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| MIL-S-8551O(AS)
4.1.1, 4.6.1, 4.6.2.1,
Test plan, systems,
DI-T-1903
4.6.2.2, 4.6.3, 4.6.5
components
Test report, systems,
DI-T-1906
4.1.2, 4.6.1, 4.6.2.1,
4.6.2.2, 4.6.3, 4.6.5
components
6.3 First article. When first article inspection is required, the item will be
tested and should be a first article sample. First article inspection shall require
a minimum of four seats of each type, class and size being purchased, representative
of standard production items. The contracting officer should include specific
instructions in acquisition documents regarding arrangements for examinations, test
and approval of the first article.
For the purpose of this specification, the following defi-
6.4 Definitions.
nitions apply.
6.4.1 Anthropometric data. US Army Natick Labs Report 72-51-CE shall be referred
to as a source document for anthropometric data on troops/passengers.
6.4.2 Occupant weights and equipment. Unless otherwise specified, the occupant
and equipment weights in table IV are applicable for design and test considerations.
6.4.3 Effective weight of occupant. The effective weight of a seated occupant in
the vertical direction is the sum of the following quantities: 80 percent of the
s
occupant body weight, 80 percent of the weight of the occupant's clothing less
boots, and 100 percent of the weight of any equipment carried totally on the occu-
pant's body above the knee level.
6.4.4 G. The term G is the ratio of a particular acceleration to the acceler-
ation due to gravitational attraction at sea level; therefore, 10G represents an
acceleration of 321.7 feet/second/second.
6.4.5 Occupant submarining. In a crash with high vertical and longitudinal
forces (measured along the seat longitudinal axis) present, the restrainted body will
tend to sink down into the seat first and them almost simultaneously be forced for-
ward. If the seat is provided with an improperly designed restraint or seat cushion,
the inertia load of the hips and thighs will pull the lower torso under the lap belt
during the crash sequence. This phenomenon is referred to as occupant submarining.
6.4.6 Dynamic overshoot. Dynamic overshoot exists when the seat occupant re-
ceives an amplification of the accelerative force applied to the seat. A loose or
highly elastic restraint system, or a cushion with a high rebound potential which
permits "bottoming out" on the seat pan, can facilitate dynamic overshoot.
6.4.7 Load factor. Load factor is the ratio of the design load or applied
static test load to the combined weight of the seat, effective weight of the occupant
and any equipment attached to the seat.
6.4.8 Graphic approximation technique. Based upon acceleration time plots from
measurements or computations, rise time, plateau duration, and G values along in the
vertical (z) axis at a specific time may be obtained using the following graphic
approximation technique, as shown in figure 17.
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