The PRK-37/P shell is lighter than the APH-6 and the shell has been cut
back in the area of the eyes allowing a greater field of vision over the APH-6. Originally
the standard HGU-33/P used a foamed in-place custom fit liner, designated PRU-39/P, but
later helmets were equipped with the VTEC form fit liner, designated PRU-39A/P. Gentex
manufactures both a Thermal Plastic Liner (TPL) and a Custom form fit liner that meet the
penetration requirements of MIL-H-84047. But these are not standard procurement for this
helmet. It should be noted that custom fit liners appear to pre-date this helmet in Navy
Service. That is, the form fit liners seem to have been around longer than the HGU-33/P.
HGU-33/P U.S. Navy Fighter Attack Aircrew Helmet was designed as a lightweight replacement
to the APH-6 series of flight helmets. The HGU-33/P performance requirements are specified
in military specification MIL-H-85047. The HGU-33/P Designation was assigned May 11, 1973
by request of the Naval Air Engineering Center. As with each new flight helmet, the
HGU-33/P is supposed to provide better comfort, fit, visibility and wind blast protection
than its predecessors. NAVAIR 13-1-6.7 specifies that the HGU-33/P as used in any
aircraft where an oxygen mask is used exclusively. This includes but is not limited to the
F-14, F-18, AV-8A, most Navy Trainers. It should be noted that any change in the
configuration of an HGU-33/P normally results in a change in nomenclature. As an example:
replacing the EEK-4A/P single visor with a PRU-36/P dual visor automatically re-designates
the HGU-33/P to an HGU-44/P.
The HGU-33/P is based on the PRK-37/P Shell Assembly. The PRK-37 Shell is
constructed of fiberglass cloth molded with epoxy resin. The helmet is painted a
non-yellowing white, conforming to MIL-C-83286B. A foam edgeroll around the periphery is
covered in black leather. The helmet shell comes in two sizes: Medium, and Large. A chin
strap is used,but the nape strap is a later addition.
The standard EEK-4 A/P visor Assembly is used. a clear and neutral gray lens are
interchangeable without removal of the visor housing. Optional lens for the EEK-4 A/P
include gradient, amber, vermillion, and for laser protection. The Navy version of the
EEK-4 A/P Visor assembly includes a blue lock knob and a visor housing with the US Navy
Decal. An optional visor kit comes with a white visor lock knob and a visor housing
The helmet is compatable with the MBU-14, -15, -16, -17 oxygen masks using the standard
oxygen mask recievers and offset bayonets. As noted earlier, the EEK-4A/P visors are
trimmed for the MBU-12/P which is the basic component for the MBU-14,-15,-16, -17 masks. There
is no provision to upgrade the HGU-33/P to use the MBU-24/P (Combat Edge) mask or
occipital bladder. However the MBU-23/P which is identical to the MBU-24/P (except for the
occipital bladder valve attachment) could be used with the HGU-33/P, but it isnt
likely. Lens would need to be trimmed for the masks????
An absorbent, washable
skull cap made of cotton is also used to absorb perspiration.
Provided via standard Navy assembly. CX4708A/AIC four conductor cord terminating with pins
for connection to the H-87B/U earphones on one end and a U-172/U plug on the other. Rubber
grommets seal the wiring at the MX-8376/AR Earcup while a larger rubber grommet surrounds
the area where the cord passes through the helmt shell. A MK-634/AIC clip affixes to the
large rubber grommet and holds the U-172/U plug (microphone plug) tightly to the helmet.
The HGU-33/P is manufactured by Gentex and Sierra Engineering. The HGU-33/P has
been replaced by the Navy version of the HGU-55/P, HGU-68/P, HGU-85/P, HGU-87/P (=HGU-68/P
with Combat Edge bladder) and HGU-89/P (=HGU-85/P with Combat Edge bladder).
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