New Delhi: Aviation experts now say that more evidence has emerged in support of the theory that AI171 crashed due to dual engine failure.
The original 18-second video, shot by a youngster from a rooftop close to the airport, has now emerged and the experts say it clearly shows the deployment of a Ram Air Turbine or RAT, even as the aircraft tried to gain altitude after its take-off.
A copy of this video was shared soon after the mishap, but it was too grainy with background voices. The student who had captured the video on his mobile, has now released the original clip that not only reveals the deployment of the RAT but the characteristic noise it makes.
But, what is a RAT?
It is a two-bladed propeller that deploys automatically and is designed to provide electrical and hydraulic power to an aircraft in an emergency.
However, it is only effective when an aircraft is cruising at a sufficient altitude, to give the pilots time to sort out the problem. It is of no use if engines fail during a take-off.
Among those who have studied the video carefully is Steve Scheibner, an experienced pilot from the US.
“On the 787, three things deploy the RAT – a massive electrical failure, a massive hydraulic failure, or a dual-engine failure,” Scheibner has said on his YouTube channel.
Scheibner says that the protrusion from the belly of the aircraft was the small door from which the RAT emerges and the little grey dot seen in the video is the RAT itself. “This is visual confirmation that the RAT deployed,” he says.
In their last message to the Ahmedabad ATC, the pilots of the Boeing 787-8 Dreamliner had spoken of loss of power and lift.
Scheibner and other pilots say the video also features the distinctive RAT sound. “It sounds like a propeller plane going by. A high-pitched squeal. If you weren’t looking at it, it sounded like a single-engined propeller plane just flew by,” Scheibner said.
“But this complicates the investigation,” Captain C S Randhawa, president of the Federation of Indian Pilots, told The Telegraph.
Randhawa, who also has experience in aviation training and safety wondered: “How and why would both the engines fail?”
Experts say the two engines have independent controls, and dual-engine failure would be extremely rare, now that the bird-hit theory has been dispelled.
Randhawa has said that there is nothing that the pilots could have done if both engines had failed at that stage.
“The engines typically take up to 90 seconds to relight – there has to be time for that,” he said.
Scheibner also says that the words of the lone survivor of the crash corroborates the RAT theory. “He says that he heard a loud noise. That may have been the RAT deploying. He also said that the lights flickered. That would happen when the RAT takes over the electricals,” the pilot said.
The London-bound Air India flight, with 230 passengers and a 12 crew members on board crashed on Thursday within 32 seconds of its take-off from Ahmedabad. Several people on the ground were also killed, including medical students and their families.
