In aircraft, an ejection 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.
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, 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, 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, Schenk found he had no control,
jettisoned his towline, and ejected. 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, 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 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 Sir James Martin and his company Martin-Baker that
was to prove 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 U.S. 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 700 knots. 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 80,000 ft 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 ejection
seats, 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 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 ACES II seat in inverted flight is about 140
feet above ground level at 150 KIAS, while the Russian counterpart - K-36DM
has the minimal ejection altitude from inverted flight of 100 feet AGL. When an
aircraft is equipped with the Zvezda K-36DM ejection seat and the pilot is
wearing the КО-15 protective gear, he is able to eject at airspeeds from 0 to
1,400 kilometres per hour and altitudes of 0 to 25 km. 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.
Documented evidence exists that pilots of the US and Indian navies have
performed this feat. As of 20 June 2011 – when two Spanish
Air Force pilots ejected over San Javier airport – the 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 him pull a screen
down to protect both his 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. Egress systems
The "standard" ejection system operates in two stages. First, the entire canopy
or hatch above the aviator is opened or jettisoned, and the seat and occupant
are launched through the opening. In most earlier aircraft this required two
separate actions by the aviator, while later egress system designs, such as the
Advanced Concept Ejection Seat model 2, perform both functions as a single
action. The ACES II ejection seat is used in
most American-built fighters. The A-10 uses connected firing handles that
activate both the canopy jettison systems, followed by the seat ejection.
The F-15 has the same connected system as the A-10 seat. Both handles
accomplish the same task, so pulling either one suffices. The F-16 has only
one handle located between the pilot's knees, since the cockpit is too narrow
for side-mounted handles. Non-standard egress systems include
Downward Track, Canopy Destruct and Through-Canopy Penetration, Drag
Extraction, Encapsulated Seat, and even Crew Capsule.
Early models of the F-104 Starfighter were equipped with a Downward Track
ejection seat due to the hazard of the T-tail. In order to make this work, the
pilot was equipped with "spurs" which were attached to cables that would pull
the legs inward so the pilot could be ejected. Following this development,
some other egress systems began using leg retractors as a way to prevent
injuries to flailing legs, and to provide a more stable center of gravity.
Some models of the F-104 were equipped with upward-ejecting seats.
Similarly, two of the six ejection seats on the B-52 Stratofortress fire
downward, through hatch openings on the bottom of the aircraft; the downward
hatches are released from the aircraft by a thruster that unlocks the hatch,
while gravity and wind remove the hatch and arm the seat. The four seats on the
forward upper deck fire upwards as usual. Any such downward-firing system
is of no use on or near the ground if aircraft is in level flight at the time
of the ejection. Aircraft designed for low-level use
sometimes have ejection seats which fire through the canopy, as waiting for the
canopy to be ejected is too slow. Many aircraft types use Canopy Destruct
systems, which have an explosive cord embedded within the acrylic plastic of
the canopy. The MDC is initiated when the eject handle is pulled, and shatters
the canopy over the seat a few milliseconds before the seat is
launched. This system was developed for the Hawker Siddeley Harrier family of
VTOL aircraft as ejection may be necessary while the aircraft was in the
hover, and jettisoning the canopy might result in the pilot and seat striking
it. This system is also used in the T-6 Texan II and F-35 Lightning II.
Through-Canopy Penetration is similar to Canopy Destruct, but a sharp spike on
the top of the seat, known as the "shell tooth," strikes the underside of the
canopy and shatters it. The A-10 Thunderbolt II is equipped with canopy
breakers on either side of its headrest in the event that the canopy fails to
jettison. The T-6 is also equipped with such breakers if the MDC fails to
detonate. In ground emergencies, a ground crewman or pilot can use a
breaker knife attached to the inside of the canopy to shatter the transparency.
The A-6 Intruder and EA-6B Prowler seats are capable of ejecting through the
canopy, with canopy jettison a separate option if there is enough time.
CD and TCP systems cannot be used with canopies made of flexible materials,
such as the Lexan polycarbonate canopy used on the F-16.
Soviet VTOL naval fighter planes such as the Yakovlev Yak-38 were equipped with
ejection seats which were automatically activated during at least some part of
the flight envelope. Drag Extraction is the lightest and
simplest egress system available, and has been used on many experimental
aircraft. Halfway between simply "bailing out" and using explosive-eject
systems, Drag Extraction uses the airflow past the aircraft to move the
aviator out of the cockpit and away from the stricken craft on a guide rail. Some
operate like a standard ejector seat, by jettisoning the canopy, then deploying a
drag chute into the airflow. That chute pulls the occupant out of the aircraft,
either with the seat or following release of the seat straps, who then
rides off the end of a rail extending far enough out to help clear the
structure. In the case of the Space Shuttle, the astronauts would have
ridden a long, curved rail, blown by the wind against their bodies, then deployed
their chutes after free-falling to a safe altitude.
Encapsulated Seat egress systems were developed for use in the B-58 Hustler
and B-70 Valkyrie supersonic bombers. These seats were enclosed in an
air-operated clamshell, which permitted the aircrew to escape at airspeeds and
altitudes high enough to otherwise cause bodily harm. These seats were designed
to allow the pilot to control the plane even with the clamshell closed, and the
capsule would float in case of water landings.
Some aircraft designs, such as the General Dynamics F-111, do not have
individual ejection seats, but instead, the entire section of the airframe
containing the crew can be ejected as a single capsule. In this system, very
powerful rockets are used, and multiple large parachutes are used to bring the
capsule down, in a manner similar to the Launch Escape System of the Apollo
spacecraft. On landing, an airbag system is used to cushion the landing, and this
also acts as a flotation device if the Crew Capsule lands in water.
= Zero-zero ejection seat= A zero-zero ejection seat is designed to
safely extract upward and land its occupant from a grounded stationary
position, specifically from aircraft cockpits. The zero-zero capability was
developed to help aircrews escape upward from unrecoverable emergencies during
low-altitude and/or low-speed flight, as well as ground mishaps. Before this
capability, ejections could only be performed above minimum altitudes and
airspeeds. Zero-zero technology uses small rockets
to propel the seat upward to an adequate altitude and a small explosive charge to
open the parachute canopy quickly for a successful parachute descent, so that
proper deployment of the parachute no longer relies on airspeed and altitude.
Other aircraft The Kamov Ka-50, which entered limited
service with Russian forces in 1995, was the first production helicopter with an
ejection seat. The system is similar to that of a conventional fixed-wing
aircraft however the main rotors are equipped with explosive bolts to
jettison the blades moments before the seat is fired.
The Lunar Lander Research Vehicle/Training Vehicle used ejection
seats. Neil Armstrong ejected on 6 May 1968; Joe Algranti & Stuart M. Present,
later. Early flights of NASA's Space Shuttle,
which used Columbia, were with a crew of two, both provided with ejector seats,,
but the seats were disabled and then removed as the crew size was increased.
Columbia and Enterprise were the only two shuttle orbiters fitted with
ejection seats. The Soviet shuttle "Buran" was planned
to be fitted with K-36RB seats, but it was unmanned on its single flight; the
seats were never installed. The only spacecraft ever flown with
installed ejection seats were the Space Shuttle, the Soviet Vostok and American
Gemini series. See also
Caterpillar Club Escape pod
Dynamic response index Lifeboat
Pressure suit References
Notes Citations
External links "Up, Out and Down - 1952 Flight article
"Safety for Service Aircrew" - 1965 Flight article
The Ejection Site Ejection History
Picture and specifications of an ejection seat
A History of Military Aircraft Egress Systems by Kalikiano Kalei
Pilot ejects before a fighterjet crash