THE 1950 HELMET EVALUATION
By the first half of the '50, the Swiss Air Force was involved in the development project of the first indigenous jet fighter/ bomber aircraft, the EFW (Eidgenössisches Flugzeugwerk) N-20 « Aiguillon » (Stinger). At the same time the De Havilland DH-112 Venom (1956) and Hawker Hunter Mk. 58 (1958), both fitted with an ejection seat, were nearing introduction into the Swiss Air Force.
Simultaneously, tests were ongoing in order to evaluate the possible installation of identical equipment on DH-100 Vampires (which received ejection seats in 1960) already in service.
Rapidly increasing jet aircraft speeds and the added forces in case of an emergency ejection at high speed would soon far surpass the protective capacity of leather C-types and fabric "Stoffhauben", in use at the time.
Information about new developments in pilots’ head protection were gathered from US publications, namely 1951 issues of « Naval Aviation News » and “Shell Aviation News” about the USN H-3, and from “The Martin Star » about the improved version of the USAF P-1, the P-1A.
Meanwhile, a member of the FAI (Fliegerärtzliches Institut - Aero Medical Institute) at Dübendorf who flew as a backseater on a USAF T-33 Shooting Star in 1949, positively reported about the helmet he wore, a P-1. Once back in Switzerland, he proposed to start an evaluation procedure in order to provide Swiss AF pilots with efficient protective helmets.
The evaluation process started in 1951 by contacting US Government departments/organisations through Swiss and American military attachés and by simultaneously contracting the Sportex company of Zürich for the import-export logistics.
The H-3 delivery took place during the summer of 1952. After some modifications, in order to make them compliant with the Swiss communication systems installed on DH 100 Vampires and piston engine Moranes still in use with the advanced pilot schools, FAI personnel tested the helmets in flight.
Despite being considered not completely satisfactory due to excessive weight, a rear hard shell shape which made head movement difficult while looking upwards and heat build-up and impaired vision, the H-3 was proposed, purely due to a lack of competitors, as the ad-interim equipment to be provided to jet pilots.
Still waiting for delivery of the P-1A, the FAI asked Sportex to include the P-1A improved version into the order, as well as the P-3 to be fitted standard with a swinging visor, and to try to expedite the provisioning process.
In early 1953 Sportex explained in a letter sent to the AF that the delivery delay was caused by the US administration not deciding about who should have taken responsibility in giving the permit to export the helmets.
In the meantime, a French model, the ”Societé les Complexes Verre Résine, Type 27”, later identified in the reports as the “French Model”, is proposed as an alternate equipment, also claiming the possibility to have it produced in Switzerland.
While wind tunnel tests with the H-3 had already started, simulating speeds up to 800 Km/h, the long awaited models P-1A and P-3 were finally delivered and handed over to the AF by late summer 1953.
Both deliveries “opened up” the possibility to obtain other flight helmet models. A comparative test campaign started during the first months of 1954 including a “new” helmet model, the USN H-5.
Distributed to selected squadrons for test flying on DH-100 and DH-112 were:
P-3 with visor;
H-3 with Polaroid M-1944 goggles;
P-3 (P-1A?), with American Optical Calobar sunglasses;
H-3, AO Calobar sunglasses;
H-5, AO Calobar sunglasses.
As found during the helmet trials, the use of M-1944 goggles was considered unsuitable due to the impaired vision field caused by plastic lenses scratches and sweat, in addition to an inadequate protection in case of ejection. A helmet-installed visor was deemed the better solution.
Until then, of all the helmets tested, only one of the two
P-3 configurations was fitted with a visor, unfortunately the latter resulted not being compatible with Martin Baker ejection seats. During simulations performed with a loaned MB ejection seat training rig it was found that the upper ejection seat initiating handle was getting stuck in the visor yoke-protruding handgrip during seat activation.
The solution was found when the British Mk.1A "Bone Dome" was integrated in the helmets evaluation list, its “Visor, anti-Glare, Mk.2”, configuration obviously compatible with the MB ejection seats fitted in DH-100/ 112/ 115 and Hawker Hunters.
With the visorless Mk.1, the Mk.1 A was part of British pilot’s equipment while conveying jets from the UK to Switzerland. It was designed as “standard RAF model” in the assessment reports.
Trial installation of a Mk.2 visor on a P-3 took place, and this configuration was duly included into the test schedule. In the meantime, another helmet, the H-4, was also added to the assessment list.
In mid-1954, a meeting took place in Dübendorf in order to assess the performed evaluations. The results of the technical and flying tests were the following:
P-3 with visor: too heavy, not compatible with MB ejection seat, test crew report of heat build-up with closed visor, visor yoke scratching aircraft canopy;
P-3 (P-1A?) without visor: too heavy, heat build-up;
H-3 without visor: hard shell rear shape creating difficulties to upper airspace monitoring (limited head movement), inner liner too hot in summer;
H-4 without visor: hard shell rear shape creating difficulties to upper airspace monitoring (limited head movement), inner liner too hot in summer, replaced/superseded by the H-5;
H-5 without visor: light, comfortable, good shell design, considered by most pilots the best model;
“French Model” Type 27: no chin and nape strap, leather padding directly in contact with pilot’s head, heat build-up, adjustment for proper fit not possible.
British “Standard Model” (Mk.1A): Compared to the P-3 slightly lighter, vision not impaired with lowered visor, compatible with MB installation.
Eventually it was decided to limit the final assessment to two models, the H-5 and the Mk.1A.
H-5
In 1956, at the end of those last trials, the board in charge of the selection designated the H-5 fitted with the British Mk.2 visor as the future helmet for the Swiss AF.
In use with A-14, A-13A and H-Type oxygen masks (later replaced by MS22001s), with a number of modifications implemented during the years, the H-5 would have had a long life within the Swiss AF and used till the end of the '80 on fixed wing aircraft, and even beyond on helicopters.