Howdy Chris, CliveL


Quote:
A displacement in the horizontal plane is, on the other hand, abnormal. It requires predominance of horizontal loads over vertical loads, which is not the case during the takeoff phase.

My guess is there was vibration as the vertical loads lessened, and not by much, until the bogie wobbled to its limit. In the crush of alarms, and confusion, the FE may have associated this extreme vibration with an immediate need to cage the engine that may be causing it. I merely suggest that pulling an engine at rotation is not done, so the conditions were likely extreme, and needed some action. I believe FE believed he was doing the right thing...

The spacer was NOT inconsequential. It may have played a direct part in crashing the aircraft so quickly after take off. The cause of the disaster was fire. Dozens of opportunities for this result were on record. Blown out fuel tanks, disintegrating tyres, loss of wing skin and hydraulics. BTSC (all Concordes) were susceptible.

That the authority allowed the operator to get off claiming it was FOD is contemptible. The aircraft was vulnerable to spontaneous tyre rupture for goodness sake. A fluke piece of metal?

There will be FOD. Easier in the long run to hold operator to account in the long run, Than bend over backwards to protect the responsibles from owning up.

Does BEA address the shimmy? I do. I do not blame shimmy, nor Titane. I blame EASA for letting things slide. The stage is ever full of scapegoats, but lacks responsibility and integrity, all too often.

We know that - he couldn't be certain...

Again, we know that with the benefit of hindsight and rigorous analysis, but the FE was confronted with alarms and indications consistent with fire (the fire alarm and gong sounded at 14:43:22.8) and likely damage. The surges were presumably triggered by the presence of hot gases in the vicinity of the intakes - but the FE didn't have the luxury of definitive evidence that we do. The startle effect would have been sufficient to cause a lapse in procedure on his part, but given the circumstances that would be entirely understandable.

@Lyman - the aircraft's tyre issues were not "spontaneous" in nature - at least some were precipitated by other problems (in one case the brakes locked on the takeoff roll). Not all incidents (in particular the first at Dulles EDIT - incorrect, see below) were investigated for the cause of the tyre failure.

Note that I'm not saying your theory is impossible, simply that given the fact we know the FE was confronted by critical warning indications it is more likely he was responding to those.

Dozy,

My point was simply that there was nothing in #2 engine failure to produce continued vibrations.

Acknowledged and understood. My point (which does not contradict yours) is equally simple - that the crew had no way of knowing that at the time, and as such would have assumed a worst-case scenario to cover all possibilities. :)

@Lyman (below) - that's an assumption. The evidence we have of tyre failures causing subsequent damage to Concorde suggest that in the cases where root cause was investigated, there were mechanical factors leading to failure of the tyre. The other incidents were never investigated to that level - there has never been a documented case of a Concorde tyre incident where there was no plausible explanation for the tyre failure (and thus no evidence to suggest tyres failed "spontaneously").

Dozy

Please read every word, I said the a/c was VULNERABLE to spontaneous rupture.

As to the rest, I like your take on the FE's predicament.

Point being, I think it took something we may not be seeing for him to counter best practice.

Correction:

I have been reliably informed that the cause of the Dulles tyre failure was investigated and determined to be an underinflation of the neighbouring tyre to that which failed - the (arguably inadequate with hindsight) fix was a mechanical device which detected mismatched tyre inflation.

This does not alter the extent of my research indicating that there was no attempt to determine the preceding cause of a tyre failure on Concorde which could not be explained.

Addendum:

As stated earlier, the required time periods for the damaged fuel tank to drain, the potential additional altitude had #2 not been shut down and, crucially, the time taken for the fire to irreparably destroy the controls were thoroughly calculated. There was no way for the aircraft to have reached Le Bourget before control was lost.

The report documents thoroughly the shortcomings of all parties involved and simply lists them, with no implicit or explicit guidance as to relative importance - the initial decision to prosecute CO was judicial - neither regulatory nor investigative.

Yes (as Clive twice stated, check section 18.2.3.3).

Pay close attention to Clive correcting me a short while ago:

Any shimmy or instability would therefore have affected all four tyres to some extent, but it was only the tyre that contacted the metal strip which failed.

Hi philip2412,

As stated by DW, all other things being the same, yes I think it would have, based on all material available.

If skidding from the start, tyres marks would be notably "unusual" from the start. Such a thing never was not reported... and certainly would have, if it was present.
And I strongly disagree with "That means the a/c will tend right": Indeed, if skidding from the start, the left side of the aircraft would have been more draggy than the right side. Not the opposite. :=


Wouldn't such an important vibration level be:
- recorded on the FDR;
- likely commented by the crew (on the CVR)?
AFAIK, no report of important vibrations on the CVR. Didn't check FDR traces, but I suggest it is to be done before pushing further your hypothesis, Lyman.
And I'm sure the FE believed he was doing the right thing, but that's not the point.

You don't know that. We are discussing this right now, and so far no hard indication has been found of its consequentiality, but BEA report strongly suggests it had none (and explains why, and describes the tests done to arrive to that conclusion).

Ahem, first, "not FOD related tyre ruptures" would be a notably more accurate description IMO. ;)
Identified causes of such tyre ruptures were adressed, if my memory serves, in the Washington'79 report, or since then.

Hi Lyman
You have spent a great amount of time discussing the missing spacer and the possible consequences of it's absence. It may be helpful if you could collect all your thoughts together in one post. I think in doing so, it can be taken for granted that you think the missing spacer is of importance, so for clarity sake it may be wise not to repeat your detailed analysis of that absence, but instead concentrate on it's relevance to the final outcome.

The jargon of BEA
Concorde trial 2 March 2010

@jcj:

That excerpt has little utility as it is shorn of any context. Were precautions taken in the design of Concorde relating to fire in general? Of course they were - and I'm sure Clive would be able to quote chapter-and-verse on the subject.

The problem is and will always be that fire on an aircraft has a nasty habit of defeating even the best attempts of engineers to minimise its impact - it only takes a minor maintenance or loading error here or an unexpected area of damage there to make the situation considerably worse than envisaged, and Concorde is most certainly not alone in having fallen victim to this unfortunate circumstance.

Additionally, M. Arslanian was well within his rights to answer the way he did, as none of the previous incidents of tyre/fuel tank damage occurred in a manner to which the BEA would have been primary investigators. The lawyer's somewhat facetious response should have resulted in an objection.

AZR,Dozy,

Thank you for your kind response !

Nick, CliveL, Chris Scott.

There is evidence the Bogie was rotating in its horizontal plane. That is clear from the images in BEA.

BEA describes such horizontal articulation as an abnormal.

If in evidence (it is), and also an abnormal, we can assume there is a possibility it played a part in the tragic crash.

Unlike the strip, the condition for wobble was present at take off, iow, part of the compromised airframe, not a foreign piece of debris. The legal implications of presence of inherent vunerability as opposed to accidental accumulation of debris are clear.

"Had no effect..." "Played no part in the crash...". "The lack of the spacer was not relevant..."

All demonstrably untrue statements.

Can the misalignment of the left main landing gear be explained in ways that do not involve the missing spacer? Certainly, but those postulates do not eliminate questions that seriously compromise any legal action Air France may entertain against Continental (United/Continental)......

thoughts?

CliveL.... The side loads provided by the misaligned bogie are apparent in the photography. What affect?

There are clues in the record of ruddering by the Captain. Nx would be conclusive, but Captain's inputs as explained in the text of the BEA seem tentative, given the extent of the excursion, and irregular, though the heading seemed consistently left in direction and rate.

There is a possiblity the bogie played a part in the Captain's perception of yaw? The a/c was not answering the right ruddering, yet three times he returned the pedals to neutral? Once he returned to 10 right, from 20?

Lyman

You can find Nx in either in Section 1.16.13.2 of the BEA report or, more exactly, in Fig 1 of Annexe 4p of that report.

Now you are just putting back to me the question I asked you in an earlier posting...

But if you are going to claim that the absence of the spacer had a significant effect on the outcome then you really should provide some more quantitative arguments than anything written so far. Everything I have seen and such calculations as one can make are consistent with the effect of the spacer being rather small - well actually I would say very small.

Thanks CliveL, your response is appreciated.

Your question is a good one, and I would like to offer that the quantitative component should have been done by BEA in the first place, after all, it is their photography.

I have offered possible approaches to glean some understanding of the affect of tyre rupture, and my suggestions have been ignored. Likewise, an attempt to quantify would be based on data supplied from BEA, data I believe is lacking in sufficiency.

It is BEA who proffered the photography, and begged the work, then did not perform it. Neglectful.

It was BEA that exonerated any complicity of the shoddy Mx by AF. Presumptuous.

It was BEA who did not provide the chemical analysis of the rubber that may have proven the Titanium had been present in the tyre's carcass. In neglecting even the attempt to prove conclusively the strip was involved, they demean the discipline itself. Lazy.

It was BEA that neglected elimination of material other than Titanium as the cause of tyre rupture, Cowcatcher/mount?

Was the area of the truck's mount inspected/analysed by BEA for abnormal wear? The landing gear had travelled several miles carrying two hundred tons, was the spacer's saddle worn?

Was the #2 tyre studiously tested for weakness, as it was two thirds through its useful life, and may have acquired weaknesses unrelated to FOD? Were the other three tyres on the left bogie scrupulously inspected for evidence of misalignment of carriage?

Has anyone found an opinion on why the Captain's rudders were not planted full right? And held?

The report can be described in many terms. Exhaustive is not one such term.

Quote:
Shimmy, as I understand it, is a cyclical rotation of the wheels about the main leg. Again at the time we are talking about, the aircraft sideslip was 3 deg. Allowing for +/- 3 deg oscillation because of the missing spacer that would mean the wheels oscillating between zero and 6 deg would it not? Why would the time they were at less than 3 deg not offset the time they were at more? Or in other words, why should shimmy change the average force?


Shimmy is analogous to a human heart in arrhythmia. A pulse of two hundred, and no blood flows, the pump is stalled. Shimmy means skid, and skid means poor traction, and irregular bite at that.

"Shimmy" makes unlikely any predictable effect of any part (cycle) of the oscillation. Therefore, because the bogie is aligned ("established") part time, one cannot then predict that the corollary alignment is of equal (balanced) force.

Note the shape of the shimmied tyre, number 1. The excursion left is broad, the return to "zero" is sharp, and shortlived. Therefore, the side load is left, and LEFT.....no balancing side load right. This demonstrates that at least in the area of the photographic evidence, the net load is constantly left. This means a bogie that is tracking well left of the longitudinal axis of the airframe.

"Shimmy" in itself does not suggest the kind of conclusion you make, some "balanced" or normed load. There is no reason to assume the shimmy was established in consistent fashion at any time, except for the three arcs of tread deposit we see. It could have been extremely irregular.

An admission. I have not found the reference to shimmy in the Report. Therefore I do not know BEA's conclusions. I'm extrapolating on evidence I see, and read elsewhere and in the BEA work.

My assumption is that BEA rejected the possibility that a missing part contributed to the crash. If they did not, and lay some responsibility on AF, that would be a welcome coincidence?

Hi Lyman,

I'm sorry, but my reaction to that is: Certainly not!
For those to be demonstrably untrue, we need far more than "just" one pic.
Do we have more? In fact yes, see below.

Yes, we could assume that, but only if the "wobble" was present for a "long" time. Was it? What elements do we have? Let's see:
- 1 picture showing what looks like the wobble, that you attributed to the missing spacer (likely, I agree); this pic also show the broken runway light; hence we know that the pic show the runway at ~2,800 meters.
- other pictures not showing the "likely wobble", or not clearly at all, taken from earlier parts of the runway;
- a rather complete description from the BEA, quoted below:

OK, so, probable wobble @ 2,800m, but no wobble on the pic showing the soot on the runway. The soot on the runway, where was it? Easy:
On the pic showing the (dense) soot on the runway, no indication of wobble at all. Only tracks from the (already destroyed/destroying) #2 tyre.
=> No wobble @ somewhere between 1,860 m and 2,300 m.
=> Shown on the picture, and confirmed in the BEA's text (§ 1.12.1.8, quoted above)
At that time (and even considering 'only' the lower value of 1,860 m despite said §), the aircraft is already on fire, meaning the strip/tyre/fuel leak/ignition events already took place.

To be sure, let's search where other relevant items were noted relative to the beginning of the runway:
1,642 m -> the first parts found are from the water deflector, from slab 139 and onwards;
1,740 m -> the titanium strip, at slab 152;
1,740 m -> a big part of tyre (transversally cut) at same slab 152;
1,820 m -> the unburnt kerozen mark at slab 163;
1,860 m -> the first traces of soot (hence: fire);
1,950 m -> the other 'fitting' part of the transversally cut tyre at slab 180.
1,957 m -> signs of an explosion and a piece of concrete separated from the runway (my comment: that shows that the leak/fire was not due to this 'explosion' whatever it really was - EDIT it was not the tyre explosion, as noted in appendix 6 of the final report (which provides a pic): "The explosion could be explained by the forward propagation of the combustion zone").

=> this clearly shows that the fire ignited one kilometer before the only picture we may consider as conclusive of a wobble (@ 2,800 m)...
=> ... and 460 m before the first "irregular tyre tracks" were noted by the BEA (@ 2,340 m).

This is why, I think, the BEA concluded (rightly) that the lack of the spacer - even if one can discern indications it made the bogie wobble around 2,340 to 2,800m from the runway beginning - was not relevant to and played no part in the final outcome, which was sadly certain as soon as the fire broke.
QED.

Regards,
AZR.

Hi AZR

Quote:
Originally Posted by Lyman
"Had no effect..." "Played no part in the crash...". "The lack of the spacer was not relevant..."

All demonstrably untrue statements.


You say then..."certainly not..."

My perverse mind sees it differently, here's why....


There is evidence the tyres were rotating in the horizontal, you agree.

That is positve proof of misalignment, a condition certified by BEA themselves as abnormal.

For the statements in the quote to be true, you offer a lack of evidence that the condition existed elsewhere. The source of your evidence of absence is blurry photography of a carbon stained runway.

Positive evidence (BEA close up photgraphy) is provided that the condition exists. A lack of evidence that it occurred elsewhere is the basis of a professional conclusion, by BEA that it had no effect on the outcome.

To a doubting reader, it seems that proof without evidence exists when the conclusion is foregone?

The "Explosion"? Have we proven without doubt it was not caused by the tyre blowout?

That would be impossible, right? Because it occurred after the fire started, and defeats the tyre as cause of fire?

hmmm......

No. Possible/probable indication yes, but not evidence. I'm no more an accident investigator than Nick Thomas is, so I too am unable to draw conclusions or say "evidence" with certainty from those photographs.

No. I you want to call my PoV about those photographs as "evidences", then what I see in pictures showing the runway before 2,800m is an evidence of lack (of wobble), not a lack of evidence.
And that's really different ;)

The source of "my" "evidence" is no more blurry than yours, my dear chap. :)
And I didn't base my arguments on the pics (or pic) alone.

Yes indeed.
And because parts of tyre were found before the "Explosion" place, as shown in my previous post.
And because, as shown in my edit of the previous post, there is a more sensible explanation provided (even if somehow hidden in the appendix 6, which explains I didn't remembered it.

I think Twas CliveL who stipulated shimmy was shown. I think it is....

Parts of tyre can depart without causing blowout, yes? A tyre explosion is consistent with concrete delamination, such as was found.

How is it deflector parts were found before tyre parts? There was damage to bogie unrelated to tyre rupture by strip?

You have photography of the runway taken from a few meters, that shows "no wobble"? The runway pictures that show carbon deposition are aerial, long distance, no?

I acknowledge you are satisfied with the results of BEA. I think the report compelling, but it is too loose, and presumes things that are not shown, nor discussed, imho....

:ok:

Hi once again Lyman
I have to congratulate you for the way you keep this thread alive. Everything is quiet and then up you pop and we are all of again on the same merry go round! You tenacity is to be admired.
As I said in an earlier post and I quote "I am not an expert in this field and I therefore have to trust those who are considered to be so."
That being the case I have serious doubts about your theories as do some others posting here. In weighing evidence(if it can be called that) one has to take into account the source of that evidence. Those of us who rely on the contents of the report, do so because we know that considerable thought and effort has been put in by the experts who compiled the report. Unfortunately on a forum like this: it's not possible to know the background and experience of people like you, who post alternative theories. Until we can find a way of overcoming that stumbling block we will continue to go round and round in circles.

Howdy Nick

That being the case I have serious doubts about your theories as do some others posting here. In weighing evidence (if it can be called that) one has to take into account the source of that evidence.

The wobble of the truck in horizontal is shown in the photograph, you see it differently?

BEA describes this horizontal rotation as "an abnormal"

Is that over-reliance on my opinion?

Hi jcjeant,

The little exercise I made just above gives me the opportunity to use its data for a follow-on about that discussion we had some pages ago:
Please, see this pic I made by adding things to the Annex 12 from final report.

Let's compare to the testimonies:
- Firefigther #1 said "black smoke" (tyre) around S6;
- Firefigther #2 said "black smoke" (tyre) around S5, then small fire;
- Firefigther #3 said small fire around S5, then big fire;
- Captain @ E5 (near the firefighters building) said fire begun at +/- 100m around W7.

I consider Firefigther #1 probably made a mistake between S6 & S5, because 'his' location (S6) is consistent neither with the other testimonies, neither with the material evidences.

Hence we can write:
1,500 m -> S5 TWY, the strip lay around there before Concorde rolled over it;
1,642 m -> first parts found from the water deflector, from slab 139 and onwards;
1,740 m -> the titanium strip finally lay there, at slab 152, along with a big part of tyre (transversally cut);
1,820 m -> the unburnt kerozen mark at slab 163;
1,860 m -> the first traces of soot (hence: big fire);
1,950 m -> the other 'fitting' part of the transversally cut tyre at slab 180;

=> The strip "travelled" ~240 m in the wake of Concorde and/or being for a moment stuck into the tyre.
=> Such a distance really doesn't feel 'magic' to me. Nor 'such a large distance', considering the forces involved.
=> The provided pic also shows that there is no inexplicable discrepency between the firefighters/captain testimonies and the events reported by the BEA, contrary to what some lawyers and/or TV shows would have us believe.

Lyman (nee Bearfoil)

Your credibility and our sanity would be massively enhanced if after all these years and thousands of posts you could demonstrate the ability to learn and make use of the rudimentary tool for block quoting others.

Honestly? No. That's not what I see. :=

That's your opinion indeed, I acknowledge that but don't agree.
I have the advantage of being perfectly able to read French, hence I have access to the (rich) appendix 6 which was never translated to English (AFAIK).

Not ignored – maybe not agreed with or understood, but not ignored as evidenced by the number of responses you get


There is quite a lot of data in the BEA report that could be used in a quantitative way if one was so inclined.


Or did not report it, which is not quite the same thing.

But the BEA report stated




I don’t know what sort of chemical analysis you had in mind, but for me a spectral analysis of the material counts as a valid chemical analysis.



Are you now suggesting that the water deflectors somehow failed and got caught under the tyre? If so, how do you explain the curved failure on the tyre and the fact that the water deflectors were made of frangible material?

Again I say yes, witnessed by their remarks...



Yep! Just take a look at the figure presented in section 1.16.13.2.
By the time he got to the point you are discussing he was 2 deg off runway heading but heading back to the runway centreline (heading 270 against the runway’s 268). In addition the lateral acceleration at the cockpit had dropped to essentially zero. The aircraft was way above Vmcg even at the point of engine thrust loss, so why would he think he needed more drag producing rudder?



Not many would agree with you there.


OK, so we can eliminate shimmy as a factor anywhere except where you found it after the aircraft left the tarmac?


But the BEA report did contain a reference to shimmy


Actually no, it doesn’t show any such thing, because the aircraft longitudinal axis was itself inclined to the aircraft path (sideslip).
Let me try another scenario on you.
The inclination of the bogie beam to the ‘normal’ setting would have been dependent on the balance of vertical and horizontal forces as BEA stated. Statically that would put the contact point at “12 o’clock” in the bearing housing., but again as the BEA state, the gear would be inclined to the vertical (camber). When rolling with intact tyres there would be no sideforce and the horizontal forces would be limited to the rolling friction – about 2~3% of the vertical forces. Not enough, I suggest, to move the contact point very far from 12.00.
It all changes after the tyre burst and loss of thrust. Now the horizontal force on each tyre is predominantly sideforce which would be proportional to ground reaction and tyre slip. When the aircraft started to diverge left under the action of asymmetric thrust the tyres became subject to right sideslip. When gear and tyres are intact this slip would produce forces pushing the aircraft left towards the runway edge and, because they act behind the CG, they would also make a small contribution to the yawing moment trying to return the aircraft to its original heading.
However, with the combination of a burst tyre and a sloppy bearing, the asymmetric side loads (two wheels aft, only one forward) would drive the bogie out of alignment in a sense to reduce the effective slip on the tyres to zero. In other words, if sideslip were numerically below the play in the bogie bearing the tyres would not be producing any side load at all!

So far as I can see, the aircraft was above this 2.75 deg limit for only a very short period between 97608 and 97613, which of course spans the time period at which you noticed shimmy, hence you can detect side load at that time.
This loss of sideforce would have reduced the lateral acceleration to the left (and runway edge) but would also have reduced the restoring yawing moment. But as argued above, the pilot had, and used enough rudder authority to bring the aircraft back towards the runway centreline.
Now factor in that the wing was carrying an increasing amount of lift in this period.
All of which of course begs the question as to whether this lateral displacement had any real consequences on the final outcome. My answer to that would be no, it didn’t, because when push comes to shove it was the failure to achieve a safe flying speed that mattered, and that was due to loss of engine thrust in a critical flight phase.

Howdy Lyman
I can accept that the horizontal rotation is “abnormal” but as I said in post 223 “Where I do agree with those who don't accept the report or parts of it, is that the many other failures brought to the fore after this sad crash should be addressed but that doesn't mean that they actually caused the crash.” Can you therefore show where in the BEA report it says that the horizontal rotation paid a significant part in the outcome of the crash? A quote out of context cannot be considered proof.
Regards Nick
p.s Lyman: My forename is actually Nixon which will forever be linked with an attempted cover up!

CliveL

Thank you for a reasoned and patient response. Here are some concerns I have.

I would not have entered the thread if France had upheld the verdict. Their reasons, I assume, have to do with a lack of compelling evidence in the public domain such that a standard of proof is unmet.

I would not be here if the accident had occurred in the USA. That France considers an accident scene as a crime scene is the threshold for my interest.
As such, the BEA document is thready, and missing some important work that imo should be present in a criminal prosecution.

Evidently France considers culpability on a par with crime. That makes no sense, imo.

The major issue is the apparent speed with which the report issues opinions, yet there is no lab or field work to support.

The strip was tested for evidence of non indigenous elastomer, with success. Yet an opportunity to take a further step was ignored, I think, when they apparently rejected the opportunity to test the tyre for presence of foreign material that may have been supplied by the chemically coated Tittanium strip.

As an example, then, BEA failed to provide irrefutable evidence that the Titanium strip destroyed the tyre(#2). WHY?

Simple. If they tested and found material, the case is made. If material was not found, the strip is found only to have generic elastomer, not necessarily Concorde elastomer.

So why risk it? The mission is not compatible with the purpose of the Court. Since BEA knows criminal prosecution is a given, their standards are low, by definition.

The Shimmy? Again an example of evidence that was taken, and left 'alone'....

You see the tyre skids, and can imagine the loads put on this airframe. I think your conclusion is that the shimmy would even itself out, and provide no net effect. What about vibration? Vibration may supply no net 'load', but have a very profound effect on the pilotage.

I contend that shimmy is not normal to heavy aircraft, and can be quite destructive, yet somehow the conclusion is that since the only evidence is after the fire, it was "inconsequential". Lack of evidence through lack of attempt is not sufficient; again, the prose in the report is used to put people in prison...

I don't disagree, necessarily, but again, the possibility is demanded to be explored to lack of consequence, not assumed to be so....

I value your time, as you know, and am grateful for the opportunity to discuss this with you.

Best regards

It was more to do with the fact that the opinion of the judge who oversaw the appeal differed from that of the judge who oversaw the original case.

Have you read it thoroughly? It's a weighty document and I haven't covered all of its contents but it's about as thorough as one could hope it to be.

The BEA report is not intended to be (nor was it ever or should it be) a basis for criminal prosecution, it is simply a collection of facts and evidence (including the detail that - contrary to your earlier assertions - AF stopped using retread tyres since January 1996, BA having done the same since 1981) from which conclusions are drawn about the circumstances surrounding the accident. The document itself covers every aspect of the evidence and the accident sequence without assigning responsibility on the part of any of the parties involved.

The judges in the case had access to it simply as one piece of evidence, and the decisions regarding prosecution hinge on the representations made by the legal representatives of the involved parties - not the report.

Incorrect - they (and others) used every technology available to them to assess the probability of the strip being the initiator of the destruction of the tyre, a process which was neither simple nor cheap (see report sections 1.16.5-1.16.5.4).

Their conclusion was that based on the probability of all the scenarios, the scenario whereby the strip contact was the initiator of the tyre's destruction made the most sense. They could not, and did not say any more than that.

As you correctly assert, the content of the report was not sufficient to prosecute on its own - and it was not intended to be. At the risk of repeating myself, the decision to prosecute was made by the judge based on the representations made by the legal teams of the parties concerned.

To make it as crystal-clear as I can, this and other BEA reports (like those of the AAIB) are never written with the intent of being used as prosecutorial aids. They tend to be very dry and scientific in nature (unlike those of the NTSB, which tend to be more forthright on assigning responsibility) and anyone who believes that the BEA has any say in the legal outcome of cases involving accidents is labouring under a significant misapprehension. The outcome of such cases is purely in the hands of the lawyers.

Lyman,


But that is where it all goes wrong, because BEA are at pains to state that their work is simply to establish causes not to present evidence for a criminal prosecution. You do them an injustice, I think, to view their work as preparation of a prosecution case.

In that you are at one with most of the Anglo-Saxon world brought up under common law, but it (Napoleonic law) is what they live by and we should respect that.

I can't agree with you there - the report devotes fifty pages to discussion of laboratory work and testing. The long gap between the accident and issue of the report does not support your implication that it was all done in a hurry though does it?

Others have commented earlier in this thread that the surface treatment of the strip might have hardness characteristics that would deter any transfer of material to the tyre. But I'm no tyre expert.

As I said earlier, the BEA mission was not to provide evidence for the judiciary. If the latter wanted additional 'proof' to cement their case they were perfectly entitled to demand it.

I don't like to 'imagine' loads put on any airframe. What I see is that in the time period where shimmy appears to be present the ground reaction on that gear was modest indeed, and the loads transmitted to the airframe would be correspondingly modest. So far as vibration is concerned I have already agreed (with Chris Scott) that vibration continued into the airborne part might have been a contributory factor to the decision to shut down #2 engine.

I have to say though that there is no sign of any 7 Hz variation in the lateral acceleration trace, and the normal acceleration traces show nothing higher than 1 Hz and even that dies out once airborne.

Indeed so but as part of my researching this topic I found a presentation that implied the C17a gear might be shimmy prone. I have no more evidence but that, although the implication of the presentation was that four wheeled bogies are not usually prone to shimmy, and of course most heavy aircraft are so equipped. The C17a gear however is a three wheeled device if I have understood it correctly

And again, the purpose of the BEA report is specifically NOT to put people in prison. If other parties seek to use it so that is their affair. We would all agree however that seeking to use data accumulated in accident or incident analyis is counter productive to the cause of improving aircraft safety standards :ugh:

Regards

PS Writing that whilst Dozy was posting changed the phasing, but I see that we are both saying essentially the same thing re the purpose of the BEA report.

CliveL

Yes, I referred back to my post thanking you for yours and found yours missing.



Until its return, may I make a single point? From the photographic evidence at the area around the shorn runway lamp, we seem to be in agreement that horizontal movement of the wheel truck is apparent. it suggests a powerful oscillation (to me), one that may have had an effect on the early rotation, subject thus far only to speculation, and dependent perhaps on my observation of the tyre marks....

Since BEA have provided the photographic evidence to the public, and have also dismissed the possibility of horizontal oscillation gleaned from that very image, may I suggest that that constitutes the possibility of a glaring error in the report?


And one question? Do you believe the skid marks evident parallel the centerline in the BEA photo (of the carbon trail and kero stain) represent the Concorde's path?

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Nick Thomas

Howdy do. There is no record to my knowledge that BEA made any representation at all of Bogie involvement in the wreck, So allow me to offer the importance of the spacer in the accident.

Let us for now say that there was no Titanium strip, and the tyre did not burst. Let us offer further that engine failure did occur, for reasons unrelated to fod, and the a/c veered leftward. This sets up horizontal movement of the bogie, and side loads on the tyres of the left MLG. Without the spacer, the bogie oscillates and vibrates. Depending on the mechanism of bogie disablement, and the clues and cues in the cockpit, might the FE have pulled #2 as he did in the actual wreck?

This was the third take off for this bird without the spacer, essentially each one a test flight, as regards landing gear. The shimmy is denied, as we see, in the report, while I maintain that it is quite possible the wreck was doubly damned, it might have crashed due the landing gear issue alone. (grantng engine failure/shut down).

Your language is misleading - they have not "dismissed the possibility" or anything of the sort. In fact Section 1.18.2 goes into considerable detail regarding the evidence they were presented with regarding the bogie (in spite of your claim that they made no reference to it at all). They simply consider it to be less likely to have had a significant effect than the metal strip contact, and with good reason.

If you're not inclined to take my word that the BEA report is merely a presentation of evidence (in the manner of an initial crime scene report with ballistics and forensics) - would you consider Clive's word on the matter?

I have been searching CliveL's post for the quoted language from BEA that rejects any involvement of the oscillation, that there even was one. It seems to have been censored out.

Would you be able to locate it?

From the ruddering the Captain did, and the direction of the a/c well left of the runway heading, is it possible to surmise that something about the ruddering prompted Captain to give up, and accept a takeoff off runway as his best chance?

At the beginning of the veer left, to the take off point, there appears no correction right. Right rudder may have exacerbated the side load on the left bogie, and made any problem with the gear bad enough to cause him to abandon rudder as correction?

The (English version of the) report is here:
http://www.bea.aero/docspa/2000/f-sc...-sc000725a.pdf

Read it at your leisure, but the content regarding the bogie is in section 1.18.2 (and its subsections).

Regarding rudder input:

In effect, the rudder inputs were *opposite* what would be expected if the missing spacer had an influence on the aircraft track prior to contact with the strip.

Many thanks Doze...

aloha

Here it is...From BEA report

(from CliveL post #264)

Quote:
"The Concorde landing gear manufacturer indicated that no cases of landing gear bogie shimmy had been reported. Examination of the parts revealed no such phenomenon.

Furthermore, the tyre marks left by tyre No 2 "showed no signs of vibration or instability."

That is what is known as a discrepancy......

By the time any evidence of oscillation is observed the aircraft was 9 seconds into a 10 second rotation, so I can't see how it could have had any effect on the earliness of the rotation. There is, as I said, no evidence of any vibration at the frequency you suggested for shimmy (7 Hz if I recall correctly) during the airborne part of the rotation through to the screen, so I conclude the oscillation had no practical effect.

You wouldn't have found any prior remarks in any of my earlier postings (your #271) - this is the first. They didn't, so far as I can see, dismiss the possibility of horizontal oscillations during rotation - they simply did not discuss it. All their remarks on loads and shimmy seem to be related to the conditions existing prior to development of any significant sideslip. Fig 73 (English version) for example specifically shows the force balances in a possible bogie deflected condition but with the aircraft following a zero sideslip path.

I have no idea why they did not discuss the bogie behaviour in the rotation unless, like me, they came to the conclusion that it had no significant effect. This at least would be consistent with their statement that the missing spacer was not a factor. Even so they might, perhaps should have mentioned it - but that omission doesn't really change anything.

Not if I am correct in suggesting that all their comments relate to the conditions prior to any significant deviation from straight path. NB, I have edited the original to correct the reference to pre-tyre failure conditions.

Well, they mention it in the section you quoted (18.2.3.3), and then go on to discuss what effect that would have had, compare that effect to the evidence presented and conclude that it was unlikely.

Also, at rotation, the fuel fire had been ignited and presented a significantly more clear and present threat to the safety of the aircraft than anything else. I'd say it's understandable that the report focuses on that from that point onwards.

There are a couple of paragraphs which refer to the camber of the bogie post-tyre failure compared with normal:

so there is evidence that the behaviour post-failure was at least studied.

CliveL

When the BEA mention "tyre marks made by tyre No. 2", are they referring to only prior to tyre burst? That means there were tyre marks visible prior to burst, so I ask again, do you note the tyre marks in the photo of the kero stain, carbon trail?

Well certainly the bogie may not have been involved, but we see it was, though post burst/fire......

I am sorry to harp, if it appears so, if you say it is not relevant, I accept that, certainly.....

I understand the possibility of oscillation in the horizontal is believed to be of no consequence to the accident. But I will not admit it did not happen in the take off roll, and dismissing that portion of a serious anomaly seems counter to a full understanding of the events....
best

Think about it logically. Post-tyre burst there would be no "tyre marks" in the usual sense of the term, as the tyre has been destroyed. From that point on it would be "debris trail" or "rubber marks".

Dozy, there are marks of tyre number two up to leaving the ground.

There are marks that likely show the shape of the carcass deficit caused by the rupture/burst.

So let me ask you.

Describe the tyre marks you see prior to the kerosene stain in the long photo. the ones that continue along the centerline.

I have some follow up questions.

Yes, but not in the phase where there was appreciable aircraft sideslip

OK, if that is your view then fine; but I see no evidence or know of any physical explanation that would support your position.