Air India plane crash: Did electrical failure of 'more-electric' B787 cause both engines of AI 171 to fail?

MUMBAI: Competing theories about what caused AI 171 to crash have generated a new set of possible explanations. Among them is the question that since Boeing's 787 replaced conventional pneumatic and hydraulic systems with electrical systems - to make the aircraft lighter to save fuel and maintenance costs - whether there was an electrical system failure.There's no consensus. But as pilots continue to look for answers, electrical system failure has emerged as one of the latest attempts, by some, to explain the tragedy.All theories start from the premise that the lone survivor heard a boom, which may indicate a single engine failure. That wouldn't have caused a modern aircraft to crash? So what else went wrong? Did the second engine fail or was it something else?Dual engine failures are rare events: seven instances have been recorded in the past seven decades, the world over.

The causes were bird strikes (US Airways Hudson river landing in 2009), wrong engine shutdown (1989 British Midland flight 92, technical issues led to the mistaken shutdown of the good engine) and fuel contamination or starvation. The possibility of bird strike has been largely ruled out in case of the AI 171 crash on June 12.But B787 is a "more-electric" aircraft. So, pilots and experts are looking at this accident differently.

A senior B787 commander said: "The boom sound indicates it's highly likely one of the two engines had a partial or complete shutdown." But what happened after that?Did the pilots shut off the good engine, like in an earlier crash? But many pilots said that the process of shutting off fuel to the malfunctioning engine begins only at 400 feet and it takes some time to execute - the aircraft had crashed before that could be completed.Did the "startle effect" - pilots' involuntary reaction to a sudden, unexpected event - make the pilots forget they had to retract the landing gear? Or, were the flaps (devices on a wing's trailing edge that, when lowered, generate lift at lower speeds) retracted instead of the landing gear? But as the B787 commander said: "Even if that had happened, with one engine intact, the aircraft could have climbed out safely to come back and land".It's the both-engines-down scenario that's making some pilots think of electrical failure. "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," said a senior Airbus commander, who has flown Boeing wide-body aircraft.