TM 1-1520-240-104-3-18 Figure 4-3-14. Forward and Aft Cargo HooksCAUTIONThe forward and aft hooks may fail to openif the slings are slack when the releasesolenoids are energized (a load of approx-imately 20 pounds is required for open-ing). The hooks can be opened by select-ing the desired hook(s) and depressingthe release switch as the aircraft is lifted toapply tension to the slings.e.CARGO HOOK EMERG Switch. The emergen-cy cargo hook release switch is on the CARGO HOOKcontrol panel. It is a guarded switch and it is labeledEMERG REL ALL (emergency release all). The switch isused to simultaneously open the three hooks, if an emer-gency situation develops. The three hooks will open re-gardless of CARGO HOOK MSTR or HOOK SEL switchpositions. Setting the switch to REL ALL, energizes anemergency hook release relay. The relay then energizesrelease solenoids in the forward and aft hooks and asolenoid valve in the center hook. The solenoid valve inthe center hook releases the aircharge stored in the low-er half of the hydraulic actuator, transferring the chargeto the upper (release) half of the actuator to open thehook. After this method of opening the hook, the hookactuator must be recharged to 2,000 to 2,100 psi. Theemergency hook release relay will automatically deener-gized after a 10 second time delay. This prevents dam-age to the hook release solenoids.CAUTIONBefore external load operations, crew–members shall familiarize themselveswith the manual emergency cargo releasemechanism installed on the helicopterWARNINGWhen the center cargo hook is openedwith the external load off the ground, thecargo hook will whip back back and forth.CAUTIONWhen the center cargo hook is opened us-ing the manual emergency release handle,the hook must be closed manually. No at-tempt should be made to close the hookusing the normal hydraulic or pneumaticmethod, since damage to the cargo hookcan result.
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