MAJOR HELMET ASSEMBLIES

By taking the basic shell assembly, PRK-37/P, and adding different liners, visors, and communication systems (fig. 4-1 5), you can make 15 different helmet configurations.

HGU-33/P HELMET ASSEMBLY. The HGU-33/P is a single lens, form-fit helmet for use in aircraft where an oxygen mask is used exclusively.

HGU-34\P HELMET ASSEMBLY. The HGU-34/P is a single lens, pad-fit helmet required

for use in aircraft where an oxygen mask is used exclusively. This helmet assembly is also an interim backup for the HGU-33/P when a formfit liner cannot be fabricated.

HGU-43/P HELMET ASSEMBLY. The HGU-43/P is a dual lens, form-fit helmet incorporating a neodymium laser protective lens for use in A-6 target range acquisition multisensory (TRAM) aircraft.

HGU-44/P HELMET ASSEMBLY. The HGU-44/P is a dual lens, form-fit helmet used in aircraft where an oxygen mask is used exclusively.

HGU-45/P HELMET ASSEMBLY. The HGU-45/P is a dual lens, form-fit helmet for use in OV-10A aircraft where an oxygen mask and boom microphone are both used.

HGU-45A/P HELMET ASSEMBLY. The HGU-45A/P is a dual lens, form-fit helmet incorporating a neodymium laser protective lens for use in the OV-10D aircraft where an oxygen mask and boom microphone are both used.

HGU-46/P HELMET ASSEMBLY. The HGU-46/P is a form-fit helmet incorporating the VTAS (Visual Target Acquisition System) visor assembly for use in the F-4 VTAS aircraft.

HGU-47(V)l/P HELMET ASSEMBLY. The HGU-47(V)l/P is a single lens, pad-fit helmet required in aircraft where a boom microphone is used or where a boom microphone and oxygen mask are used interchangeably.

HGU-47(V)2/P HELMET ASSEMBLY. The HGU-47(V)2/P is a single lens, pad-fit helmet incorporating a boom microphone without amplifier and the CX-13155/A communication cable for use in C-1A and C-2A aircraft.

HGU-47(V)3/P HELMET ASSEMBLY. The HGU-47(V)3/P is a single lens, pad-fit helmet incorporating a boom microphone without amplifier and the CX-13164/A communication cable for use in T-34 aircraft.

HGU-47(V)4/P HELMET ASSEMBLY. The HGU-47(V)4/P is a single lens, pad-fit helmet incorporating a boom microphone without amplifier and the CX-4832A/AR communication cable for use in P-3 aircraft.

HGU-49/P HELMET ASSEMBLY. The HGU-49/P is a single lens, form-fit helmet incorporating a boom microphone and CX-13128/A communication cable for use in S-3A aircraft.

HGU-50/P HELMET ASSEMBLY. The HGU-50/P is a single lens, form-fit helmet incorporating a binaural headset required for use in the aft stations of the EA-3B aircraft.

HGU-52(V)1/P HELMET ASSEMBLY. The HGU-52/P is a single lens, form-fit helmet incorporating a boom microphone and CX-13155/A communication cable for use in A-3 aircraft.

HGU-52(V)2/P HELMET ASSEMBLY. The HGU-52(V)2/P is a dual lens, form-fit helmet incorporating a boom microphone and CX-13155/A communication cable for use in E-2 aircraft.

MAJOR HELMET COMPONENTS

The following helmet components are available to achieve the desired configuration for the aircrew member helmet.

PRK-37/P HELMET SHELL ASSEMBLY. The PRK-37/P helmet shell assembly is intended to protect the head during in-flight buffeting and emergency situations such as ejection, bailout, or crash landings. It resists projectile penetration and distributes impact forces over the entire head. The helmet shell is the platform for other components such as the visor assembly, communication devices, and the oxygen mask.

PRU-39/P HELMET SHELL LINER AS-SEMBLY. The PRU-39/P is a helmet shell liner that is a form-fit, foam-in place type assembly, which is installed in the PRK-37/P helmet shell assembly. The PRU-39/P consists of a rigid polyurethane foam liner molded to fit the aviator's head. The KMU-439/P (liner mold kit) is positioned on the pilot's head, and foam chemicals are injected into it. The liner is finished with a soft urethane foam comfort pad and leather covering. When properly fitted, the liner provides impact energy absorption, helmet stability, and comfort.

PRU-39A/P HELMET SHELL LINER ASSEMBLY. The PRU-39A/P is a helmet shell liner that is form-fit and constructed from oneply fiberglass backing (contour-molded to fit within the PRK-37/P helmet shell), a leather covering, and a comfort pad. The leather covering and comfort pad are cemented to the fiberglass backing. The fiberglass backing has two holes for introduction of foam chemicals. When properly fitted, the liner absorbs impact energy and makes the helmet stable and comfortable. The aircrew member wears a perspiration-absorbing cotton skull cap to extend the life of the liner.

PRK-40/P HELMET SHELL LINER AS-SEMBLY. The PRK-40/P helmet shell liner, which comes in two sizes and consists of a premolded 1/2-inch thick polystyrene foam liner, is molded to fit inside the PRK-37/P helmet shell assembly. Final fitting of the PRK-40/P is accomplished by a series of different fitting pads. Also included in the assembly is a nape strap to allow a snugger fit. When properly fitted, the liner is designed to provide impact energy absorption, helmet stability, and comfort.

EEK-4A/P HELMET VISOR, SINGLE LENS. The EEK-4A/P is a single lens helmet visor assembly. When installed on the helmet shell, it protects the face and eyes from impact, projectile penetration, sun glare, dust, windblast, and fire. Each assembly comes with interchangeable clear and neutral lenses.

PRU-36/P HELMET VISOR, DUAL LENS. The PRU-36/P is a dual lens helmet visor assembly, which provides the aircrew member with the same protection as the EEK-4A/P.

EEK-3/P HELMET VISOR, DUAL LENS. The EEK-3/P is a dual lens helmet visor assembly, which gives the aircrew member the same protection as the EEK-4A/P. Each assembly comes with a neodymium laser protective inner lens and an interchangeable clear and neutral outer lens.

R-1825/AVG-8, R-1826/AVG-8 HELMET VISORS. The R-1825/AVG-8 mounts on a large size helmet shell while model R-1826/AVG-8 mounts on a medium. The receiver includes a parabolic visor, which provides the pilot with a collimated reticle image. Two sensor electronic assemblies, one mounted in each side of the receiver housing, assist in converting the pilot's line of sight into aircraft coordinates. The main assemblies of the receiver are the housing, the visor assembly, and the harness assembly.

COMMUNICATION CABLE ASSEM-BLIES. Each of the helmet assemblies is outfitted with the appropriate communication components for operation with aircraft ICS (Intercommunication System).

M-87/AIC BOOM MICROPHONE AS-SEMBLY. The boom microphone assembly provides communication when the oxygen mask is not in use, as well as walkaround capabilities.

NOTE: Detailed information on the fabrication of the form-fit liners can be found in the NAVAIR 13-1-6.7.

SIZING THE PRK-37/P

When building up the HGU pilots protective helmet, it is very important that you start with the proper size helmet shell (PRK-37/P). The PRK-37/P is available in four sizes, (medium, medium/large, large, X-large). To determine the proper size, you must first measure the circumference of the head, at the hatband line, with a tape measure. Once you have the correct measurement, you can determine the equivalent helmet size by referring to table 4-3.