Ahmedabad Plane Crash: Deployment of RAT Indicate Total Electrical or Hydraulic Malfunction: Experts
Manas Dasgupta
NEW DELHI, June 17: Even as the official sources said the investigation into the crash of the London-bound Air India from Ahmedabad on June 12 may take about a year, new evidence unearthed on Tuesday indicated 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 killing at least 274 people including all but one of the 230 passengers, all the 12 crew members and at least 33 people on the ground, including some medical students.
Official sources said the investigation into the Ahmedabad plane crash could take at least a year. The Aircraft Accident Investigation Bureau (AAIB), which is the lead investigator, will be assisted by Boeing and the United States National Transportation Safety Board (NTSB) to decode the black boxes which have been recovered. If need be, there may be an interim report or the black boxes may be sent abroad for analysis, but that is still to be decided by AAIB.
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.
Some veteran aviation experts said they 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 was 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,” the experts 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,” they explained.
A 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.
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.
Meanwhile, a separate government committee has been set up to examine the crash from technical, operational, and regulatory standpoints. Its report is expected within three months.
Far from the speculations, it is only the black boxes — the cockpit voice recorder and the flight data recorder, both of which have been recovered from the AI plane debris – that contain the truth. A team from the NTSB and Boeing is already here to help the AAIB decode them and offer critical insights into the flight’s final moments.
The AAIB has so far probed 121 serious accidents and 102 accidents since it was set up in 2011. But AI 171 is its biggest challenge.
The AAIB had taken almost a year to release a final report in the last big air crash in India – the August 7, 2020 accident in Kozhikode when a Boeing plane crash of an Air India Express Flight killed 18 people.
The detailed probe into the Ahmedabad plane crash could finally reveal what the plane should have done, and what it ultimately did. This is said to be a double-engine failure at the lowest height (650 feet) in history. But the truth could take time.
