Non-standard egress systems include Downward Track (used for some crew positions in bomber aircraft, including the
B-52 Stratofortress), Canopy Destruct (CD) and Through-Canopy Penetration (TCP), 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, a number of 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 (two of them, EWO and Gunner, facing the rear of the airplane) fire upwards as usual. Note that any such downward-firing system is of no use on or near the ground unless the aircraft is upside-down 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 (e.g., the BAe Hawk and the Harrier line of aircraft) use Canopy Destruct systems, which have an explosive cord (MDC - Miniature Detonation Cord or FLSC - Flexible Linear Shaped Charge) 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.
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. 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-6 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.
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07-07-2009, 19:51
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