Sikorsky HH-60L Hoist Cable Damage Highlights Need for Cable Guards (N964SB, Santa Barbara County Fire Department)
The helicopter was also equipped with a belly-mounted Kawak Aerial Liquid Delivery System (ALDS) firefighting tank system and elongated landing gear. The Department of the Interior (DOI) & US Forest Service (USFS) SAFECOM aviation safety reporting system report states:
…the helicopter slowly approached the deployment location with the Crew Chief seated at the rear door [i.e. the right hand cabin door].
As the rescuer neared the ground, a cable swing developed in which the crew chief determined to be excessive.
The Crew Chief decided to bring the rescuer back up to the helicopter…
As the cable length reduced the swing amplitude consequently increased and…
…the cable swung forward of the aircraft sidestep and wrapped around the backside of the cable guard where two bolt heads were protruding.
These screws are reported to have had “sharp edges” and “about 1/4″ of threads showing”. This contact resulted in extensive damage to the hoist cable with 7 of the outer cable strands becoming sheared.
The rescuer made it into the aircraft safely, but the cable was not able to be reeled all the way into the drum. The cable hook was secured to the aircraft’s upper strut tiedown and the aircraft was flown back to base, where the cable was changed, and the aircraft was placed back into service.
Kawak is developing a user-installed kit “that will prevent the deployed cable from coming in contact with any structure on the tank or step.” It will add a “simple but robust bar guard, and will have rub strips along the whole length” and kits and a Service Letter will be distributed to operators free of charge.
This highlight the importance of cable guards and considering the credible cable swing arc. The Flight Safety Foundation (FSF) BARSOHO offshore helicopter operations Safety Performance Requirements contains Control 12.4: Hoist Cable Protection:
Hoist cables must be protected from damaging contact with aircraft structure.
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