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Keep an Eye Out | Brass and Rubber

By Jim Crouch

Keep An Eye Out | December 2019
Sunday, December 1, 2019

Oil and water, Red Bull and milk, brass grommets and rubber bands: all things that don’t mix together well. Yet, the vast majority of jumpers use parachute deployment bags that contain brass grommets and pair them with rubber bands (or rubber Tube Stows) that pass through the grommets to stow the suspension lines. It’s not much of an issue for a rig that is jumped regularly, but it will be a problem if the rig remains undisturbed for long periods of time. If a rig spends months in storage, a chemical reaction between the rubber and brass will eventually oxidize the grommets and destroy the stow bands. This reaction may also damage any nearby nylon parachute material.

Once a jumper or rigger discovers this type of damage, they can replace the rubber bands or Tube Stows and clean up the grommets using a wire wheel attachment on a Dremel tool. It is usually not necessary to replace the grommets. If you plan to store your parachute system for months at a time, removing the main parachute from the deployment bag and storing everything in a climate-controlled environment is always best.  

Although a problem for main systems, this is generally not a problem for reserve systems, because manufacturers do not usually use brass grommets on their reserve freebags.

Jim Crouch | D-16979 and FAA Senior Rigger
Tampa, Florida

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