Ejection seat
In aircraft, an ejection seat or ejector seat is a system designed to rescue the pilot or other crew of an aircraft 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.
History
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. Compression springs installed under the seat were tested.The modern layout for an ejection seat was first introduced by Romanian inventor Anastase Dragomir in the late 1920s. The design featured a parachuted cell. It 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.
The design was perfected during World War II. Prior to this, the only means of escape from an incapacitated aircraft was to jump clear, 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 was being used in tests of the Argus As 014 impulse jets for V-1 flying bomb development. It had its usual Heinkel HeS 8A turbojets removed, and was towed aloft from the Erprobungsstelle Rechlin central test facility of the Luftwaffe in Germany by a pair of Messerschmitt Bf 110C tugs in a heavy snow-shower. At, Schenk found he had no control, jettisoned his towline, and ejected. The He 280 was never put into production status. 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, and the first real use occurred by Lt. Bengt Johansson. on 29 July 1946 after a mid-air collision between a J 21 and a J 22.
As the first operational military jet in late 1944 to ever feature one, the winner of the German Volksjäger "people's fighter" home defense jet fighter design competition; 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 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 James Martin from Northern Ireland and his company Martin-Baker that proved crucial.
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 US ejectee. Lynch demonstrated the ejection seat at the Daily Express Air Pageant in 1948, ejecting from a Meteor. 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.
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. The highest altitude at which a Martin-Baker seat was deployed was 57,000 ft . Following an accident on 30 July 1966 in the attempted launch of a D-21 drone, two Lockheed M-21 crew members ejected at Mach 3.25 at an altitude of. 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 US Air Force and US 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 ejection seats, where after the pilot ejected, the ejection seat would fly them to a location far enough away from where they ejected to where they 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 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. 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.
Pilot safety
The purpose of an ejection seat is pilot survival. The pilot typically experiences an acceleration of about 12–14 g. Western seats usually impose lighter loads on the pilots; 1960s–70s era Soviet technology often goes up to 20–22 g. Compression fractures of vertebrae are a recurrent side effect of ejection.It was theorised early on that ejection at supersonic speeds would be unsurvivable; extensive tests, including Project Whoosh with chimpanzee test subjects, were undertaken to determine that it was feasible.
The capabilities of the NPP Zvezda K-36 were unintentionally demonstrated at the Fairford Air Show on 24 July 1993 when the pilots of two MiG-29 fighters ejected after a mid-air collision.
The minimal ejection altitude for the ACES II seat in inverted flight is about above ground level at, while the Russian counterpart, the K-36DM, has a minimal ejection altitude from inverted flight of.
When an aircraft is equipped with the NPP Zvezda K-36DM ejection seat and the pilot is wearing the КО-15 protective gear, they are able to eject at airspeeds from 0 to and altitudes of 0 to. The K-36DM ejection seat features drag chutes and a small shield that rises between the pilot's legs to deflect air around the pilot.
Pilots have successfully ejected from underwater in a handful of instances after being forced to ditch in water. The first recorded case was Lieutenant B. D. Macfarlane of the Royal Navy Fleet Air Arm when he successfully ejected underwater using his Martin-Baker Mk.1 ejection seat after his Westland Wyvern had ditched on launch and been cut in two by the carrier on 13 October 1954. Documented evidence also exists that pilots of the US and Indian navies have also performed this feat.
when two Spanish Air Force pilots ejected over San Javier airportthe number of lives saved by Martin-Baker products was 7,402 from 93 air forces. The company runs a club called the "Ejection Tie Club" and gives survivors a unique tie and lapel pin. The total figure for all types of ejection seats is unknown, but may be considerably higher.
Early models of the ejection seat were equipped with only an overhead ejection handle which doubled in function by forcing the pilot to assume the right posture and by having them pull a screen down to protect both their face and oxygen mask from the subsequent air blast. Martin Baker added a secondary handle in the front of the seat to allow ejection even when pilots weren't able to reach upwards because of high g-force. Later the top handle was discarded because the lower handle had proven easier to operate and the technology of helmets had advanced to also protect from the air blast.