on 11.07.25 the preliminary report was published by the Indian AAIB. This note relates to my initial assessment of the aircraft accident (specifically my hypotheses #1-#5) and is intended to interpret the information published in the prelim. report.
DISCLAIMER: This is a private analysis without any guarantee for the accuracy of the reported facts and conclusions.
From the preliminary report, my hypothesis #1, #3 and #4 can be confirmed as invalid due to the documented A/C configuration at the crash site and official probes into fuel quality. There are also no apparent, critical technical or maintenance items related to the incident. From the flight data and voice recorder (FDR, CVR) readouts the following sequence is documented, following an uneventful take-off run
- 08:08:39Z aircraft left the ground
- 08:08:42Z engine #1 fuel cutoff switch transitioned from RUN to CUTOFF
- 08:08:43Z engine #2 fuel cutoff switch transitioned from RUN to CUTOFF
AUDIO: “one of the pilots is heard asking the other why did he cutoff. The other pilot responded that he did not do so“ - 08:08:47Z the ram air turbine (RAT) is confirmed to supply hydraulic power and there is visual confirmation that the RAT was already deployed in the very initial climb phase, right after take-off, well within the perimeter of the airport.
08:08:52Z engine #1 fuel cutoff switch transitioned from CUTOFF to RUN - 08:08:54Z APU startup sequence initiated (also visually confirmed by the APU inlet door found open at crash site)
- 08:08:56Z engine #2 fuel cutoff switch transitioned from CUTOFF to RUN
- AUDIO (08:09:05Z) “MAYDAY, MAYDAY, MAYDAY”
thereafter, engine parameters and APU/RAT deployment are consistent with dual engine failure (below engine idle thrust) with attempted auto-re-ignition sequence applied to both engines, which however came too late to restore thrust prior to crashing into the ground.
“fuel control switch“: for LH/RH engines, both are located directly below the thrust levers on the center console. Per definition a “switch” is a physical device with a physical state (switch lever position) and an (electric) logic state that is directly related to its physical state and wherein the logic state is electrically transmitted to the intended target of the switching process (here: electro-mechanical fuel valves). The switching process – usually – consists in 1) actuating the switch lever, 2) the altered switch lever position changing the (electrical) logical state, 3) the electrical state change being propagated to the device targeted by the switch. 4) the switch target responds to the change.
With regard to the FDR events recorded, it can be assumed (though, this detail has to be confirmed) that the “fuel cutoff switch state (RUN|CUTOFF)” does not necessarily reflect the absolute physical position of the switch lever (sensed via any hypothetical secondary FDR-specific logic circuit which would be INDEPENDENT from the switch actual logic output state) but it is recorded from the apparent electrical output logic state “downstream” in the switching process.
In this light, the following scenarios could apply:
- The switches have been physically altered to CUTOFF by human intend.
- The switches have been physically altered to CUTOFF without human intervention.
- The switches have not been physically altered, but downstream to the “designed” switching process, another event altered the logical (electric) switch state.
To start with scenario 2, I think this can be ruled out since both switches are (independently) physically guarded and their operation requires overcoming a physical switch lock specifically designed against unintentional physical operation of the switches.
Scenario 1 could be one of the following:
- a standard procedure requested by aircraft malfunction. This would require observation of any prior fault, communication by the crew and execution of the respective checklist procedure. Engine cutoff (or switch cycling) as an action item does only occur in procedures related to engine fire or re-ignition following an in-flight engine malfunction. None of these factors have been observed in FDR and CVR data recorded and as such I rule out the possibility that an intential engine cutoff was based on procedure.
- suicidal intent by one crew member. This scenario is physically possible, however I would rule this out based on the following observations:
- a) it is unlikely that the rapid (1s interval) action to move both fuel switches from RUN to CUTOFF by one pilot moving hands towards the center console is not noticed in the peripheral field of view of the other pilot being focused on flying the aircraft. It is in fact a strength of peripheral vision to detect such motion.
- b) an action as decribed in (a) and not being compatible with any trained procedures, would have clearly resulted in a strong response by the other pilot, verbally by assertive language and/or physically by action (or open struggle) to re-establish the correct fuel switch setting.
- c) the CVR recording of both persons rather reflects complete surprise and astonishment at the observation of the fuel valve status. It is unclear if this observation by the person asking is based on physical position of the switches or alerts on the engine monitoring displays that mirror the effects of a fuel cutoff logical switching. The response of the “accused” pilot reflects a defensive position and surprise and – in my opinion – is not compatible with aggressive suicidal intent or the feeling of one’s deadly plan just having been discovered and compromised by a another person.
- d) the time from recorded CUTOFF to recovery into RUN state is excessively long and almost identical (10/11 seconds) for both engines. If fuel control switches were indeed physically selected to CUTOFF and visually identified as such, any corrective action should have occured way much faster or should have resulted in at least a struggle audible on the CVR audio. This hints rather towards a scenario where switches are indeed in the RUN position, the CUTOFF state being introduced elsewhere “downstream” and pilots remained passive to witness automated engine recovery.
- e) extending the argumentation of (d) it is also unlikely that a pilot with suicidal intent would not have used the recovery time available to crash the aircraft by other means, i.e. pulling back thrust levers, making control column inputs, introducing fatal aircraft configuration (i.e. speed breaks)
This eventually leaves us with scenario 3, some sort of a “wicked” electrical effect that either introduced almost synchroneous fuel cutoff electrical logic state into the wiring (between physical switches and targeted valves) OR directly into the EEC/FADEC logic generating equivalent fuel switch logic state based on other factors than fuel control switch logic state alone. Let’s note that both engines independently operate completely autonomous with regard to their commanded thrust/fuel state. Once received by the EEC/FADEC logic of either engine, the state will be executed (independently from A/C hull electric supply) as long as fuel and air can be fed into combustion. The nearly synchronous shutdown of both engines by closure of both fuel valves therefore points towards a logic in which the commanded state originates from an engine-independent but single origin. This origin must be located inside the A/C hull since engines cannot command each other mutually.
as a consequence I maintain hypothesis 5 of my previous analysis with the alteration that apparently no major cascading electrical fault (this would have been obvious in the FDR readout) led to the observed fuel control states, but the causal event would be rather limited to affecting downstream electric logic state of the fuel control switches or any other electric logic state having the authority to close fuel valves, for example EEC/FADEC TCMA. Since the event is tightly bound to A/C physical rotation on the take-off timeline, this could hint towards an effect driven by inertia on the electrical signalling, for example:The motion of amounts of water from condensation or any lose wiring.