would inevitably have been an accident.

Rattus
6th Jun 2003, 02:55
quote:
--------------------------------------------------------------------------------
There's no way you could spot a fractured spar (or similar) on a walkround
--------------------------------------------------------------------------------

This actually a lot easier on a fabric covered aeroplane than on a metal one - another very good reason for flying a Robin. During the walkround, drum your fingers on the fabric between each pair of adjacent ribs and listen. Even if the skin isn't wrinkled, any lack of tautness will be audible as a much duller sound. You should certainly be able to spot a damaged rib by this method.

MLS-12D
6th Jun 2003, 05:37
There have been lots of incidences of structural failure after loss of control in IMC or very severe turbulence, but structural failures (this weekend's tragedy apart, where we don't yet know the cause) where the aeroplane has not exceeded its design limts are (AFAIK) just about non existant. Anyone know of any?Well, there was the time when the main spar failed and the left wing folded up on Neil Williams' Zlin, back in 1970 (see further this little article (http://www.eaa309.org/News%20Letter/Mar02/page8/page6.html)). I don't know if he exceeded the design limits, but I doubt it given his experience; plus I understand that the factory replaced the airplane, which suggests an implicit acknowledgement of some sort of design or manufacturing defect.