SEQUENCER MODES

Electronic sequencer timing (table 5-2) commences when the start switches close. Mode selection is dependent on altitude and airspeed parameters. (See figure 5-35.)

All modes. The start switches close after approximately 39 inches of seat travel and, after 0.04 second, the drogue deploys onto the bridle to stabilize and decelerate the seat.

Mode 1, low speed - low altitude. The drogue ^{bridle is released,} the parachute deployment rocket motor fires to deploy the personnel parachute, and the harness release system operates to free the occupant from the seat. The occupant is momentarily held in the seat bucket by the sticker straps.

Modes 2, 3, and 4, medium and high speeds - low altitude and all speeds - medium altitude. The parachute deployment rocket motor fires to deploy the parachute, the drogue bridle is released, and the harness release system operates to free the occupant from the seat. The occupant is momentarily held in the seat bucket by the sticker straps.

Table 5-2.-Sequencer Timings

Notes to Table 5-2

1. All times are referenced to seat catapult initiation. To obtain times referenced to sequencer start switches, subtract 0.18 sec.

2. Mode selection environmental sensing takes place between 0.245 sec and 0.305 sec (8 microprocessor cycles).

3. In Mode 5 operation, altitude sensing recommences at 4.80 see, continuing until the seat falls to 18000 ft. t = time interval between 4.80 sec and falling to 18000 ft.

4. Mode decision parameter values are stored in the on-board NOVRAM.

Figure 5-35 Ejection Sequence

Mode 5, all speeds - high altitude. The drogue bridle remains connected until the seat has descended to 18,000 feet. This arrangement prevents prolonged exposure to low temperature and thin air and enables the occupant to ride down in the seat, controlled by the drogue and supplied with emergency oxygen, to a more tolerable altitude. The seat attitude will be horizontal with the occupant facing down. When the seat has descended to 18,000 feet, the drogue bridle is released, the parachute deployment rocket motor fires to deploy the personnel parachute, and the harness release system operates to free the occupant from the seat. The occupant is momentarily held in the seat bucket by the sticker clips.

All modes. The personnel parachute, when developed, lifts the occupant and survival kit from the seat, pulling the sticker lugs from their clips. This arrangement ensures that there is no possibility of collision between seat and occupant after separation.