How ocean scientists came upon IAF aircraft missing for 7.5 years

Over seven years after an Indian Air Force (IAF) AN-32 aircraft went missing in 2016, scientists at the Chennai-based National Institute of Ocean Technology (NIOT) stumbled upon its debris when they were testing the instruments of their newly acquired autonomous underwater vehicle (AUV) for seabed mapping in December.

It was during such a testing expedition undertaken by scientists from NIOT, the National Institute of Oceanography and the National Centre for Polar and Ocean Research onboard Research Vessel Sagar Nidhi on December 9-10 last year, about 310 km off the Chennai coast, the instruments on the AUV picked up some strong SONAR reflections from the seabed at a depth of 3,400 m.

The strong signals intrigued the scientists who then decided to guide the AUV to dive deeper for a closer look.

"Then we dived a little deeper and took some photographs which were shared with the Indian Air Force through the Ministry of Earth Sciences," G A Ramadass, Director, NIOT told PTI.

S Ramesh, a deepsea technology expert at NIOT, said the strong sonar signals were picked up by the AUV when it was 30 meters from the seabed.

"We then took it closer to about five meters from the ocean bed where the debris was found," he said.

Ramadass said the photographs were very clear and there was not much sedimentation even seven years after the accident.

Ramadass said the IAF confirmed that the debris was of the AN32 aircraft that had gone missing more than seven years ago.

Another scientist said initially the debris was thought to be of a shipwreck, but on closer examination, the researchers were able to identify the tricolour roundel found on IAF aircraft.

The scientists were carrying out the instrument testing of the AUV at the same site which was the last known location of the IAF aircraft that went missing on July 22, 2016, with 29 personnel onboard.

The NIOT joined the search operations in July 2016 along with other agencies and used surface ships and remotely operated vehicles for the purpose.

"At that time we did not find anything," Ramadass said, adding that the scientists stumbled upon the debris while calibrating instruments of the AUV.

A defence ministry statement said the search by NIOT was conducted at a depth of 3,400 metres using multiple payloads, including a multi-beam SONAR, synthetic aperture SONAR and high-resolution photography.

The Defence Ministry said scrutiny of the images captured by an autonomous underwater vehicle (AUV) deployed by the National Institute of Ocean Technology recently found to be confirming that the wreckage located 310 km off the Chennai coast is of an An-32 aircraft.

'The search images were scrutinised and found to be conforming with an An-32 aircraft. This discovery at the probable crash site, with no other recorded history of any other missing aircraft report in the same area, points to the debris as possibly belonging to the crashed IAF An-32,' the ministry said in a statement.

The AUV, procured from Norway in 2022, can dive up to a depth of 6,000 meters to map the seabed and was on an expedition to look for gas hydrates in the Bay of Bengal.

N R Ramesh, a senior scientist at NIOT, said the AUV can be pre-programmed for carrying out underwater surveys and its entire journey can be monitored from the research vessel.

A single mission of the AUV takes about 26-28 hours from lowering into the sea to its retrieval after the survey.