“Who saves a life, saves all mankind”

(Proverbs of the Talmud opening the film “Schindler’s List”)

It was past midnight on June 10, 1969 when the Vought A-7 Corsair II aircraft approached for landing aboard the USS Constellation (CV-64) on the south coast of California with good visibility and calm sea. The pilot flew the stabilized glideslope and “on the ramp”, with the appropriate descent rate, hooking the tailhook at 135 kt on cable number 03. Unfortunately, perhaps because of a gust of wind by a starboard or insufficient pressure on the pedals, he ended up landing misaligned with the longitudinal axis of the ship, sliding to port. The number 03, not withstanding the traction, broke, and the aircraft eventually plunged into the icy waters of the Pacific Ocean.

From this moment, everything happened very quickly for the young Captain-Lieutenant. Knowing that an aircraft sinks an average 3 meters per second into the water, and that under 30 meters the chance of survival was negligible, he commanded the ejection submerged in the dark water (see video illustrative at the end of the article). He surfaced the surface in a split second, got rid of the parachute, inflated the lifejacket, and waited for the rescue helicopter. He would live to fly again, fight the Vietnam War and go to the reserve twenty-three years later as Commander.

Things were not always like this. To achieve this technical proficiency and operational effectiveness, where a set weighing about 230 kg, consisting of crewmember plus seat rises to 30 meters in height in less than 0.2 seconds, the US Navy and the United States Air Force (USAF) have paid a heavy price in terms of human lives and aircraft. The long epic goes from the canvas and wood planes to the supersonic jet of composite and titanium, and this is its history.

In the final days of World War I, in 1918, a pilot who had to leave his plane in theory needed only to lean on the seat (once the cockpit was open), to launch into the blue and open his parachute, for the speed of the aircraft hardly exceeded the number of 200 km / h and operated at altitudes where hypoxia was not a factor to be considered. In practice, 1/3 of the pilots who had to do this did not survive the procedure.

The fact is that, in order to abandon an aircraft, it had to be considered that it should be in straight and level flight or at least out of the “abnormal” attitude envelope (ie not being screwed, abrupt dives, etc.), and the crewman in reasonable conditions of physical vigor to coordinate the jump into the void. So much effort to undertake if the man was injured.

Thus, during the 1930s, British, Swedish and German designers dedicated themselves to studies of aircraft abandonment systems by means of crew ejection, although only the latter had some success, pressed down by the challenges presented by the new dive attack aircraft. They have studied in all forms of artifacts to propel the seat out of the aircraft, such as explosive springs, even through compressed air, which was abandoned because it is difficult to maintain and its storage devices are very heavy.

By the end of World War II, the scenario had changed dramatically, since the speed of some aircraft was already approaching the sound barrier, the cockpit was closed and was often fought at the limit of the troposphere. Thus, a more efficient exhaust system design has ceased to become an alternative to becoming a necessity. The Germans had conducted about 60 successful ejections since 1942, and their advanced studies, whether of a technical nature or in the field of aerospace medicine, were leveraged by the allies.

The United States, several companies engaged in ejection seat designs, but there was a difference in concept between the Navy and the Air Force. In the first, an ejection system was recommended that operated in “zero zero” conditions (velocity and zeroed altitudes), and directed upwards. The Air Force, on the other hand, believed that the ejection could only be safely over 250 feet high and directed downwards (to avoid collision with the rudder / stabilizer assembly).

Fig 1   Zero zero ejector seat

Although using British solutions, the Navy position prevailed, supported by the premise that the ejection in aircraft carriers could not be given down for obvious reasons, in addition to having to meet the “zero-zero” operating condition, (Fig. 1).

Nevertheless, some Air Force aircraft implemented the mixed ejection system, with part of the crew ejecting upwards and downwards (Fig. 2).

Fig 2 – Scheme of B-52 ejection

Once these issues were resolved, it was a question of appropriating the “design” of the seats to avoid damage to the crewman spine. The solution adopted today is a reasonably inclined seat, so that the force “G” does not strike directly on its back, dissipating by the angulation. There was also concern about the legs because if they roamed freely, they could crash somewhere in the aircraft and cause serious injuries. It was decided to adopt restriction tapes that automatically pick up the legs when the ejection control is activated.

Fig 3 – Seat base with survival kit.

In the mid-1950s the designers faced another problem: the advent of supersonic aircraft and their complex associated aerodynamics. In addition, operated near the stratosphere, the crew member that eject ran the risk of dying of hypoxia. It was necessary to expand the envelope of operations. Barometric devices were then installed in the seat that would only automatically open the parachute below 7,000 ft (for the seat considered in this article). Should this occur, the pilot was continually supplied with emergency oxygen, until the altitude of automatic opening.

One aspect that can not be overlooked when analyzing the development of ejection systems is the improvement of crews combat and survival equipment, which were an integral part of the seats, and were designed to provide subsistence conditions in jungles, deserts and polar regions, as well as the oceans.

Fig 4 – Maintenance of one of the 1400 pieces that make up a modern seat.

Over 70 years of continuous improvement, ejecta seats have saved more than 12,000 crew members in every military on the planet. They have become so effective that even a wounded or semi-conscious aviator can trigger it with a reasonable chance of success. They are living proof of the inventiveness of human inventive capacity which, while developing an application originally intended for war, has created an invaluable instrument of flight safety and preservation of our most precious possession: life.

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