Ejection seat

Various ejection seats

In aircraft, an ejection seat or ejector seat is a system designed to rescue the pilot or other crew of an aircraft (usually military) in an emergency. In most designs, the seat is propelled out of the aircraft by an explosive charge or rocket motor, carrying the pilot with it. The concept of an ejectable escape crew capsule has also been tried. Once clear of the aircraft, the ejection seat deploys a parachute. Ejection seats are common on certain types of military aircraft.


Martin-Baker WY6AM ejection seat.
United States Air Force F-15 Eagle ejection seat test using a mannequin.

A bungee-assisted escape from an aircraft took place in 1910. In 1916 Everard Calthrop, an early inventor of parachutes, patented an ejector seat using compressed air. [1]

The modern layout for an ejection seat was first proposed by Romanian inventor Anastase Dragomir in the late 1920s. The design, featuring a parachuted cell (a dischargeable chair from an aircraft or other vehicle), was successfully tested on 25 August 1929 at the Paris-Orly Airport near Paris and in October 1929 at Băneasa, near Bucharest. Dragomir patented his "catapult-able cockpit" at the French Patent Office. [note 1]

The design was perfected during World War II. Prior to this, the only means of escape from an incapacitated aircraft was to jump clear ("bail out"), and in many cases this was difficult due to injury, the difficulty of egress from a confined space, g forces, the airflow past the aircraft, and other factors.

The first ejection seats were developed independently during World War II by Heinkel and SAAB. Early models were powered by compressed air and the first aircraft to be fitted with such a system was the Heinkel He 280 prototype jet-engined fighter in 1940. One of the He 280 test pilots, Helmut Schenk, became the first person to escape from a stricken aircraft with an ejection seat on 13 January 1942 after his control surfaces iced up and became inoperative. The fighter, being used in tests of the Argus As 014 impulse jets for Fieseler Fi 103 missile development, had its usual HeS 8A turbojets removed, and was towed aloft from the Erprobungsstelle Rechlin central test facility of the Luftwaffe in Germany by a pair of Bf 110C tugs in a heavy snow-shower. At 2,400 m (7,875 ft), Schenk found he had no control, jettisoned his towline, and ejected. [2] The He 280 was never put into production status and the first operational type built anywhere, to provide ejection seats for the crew was the Heinkel He 219 Uhu night fighter in 1942.

In Sweden, a version using compressed air was tested in 1941. A gunpowder ejection seat was developed by Bofors and tested in 1943 for the Saab 21. The first test in the air was on a Saab 17 on 27 February 1944, [3] and the first real use occurred by Lt. Bengt Johansson [note 2] on 29 July 1946 after a mid-air collision between a J 21 and a J 22. [4]

As the first operational military jet in late 1944 to ever feature one, the lightweight Heinkel He 162A Spatz featured a new type of ejection seat, this time fired by an explosive cartridge. In this system, the seat rode on wheels set between two pipes running up the back of the cockpit. When lowered into position, caps at the top of the seat fitted over the pipes to close them. Cartridges, basically identical to shotgun shells, were placed in the bottom of the pipes, facing upward. When fired, the gases would fill the pipes, "popping" the caps off the end, and thereby forcing the seat to ride up the pipes on its wheels and out of the aircraft. By the end of the war, the Dornier Do 335 Pfeil — primarily from it having a rear-mounted engine (of the twin engines powering the design) powering a pusher propeller located at the aft end of the fuselage presenting a hazard to a normal "bailout" escape — and a few late-war prototype aircraft were also fitted with ejection seats.

After World War II, the need for such systems became pressing, as aircraft speeds were getting ever higher, and it was not long before the sound barrier was broken. Manual escape at such speeds would be impossible. The United States Army Air Forces experimented with downward-ejecting systems operated by a spring, but it was the work of Sir James Martin and his company Martin-Baker that was to prove crucial.

Seat on display at RAF Museum Cosford.

The first live flight test of the Martin-Baker system took place on 24 July 1946, when fitter Bernard Lynch ejected from a Gloster Meteor Mk III jet. Shortly afterward, on 17 August 1946, 1st Sgt. Larry Lambert was the first live U.S. ejectee. Lynch demonstrated the ejection seat at the Daily Express Air Pageant in 1948, ejecting from a Meteor. [5] Martin-Baker ejector seats were fitted to prototype and production aircraft from the late 1940s, and the first emergency use of such a seat occurred in 1949 during testing of the jet-powered Armstrong Whitworth A.W.52 experimental flying wing.

Early seats used a solid propellant charge to eject the pilot and seat by igniting the charge inside a telescoping tube attached to the seat. As aircraft speeds increased still further, this method proved inadequate to get the pilot sufficiently clear of the airframe. Increasing the amount of propellant risked damaging the occupant's spine, so experiments with rocket propulsion began. In 1958, the Convair F-102 Delta Dagger was the first aircraft to be fitted with a rocket-propelled seat. Martin-Baker developed a similar design, using multiple rocket units feeding a single nozzle. The greater thrust from this configuration had the advantage of being able to eject the pilot to a safe height even if the aircraft was on or very near the ground.

An Aviation Structural Mechanic works on an ejection seat removed from the cockpit of an EA-6B Prowler aboard USS John C. Stennis.

In the early 1960s, deployment of rocket-powered ejection seats designed for use at supersonic speeds began in such planes as the Convair F-106 Delta Dart. Six pilots have ejected at speeds exceeding 700 knots (1,300 km/h; 810 mph). The highest altitude at which a Martin-Baker seat was deployed was 57,000 ft (17,400 m) (from a Canberra bomber in 1958). Following an accident on 30 July 1966 in the attempted launch of a D-21 drone, two Lockheed M-21 [6] crew members ejected at Mach 3.25 at an altitude of 80,000 ft (24,000 m). The pilot was recovered successfully, but the launch control officer drowned after a water landing. Despite these records, most ejections occur at fairly low speeds and altitudes, when the pilot can see that there is no hope of regaining aircraft control before impact with the ground.

Late in the Vietnam War, the U.S. Air Force and U.S. Navy became concerned about its pilots ejecting over hostile territory and those pilots either being captured or killed and the losses in men and aircraft in attempts to rescue them. Both services began a program titled Air Crew Escape/Rescue Capability or Aerial Escape and Rescue Capability (AERCAB) ejection seats (both terms have been used by the US military and defence industry), where after the pilot ejected, the ejection seat would fly him to a location far enough away from where he ejected to where he could safely be picked up. A Request for Proposals for concepts for AERCAB ejection seats were issued in the late 1960s. Three companies submitted papers for further development: A Rogallo wing design by Bell Systems; a gyrocopter design by Kaman Aircraft; and a mini-conventional fixed wing aircraft employing a Princeton Wing (i.e. a wing made of flexible material that rolls out and then becomes rigid by means of internal struts or supports etc. deploying) by Fairchild Hiller. All three, after ejection, would be propelled by small turbojet engine developed for target drones. With the exception of the Kaman design, the pilot would still be required to parachute to the ground after reaching a safety-point for rescue. The AERCAB project was terminated in the 1970s with the end of the Vietnam War. [7] The Kaman design, in early 1972, was the only one which was to reach the hardware stage. It came close to being tested with a special landing-gear platform attached to the AERCAB ejection seat for first-stage ground take offs and landings with a test pilot. [8]

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