9
Chapter 2: Helmet Preparation and Operation
Measuring Head Length
Measure the aircrew member's head length as follows:
1. Use a caliper and a ruler as shown in
to measure the distance (to the nearest .1 inch
or 2.5 mm) from the point between the eyebrows
to the back of the head. This is the
head length
.
Ensure that the caliper touches the skin lightly
and does not indent the skin surface.
2. Record the measurement.
Measuring Head Width
Measure the aircrew member's head width as follows:
1. Use a caliper and a ruler as shown in
to measure the maximum horizontal width (to the
nearest .1 inch or 2.5 mm) of the head above
the ears. This is the
head width
. Ensure that
the caliper touches the skin lightly and does not
indent the skin surface.
2. Record the measurement.
Selecting Helmet Size Based on Measurements
Compare the head length and head width measurements to the sizing parameters shown in
Table 2-1
, and select the helmet size.
NOTES:
•
The dimensions shown in
Table 2-1
are intended as guidelines. At times, the next smaller or
larger size may be needed.
•
If the measurements fall into different size ranges, select the larger size.
Table 2-1. Size Data for HGU-55/P
Head Length, inches (mm)
Maximum Head Width, inches (mm)
Helmet Size
7.2 to 7.8 (183 to 198)
7.7 to 8.3 (195 to 211)
8.2 to 8.7 (208 to 221)
6.2 (157)
6.5 (165)
6.8 (173)
Medium
Large
X-Large
2-2 2 Fitting the TPL, SCL, or XLiner
• TPL:
Refer to TP0008.
• SCL:
Refer to TP0236.
• XLiner:
Refer to TP0265.
Caliper
Ruler
Measurement
point at back
of head
Measurement
point between
eyebrows
POINTS TO
MEASURE
Maximum horizontal width
POINTS TO
MEASURE
Caliper
Ruler
Figure 2-2. Head Length
Figure 2-3. Head Width
