Electrical failure caused Air India plane to crash? Pilots deliberate upon possible causes

The lone survivor said that he heard a boom about 30 seconds after taking off and the plane crashed.

Following the London-bound Air India Flight AI171 crash near Ahmedabad airport involving a 787 Dreamliner, many theories have emerged to explain the cause of the horrific accident.

As pilots continue to look for answers, the possibility of an electrical system failure has surfaced as a likely reason, according to Times of India.

The lone survivor, Kumar Ramesh (45), told Hindustan Times that he heard a boom about 30 seconds after taking off and the plane crashed.

Was engine failure the cause?

“The boom sound indicates it's highly likely one of the two engines had a partial or complete shutdown,” a senior B787 commander told TOI. According to experts, there are very few chances that a lone engine failure would have caused a modern aircraft to crash.

Dual engine failures are rare events as only few such instances have been recorded in the past seven decades across the world.

Some such examples were bird strikes (US Airways Hudson river landing in 2009) and wrong engine shutdown (1989 British Midland flight 92). Also, the possibility of bird strike has been largely ruled out in case of the AI 171 crash.

However, pilots say the B787 is a "more-electric" aircraft. More Electric Aircraft (MEA) refers to aircraft where non-propulsive systems, like hydraulics and pneumatics, are replaced with electrical systems, leading to potential benefits such reduced weight and fuel consumption.

According to many, the sudden boom sound may have made the pilots forget that they had to retract the landing gear. There are also some questions on whether the flaps were retracted instead of the landing gear.

However, the senior B787 commander does not agree. "Even if that had happened, with one engine intact, the aircraft could have climbed out safely to come back and land,” the commander told TOI.

Meanwhile, the scenario of both engines down as a theory is also being examined.

"Preliminary assessments indicate that at some point during the take-off one or more VFSGs (Variable Frequency Starter Generators: these start engines and provide main electrical power during flight) may have failed or become electrically isolated, resulting in partial or total loss of engine control," a senior Airbus commander, who has flown Boeing wide-body aircraft, told TOI.

According to pilots, APUs or auxiliary power units usually take more than 90 seconds to reach engine RPM and support flight. Thus, these units are unsuitable for responding to a sudden, dual-engine flameout scenario during takeoff or landing.

Another senior pilot said a VFSC (Variable Frequency Starter/Converter) failure could potentially lead to an EEC (Electronic Engine Control) failure.

“If both engines and APU (auxiliary power unit, back-up of sorts, but doesn’t provide as much power as the engines) fail or disconnect from the power system, EECs may stop controlling thrust, even if engines are still running. In such cases, the engines can get stuck at idle, leaving pilots with no way to increase thrust,” the senior pilot told TOI.

However, according to pilots, the simultaneous failure of engines and APU is rare.

Pilots told TOI that APUs take over 90 seconds to reach up to the engine RPM and support flight. Since the entire event began and ended in 32 seconds, there was not enough time or altitude for APU to come into the picture.

Some senior pilots said early findings suggest a potential electrical systems malfunction.

Deployment of RAT

The deployment of RAT or Ram Air Turbine is another theory which points at dual engine failure.. RAT is a small wind turbine that juts out from the underbelly of the aircraft. It supplies power to run the critical control surfaces of the aircraft.

According to some pilots, there was a small, hazy, black patch seen under the aircraft. It makes them think that RAT may have been deployed. Unlike APU, RAT cannot provide power to safely land an aircraft.

Capt Amit Singh, an air safety expert, indicated possible cargo overloading. “That would explain why the plane took a longer length of runway to take off. It also explains why, after one engine failure, it failed to maintain altitude and crashed”.

A senior B777 pilot also told TOI that the pilots mistakenly entered the zero-fuel weight, not accounting for 50-60 tonnes of fuel that the aircraft had at take-off. “

However, a B787 commander said the aircraft systems, based on the weight acting on its wheels, would have alerted the pilots in such a scenario.