The Stencel seat is equipped with a mode sequencing system that controls four automatic ejection modes. The system includes a parachute container opener that is activated by gas pressure from the 7,000-or 14,000-foot aneroid initiators, or the seat and man separation initiator. The WORD rocket is also part of the system. The WORD rocket, mounted on the back of the seat, is connected to the drogue bridle assembly on one end and to the parachute WORD bridle on the other end. The WORD rocket motor is released from the seat and fired by a lanyard as it falls away from the seat during low-speed ejections or by the pull of the drogue during high-speed ejections. The ejection sequence follows one of four modes, depending on aircraft airspeed and altitude. Mode 1 includes ejections where the air-craft is operating below 7,000 feet and at a speed less than 225 knots. Mode 2 includes an altitude below 7,000 feet, but at a speed greater than 225

knots. Mode 3 occurs above 7,000 feet, but below 14,000 feet, at any airspeed. Mode 4 occurs above 14,000 feet at any airspeed. Figure 6-33 presents a comparison of the various modes.

MODE I.- Mode 1 (fig. 6- 34) is for a low-speed, low-altitude ejection. After the catapult outer tube assemblies have traveled upward a distance of approximately 31 inches, ballistic gases are ported through the inner trombone assemblies to actuate the 0.1-and 1.3-second time delays in the multiple delay initiator and the 3-second delay initiator. Gases from the 0.1-second delay actuate the drogue and WORD release and arm the 14,000-foot aneroid initiator. Below 14,000 feet, the initiator immediately actuates and gases pass through the right trombone to actuate the parachute container opener. Upon actuation of the WORD motor and drogue release assembly, the aerodynamic drag of the drogue parachute

Figure 6-33.- SJU-8/ A mode of operation.

pulls the WORD motor away from the seat back. are attached to alternate suspension lines on This action extracts the firing lanyard from the the parachute canopy skirt in a 360-degree motor and ignites the WORD motor. pattern. This opens the parachute and allows the canopy to fill quickly. If the spreading gun fails When the WORD rocket is fired, it extracts to fire, a fail-safe collar releases the slugs and the parachute from its container. The parachute allows normal parachute inflation. If mode 1 fails, drag pulls a lanyard that fires the ballistic mode 2 will automatically provide the ejection spreading gun. The gun expels metal slugs, which sequence.

Figure 6-34.- Mode 1: low speed/ low altitude.

MODE 2.- Mode 2 (fig. 6-35) is for a airspeed is above 225 knots. The flow of gases high-speed, low-altitude ejection. The primary is delayed until the 1.3-second delay initiator fires. initiation of the mode 2 sequence is identical to This delay reduces the parachute's opening shock. that of mode 1. To reduce parachute opening When the 1.3-second delay initiator fires, the loads, the drogue decelerates and stabilizes the ballistic gases are directed to the 7,000-foot seat before the parachute opens. In mode 2, the aneroid-actuated initiator. Since the altitude is output of the 0.1-second initiator is blocked by below 7,000 feet, the initiator fires. This actuates the low-speed selector valve (LSSV) because the WORD motor and drogue release assembly

Figure 6-35.- Mode 2: high speed/ low altitude.

and operates the parachute container opener 14,000 feet) ejection, which may occur at any assembly. The remainder of the mode 2 sequence airspeed. The primary initiation of the mode 3 is identical to the mode 1 sequence. If the mode sequence is identical to that of mode 1. At 2 sequence should fail, then the mode 3 sequence ejection, the airspeed and altitude sensors and automatically provides the ejection sequence. low-speed selector valve (LSSV) block the gases from the 0. l-second delay initiator. The MODE 3.- Mode 3 (fig. 6-36) is an 1.3-second delay initiator fires and arms the intermediate altitude (above 7,000 feet and below 7,000-foot aneroid initiator, which is delayed

Figure 6-36.- Mode 3: intermediate altitude.

because ejection occurs above 7,000 feet. When mode 3 fails, then mode 4 automatically provides the 3-second delay initiator fires, its gases actuate the ejection sequence. the drogue and WORD release and arm the 14,000-foot aneroid initiator. Since ejection MODE 4.- Mode 4 (fig. 6-37) is an ejection occurs below 14,000 feet, the initiator fires above 14,000 feet at any airspeed. The primary immediately through the right trombone to initiation of the mode 4 sequence is identical to operate the parachute container opener. The that of mode 1. At ejection, the ballistic gases remainder of mode 3 is identical to mode 1. If from the 3-second delay initiator actuate the

Figure 6-37.- Mode 4: high speed/ high altitude.

WORD motor and drogue release assembly and arm the 14,000-foot aneroid-actuated initiator. Meanwhile, the 1.3-second delay initiator arms the 7,000-foot aneroid-actuated initiator, which acts as a backup. The seat and pilot, which are stabilized by the drogue parachute, descend to 14,000 feet pressure altitude. At that point, the 14,000-foot aneroid-actuated initiator fires, actuating the personnel parachute container opener assembly. The personnel parachute assembly is then deployed by the aerodynamic forces acting on the drogue parachute assembly. Should either the 3-second delay initiator or the 14,000-foot aneroid-actuated initiator fail, the sequence would proceed as described above, except that free fall would continue to 7,000 feet pressure altitude. There, the 7,000-foot aneroid-actuated initiator would actuate the personnel parachute container opener assembly. The

personnel parachute assembly would then be deployed by the drogue parachute assembly.