The pilots’ “spatial disorientation” led to the helicopter crashing into the ground
By Vikas Gupta
Defence News of India, 14 Jan 22
A Tri-Service Court of Inquiry has presented its preliminary findings into the Mi-17 V5 helicopter crash that killed Chief of the Defense Staff General Bipin Rawat and 12 others on December 8.
According to a Ministry of Defense (MoD) press release on Friday, “the investigation team analyzed the Flight Data Recorder (FDR) and Cockpit Voice Recorder (CVR), in addition to interview all available witnesses to determine the most probable cause of the accident.”
“The court of inquiry ruled out mechanical failure, sabotage or negligence as the cause of the crash. The crash was the result of cloud entry due to an unexpected change in weather conditions in the valley This led to spatial disorientation of the pilot resulting in controlled flight into terrain,” the Court of Inquiry said.
“Controlled Flight into Terrain”, or CFIT, is the dark term used to describe an aircraft hitting the ground while the pilot(s) have full control of the machine.
Spatial disorientation is the inability of a pilot to correctly interpret an aircraft’s attitude, altitude, or speed relative to the ground or other reference points. It is more critical at night or in bad weather, when there is no visible horizon, because vision is the dominant sense of orientation.
For example, a pilot flying above the snow with the sky obscured, loses his depth perception. Or a pilot flying in cloud, or in poor weather conditions when the horizon is not visible, may feel like they are leaning left or right as they fly straight and in landing. This could lead to over-correction, which could be disastrous if the pilot does not recover in time.
According to Wing Commander Abdul Naseer Hanfee, a decorated helicopter pilot who has extensive experience flying the Mi-17 helicopter in the Nilgiri Mountains, where the crash occurred, there is often a huge accumulation of humidity in these hills which turns into clouds. when the temperature rises.
When helicopter pilots try to fly through these clouds, they become disoriented in space, causing them to crash into the ground.
Experienced pilots, such as the two who flew this helicopter, would return to their base at Sulur, outside Coimbatore, and return when the clouds cleared somewhat. The investigation did not mention why the pilots did not do this.
Lessons will be learned from this accident, Hanfee said. This is also apparent from the Ministry of Defense statement, which states: “Based on its findings, the Court of Inquiry has made certain recommendations which are under review.”
