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The PRK-37 helmet shell assembly
by: Steven C. Norris

About 1978, the U.S. Navy began using the PRK-37/P Helmet Shell as the basis for nearly all of its non-helicopter flight helmets. Collectors, dealers and a few authors have misidentified or failed to identify the variations of the PRK-37/P. The following information is several years old and does not take into account recent developments for U.S. Navy flight helmets. But, should clear up some of the mystery surrounding the PRK-37 Helmet shell.

For starters, the PRK-37 helmet shell is listed as a Lightweight version of the APH-6 series helmet. The manual goes on to explain how various components are attached to the basic shell assembly to get the desired configuration (and there are a bunch). The parts of interest:

Visor Assembly Parts

EEK-3/P Laser Protective Visor Assembly. Looks like the standard dual visor assembly only has the Green colored laser protective visor instead of the tinted visor.
EEK-4A/P Single visor Assembly. Standard Navy single visor assembly.
PRU-36/P Dual Visor Assembly. Side actuated standard dual visor assembly.
VTAS Dual Visor Assembly. Visual target Acquisition System (VTAS)

Liner Assembly Parts

PRU-39/P or 39A/P Form fit Liner. Take a cast of the wearers head and make a liner off of it, custom fit.
PRK-40/P Liner Assembly. Two piece Styrofoam liner used with sizing pads

Communications Headset Assembly

The standard Navy communications setup with CX-4708A/AIC cable with two H87B earphones, with the U-172/U connector and MK-634/AIC Clip.
AM-3597C/A Boom Microphone amplifier and mounting bracket. Used helmets that use the M-87/AIC boom microphone which require amplification.
CX-13164/A communications cable is used with the AM-3597C/A Boom Microphone amplifier and mounting bracket. This cable adapts the boom mic and amplifier to the OV-10 aircraft.
CX-13155/A communications cable. Slight variation of the CX-13164/A. It is also used with the AM-3597C/A Boom Microphone amplifier and mounting bracket. This cable adapts the boom mic and amplifier to non-fighter type aircraft (S-2, E-2A, EA-3 etc.)
CX-4832A/AR Communications Cable. Adapts the flight helmet to communications equipment on the P-3A/B/C aircraft. CX-13128/A Communications Cable. Adapts the flight helmet to communications equipment on the S-3 aircraft.

The Finished Units

HGU-33/P: PRK-37/P shell, EEK-4A/P single visor, PRU-39 Form fit liner and Headset. Officially for use in aircraft where an oxygen mask is used exclusively.
HGU-34/P: PRK-37/P shell, EEK-4A/P single visor, PRK-40 liner assembly, and Headset. Officially for use in aircraft where an oxygen mask is used exclusively and the guy didn't have time to get a cast of his head made. The only difference between a -33 and -34 is the liner. It gets better.
HGU-43/P: PRK-37/P shell, EEK-3/P laser protective dual visor, PRU-39 Form fit liner and Headset. For use in A-6 TRAM aircraft. (HGU-33/P with a laser protective dual visor).
HGU-44/P: Same as the HGU-43/P only use the PRU-36/P dual visor or same as the HGU-33/P only with the PRU-36/P visor.
HGU-45/P: Same as the HGU-44/P only a boom microphone is attached, and the CX-13164/A communications cable is used with the AM-3597C/A Boom Microphone amplifier and mounting bracket. This helmet is used in the OV-10A aircraft when both an oxygen mask and boom microphone is used.
HGU-45A/P: Same as the HGU-45/P only swap the PRU-36/P for an EEK-3/P laser protective dual visor assembly for use in OV-10D aircraft.
HGU-46/P: PRK-37/P shell, VTAS Dual visor assembly, PRU-39 Form fit liner and Headset. Used in F-4 aircraft equipped with Visual target acquisition system.
HGU-47(V1): PRK-37/P shell, EEK-4A/P single visor, PRK-40 liner assembly, and Headset boom microphone is attached, and the CX-13155/A communications cable is used with the AM-3597C/A Boom Microphone amplifier and mounting bracket. Used by pilot, co-pilot and crew-members on the following aircraft: S-2, E-2 A/B/C TE-A2, KA-3B, TA-3B, T-28B/C.
HGU-47(V2): PRK-37/P shell, EEK-4A/P single visor, PRK-40 liner assembly, and Headset boom microphone is attached, and the CX-13155/A communications cable is used. No amplifier is used. Used by pilot, co-pilot and crew-members on the following aircraft: C-1A , C-2A.
HGU-47(V3): PRK-37/P shell, EEK-4A/P single visor, PRK-40 liner assembly, and Headset boom microphone is attached, and the CX-13164/A communications cable is used.No amplifier is used and the cable is the CX-13164/A instead of the CX-13155/A. Used on the T-34 Aircraft.
HGU-47(V4): PRK-37/P shell, EEK-4A/P single visor, PRK-40 liner assembly, and Headset boom microphone is attached, and the CX-4832A/AR communications cable is used on P-3 A/B/C.
HGU-49: PRK-37/P shell, EEK-4A/P single visor, PRU-39 Form fit liner, standard Headset and boom microphone is attached. The CX-13128/A communications cable is used with the AM-3597C/A Boom Microphone amplifier Used in the S-3 aircraft.
HGU-50: PRK-37/P shell, EEK-4A/P single visor, PRU-39 Form fit liner. Standard headset wiring is replaced with the 20039 Communication cable. The helmet is equipped with a boom microphone and two CX-13154/A communications cables are used with the AM-3597C/A Boom Microphone amplifier. The helmet is used in the aft stations on EA-3B aircraft.
HGU-52: PRK-37/P shell, EEK-4A/P single visor, PRU-39 Form fit liner and standard headset. The helmet is equipped with a boom microphone and the CX-13155/A communications cable used with the AM-3597C/A Boom Microphone amplifier. The helmet is used on E-2 and A-3 type aircraft.

If you have some additional information or corrections about this article please contact Steven C. Norris or us to make this datasheet even more complete.