Advisory
Circular 4
Subject:
SHOULDER HARNESS-
bte: G/4/93
ACNo:=-34
Initiated by: AIR-120
ChQp:
SAFETY BELT INSTALLATIONS
1. PURPOSE. This advisory circular (AC) provides
. information and guidance pertinent to an acceptable means,
but not the only means, for installation of shoulder harness
and safety belt restraint systems at all seat locations on
all previously type certificated aircraft.
2. RELATED FEDERAL AVIATION REGULATIONS (FAR) SECTIONS.
Sections 23.5G1, 23.785, and 23.1413 of FAR 23; Sections
27,561, 27.785. and 27.1413 of FAR 27; Sections 29.561,
29.785, and 29.1413 of FAR 29; and Sections 91.107 and 91.203
of FAR 91.
3. BACKGROUND.
a. Basic principles. This AC focuses on basic
principles regarding design and installation of combined
shoulder harness and safety belt restraint systems which
evolve to satisfy the applicable requirements of the FAR. In
particular, the following subjects are discussed:
(1) common shoulder harness - safety belt designs;
(2) types of hardware available;
(3) ramifications of some hardware combinations;
(4) effects of the installation geometry;
(5) strength characteristics needed to accommodate
an accident loading environment; and
(6) structural attachment concepts.
b. Emphasis.
Emphasis is placed on performance of a
combined shoulder harness and safety belt installation in an
accident environment.
The accident environment produces
dynamic action and reaction forces which peak to some value
and decline to zero or reverse direction in m,llllseconds, and
most accidents will involve more than one force application
cycle.
Interaction between the occupant and the seat should
be considered, as well as the interaction between the
occupant and the shoulder harness-safety belt installation.
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