Ejection of a pilot from an aircraft that is crashing or has been hit is made possible by a special system with rocket power beneath the seat that is activated by the pilot.
The rocket pushes the seat with the pilot upwards by about 30 meters. While this is a life saving measure, ejection from a fighter jet can have serious consequences. This is because of the forces involved.
The forces acting on the body are dependent on the velocity at which the fighter jet is flying. Higher the velocity, greater the impact. The energy transfer to the body is a function of square of the velocity ( E = 1/2 mv2).
When the seat is ejected, first a small chute opens out and as the pilot starts falling down a larger chute opens and the seat falls away. At altitude of about 3000 meters all this happens quickly and there is not much problem of oxygen supply.
Most dogfights of fighters jets occur between 3,000 to 6,000 meters above ground. However if it is at a higher altitude, problems of oxygen deficit could be there so there is a small oxygen cylinder attached to the seat.
If the seat is damaged in the collision or dogfight then the pilot has a serious risk to his life.
Injuries happen because the forces that act on the body are several times the gravitational force (may be as high as 15 times normal G), and the result could be fractures and dislocations.
In a study on ejection injuries, the risk for injuries was approximately 30-50%. Fractures were seen in the thoracic spine (10%), fractures of the legs (12%), and also about 3% had fractures of the arms.
Asymptomatic vertebral fractures were observed in some. Sometimes, the force of ejection can be so great that a pilot's head can suddenly snap forward or back, causing neck or other injuries.
In fact, ejection and aircraft accidents remain the leading cause of vertebral fractures. During an aircraft ejection, the pilot is exposed to accelerations to the point of human tolerance, which may cause spinal injuries.
Many nations have reported a spinal trauma rate of about 20-30%. 42% of them sustained 24 spinal fractures, most of the time with a simple compression of the thoracic segment. Most of the injuries occurred on parachute landing (40%).
They could have serious ankle injuries on landing. Overall, the main reasons for severe injury were parachute landing impact (69%) and Ejection Mechanism failure (23%).
One must admire the courage of Wing Cdr. Abhinav who must have known all the risks of ejection and chose to eject daring to brave the consequences.
Dr. Mathew Varghese is Senior consultant and Head, Department of Orthopedics, St.Stephen's Hospital, Delhi