Developed as a replacement for the SPH-4 helmet series, the HGU-56/P provides a platform for a range of modules.

During the service life of the SPH-4 series helmet, it was evident that several crashes with military helicopters could have had a different ending. The protective capability of the SPH-4 could have been a lot better. In the past, helmets were developed to function as a vehicle to carry the communication devices and provide protection against sun, sound and debris. The US Army Aero medical Research Laboratory established the requirements for a new aircrew helmet. This was based on the result of studies performed on helicopter crashes involving SPH-4 series helmets. When the US Army laid out the operational requirements for the HGU-56/P, they recognized that the helmet was being drawn into the mission scenario of the aircraft itself through the need for helmet-mounted sights, displays and night vision goggles. It also needed a better side impact protection. 

Helmet components:
The helmet shell is constructed of advanced graphite and polyethylene. The helmet shell protects the head from impact and sharp objects and weights less then older designs. On the back of the helmet is a build in airway for an air-conditioner to vent across the head and visors for cooling and defogging. This blower adapter assembly, located at the right rear, is designed for the future addition of a blown air cooling system. The adapter features a locking tab that prevents accidental disconnection of the blower hose. A hinged cover assists in keeping dust out of the connector assembly when the hose is no in use.

The energy-absorbing liner absorbs and reduces impact forces. It is made of polystyrene material. Channels and cutouts in the liner allow space for internal components. The liner is attached to the inside of the helmet shell via hook and pile fasteners.

The thermoplastic liner (TPL) consists of molded polyvinyl acetate sheets. A washable cloth cover covers these. The preformed TPL will fit most head shapes. If necessary, the TPL can be heat softened and custom-fitted. A ventilated thermoplastic liner is also available for operations in climates where additional ventilation is desired.

Retention assembly, this consists of two ear cup retaining pads that support the ear cups and the ear cup spacer pads, a chinstrap and a nape strap pad. The chinstrap is made of nylon webbing reinforced with aramid tape. It helps holding the helmet in place. D-rings allow tightening and loosening this strap. The nape strap pad is located at the inside rear of the helmet (beneath the TPL). It improves stability by reducing forward rotation when the nape straps are adjusted snugly. The retention assembly is also available with a square buckle to meet user requirements. The assembly can withstand a 400 pounds pull.

The ear cups are attached to a retaining pad. Spacer pads may be installed behind them to improve fit. Ear seals provide comfort and sound attenuation to protect against hearing loss and improves communications in a noisy environment. The ear cups are of injection molded design and has superior energy absorption to protect from side impact. 

The communications system consist of a pair of earphones in the ear cups, a communications cord and a swivel assembly. The earphones are tucked inside each receiver retainer and are backed by a filler pad. The communications cord attaches the ear cups and microphone to the helmet shell. The swivel assembly holds the boom, which serves as a mount for the microphone. This boom showed to be a lot less strong then the older ones and tend to break a lot.

The dual visor assembly has a neutral and clear visor lenses. These are operated via actuating knobs on top and on the side of the assembly. The housing provides a quick-disconnect mounting area for ANVIS goggles. The housing is also available with a direct ANVIS mount. Other lenses are also available. These include amber, high contrast, blue, gradient and laser protective lenses.
The outer neutral visor is raised and lowered by the left-hand actuating knob. The inner visor is raised and lowered via the right-hand actuating knob. A tab on top of the ANVIS mounting platform allows for one-handed attachment and removal of the goggles.

The helmet is also suited for the Cobra dual visor assembly that allows use of the helicopter's tracking system and build in helmet sight. An oxygen mask adapter allows the use of standard USAF mask for high altitude operations. For operations with open doors and windows while flying, the helmet can be fitted with a blast shield.

The helmet is available in six different sizes. The design of the shell makes it compatible with the M-43 US Army chemical warfare mask and hood.

More information on the HGU-56/P can be found in our ANVIS and THG articles.