Exclusive: How an Indian Air Force An-32 plane was found in the depths of Bay of Bengal

Amid the dark depths of the Bay of Bengal, during routine testing and calibration of an Autonomous Underwater Vehicle(AUV), a significant clue emerged out of the blue and brought closure to an 8-year-old military aviation mystery, that had claimed the lives of 29 Indian Armed Forces personnel. Based on underwater data collected and analysed by India's National Institute of Ocean Technology(NIOT), Chennai, the Indian Air Force has been able to trace and identify the debris of their Russian-origin An-32 aircraft that had "disappeared" onJuly 22, 2016, during a routine mission over the Bay of Bengal, off India's east coast.

Recalling how it all unfolded, Dr. G.A. Ramadass, Director, NIOT told WION that the breakthrough finding happened during a deep ocean exploration mission.

"From Kongsberg Maritime, Norway, we procured a sophisticated AUV, Ocean Mineral Explorer 6000, which is capable of functioning fully autonomously, diving to depths of 6kms(6000m) and operating for 48 hours non-stop. We just have to program the vehicle and then it is on its own, until the time it re-surfaces. After it is retrieved, we download the data and study it", he said.

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As a coincidence, the vehicle was deployed around the approximate last-known location of the missing aircraft and was recording observations at depths of 3.5 km.

According to him, the NIOT team was not searching for this aircraft that had gone missing eight years ago(for which the massive search had already been abandoned in the same year). However, when they studied the SONAR(Sound Navigation and Ranging) data from the AUV, they noticed strong reflections (indicating the presence of some foreign object on the seafloor).

"Natural objects on the ocean floor have sediments on them and they give very dull SONAR reflections or don't reflect much. However, man-made objects reflect SONAR pings and these reflections give us a clear idea of the presence of foreign objects. The aircraft was not in an intact condition, it was scattered debris. Despite that, we were able to derive adequate data and share it with the Air Force, via the Ministry of Earth Sciences,"Dr S. Ramesh, the Chief Scientist for this operation told WION.

He added that the pre-programmed underwater operation had to be meticulously planned, as they did not have real-time control of the vehicle.

So, the vehicle had to be pre-fed instructions to perform SONAR observations from 30m above the seafloor and imaging observations at 5m above the seafloor, he added. However, thevehicle can only perform in-situ studies and cannot collect or return samples.

On Friday, January 12, 2024, the Indian Defence Ministry announced that the "search images were scrutinised and found to be conforming with an An-32 aircraft". They also reasoned that there was no other recorded history of a missing aircraft report in the same region, and therefore this debris possibly belonged to the crashed IAF An-32 (tail number K-2743). According to the Defence Ministry, the debris was spotted 140nautical miles(approx 310kms) from the Chennai coast.

In the morning hours of July 22,2016, the ill-fated Indian Air Force An-32 plane carrying 29 personnel had taken off from Air Force Station Tambaram, Chennai, on a routine mission to Port Blair, over the Bay of Bengal. As it was flying its 1300kms (approx) journey over the Bay of Bengal, the plane is said to have "disappeared" from radar. Its last-known position was 280 km east of its origin Chennai.

After this incident, the Indian armed forces launched a massive, multi-pronged search and rescue effort, involving ships, submarines and aircraft. With the efforts not yielding results, the search operation had been called off in September of that year, nearly seven weeks after the disappearance.

"Even during the 2016 operation, NIOT had deployed our ships and Remotely Operable Vehicles(ROVs). Back then, we had been carrying out the search from the sea surface using the best assets we had at that time. However, operating SONAR from the surface level does not offer usable results(quality data) at depths of 3000m and more, where we now know that the aircraft is located" DrRamadass explained.