THE SWISS GUENEAU 316
At the end of 1969, due to the outgoing wear and tear of the H-5s, a requirements specification enacted the launch of an evaluation procedure aiming to find an improved replacement helmet for Martin Baker ejection seats equipped aircrafts.
According the above specifications, the helmet had to meet the following criteria:
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Have two visors, one of which clear as protection from bird strikes, air draught and hydraulic oil, suitable for night missions;
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Have a dark visor; both to be protected against mechanical damage by a cover hood;
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If necessary, the capability to replace one of the two visors with a gold-plated one as atomic flash protection;
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Have a larger field of vision than the H-5;
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Have a greater neck clearance than the H-5 to ensure better upward airspace surveillance;
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Have good fit on the head through adaptable foam filling, effective ventilation against heat build-up and lightweight;
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Have well-fitting ear cups, to ensure maximum noise attenuation and thus good radio reception;
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NT-49505 (MIL-E-17884 B) headphones, CX-4707/AIC cable and U-174/ U Plug;
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In addition, visors adjustment knobs installed on helmet sides, so as not to hamper the ejection seat activation.
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The specification foresaw the supply of 120 helmets and the same number of gold plated visors by the end of 1970; in addition, the possibility of providing the same type of helmet to helicopter crews to be considered.
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Unfortunately, we do not know what happened and which helmets were taken into account during the evaluation, some evidences found and the above specifications suggest versions of the HGU-26 including the "ramshorn" one. Fact is that the documentation in this regard takes us to 1974, the only remaining evaluated helmet to be the Gueneau 316 of whose assessment results made public.
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The main issue being the helmet proved to be too heavy for helicopter pilots, as they fly normally longer than jet ones. This result in a longer wearing time and increased fatigue.
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Due to this, the requirement specification that the new helmet to be supplied to helicopter crews abandoned, the procurement of new helmets only pursued for jet pilots; as a temporary solution the continued use of the phased out H-5s (from jet ) for helo pilots.
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Following the first evaluation carried out, before the large-scale (reduced to 70 helmets) trial distribution, a number of modifications to the original French standard 316 implemented:
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Removal of the clear visor (g-depending) lowering mechanism;
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Both visors separate locking and adjustment capability;
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Limiting the rotation of the helmet’s oxygen masks coupling;
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Use of padding inserts of different thicknesses for better fit;
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Installation of adjustable neck strap;
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Installation of chinstrap;
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Replacement of the original communication harness with a SPH-4 one;
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Installation of Cosmetan dark visor.
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In both French and Swiss versions, the left oxy mask bayonet is mechanically locked into the receiver to prevent the mask from accidentally disengaging completely. To remove the bayonet from its receiver's slot, The French version requires the locking screw removal. By the modified version, unlocking is done by means of a spring plate. Swiss receivers are also limited in rotation.
Details of the Swiss modified LH bayonet receiver.
LH the original neck strap, RH the adjustable one.
​The French 316 not provided with a chinstrap, installed on the Swiss ones.
ULMER masks, 79 N, 82 A, and 82 H, tested together with the helmet were declared as not suitable or not fit for military use (“Nicht Truppentauglich”). Rectifying the identified deficiencies possibly involving considerable expense, efforts to achieve it not put into action. To ensure the helmet compatibility with those in use, as the MS22001 and MBU-5, the original helmet communication harness replaced by the SPH-4 one, though the low impedance (19 Ohm) Silec S-3061 earphones remained installed.
Swiss helmets have the earphones securing straps pointing upwards as the ones fitted to the Gueneau 317. The reason for this arrangement is not mentioned in the documents we have available, but possibly due to the comm harness U-174/ U plug bracket installation .
installation of the boom mike bracket;
And as per the specification requirements, anti-nuclear flash visors were tested, but never put into service.
Eventually the 316 was put into service, on all types of fixed wing jet and “slow movers" like Pilatus P-3, PC-6/ 7/ 9 of the Swiss AF inventory, unfortunately not without flaws.
As already emerged during the tests, the helmet was considered too heavy; additionally, the metal grommets/ eyelets fitted to the helmet had a tendency to scratch the narrow (and costly) jet aircraft canopies.
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To overcome this problem, a number of attempts made, such as the application of padding on the top/front of the helmet shell. Reportedly, this solution rejected due to the fact the padding blocking the shell's vent holes thus creating problems in case of an ejection.
In order to solve the above problems, a dedicated leather pads/ bumper kit fitted to the helmet's shell.
The pads, made of the same grey leather used for the "Pilotenjacken" (pilot jackets), were glued to the helmet shell, effectively covering the top metallic grommets/eyelets and the visor knobs.
Small round neoprene pads also applied in front and aft of the visor mechanism mounting plates, and below the two top/centre (unpunched) leather pads.​
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The solution not being completely satisfactory, the life in service of the 316 on fixed-wing aircraft came to an early end.
While still issued as "on loan" helmets for student pilots on Pilatus PC-7’s in the late 1980's, was superseded by the DH-151 respectively the HGU-55/P.
A "Modifiziert" was tested with the French/ German low visibility grey camouflage paint and a French Ulmer 82 J oxygen mask.
Despite the 316 deemed unsuitable for helicopter operations already at the early stage of its evaluation, due to its weight and the longer mission durations for helicopters compared to those for fixed wing aircraft, the Gueneau 316 was in some cases used on Sud Aviation Alouette II/ III helicopters, instead of the standard SPH-4. This might have been a question of "personal choice" of – possibly- ex jet pilots.
The helicopter helmet has the same configuration as the jet one but with the M-87/ AIC boom mike fitted to the typical Swiss mike bracket.