Does RAT Hold Key To Air India Probe? Turbine Had Deployed Before Crash
India saw one of its worst aviation disasters, in which at least 270 people were killed, last week and new evidence indicates that both engines of the Air India Boeing Dreamliner 787-8 may have failed or it may have suffered a total electrical or hydraulic malfunction.
Clearer audio and video from the June 12 crash show that the Ram Air Turbine or RAT - a small propeller-like device which deploys automatically when there is a dual-engine failure or total electronic or hydraulic failure - was deployed on the Dreamliner, which crashed just 32 seconds after taking off from the Ahmedabad airport.
The distinct high-pitched whine of the RAT can be clearly heard in the audio in the absence of the roar of the aircraft's jet engines and its deployment can also be made out in the video, which shows the plane struggling to maintain altitude and then beginning to descend rapidly.
The RAT uses wind speed to generate emergency power and experts say its deployment, which happens automatically, points to three possible scenarios - both engines of the aircraft failed, it suffered an electronic failure, or its hydraulics failed.
Veteran Indian Air Force Pilot and aviation expert Captain Ehsan Khalid said he had suspected dual engine failure on the day of the crash itself, after the video emerged, as the aircraft was not 'yawing' (turning abruptly) and it is nearly impossible for birds to hit both engines at the same time.
"Dual engine failure was almost everybody's guess. The lone survivor of the crash had also said he heard a sound, which could be the deployment of the RAT; the racing of an engine, which could have been the propeller turning and picking up speed; and he saw red and blue lights, which could have been the emergency power connecting and the emergency lights turning on," he said.
"The aircraft was actively flying and it was not able to maintain its height. It was a dual loss of power, which would obviously lead to lower speed and a loss of lift (the upward force that opposes gravity and allows an aircraft to fly) and the plane will continue to go down the way it did. The Ram Air Turbine deploys when there is a dual engine failure or electrical failure or hydraulic failure," he explained.
The former Air Force pilot said an electrical failure, in certain conditions, could have led to the engines shutting down.
"The engines shut down at precisely the same time. If there had been even a two-second difference, there would have been a predominant yaw to the left or the right. The engines have shut down digitally, precisely, and at the same time, which could have only happened due to a malfunction in the software, which was executed by a wrong signal from the sensors, which could have come from an electrical failure," he said.
Professor of airspace Dr Aditya Paranjape also said the evidence points to both engines failing to provide thrust.
"Airplanes are configured to climb out with just one engine operational, it is a standard manoeuvre known as a one engine out climb. That manoeuvre additionally requires that the rudder be deflected in the direction of the working engine to balance out the differential yawing movement, which we don't see here... The loss of power is identical on both sides of the airplane," he emphasised.
32 Seconds Of Terror
The Boeing 787-8 Dreamliner, which was operating as Air India flight AI-171 to London, had taken off from Ahmedabad on the afternoon of June 12 and crashed into the complex of the BJ Medical College - an aerial distance of less than 2 km. The crash took place at 1.38 pm, just 32 seconds after the aircraft took off.
Of the 242 people, including 10 crew members and two pilots, on board the flight, only one - 40-year-old Vishwash Kumar Ramesh, a British-Indian who was returning to the UK after a visit - survived. At least 30 people on the ground, including trainee doctors, were also killed.
A bird hit was suspected to be the initial cause of the crash but it has been ruled out now as no bird carcasses were found on the runway and the two available videos don't show any fire, sparks, smoke or debris around the engines.
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