Maintaining Existing Harnesses
It’s easy to overlook seat belts and harnesses during routine
aircraft maintenance. However, they play a crucial role in
aircraft safety and are designed to withstand tremendous
loads in an accident. Any damage or wear can compromise
these capabilities significantly.
When evaluating a harness, begin at the buckle or latch
mechanism. It should operate smoothly and not show
significant signs of wear. When the belt is under tension,
the buckle should still be able to release without significant force. If the mechanism is loose or does not operate
smoothly, it should be replaced.
The harness webbing is the next thing to inspect. Over
time, the webbing can fray or deteriorate due to mechanical wear, UV exposure, or chemical damage. Fraying is easy
to inspect for, but other types of damage can be more difficult to identify. Look for a fuzzy layer on the surface of the
fabric or a warp in the weave. If one of these issues is present, the harness material needs to be repaired or replaced.
Fortunately, re-webbing seat belts and harnesses is
a straightforward and relatively inexpensive process.
There are a number of excellent repair facilities that can
replace the latches, re-web the belt, and even switch the
belt out for a new color that will match your aircraft’s
Finally, inspect the mounting points themselves. The
mounting bolts and spacers should be secure and not
show signs of wear.
Harness Options and Fitting
Seat belts and harnesses are typically categorized by the
number of straps, or attachment “points,” in the harness.
For example, a two-point system is a simple lap belt
system. This design is less than ideal because, while
it prevents the occupant from being thrown from the
vehicle, it creates a pitching moment for the entire,
unsupported upper torso that can result in significant
However, the “ultimate” solution is the
five-point harness system.
A better approach is the common three-point restraint
system, which adds a single diagonal shoulder strap to the
lap belt. Most aircraft use this design, but have a fixed shoulder strap that is separate from the lap belt and attaches to
the male seat belt buckle with a locking clip. This two-piece
design is necessary mainly because most aircraft do not have
Inertial-reel shoulder harnesses are a significant advantage because they automatically adjust to fit the occupant
and remove the slack from the restraint system. Slack is one
of the most common reasons that injuries occur, even when
occupants are wearing seat belts. During an impact, the
occupant’s body continues to move forward until the slack is
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