Now, focus shifts to cause of IAF chopper crash in Tamil Nadu

New Delhi: The nation's focus has now shifted to the probe into the December 8 horrific IAF helicopter crash that killed the Chief of Defence Staff, General Bipin Rawat, and 12 others at Coonoor in Tamil Nadu's Nilgiri district.

Air Marshal Manavendra Singh, who is leading the inquiry into the chopper crash, is the most experience helicopter pilot of the Indian Air Force. Currently the Air Officer Commander in Chief, Training Command, in Bengaluru, Air Marshal Singh had earlier headed the Thiruvananthapuram-headquartered Southern Air Command.

The probe team has as its members senior officers from the aviation wings of the Army, Navy and Air Force.

Term of reference
The first question being probed is what caused the crash.
There are three possibilities:
1. The rotors hitting the mountain or a tree
2. Heavy mist hampering visibility, leading to the chopper crash into the mountain (CFIT: Controlled flight into terrain. It occurs when an airworthy aircraft under the pilot's complete control, inadvertently flies into an obstacle)
3. Crash while airborne. It could occur if an on-board explosive goes off.

Probe method
The remains of the chopper will be collected from the scene of crash and they will be assembled at the IAF airbase at Sulur in Coimbatore. The crash could vary according to the circumstances, and it is called a disintegration pattern. Assembling the parts, and subjecting them to forensic tests will reveal the possible cause of the crash.

The second question pertains to what had led to the crash. The probe team will rely on the now-retrieved flight data recorder, widely known as the black box, and the cockpit voice recorder. Both the recorders are now in the custody of the investigating team.

The team may seek the assistance of Russian experts, if the recorders have been damaged. The Mi-17 V5 helicopter that had crashed was made in Russia.

Incidentally, the flight data recorders of a Lockheed Martin-made C-130J Super Hercules military transport aircraft that had crashed at Gwalior in Madhya Pradesh in 2014 March, and of an Indian Coast Guard's Dornier that crashed into the sea off the Tamil Nadu coast in June, 2015, were sent to the US for retrieving information.

The events before the takeoff and the helicopter's technical aspects, too, will be probed. The statements of engineers who maintained the chopper, and the Commanding Officer of Sulur air base will be recorded to ascertain who had cleared the flight despite inclement weather.

Helicopters are banned from flying VIPs in bad weather conditions. The investigators will also try to ascertain whether General Rawat insisted on flying to Wellington in adverse weather conditions. Even if the General had insisted, rules mandated the pilot against flying.

The Indian Air Force has classified the Nilgiri mountain ranges as a grey zone. It means that the area is prone to sudden, unexpected changes in weather conditions after 11 am. There is an unwritten rule that VIP flights in grey zones should reach their destination before 11 am. The ill-fated helicopter, however, took off from Sulur at 11.48 am. It has to ascertained whether the General and his entourage were late in reaching Sulur from Delhi.

Sabotage angle

Military sources said the possibility of a sabotage leading to the crash was slim. However, the probe team will be investigating a sabotage angle also.

Statement of Group Captain Varun Singh

Group Captain Varun Singh, battling serious burn injuries sustained in the crash, is the only person who could provide a clear picture of the incident. He is currently undergoing treatment in the Military Hospital at Bengaluru. His statement will be recorded once he is out of danger.

Final message

"Descending to the land" was the last message Sulur air base received from the helicopter.

At 12.08 pm, the airbase lost contact with the chopper, which had left Sulur at 11.48 am. The final message was received a few minutes before the last contact.

It has been believed that the pilot would have alerted the air control if he had foreseen any danger.

There are strong indications that a 'white out' after the helicopter had descended and flew into the mist led it to crash into the mountain or a tree. A white out is blindness caused by exposure to sudden light or heavy mist.

In such circumstances, helicopter pilots are supposed to ascend and change course. The probe team will also check if Wing Commander Prithvi Singh Chauhan had executed this manoeuvre.