'This was textbook emergency response under stress.'
"The Emergency Locator Transmiter, the most vital flight safety equipment should have worked but failed hinting at a deeper electrical failure," explains Captain Ehsan Khalid, aviation instructor, examiner and former IAF pilot in the concluding part of the interview on the AI 171 crash with Rediff's Archana Masih.
- Part 1 of the Interview: 'Why Did Pilot Wait For 10 Seconds To Reverse Switch?'
One of the unexplained aspects in the report is why did the Emergency Locator Transmitter, a life-saving critical flight safety equipment, not get activated after the crash?
The AAIB mentioned in just one line that the Emergency Locator Transmitter [ELT] did not activate. AAIB should have devoted at least two paragraphs to explain it.
The photograph of the recovered ELT shows that it is not burnt or mutilated.
ELT is a life-saving critical flight safety equipment. It is almost impossible to fail a serviceable ELT by fire, water or by impact.
The question is why did it not activate?
This means that this was another equipment which was not found to be working in the aircraft.
The biggest maintenance activity the Boeing 787 fleet should have undertaken was to test its ELT. Neither the AAIB mentioned this in its report nor did any regulatory authority deemed it fit to carry out one time check on all ELT.
The ELT has a battery of its own. It is powered by 28V DC and activates on its own on impact if set to ARM.
It sends out a satellite signal so that the location where the aircraft has crashed can be identified.
Once it is activated, it can't be deactivated till the battery goes dead.
The pilot can do nothing to switch it off if it is activated.
It has ARM, ON, Reset position.
There is no OFF position for pilot to select.
ELT was found to be physically intact and not much physical damage.
Since it's an electrical switch, it is possible that the electrical cascading effect caused this switch to move from its ARM position and therefore, the ELT did not work.
We have assumed that the aircraft was fully serviceable before takeoff, then why was there no ELT signal after the crash?
Did the electrical polarity reversal change the ELT from ARM mode?
Could the fuel switches and the RAT [Ram Air Turbine] switch also have reversed their polarity in a similar electrical storm?
The ELT, the most vital flight safety equipment, should have worked but failed, hinting at a deeper 28v DC failure.
What could this mean?
There seem to be two separate activities happening before the crash -- the RAT got deployed and the ELT malfunctioned.
The ELT did not activate and RAT deployed before the engine switches were moved is actually indicating a cascading electric failure.
What is surprising is that that ELT switch, the fuel switch, the RAT switch and the WOW [Weight on Wheels] switches are all 28 Volt DC.
It is reasonable to conclude that there was something cooking up in the 28 Volt DC.
Which in turn had a cascading effect?
There seems to be an electrical problem that was developing. The signs for these were showing in the previous flight.
There was a video posted by a passenger on the previous flight that the light switch, entertainment system, air conditioning were not working.
POS STAB XDCR operates on 28V DC and a fault was reported on the earlier flight.
The fault was cleared within 40 minutes of being reported.
This could have been an early sign of 28V instability and became catastrophic in this flight.
It probably caused the malfunction of the RAT, fuel switches and ELT.
Multiple systems operating on 28V DC were found malfunctioning. CORE network faults affect signal transmission which could have corrupted fuel, RAT, ELT signals simultaneously.
We do not know what would cause it. But these are secondary evidences that there were multiple failures indicating that something was cooking up -- and an electrical storm building up within the aircraft and finally it gave up.
No theory of suicide covers two things:
- Why did RAT deploy on rotation?
- Why ELT did not work?
How would you puncture the theory of pilot error?
The pilots fought till the end. This was textbook emergency response under stress. They showed discipline and professionalism, contradicting the narrative of suicidal intent.
The crash was not a suicide, but a possible cascading collapse of 28V DC subsystems, likely worsened by underlying CORE network instability or corruption of WOW [weight on wheels] logic signals or both.
The chain reaction ensued thus:
Discrete switch corruption especially WOW signal and its logic corruption
Instrument blackout
RAT auto deployment logic corruption
Engine shutdown
ELT failure
Data recorder destroyed by electrical damage
It demands a deeper forensic investigation into 28V DC architecture and systemic vulnerabilities in the B787 and similar aircraft.
Was there ever WOW switch transient malfunction reported on this aircraft? If yes, then when was it?
Feature Presentation: Aslam Hunani/Rediff
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