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During the mid-1980s, the Swiss AF was looking for an aircraft suitable to replace the Mirage III. Among those evaluated the Northrop F-20, Mirage 2000, F-16 and the F/A-18, the evaluation winner.

Due to the ever-improving performance and air combat tactics, pilots were increasingly exposed to high acceleration. As a result, according to the Dübendorf FAI (Fliegerärtzliches Institut - Aero Medical Institute); spinal disorders were increasing observed with the weight of the pilot's helmet/mask system playing a significant role.

The FAI consequently proposed to the AF to evaluate/ purchase new lightweight helmet and mask systems, with the lowest possible weight, optimal centre of gravity and good wearing comfort.

The helmets currently in use were the Gueneau 316 and the Protection, Inc. DH-151, equally considered of "old" design and no longer compatible with the performances of the new aircraft generation, especially in terms of weight.

The “new” HGU-55 was entering in service, planned to replace them both. According to those who had managed its introduction there was not a real evaluation, the HGU-55 deemed the best option regarding system compatibility with the also new Northrop F-5E/F Tiger II.

In the meantime, most likely for economic reasons - "local" and "ad interim" solutions sought. Given the availability of spare parts, HGU-55 "lookalikes" created with shells of grey painted DH-151 fitted with modified Gueneau 316 and HGU-55 bungee visors.

The request to procure helmet-mask systems with the lowest possible weight, optimum centre of gravity and good wearing comfort instead of the existing equipment arise. The goal was not to exceed a total helmet/mask weight of 1 Kg.

The combined technical testing and troop trials had the following main objectives:

  • The review and assessment of the new available helmet/mask systems design;

  • The assessment of their weight and center of gravity position;

  • Compare them with the systems already in use at the Swiss AF;

  • Evaluate them during operation and air combat in terms of protection, comfort and safety requirements;

  • Analysis and comparison of the technical differences between the three systems, including their impact on handling and protection;

  • Based on the results, select a system; assess its technical maturity and suitability for troops use with subsequent application for type procurement.

A pre-assessment took place during 1986 with a prototype proposed by Gueneau.



Gueneau supplied three specimens identified as S-001/002/003. The definition S-00x (S - Suisse?) simply identified a helmet and not the helmet’s model (unknown to date).

Evaluated on ground and in flight on F-5 and Mirage III, the helmet was fitted with an Intertechnique EROS (Équipement Respiratoires à Oxygène de Secours) MP91 oxygen mask.

  • Positively rated the helmet's low weight, comfort, visibility, and mobility in the cockpit, however, several problems were also observed:

  • Given the peculiarity of its construction, in order to have a proper seat of the mask and earpieces it was necessary to tighten its harness a lot, creating painful pressure points. On the other hand, during long times in cockpit on the ground with the mask worn loose for better ventilation , the helmet’s ear cups were moved away from the ear and the radio communication possibly overheard in the presence of additional external noise sources; Even with the system adjusted, noise attenuation and communication quality deemed insufficient;

  • The adjustment of the mask with 3 variable suspension points deemed difficult and time consuming, as the helmet with its 3-piece shell also not having a defined fit;

  • Suboptimal nape strap installation; awkward anti-glare visor control operation, in conflict with the (Mirage III) ejection seat operating handle.

In short, apart from its low weight, the prototype had no advantages and many disadvantages. In addition to those mentioned above, there were also doubts about its real ability--given its configuration--to protect against impacts. For this reason, the Gueneau S-00x evaluation was discontinued.


GUENEAU prototype S00x

EROS MP91 oxygen mask 

The evaluation resumed in 1988.

Three helmet/mask systems from three different manufacturers were available for the tests. Two set intended for flight evaluations, one for laboratory testing:



Various communication system configurations were also tested; products from Electro Voice, Astrocom, Holmco, Gentex, Racal and SILEC were installed on helmets and masks; their performance evaluated in flight and in the laboratory.

Additionally, one ea. GENTEX HGU-55/P (the helmet already in service with the Swiss AF) available for benchmarking purposes. The tests to be carried out:

  • Flight tests regarding comfort, handling, safety and protection;

  • Evaluation of technical compatibility with F-5 E/F; Mirage III S/RS; Hunter; Hawk and PC-7;

  • Measurement to determine the field of view restriction with the helmet worn;

  • Noise attenuation measurement and impact penetration assessments to be performed at the EMPA - Eidgenössische Materialprüfungs- und Forschungsanstalt (Swiss Federal Laboratories for Materials Science and Technology) in Dübendorf;

  • Wind tunnel tests;

  • Troop use suitability tests.


During the flying tests, performed for 220 missions, all helmets developed problems solved in cooperation with the manufacturers. Nevertheless all three types still had some, unacceptable, shortcomings.


The system generally rated positively, with some exception. Main one the visor too close to the eyes, so people who wear glasses could not wear the helmet due to lack of space.


  • Good noise attenuation;

  • Very good freedom of movement thanks to large neckline;

  • Good mask fit in all situations;

  • Stable and sturdy visor actuating mechanism;

  • Good donning comfort.


  • Helmet “sitting high” on the back of the head;

  • Helmet not suitable for eyeglass wearers, as the distance between the visor and the face being too small.



The Titlis turned out to be the heaviest helmet of the lot, and it showed manufacturing defects; the specimens supplied had to be sent back to the factory for repair and corrective actions.


  • Very good wearing comfort;

  • Good center of gravity;

  • Very good mask fit even under high “g”.



  • Turning the head upwards and backwards produces unpleasant to painful pressure on the nose area;

  • Poor (tinny) audio quality;

  • Mask support cumbersome to operate;

  • Oxygen hose obstructing the view of the left cockpit side panel severely;

  • Chinstrap configuration not acceptable as not provided with a quick release system;

  • Visors operation poor. Single-handed operation hardly possible. Friction between dark and clear visor too high.



We do not have detailed documentation available; however, the helmet described as a possible development of the HGU-55/P.



  • Very good and comfortable ear cup position, optimal adjustability,

  • Good noise attenuation, good comm quality;


  • The mask exerting sometimes painful pressure on cheekbones;

  • Comparatively the greatest visual obstruction due to the mask body;

  • Freedom of movement to the upper left restricted by the too short oxygen hose;

  • Single-handed operation of the two visors only possible to a limited extent, lateral fit of the two visors is not stable.



HA-LP G010-2000-02 oxygen mask. 

The opinion of the pilots regarding comfort, use, freedom of movement and weight ranked the ZEUS and the H-ATS as the best options; the Titlis, in the form tested due to its weight, flaws identified and development still needed at the bottom of the list.

Although all the systems tested have made significant improvements over the existing helmets and masks such as smaller mass, better centre of gravity, appropriate fit and stability at high (ejection) speeds (from wind tunnel tests), none of the tested three system reached the mass requirement of max. 1 kg weight and fully met the requirements.

In comparison with the HGU-55/ HA-LP/PPB oxygen mask, which weights around 1.6 kg, there was no decisive gain for the user. In fact, the “winner”, out of competition and never subject of a "real" evaluation was the HGU-55, in service to this day.

The "light helmet project" closed by the end of 1989, as none of the three evaluated systems achieved the desired requirements. However, as the need for a reduction in helmet mass undisputed, it was agreed to follow market developments and reactivate the procedure as applicable.

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