Monday, 25 May 2015

Pan Am 103 and the mach stem effect

[What follows is excerpted from a report published on the BBC News website on this date in 2000:]

An air accident investigator has told the Lockerbie trial there was a significant mathematical error in the official report on the disaster.

In highly technical but potentially crucial evidence, Christopher Protheroe said he informed prosecution lawyers in a meeting on Monday that a complex formula used to calculate blast wave effects after an initial explosion had been incorrectly applied in the 1990 report.

He admitted that correct calculation of the so-called "mach stem" phenomenon would indicate that the bomb which destroyed Pan Am Flight 103 over Scotland went off closer to its fuselage skin than originally thought.

The effect is created when a bubble of super-heated gases expands violently after explosives are detonated.

The report by the UK's Air Accident Investigation Branch (AAIB) indicated that damage discernible in debris from the forward cargo hold showed that the distance would have been about 25 inches (63 cm).

On evidence on Thursday, Mr Protheroe said the distance, if calculated correctly, would be about 12 inches (30 cm).

The prosecution alleges that Abdel Basset al-Megrahi and Al-Amin Khalifa Fahima, working as Libyan intelligence agents, planted a bomb in an unaccompanied suitcase in Malta which was eventually loaded onto the doomed aircraft in London.

Earlier, Mr Protheroe held up a model of the jumbo jet, with red, green and yellow patches showing how the plane had disintegrated in mid-air. (...)

He described how the blast initially blew a 20 by 20 inch (50 cm) hole in the fuselage and created further "starburst fractures" and "petalling" of the plane's metal skin from the subsequent explosion of hot gases.

AAIB photographs produced in court of a partial three- dimensional reconstruction of the smashed plane showed clear evidence, Mr Protheroe said, of a "shatter zone" in the left front cargo bay almost directly under the second "A" in the Pan Am logo on the side of the jet's giant forward cabin.

The trial was adjourned again, this time to allow a baggage container from the aircraft to be brought into court.

Air accident investigators have reconstructed the metal container, which is too big to be brought through the courtroom doors.

It may have to be taken apart and rebuilt again in front of the three judges in a process which could take a whole day.


  1. Living with the "Lockerbie Affair", 2015 > for the moment only in German language:

    Auch das FBI Laboratory wurde für den vorsätzlich verursachten Beweisbetrug iim Lockerbie-Fall, mit dem inzwischen bekannt gewordenen MST-13 Timerfragment (PT-35) von der Scottish "Gray Eminence" getäuscht und betrogen !

    Anfang Juni 1990, bei einem angekündigten Besuch von Scottish Officials, beim FBI Labor in Washington & Virginia, wurde von Scottish Experten, Allen Feraday (RARDE) nachweislich ein gefälschtes MST-13 Timerfragment (PT-35) zur Analyse und zum Vergleich mit einem funktionsfähigen MST-13 Timer (K1 / TOGO) übergeben.

    Das Fragment (PT-35) stand zuvor den Experten, Feraday & Dr. Hayes, als grünes Sample-Duplikat zum Vergleich mit dem "schwarz verkohlten" Original (PT-35) zur Verfügung.
    Das Fragment wurde am 27. April 1990, bei Fa. Siemens in Deutschland in zwei Teilstücke zersägt: Grosses Teilstück, als (Nr. 353 = PT-35/b) - das kleinere Teil, als (Nr. 419 = DP-31/a) bezeichnet.
    (Foto 334, original Fragment (PT-35) "circuit board, black carbonized" fabriziert aus 8 Lagen Fiberglas, nicht verwendet in den, nach Libyen gelieferten MST-13 Timer);

    (Foto 335, Sample-Duplikat mit gleicher Bezeichnung, als (PT-35) jedoch fabriziert aus 9 Lagen Fiberglas und beidseitig überzogen mit grünem Lötstop-Lack. Die nach Libyen gelieferten MST-13 Timer wurden mit solchen grünen "Circuit Boards bestückt).

    Ende Mai 1990 wurde das grüne Duplikat bei Chief chemist, Alan Worrol (ex Ferranti) in Oldham, ebenfalls (wie bei Siemens) in zwei Teile zersägt und gleich bezeichnet, mit (Nr. 353 = PT-35/b) und ( Nr. 419 = DP-31/a).

    Notabene: Somit konnte dem FBI kein komplettes MST-13 Timerfragment (PT-35)übergeben worden sein, da beide PT-35 Fragmente zu diesem Zeitpunkt, je in zwei Teile getrennt waren !
    Deshalb steht fest, Feraday muss dem FBI, das "grüne" Fragment (PT-35/b) und potenziell auch das Teilstück (DP-31/a) zum Vergleich mit dem MST-13 Timer (K1) (Togo Timer) und für eine forensische Analyse, übergeben haben !

    Please see the interview from ex FBI Agent Mr. Fred Whitehurst:

    by Edwin Bollier, MEBO Ltd. Telecommunication Switzerland. Webpage:

  2. I admit to not understanding the Mach Stem calculations, but the judges dismissed this controversy by noting that a blind aardvark could see from the condition of the container that the explosion had occurred inside the container and not somewhere within the airframe.

    I have to agree with this. Twelve inches from the outer skin isn't inside the container, and the blast was definitely inside the container. Somebody else has dropped a stitch somewhere.

  3. How long does it take for a man to walk to the top Mount Everest, a 25 km walk?
    A normal man should walk at least 5 km pr. hour so our mathematical model is
    D = H*5
    where D is the distance and H is the hours I walk.
    We see that if D=25 then
    H = 25/5 = 5.
    Five hours it should take him.

    Would I be willing to claim in court, that a normal man should be able to walk to the top Mount Everest in 5 hours?
    Some scientists would.

    OK, in this case I would run into the problem that the judges and jury are well aware that we have overwhelming empirical evidence that it takes good climbers several weeks to reach the top.
    They can instantly see that my model D=H*5 has nothing to to with realities, as their level of math and the understanding of the real world is sufficient.

    But what if it was much more complicated and I was some kind of respect-inducing expert?

    Collected data -> model assumptions -> applied calculations -> interpretations of the result back to the real world.
    It works fantastic at time, typically when
    a) There are few parameters
    b) The size of the parameters are well known
    c) The behavior of the system is not sensitive to chaotic events

    Unfortunately, for most situations - like in our walk-to-top-of-everest example - we have the opposite of a, b and c, and for this reason the interpretations of the calculations back to the real world can be anything from hardly usable to completely worthless.

    Finding debris of a plane and talking about a difference between 30 cm or 60 cm for an explosive of essentially unknown size and where even the exact composition is unknown is, along with 100 other parameters, is frankly, the work of an [I have self-censored this expression]. Fine credentials will not help.

    Of course the (strong) possibility remains that the press simply filtered out the careful limitations expressed by the scientist, as this is common too.

    Science and 'science' work great with juries, and as said, for reasons unknown to me, the other side fails to call in genuine scientists who could explain how mad it is.
    In the below case the objections came much later, in one case too late.

    Sally Clark
    "...Sir Roy Meadow, who testified that the chance of two children from an affluent family suffering sudden infant death syndrome was 1 in 73 million. "
    May Ms. Clark, like Megrahi, rest in peace.

    Lucia de Berk
    "The verdict depended in part on a statistical calculation, according to which the probability was allegedly only 1 in 342 million that a nurse's shifts would coincide with so many of the deaths and resuscitations purely by chance. "
    She is luckily still alive.

  4. Look up the "sharpshooter's fallacy".

  5. Actually, I'm told the Mach Stem calculations are well-established and reliable. But Christopher Peel, who headed a lengthy research project into why the plane broke up, got his sums wrong. The wrong sums seem to have placed the explosion more or less where we can see it actually was. Somebody coached Richard Keen to demonstrate that the sums were wrong and Peel crumpled like a wet paper bag, apologising profusely and protesting that he hadn't deliberately misled the court.

    But Keen's allegedly correct calculations placed the explosion somewhere it couldn't have been according to the obvious, sensible evidence of our own lying eyes. I therefore conclude that there are more dropped stitches in this pullover than anyone has yet identified.

  6. Thank you for always interesting posts.

    "Actually, I'm told the Mach Stem calculations are well-established and reliable."
    I am sure they are. So are calculations how far a man can walk within a time period.

    But they are models, based on assumptions.. When applied to a real and very complex world things becomes uncertain, often to the point of useless.

    The only reason why somebody gets away with modelling chaos into simple formulas is, that there is not empirical refusal.

    The very best we can use Mach Stem Calculation for is to say "According to our model, yes, the plane might in fact break in a way that it did" or "It is unlikely that this could ever happen".

    Does the damping of being placed inside a container make any difference?
    Has the density of material surrounding the bomb been estimated and included?
    Would it matter if it was 400 or 600 gram, a quantity that is totally unknown.
    Which walls are met inside the plane?"
    What impact would their weight and strength have?

    Anyone saying "Oh, we can exclude that and other factors in the application of our model, without further explanation, testing and empirical analysis, and so we correctly have 30 cm, not 63 cm" are living in a world that is incompatible with real life.

    Do you have a tiled floor in your kitchen? Hold a glass in a certain height and let if fall. It might break, it might even not. I have tried both, haven't you?
    Now invite the entire world of scientists in and let them estimate just how many centimeters you held the glass over the floor. 30 or 63?

    Well, a jury might believe in one of their results. You wouldn't.

  7. For once, I go with the judges. Anyone with eyes in their head and sight of the baggage container can see the explosion was inside it. The condition and location of the fragments of the brown Samsonite are also inescapably consistent with the explosion having been inside that suitcase.

    The forensic scientists weren't really that far out in their estimate of the position of the explosion. The damage to the struts of the container confirms that. The only question is how the bomb suitcase was packed into the container so that the centre of the explosion ended up in that awkward corner.

    I feel fairly confident that nobody needs to worry about Mach Stem calculations to figure any of this out. They may illuminate the question of how a fairly small explosion managed to cause the entire plane to disintegrate in a matter of seconds, but they are entirely superseded by the simple evidence of these blast-damaged aluminium struts when it comes to determining the position of the centre of the explosion.