In 1962 the United States Air Force was working furiously to develop an ejection system for
pilots of the new Convair B-58 Hustler.
The first jet bomber capable of mach 2 flight.
Bailing out at the speeds and altitudes the B-58 was designed for with conventional ejection
seats of that era would have resulted, at best, n severe injury.
Windblast would have likely rip your helmet and air supply off, the force of air would
violently contort your limbs, with the explosive thrust of the ejection seat compressing your
spine, and if all that didn’t kill you.
You may just freeze to death, with eternal temperatures dipping to as low as -50 degrees
celsius.
And so the Stanley Aviation Company and Convair began a partnership to develop a fully enclosed
escape capsule, which would fold shut before ejection and shelter the crewmen from the
environment, but they couldn’t start testing this new concept on humans.
The conditions were simply too hostile to risk a human on, so they came to the next
logical alternative.
The United States Air Force strapped a drug up Black Bear called Yogi into the capsule
and launched it at 35,000 feet at supersonic speeds.
[1]
So how the hell did the world of aviation come to the point of needing to fire live
black bears at supersonic speeds?
Ejection seats were not always necessary in flight.
At the relatively slow speeds of WW1 and early WW2 era planes pilots could simply unstrap
their restraints and jump overboard, like this German pilot being pursued by an RAF
Tempest.
But as the war progressed and jet propulsion technology advanced, British Intelligence
began to receiving reports of German pilots being “fired into the sky” from defeated
German jets.
As usual, the Germans were well head of the competition in experimenting with new technology,
and the medical branch of the Luftwaffe was busy testing the physical limits of the human
body to withstand G forces.
The designers of these devices had a difficult balancing act to co-ordinate.
It was essential that the ejection provided enough acceleration for the pilot to safely
clear the aircraft, while not accelerating them so fast that they could suffer injury.
The first thing these designers needed to consider was how to power a device like this.
They needed a way of storing potential energy that could be released rapidly in order to
achieve the necessary acceleration in an emergency situation.
Early designs simple called the pilot to manually release the canopy before triggering a compressed
spring that would hopefully launch the pilot clear of the plane like some sort of Wile
Coyote scene.
This had some obvious inherent flaws.
The springs did not possess the necessary potential energy to launch the weight of the
pilot and seat upwards to safety, and requiring the pilot to manually release the canopy in
an emergency situation was incredibly dangerous.
As Douglas Davie discovered to his demise in 1944, during a test flight of the the British
prototype twin-engined jet fighter, the Meteor.
While performing a high speed test the aircraft lost one of it’s engines sending it into
an uncontrollable spin due to differential thrust.
At this time Britain had not put serious consideration into escape mechanisms, and Davie was forced
to open the canopy manually, which snapped shut and severed his arm.
He was then either then thrown out of the plane by the g-forces of the hurtling aircraft,
or somehow managed to haul himself out.
Only to be critically injured by the aircraft’s tailplane. [2]
This gruesome event highlighted to the British the need to develop ejection mechanisms, and
with the end of the war coming, they would have plenty of German engineering to gain
inspiration from.
The Germans were racing ahead of the competition, thanks to the huge amount of resources the
Germans poured into experimental aircraft.
By definition, these aircraft were unpredictable, and so the Germans also lead the way in developing
escape mechanisms.
Helping save talented test pilots like Helmut Schenk, who was the first man in history to
use an ejection seat in an emergency situation, while testing the Heinkel He-280 jet fighter.
This seat did not use springs to power the ejection, but compressed air.
An important improvement in energy storage, but required a significant amount of additional
mechanisms and heavy parts to operate, like valves and pressurised air tanks.
Despite the relatively cumbersome design of these ejections seats, by the end of the war
it is reported that up to 60 luftwaffe airmen had used these devices to escape their aircraft,
and every experimental aircraft the Germans tested came equipped with an ejection seat.
After the war the Allies took over as the forerunners of ejection seat design.
Most notably by an Irish engineer, James Martin.
Who founded the Martin-Baker company alongside Captain Valentine Baker.
They conducted their own tests of human endurance using this tripod launcher.
Another Irish man, Bernard Lynch, being the brave human guinea pig.
They used an explosive cartridge to power the launch, instead of compressed air, and
gradually upped the explosive power.
With explosive upward trajectories like, injury becomes much more likely if the pilot does
not remain upright in his seat, a difficult task when under such immense g-forces.
And so Martin Baker cleverly built the trigger into a retractable head cover which restrained
the pilots head in an upright position, and protected it from windblast.
While revolutionary in it’s design this ejection seat was incredibly simple compared
to modern ejection seats.
Every step of the process was manually except for the deployment of the drogue shoot, which
was triggered when a fifteen foot wire attached to the firing mechanism and the cockpit floor
reached the end of it’s line on ejection.
The pilot needed to jettison the canopy manually, pull the face curtain trigger, wait as the
drogue shoot decelerated and stabilised his fall, then unbuckle his belts and jump clear
of the seat to deploy his own parachute.
An impossible task if the pilot was knocked unconscious during the ejection sequence.
Martin-Baker won a contract with the RAF for all future aircraft to be fitted with this
first generation seat, and it saved it’s first life in 1949 when Jo Lancaster was testing
the Armstrong Whitsworth A.W.52, an experimental flying wing aircraft, which entered an uncontrollable
pitch oscillation due to aerodynamic flutter of it’s elevons.
Lancaster escaped and survived to tell the story, but there was plenty of work left to
do.
Lancaster was lucky, as the problem was encountered at relatively high altitude.
Leaving him plenty of time to deploy his parachute, but most problems occur during take off and
landing, and so the next vital step in ejection seat design was developing a zero-zero ejection
seat.
A seat capable of saving the pilots life at zero velocity, and zero altitude.
Here we are beginning to strike the limit of human endurance.
To safely evacuate an aircraft at an altitude this low would require significant sustained
acceleration to ensure clearance of a crash and an explosion, and provide enough height
to safely deploy a parachute.
With tolerances this tight we first need to automate more steps.
By the 1960s both Martin-Baker, and their American counterpart Weber were developing
these zero-zero seats.
[5] By this time Webers seats had saved over 500 lives, and had been fitted in aircraft
like the f-106 and the gemini space capsule.
The F-106 served in the US Air Force for over 40 years and during that time was fitted with
three different ejection seats.
The interim seat, the Supersonic Rotational B-seat, and finally the zero-zero Rocat. [7]
Each showing the gradual change in design ethos to what would eventually become the
modern day standard design template.
The interim seat was highly automated, with a carefully choreographed ballet of mechanical
triggers
like an advanced rube goldberg machine, all starting with the pilot pulling these ejection
handles.
Triggering an explosive initiator [5] to fire which would began a chain reaction of events
through the hot gas emanating its fix volume chamber.
This hot gas would flow through ballistic hoses to other firing pins in propellant powered
actuators, the pressure of the gas would remove the firing pins.
Allowing the actuators to fire and unlatch the canopy, and forcefully remove it from
the aircraft.
As the canopy cleared the aircraft it would pull a lanyard, which would trigger the explosive
cartridge that would lift the seat clear of the plane.
As the seat travelled up the rails it would impact another trigger firing a final time
delayed initiator, which would activate the drogue shoot and release the seat buckles.
The pilot would then either freefall, or, if they had attached their zero delay lanyard,
would have their parachute deployed automatically as they fell free of the seat.
This carefully timed sequence was a massive improvement to manual steps of old, but it
was missing two vital things.
It was not capable of supersonic ejections or zero-zero ejections.
Initially pilots pushed for supersonic capabilities, and so one of the most intricate and fascinating
ejection seats in history, the B-seat, was developed.
This seat was designed to raise and rotate into the airstream, where the bottom of the
seat would protect the crew from airblast and act as an aerodynamic surface to provide
lift, raising the seat away from the aircraft.
At this speed the seats need extra lift to ensure they will clear the plane on time,
and to help with that goal rocket motors would fire to lift the seat to safety.
The seat had two telescoping booms that helped stop the seat from rolling violently on ejection.
This was an ingenious design, but absurdly complicated with over 30 pyrotechnic devices
from initiators, explosive bolts and wire cutters.
This complexity led to a number of fatal ejections, and with mounting statistical evidence that
supersonic ejections were much less likely than a slow and low ejection, a replacement
was requested.
And thus the zero-zero seat was developed, using the interim seat as a base.
Adding rocket motors to provide the necessary height to clear the plane after the initial
ejection, and adding an explosively deployed parachute to ensure it opened quickly.
Unlike the escape capsule of the B-58 this system was not tested with a bear.
It was tested by a lunatic by the name of Jim Hall.
Jim Hall is quoted saying “I have been kicked in the ass harder than that”.
This may well have been the source of the liar liar pants on fire phrase.
This zero-zero design has been the template for all ejection seats since, with Martin-Baker
becoming the world leading manufacturer adding incremental improvements over the past 60
years.
Adding sensors and flight computers, along with vectoring nozzles for the rockets to
ensure the optimum trajectory of the seat, even with the plane rolled upside down.
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