Lyman,
As such, the BEA document is thready, and missing some important work that imo should be present in a criminal prosecution.
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.
Evidently France considers culpability on a par with crime. That makes no sense, imo.
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.
The major issue is the apparent speed with which the report issues opinions, yet there is no lab or field work to support.
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?
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.
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 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.
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.
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 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.
I contend that shimmy is not normal to heavy aircraft,
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
Lack of evidence through lack of attempt is not sufficient; again, the prose in the report is used to put people in prison...
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
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.