This is another update to my article Air India Crash: When 2 + 2 Does Not Compute, with evidence and argument in support of my assertion that the AAIB Preliminary Report is worthless.
"It is hard to imagine a text more likely to sow confusion and encourage speculation than the partial summary of the fate of the Boeing 787 in Ahmedabad"
The Times, India1.
The AAIB preliminary report2 paraphrased merely a snippet of the CVR record of what the pilots said. Did it also paraphrase merely a snippet of the FDR?
In the cockpit voice recording, one of the pilots is heard asking the other why did he cutoff. The other pilot responded that he did not do so.The AAIB preliminary report is a classic example of misdirection.
The report says that Air India complied with all relevant airworthiness directives.
It does not list all relevant ADs, or even a few relevant examples, but gives details of an entirely irrelevant directive about switches. Thisappears to be something of a straw man3.
It omits mention of a far more important AD4 - the one concerning dual engine rollback at liftoff.
The report says - with no supporting evidence - that "switches" "transitioned" to "off". This gives rise to a few points:-
1 - Chunky toggle switches are never said to "transition", but that term may certainly be used for fuel valves.
2 - The faulty switches were of a different design to the ones used on the 787-8.
3 - The 787-8 switches are from a different manufacturer5.
4 - These are not ON-OFF switches - they are ON-ON switches which feed voltage to one of two sets of output lines.
5 - The switches do not control the fuel valves directly, but rather through relays, as described in my original article.
6 - The report, for reasons known only to its authors, fails to mention the four per engine fuel cutoff switches / relays described in my original article. Only one of the four is under the control of the pilots. Indeed, the AI 171 pilots may not even have known of the existence of relays.
There can be only one reason to make a special point about the switches and that is to direct public attention away from other possible causes of this accident.
Screenshot from the AAIB preliminaryreport
The Strange "01" Time Gap
The use of "01" is of specific interest. Does it indicate 0.1 - 1 tenth, 0.01 - 1 hundredth of a second perhaps? Only relays can switch over in milliseconds. Also the use of "about" instead of using error bars is decidedly unprofessional.
"At this stage of investigation, there are no recommended actions to B787-8 and/or GE GEnx-1B engine operators and manufacturers"But what about the many other providers of components, and why no recommended action regarding the pilots? Could it be that the report's authors have no valid reason to suspect pilot error of malice?
Blaming the captain has a long and ignoble history.
The AAIB, through classic misdirection, has the world at large blaming the pilots but does not itself actually say that the pilots are to blame. The report's authors, who did not sign the report, clearly intend to invoke plausible deniability.
In a parliamentary debate on the construction of harbours of refuge, he Board of Trade opposed the costs of such construction on the grounds that most losses of ships were down to poor seamanship.
Another deduction was made on account of losses attributable to bad seamanship. Bad seamanship! Did they not know that the coasting trade trained the best seamen that England had ever possessed, and how could the author of this document judge whether or not a vessel had been lost by bad seamanship when the crew had all perished?
He would not trouble the House further with the document, but would pass on to the real facts of the case.
Mr. Lindsay, Commons Hansard6, April 26 1864
Is India's AAIB Independent?
The accident investigation authority must be strictly objective and totally impartial and must also be perceived to be so. The authority should be established in such a way that it can withstand political or other interference or pressure. Many States have achieved this objective by setting up their accident investigation authority as an independent statutory body or by establishing an accident investigation organization that is separate from the civil aviation administration.
Manual of Aircraft Accident and Incident Investigation7
The preliminary report needs to be superceded by something well written and far more accurate. The AAIB would do well to read the CENIPA8 report linked below to see an example of a well-written accident report.
If the pilots are to blame, so be it.
If a manufacturer or an airline is to blame, so be it.
fiat justitia ruat caelum
Let justice be done though the heavens fall.
sources
1 - Air India crash report feeds rumours and wounds national pride
https://www.thetimes.com/world/asia/article/air-india-flight-crash-repor...
2 - AAIB Preliminary Report
https://aaib.gov.in/What's%20New%20Assets/Preliminary%20Report%20VT-ANB.pdf
3 - straw man fallacy
https://en.wikipedia.org/wiki/Straw_man
4 - FAA EASA_AD_US-2006-20-51R1_1
file:///D:/Downloads/EASA_AD_US-2006-20-51R1_1.pdf
5 - 4TL837-3D datasheet
https://www.allelcoelec.com/datasheets.da/4tl837-3d.pdf
6 - Hansard Volume 174: debated on Tuesday 26 April 1864
https://hansard.parliament.uk/Commons/1864-04-26/debates/ad098ada-43e7-4...
7 - Manual of Aircraft Accident and Incident Investigation
https://skybrary.aero/sites/default/files/bookshelf/3282.pdf
8 - CENIPA Interim Report ATR 72-212A (500) Accident on 9 August 2024
https://dedalo.sti.fab.mil.br/en/85259
edit - added links
Air India Crash: When 2 + 2 Does Not Compute
Air India Crash: Update #1
Air India Crash: Update #2 - The AAIB Report Revisited
Air India Crash: Update #3
Comments