The Ejection Site

North American Aviation (NAA) is more famous for some of their aircraft, but they also produced some of the more interesting egress systems. Their systems varied from lightweight, low speed seats up to high speed seats and capsules. They provided systems for several experimental aircraft, including the NAA built XB-70 Valkyrie. The T-2 Buckeye seat was the first production seat to utilize a rocket catapult. Some examples of their egress equipment are:

From the mid-1950s thru the 1970s, NAA or North American Rockwell, was continuously involved in ejection seat design. The A3J-1 seat which became the HS-1 and later the HS-1A seat was one of the most capable open ejection seats made for a production aircraft. The X-15 space research vehicle utilized a NAA seat which was rated up to Mach 4 and 120,000 feet.

Probably their most produced model was the LS-1 seat for the T-2J Buckeye. This seat was the first seat to use a rocket-catapult (ROCAT) which is a tubular device in the center of the back of the seat. A ballistic cartridge is the catapult section, and it begins seat motion on its initiation by forcing the inner section of the assembly to move under the pressure of the gas it generates. The inner section of the unit is the rocket and it is ignited near the end of the catapult stroke so that on seat/rail separation the rocket is near peak thrust. This additional thrust propels the seat upward and forward due to the angle of the nozzles. The addition of the rocket portion of the system allowed for a lowering of the required forces from the ballistic catapult, and allowed for extended trajectories for low speed or stationary ejections. The LS-1 seat has saved many aviators.

The LW series of seats began in the late 1950s with the LW-1 seat. Designed for V/STOL type aircraft, it was a particularly light weight seat (hence LW). The seat used a very lightweight frame which had as a separate unit the backpad and headrest. On the back of this unit was mounted the main recovery parachute. Due to the aft seat structure and the ROCAT in the center of it, the recovery parachute was mounted vertically in a narrow pack along the left side of the seat. The survival kit was a rigid seat form with a soft pack suspended underneath it. Seat separation was automatic and executed by a 0.2 second delay cartridge which would then fire a drogue gun. The drogue chute would be deployed and it would immediately withdraw the main parachute from the pack. The shroud lines would pull the risers upward and release a latch holding the back section to the seat. The drag from the parachute would then allow the seat frame to fall away from the aircrew, leaving him with the backplate and headrest as well as the survival kit. The headrest was fitted with a flat plate canopy breaker for use in through-canopy ejections.

The LW-2 seat was a direct decendant of the LW-1 seat. The separate back plate was integrated into the seat frame, and a airspeed/altitude mode selector was developed. This unit mounted on the bulkhead aft of the seat and by means of a plunger which engaged a striker on the seat during ejection would select either a high speed/altitude mode, or a low speed/low altitude mode. The difference was in the seat separation delay. In the high speed mode, the seat would deploy a drogue chute and would delay main parachute extraction for some time.

The LW-3B was a decendant of the LW-2 seat with significant changes to it. Used in the OV-10 Bronco, this was the only seat of the LW-series family to be produced in any numbers.

Another major system created by NAA/Rockwell was the XB-70 ejection capsule. This was an ejection seat with a two piece clamshell covering which came together to protect the aircrewman against the extremes of altitude and airspeed that the XB-70 Valkyrie could reach. Tested by rocket sled, this capsule could protect against supersonic forces, and was pressurized to protect the aircrew in case of decompression of the aircraft. Stabilizing booms kept the capsule under control at high speed. Due to the heavy weight of the capsule at ground impact, absorbtion bags were fitted to the bottom to attenuate the impact.