The first ejection seats date back to an early 1940s Swedish designer. From the 1940s to the mid 1960s, ejection seats were designed much like a parachute in that the passenger had to manually control the ejection of the seat. The ejection process primarily consisted of a rocket and compressed air.
Because excessive force was used to initially eject the seat, designers modified the ejection seat beginning in the mid 1960s to include a rocket sustainer. The seat would still be forcefully ejected, though automatically at this time instead of manually. However, the sustainer would moderate the acceleration of the seat, lessening the danger somewhat.
Beginning in the mid 1970s, other safety devices were added including automatic deployment of survival gear and parachute deployment based on altitude. As the computer age expanded, sensors and computers were added to the seats.
Ejecting from an aircraft is typically a last resort. Usually a pilot has no other choice but to eject or risk losing his or her life. Ejection has its own risks, however. The plane is probably flying at extremely high speeds, and just the force of the ejection from a speeding plane can be very dangerous to pilots. Still, the complex structure of ejection seats has saved many lives.
Ejection seats are made so that they move so quickly and with such force that the chair clears the aircraft, leaving no chance that the pilot will come in contact with his damaged or malfunctioning plane. Everything works in a matter of seconds. This is very important because that is probably all the time the pilot has to escape.
Ejection seats look like regular seats, but they have rollers which are attached to rails in the cockpit. The rails are angled in the direction of ascent, and when activated, the chair is catapulted into the air. Activation is either by the pilot pulling a face cover down to protect his face, or when the pilot uses an installed pull handle on the seat.
Once the catapult has vaulted the seat out along the rails, a rocket boosts the seat up and away from the plane. The rocket motor is located under the seat. To keep the pilot’s legs in place and protect them from hitting anything as the seat is propelled, leg restraints are automatically triggered.
Of course, the plane has to have an opening for the pilot and seat to pass through. Most planes either have escape hatches or canopies. Escape hatches are mounted with explosive bolts which are designed to blow off the roof of the plane immediately before the seat is ejected. Canopies, or clear covers, are either signaled by an assisted egress or exit system to detach from the plane, or they have an explosive charge which shatters them before the seat ejects.
It will not take any longer that four seconds for the pilot to eject from the plane after he or she has pulled down the face cover or pulled on the pull handle. After the seat has cleared the plane, a drogue gun fires a metal slug which causes the parachute to pop out of the top of the seat.
The main parachute from the pilot’s pack will inflate on an altitude sensorâ€™s command. After this happens, a seat-man-separator motor ignites causing the seat to separate itself from the pilot. The pilot should then float safely to earth. When you consider the complicated intricacies and timing that surround the construction and use of ejection seats, they really are amazing, life-saving devices.