FOLLOWING THE CRASH of Air India Flight AI-171, a Boeing 787 Dreamliner that crashed moments after take-off from Ahmedabad on June 12, there was a lot of speculation about what cost 260 lives, ranging from fuel contamination and bird strikes to pilot error and mechanical malfunction.
The absence of official data had so far created a vacuum filled with fragmented theories. However, the preliminary report of the Aircraft Accident Investigation Bureau, released on July 11, reveals that both engines flamed out within seconds of take-off because their fuel control switches were moved to the ‘cut-off’ position.
The fuel switches, located below the thrust levers on the central pedestal between the two pilot seats, are manually operated and require deliberate action by the pilots to physically move them between ‘cut-off’ and ‘run’ modes.
The switches are spring-loaded, with a locking mechanism, and are also enclosed by a mechanical gate to remain in position. To change it from run to cut-off, a pilot has to first lift it manually and then move it down or vice versa. These actions have to be repeated twice for the two switches.
As per the report, both switches moved to the shut-off position within a gap of one second, which is highly unlikely under normal circumstances. It is quite a complicated situation to analyse and is hard to digest.
The switches, with advanced locking features, are designed to prevent any inadvertent operation that could starve engines of fuel. There is a critical 2018 Federal Aviation Administration advisory about these very switches, which requested inspection by carriers and operators based on reports from operational Boeing 737s. The advisory from the US body noted that some installations of these switch modules had occurred with the locking feature in disengaged mode, and if confirmed, carriers and operators were advised to replace them at the next opportunity.
The FAA’s Special Airworthiness Information Bulletin was to the point: “While the aeroplane is on the ground, check whether the fuel control switch can be moved between the two positions without lifting up the switch. If the switch can be moved without lifting it up, the locking feature has been disengaged, and the switch should be replaced at the earliest opportunity.” However, it explicitly also said that it is “not an unsafe condition with respect to airworthy concern”.
Devastating consequences
THE DREAMLINER is the most advanced technology of its time. It is a marvel of engineering, but no system is immune to rare, complex failures. The pilots’ final few words, captured on the cockpit voice recordings, tells the human story with the technical catastrophe lurking. One did ask the other, “Why did you cut off the fuel?” The other replied, “I didn’t do so.” They took immediate action and pushed the switches back to the run position, as understood from the report findings. This shows they were caught unawares and went all out to salvage the situation.
This action resulted in the relighting of the engines, followed by ignition, fuel flow and thrust recovery sequence; but only one of the engines was able to get activated. At just 500 feet above ground level, where the aircraft is in absolute power-hungry mode, it is practically impossible to gain that sort of thrust and to climb further by putting the fuel switch back in run position.
Also, the landing gear remained extended during the aircraft’s climb. Retracting the gear is essential to reduce drag and ease the strain on the engine thrust during take-off.
A subtle prelude
IN THE HOURS leading up to the fatal flight, passengers aboard the same aircraft on its earlier leg from Delhi to Ahmedabad reported non-functional USB ports, dead in-flight entertainment system and intermittent air-conditioning failures.
Seemingly trivial at the time, these cabin-level glitches might have been the first signs of deeper trouble lurking in the Dreamliner’s electrical architecture.
In the Boeing 787—a largely electric aircraft—such issues are rarely isolated.
Most of the cabin and control systems, including those for fuel, hydraulics, avionics and even engine controls, are powered by a complex web of four alternating current (AC) buses, which in turn are fed by Variable Frequency Starter Generators (VFSGs), two mounted on each of the Dreamliner’s two main engines.
These generators are not just power sources; they are foundational to the aircraft’s functionality and are themselves powered by the mechanical power of these dual engines. Any fault in one, and VFSGs can cause electrical failures with ripple effects that reach the cockpit, control surfaces and, most critically, the thrust management computers known as FADECs (Full Authority Digital Engine Control). Although the Auxiliary Power Unit, the backup power source, can power the VFSGs in this situation, the spool up time and manual action to put it on rules it out in such tight circumstances during initial climb and low altitude.
The long take-off roll: a clue ignored?
THE ADS-B (Automatic Dependent Surveillance-Broadcast)—a technology that allows aircraft to broadcast their position, altitude, etc—and the surveillance footage show the Dreamliner taking an abnormally long time to lift off, nearly exhausting the full runway. This sluggishness during the take-off roll (distance travelled on the runway) could suggest suboptimal thrust—a possible outcome of irregular fuel delivery, faulty thrust control or power inconsistencies affecting engine performance. Weather conditions were stable with visibility being clear.
The aircraft climbed to 625 feet before disappearing from radar. In those fleeting seconds, data analysts have pieced together a disturbing sequence: signs of thrust drop, loss of altitude gain, and then, deployment of the Ram Air Turbine (RAT)—a last-resort emergency generator that automatically activates when all main and auxiliary power sources fail.
That the RAT deployed so early into the flight is in itself alarming. This is designed to be a rare occurrence, typically triggered by the total loss of both engines or a complete electrical blackout. For it to happen immediately after take-off points toward an instantaneous loss of onboard power distribution, probably a result of ‘dual engines shut down’ as mentioned in the AAIB report.
Other theories don’t hold
ALTERNATIVE HYPOTHESES had emerged in public forums earlier, including fuel contamination, flap misconfiguration or bird strikes. Each has its own shortcomings.
Fuel contamination tends to degrade engine performance over time; it will not result in an immediate and total power loss. Moreover, modern fuelling systems have layered filters and quality checks. Even a microscopic presence of foreign elements typically gets flagged before fuelling is complete.
Misconfigured flaps would typically trigger the take-off warning system that includes both visual and audio alerts via the Engine Indicating and Crew Alerting System (EICAS). The pilots are trained to abort take-off if configuration issues are flagged.
In this case, the aircraft did achieve liftoff, although it displayed some sluggish acceleration before its abrupt stall, and is thus unrelated to the misconfiguration theory.
Likewise, bird strikes usually leave visual evidence—flames, smoke trails, or at least an audible anomaly—none of which were present in the surveillance and mobile footage.
Electrical vulnerabilities of 787s must be re-examined
FIRST, THERE MUST be a thorough review of the aircraft’s electrical systems, particularly how faults are isolated and the power prioritisation. Second, airlines should be encouraged to report and investigate even the smallest anomalies; what might seem minor initially could well be the aircraft whispering distress signals. Third, regulators need to rethink how these scenarios can be simulated and prepare for cascading failures.
The manufacturer should consider complete de-cluster of flight-critical and non-critical systems right at the source level, supported by triple fallback redundancies wherever feasible. While aircraft like the Dreamliner have extensive redundancies, a few shared electrical paths and some clustered power dependencies may create single points of failure that, under rare conditions, can trigger systemic breakdown.
A two-pronged redesign approach is the need of the hour—upgrading the VFSGs to hybrid systems with dual-input power sources (such as fuel cells or battery-boosted drives), and the addition of a fifth stand-alone generator—unlinked to either engine—to serve as an emergency backup in case of total electrical cascade.
While technically challenging, such innovations could significantly reduce the chances of an entire aircraft’s electrical spine going dark in-flight.
If this independent reconstruction is anywhere close to the truth, the tragedy of AI-171 is not just a case of mechanical misfortune, but a warning shot across the bow of modern aircraft design. Redundancy, the backbone of aviation safety, must not only exist on paper, but be tested against the rarest cases, including simultaneous system degradation at low altitude in a simulated environment.
More urgently, minor cabin system glitches must be reinterpreted not merely as passenger inconvenience but as early warning signals.
Until the cockpit voice recorder and flight data recorder data are fully decoded, the final picture will remain incomplete. But this story drawing from technical patterns and known behaviour of the 787 gives possible indications on what might have gone wrong and what needs to be reviewed on priority.
The writer has more than two decades of experience in the airline cargo industry and is an aviation expert.