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In September 1969, Popular Mechanics Explored the Complicated Mechanics Behind the Ejection Seat

Popular Mechanics

During the Vietnam War, the Navy and Air Force had a problem: a lot of their planes were being shot down behind enemy territory. Although the two armed services had perfected pilot recovery to a “fine art,” as Popular Mechanics describes in the September 1969 issue, three new ejector seat designs aimed to make successful rescues even more frequent. How? By flying (or sailing) a pilot to friendly territory.


The pilot lined up his jet, nursing the sight onto the designated target. Then he dived in low and fired his missiles, watching them streak out before him. It was a good run and a good hit.

Before he could congratulate himself he heard a thunk. Red lights flashed on his instrument panel.

He pushed the mike button. “I’ve been hit.”

The flight leader called back: “I see it. You’ve got smoke.”

“I’m losing fuel pressure. I may have to punch out.”

“Try to make it to the coast.”

“I can’t. My engine just quit.”

“Roger,” said the flight leader. “We’ll try to get a chopper in for you. Good luck.”



The other pilots watched as the canopy peeled off the crippled plane. Then the seat, with the pilot in it, rocketed out. When well clear, pilot and seat separated, a parachute billowed, and the pilot floated to the dense jungle-in the heart of Vietcong territory. His chances of being picked up by helicopter were reasonably good. Air rescue has become a fine art in Vietnam.

But his chances of falling into enemy hands were even better. The problem has prompted Navy and Air Force brains to seek a solution. What if a pilot could “fly” his seat to friendly territory, or to an area that would make rescue more certain?

The Air Force and the Navy are working together to develop a “flying ejection seat” that can be stowed on a standard cockpit seat, deployed after the seat ejects, and, with a small jet engine, keep the pilot airborne until he can select his landing site.

Three versions of the AERCAB (Aircrew Escape/Rescue Capability) are now under study. One is based on the Rogallo wing, a triangular-shaped cloth supported by three keels. The Air Force’s Wright-Patterson Flight Dynamics Laboratory is testing it with Bell Aerosystems Co., of Buffalo.

The second version is a two-bladed, free-swinging rotor that, with a jet engine, converts the seat into a gyrocopter. The Navy Air Development Center, Johnsville, Pa., is studying this version. Contractor is Kaman Corp., Bloomfield, Conn.

The third version is based on the Princeton sailwing, which features cloth-covered wings and tail surfaces held taut by spring-loaded metal bars and cables. The Navy Air Development Center is studying this version with Stratos Western Div. of Fairchild Hiller Corp., Manhattan Beach, Calif.

Whichever system is picked must meet these specifications:

  • Pilot has option of using the system-or his own parachute if he knows he’s over friendly territory.
  • After punch-out, the system will be automatic, but pilot will have option of overriding it at any time. The automatic feature insures that a wounded (or semiconscious) pilot can use it, with the seat flying a predetermined heading and altitude.
  • A barometric sensor will keep the system from deploying until it descends to 10,000 feet. If it deployed above that altitude, the pilot could suffer from exposure and use up his oxygen too quickly. If the pilot punches out below 10,000 feet, deployment sequence begins immediately.
  • Seat must be capable of a speed of 100 knots, a rate of climb of 1000 feet per minute and a range of about 50 miles.
  • System will include survival equipment and a locator beacon to aid air rescue.
  • The automatic feature will include separation from the seat and deployment of pilot’s own chute above 200 feet at the end of 30-minute flight. Though the gyrocopter and the Princeton wing would seem capable of taking the pilot all the way to the ground, the services have not made this mandatory. But they have asked for some glide capability when seat is unpowered.

    Feasibility tests, including actual flights of models and wind-tunnel tests, will determine which of the three versions is the most stowable, the most easily deployable, and the most stable in flight. After that the services will select the power of the engine (they’re thinking of up to 250 pounds of thrust) and decide whether to design a new seat or go with the one now in use.

    The current ejection seat (Navy and Air Force seats are basically the same) has almost perfect dependability. Pilots have punched out successfully from zero-zero attitude (no altitude, no ground speed) up to and through the sound barrier. Should ejection be necessary at high speeds with the new systems, built-in devices will slow down the seat before deployment begins.

    Here’s how a typical punch-out would work with each system, assuming an altitude below 10,000 feet and subsonic speeds. The initial sequence would be identical for all.

    As in the present Air Force seat—to use it as an example—the pilot pulls up on two red handles alongside the seat below his knees and follows through until his helmet hits the headrest. Cables yank his feet back against seat to make certain his legs clear the instrument panel on the way out.

    The canopy blows off, rockets ignite, and the seat rides on rails out of cockpit. The angle of ejection is slightly forward to brace pilot and seat against the rush of wind. In the current system, at this point pilot and seat separate, and pilot’s chute opens.

    With the new systems, a deceleration chute about six feet in diameter would open. This would slow the seat to a safe speed before start of deployment sequence. If the pilot ejected at a high subsonic speed, say about 600 knots, the chute would remain reefed; that is, restricted by a cord from opening to its full diameter. After some speed was lost, the cord would be cut, and the chute would open fully, slowing down the seat even more.

    Once the seat has decelerated, the sequence changes for the three systems.

    popular mechanics

    Fred L. Wolff / Popular Mechanics

    Bell’s Rogallo wing, simplest of the three, may be deployed by a timer or by actuators triggered by pull of the deceleration chute. In either case, the V-shaped wing would peel off from the back of the seat and extend to a length of about 7 feet and a width, at the trailing edge, of 13 feet. Each of three keel bars would have at least two sections, one nesting inside the other when stowed. A spreader bar would also extend during deployment, holding the three keels rigid and insuring proper “fluff” to the cloth wing.

    The wing will have an angle of attack of about 30°. The pilot, still strapped to his seat, lies face down. By moving a control stick, he can tilt the wing up to climb, down to descend or sideways to turn. The engine, on the back of the seat, starts when the wing deploys and is controlled manually by a throttle on an armrest.

    While Bell’s Rogallo-wing system has the advantage of simplicity, a pilot might feel awkward flying through the air face down. Also, he couldn’t land strapped to a huge seat, so he has to jettison the seat and parachute down.

    popular mechanics

    Fred L. Wolff / Popular Mechanics

    The Stratos Western version of the Princeton sailwing looks like an airplane. With a lift-over-drag ratio of 5 to 1, it can glide long after fuel runs out.

    Its deployment sequence goes like this: After deceleration chute has slowed down the seat, a tail boom—made up of sections nested inside one another—is extracted from its stowed position and extends to full length. The last section has notches in it that run almost the entire length. The tail surfaces are folded and stowed in these notches. When the section is exposed, the tail surfaces, under spring tension, pop out and lock in place. Aluminum spars, hinged at the forward end, form the leading edges, pulling cables taut to form the trailing edges. The tail surfaces are made of Dacron, and the horizontal stabilizers form an inverted V so that the notches are distributed evenly.

    The wings are hinged at two points. The inboard section of the leading edge, also made of aluminum, is hinged to the seat; the outboard section, which nests inside the inboard section, swings out further on a hinge at outer end of the inboard section. Fully extended, the wing locks in place and pulls taut the cable for the trailing edge, the cloth and two ribs that provide additional strength.

    The fuselage is completed by blowing up a preformed rubberized-cloth nose section. This gives the system better aerodynamic qualities and lengthens the vehicle to 14 feet. Its wingspan is 16 feet.

    A stick on the seat floor manipulates bladders (airbags) inside the wings, which warp the wings for pitch and roll. The engine is attached to the bottom edge of the seat, and may also be controlled by a throttle on the armrest.

    Stratos Western designers believe that pilots might feel more at home in the sailwing, since they sit straight up in something that resembles an airplane. Because pilots might be tempted to fly it all the way down, the designers added a small landing gear. But in most cases the pilot would separate from the unit above 200 feet.

    popular mechanics

    Fred L. Wolff / Popular Mechanics

    The Kaman gyrocopter is called SAVER (Stowable Aircrew Vehicle Escape Rotoseat). Engineers at Kaman Corp. say SAVER is the only system designed to take the pilot all the way to the ground without separation, although he still has the option of using his chute.

    The engine is nested on the seat back, with two rotor blades folded behind it. At deployment, blades swing out and up, pulling their control arm along. They then swing down on hinges, extend to full length (15 feet) and lock into place. Meanwhile, stabilizing surfaces, shaped to fit along each side of the seat and still be aerodynamically correct, swing back and lock. The engine drops from its nested position and ignites. Forward thrust makes the rotor blades spin, and the blades alone provide lift and control.

    A second version of the copter, being developed at Catholic University, Washington, D.C., closely resembles the Kaman vehicle and has a similar deployment sequence. All three systems deploy relatively fast—from six seconds for the Rogallo wing to eight for the Princeton sailwing.

    No matter which version is chosen, engineers are thinking of adding refinements. Instruments might be built in to indicate speed, altitude and fuel consumption. The final criterion will be dependability. And, whichever company’s system proves itself in combat, pilots will surely come back to say, even to the two losers, “Bless you, one and all.”

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