“Spatial disorientation” of the pilot flying the helicopter in which former Chief of Defence Staff Bipin Rawat died led to the chopper’s crash, a court of inquiry said in a preliminary finding. The term refers to the inability of a person to determine true body position, motion and altitude.

Bipin Rawat and 12 others, including his wife Madhulika Rawat, had died when their helicopter crashed near Coonoor, Tamil Nadu, on December 8. The only survivor, Air Force group Captain Varun Singh, had also succumbed to his injuries on December 15.

In a statement on Friday, the ministry said that the chopper entered into the clouds due to an unexpected change in weather. “This led to spatial disorientation of the pilot resulting in Controlled Flight into Terrain,” it said.

The United States’ Federal Aviation Administration defines Controlled Flight into Terrain as an “unintentional collision with terrain”, including ground, mountain or a body of water, when the aircraft is under the pilot’s control.

In its statement, the ministry also said that the court of inquiry has ruled out any mechanical failure, sabotage or negligence as a cause of the accident.

“Based on its findings, the court of inquiry has made certain recommendations which are being reviewed,” the statement said.

The inquiry panel’s findings are based on the analysis of the the flight data recorder and cockpit voice recorder as well as “questioning all available witnesses” to ascertain the most probable cause of the accident, the statement added.