The Mk 26 GMLS has three exercise and emergency accumulator type of power drive systems.

They permit limited, but total, GMLS operation under the following conditions:

1. During maintenance procedures

2. While performing or completing necessary GMLS functions should one or more main power drive systems fail

3. For operating GMLS equipments at reduced rates and fluid pressures when purging air from hydraulic components during initial start-up or after corrective maintenance actions

Figure 4-67.-Mk 26 GMLS emergency drive; typical arrangement for all power drives.

These exercise and emergency systems can be operated from any normal, alternate, or emergency 440-volt ac ship power source. Power selection is made at the PDC by the MCC operator. The major components of the exercise and emergency systems are hydraulically incorporated with components of the main power drive systems. However, no tactical operations can be performed using the exercise and emergency systems (i.e., firing a missile).

RSR/HOIST EXERCISE AND EMERGENCY ACCUMULATOR TYPE OF POWER DRIVE.- The A- and B-side RSR/hoist exercise and emergency power drives provide two alternate sources of hydraulic operating pressure. They can operate the RSRs, hoists, strikedown equipments, blast doors, and jettison devices. They also provide fluid to operate the A- or B-RSR/hoist emergency drive motors and the train emergency drive motor.

The components of an emergency power drive are shown in figure 4-68. A small electric motor drives a small gear pump located inside the main fluid supply tank for each RSR/hoist system. The output of the pump charges a small accumulator flask. Exercise and emergency fluid pressure is developed between 800 and 935 psi. The emergency fluid is then distributed to the appropriate components of the GMLS listed in the last paragraph.

Because of the small size and capacity of the components of the emergency system, the GMLS equipments operate' at greatly reduced rates of speed. Through the RSR/hoist emergency drive motor, the RSR can be indexed slowly in either direction. When selected, the hoist can be lowered with or without a missile. However, because of a weight factor, it can only be raised when it is empty.

Figure 4-68.-RSR/hoist exercise and emergency accumulator system, power drive components.

A manual transfer valve assembly (fig. 4-69) is mounted to the bulkhead in the strikedown area. Two hand-operated levers control four directional valves. They route both PA and tank fluids from the RSR/hoist power drives. These fluids are directed to the strikedown mechanism and train emergency drive. These "fluids" may be from either the main accumulator systems or from the exercise and emergency

accumulator systems. In the OFF position, the strikedown and train emergency drive equipments are isolated from any hydraulic fluid supply. When either lever is positioned to ON, operating fluid is ported to these equipments. Locking pins prevent both levers from being ON at the same time. In this manner, hydraulic fluids cannot intermix between the A- and B-side systems.