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The HGU-33/P flight helmet
by: Steven C. Norris
Last updated 1 June 2007

The 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 it’s 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.

Helmet Shell
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 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.

Visor Assembly
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 without decal.

Oxygen Masks
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 isn’t likely. Lens would need to be trimmed for the masks????

An absorbent, washable skull cap made of cotton is also used to absorb perspiration.

Communications
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.

Known Manufacturers
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).

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.