The FAA has released SAFO (Safety Alert for Operators) #16015 which discusses the possibility of dynamic rollout with certain hoist hook types.While I’m very glad the FAA has released the report, it was a bit muted in its recommendations.

It advises operators to:

  • Develop procedures which list the specific D-Rings or equipment which may be attached to a specific rescue hook wherein the possibility of D-Ring reversal is physically impossible.
  • Use only rescue hooks which have a mechanical locking keeper or guards to prevent D-ring reversal or dynamic roll-out.

Those are good recommendations but fall short both individually and in combination in making roll-out a physical impossibility.  Here’s why:

The picture above is from a Royal Canadian Air Force report  regarding an incident in 2013 where a dynamic rollout occurred.  The hoist hook in that incident met the recommendation that a hook have a “mechanical locking keeper” or guard to prevent roll-out.   The disconnect is the phrase “mechanical locking keeper.”  The pip pin that was to be installed by procedure to prevent rollout us mechanical in nature, much like the locking mechanism on the hoist hook below.  However, in both instances, the lock requires the operator to manually move the lock into place.

This hook with a manual lock and exposed hook beak is susceptible to dynamic rollout. Use of the LSC #190 series slings with this hook are not authorized by LSC.

The popular hook pictured above requires the operator to move something. If an operator has to move something they can miss that step or inadvertently unlock the hook in certain conditions. The word, in my opinion,  missing from the FAA recommendation is “automatic.” If the hook doesn’t automatically lock, then rollout can (and on a long enough timeline ‘will’) occur.

Many teams rely on a set of procedures to reduce the risk of rollout, and those procedures can be effective. However, the environment doesn’t care about procedures. The motion of the helicopter and the seas, with the hook dangling between them, can create dynamics that no procedure can fully account for. And those teams who use other methods to defeat rollout often trade one risk for another.  The addition of large rings an carabiners provide options and reduce rollout from the hook, while increasing complexity and more moving parts that may fail.

Far and away the most reliable way to eliminate the possibility of rollout is to make it physically impossible by using a hook that automatically locks so that “hooked-in” is “hook-in” until the operator physically and deliberately unhooks.

For more information on dynamic rollout, watch our video (from October 2015) on the subject.