THE 456th FIGHTER INTERCEPTOR SQUADRON

T PROTECTORS OF  S. A. C.

 

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The History Of Flight Helmets

 

Aircrew Protection in the Jet Age:

by Christopher T. Carey

 

 

 

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   Who, among aviation buffs and action fans alike world over, could ever forget the exciting scenes of fighter jock’ icy-calm bravado as pilots repeatedly pushed the aircraft combat performance envelope to the limits in such movies as ‘TOP GUN’ and ‘THE RIGHT STUFF?’ It took a pretty beat libido and low testosterone titer to sit there and watch these stirring adventures in the wild blue yonder without feeling a distinct thrill shoot down the spine like a Sidewinder missile.

 

    Unfortunately, for every natural born, eagle-eyed Chuck Yeager, there are several thousands of poor souls who, despite having spent a lifetime blazing new paths across the sky in their daydreams, were not favored by fate with the right combination of abilities, circumstance and opportunity, to achieve such a lofty ambition as actually piloting a state of the art fighter aircraft beyond the speed of sound and into the heat of combat.

 

    Today, one of the most interesting means these legions of armchair fighter jocks have at their disposal to expiate these unrequited yearnings is to collect aircrew accoutrements and protective flight gear. Perhaps you can’t actually walk the walk and talk the talk of the righteous brotherhood of military pilots but you can certainly pursue the fascinating hobby of surrounding yourself with the tools of their trade and in so doing, vicariously bask in the undiluted glory of their calling.

 

    Of all these ‘tools’ used by the military pilot, perhaps the most glamorous of them all (to the wannabe Tom Cruise) is the pilot’s flight helmet. Just as in the medieval era, when a knight’s ornately decorated helm simultaneously symbolized all of those chivalrous qualities that ennobled him as a fearless fighting man, the protective helmet an aviator or aircrewman wears visibly sums him up as a card-carrying member of this elite fraternity of fliers. Each flight helmet visually tells a unique story about the special requirements for pilot safety and protection modern high-performance military aviation has demanded over the years, as the technology of military flight has continued to advance in quantum leaps. Additionally, personalized color schemes and decorations may also serve to mark various specimens as unique examples of their type.

 

 

 

Some Early Aircrew Protective Helmet History:

 

 

Spalding stiff leather aviator helmet, about 1920

  Today, almost 100 years since the first powered, heavier-than-air flight took place, the advances in aircrew protective equipment span such a great broad range that for reasons of convenience and necessity, collectors of flight helmets fall into two categories: 1) the era of propeller-driven flight, and 2) the jet era. It is fairly easy to see, in examining flight headgear from the earliest days of flight through the present, that it has been largely the increasing challenge to pilot safety in terms of the physics of flight encountered that has dictated the form and substance of latter-era protective headgear.

 

    In the early years of the 1900s through the end of the Second World War, the aviator’s helmet was made of soft leather and intended purely to protect him from wind and cold. As advances in wireless radio communications developed, the leather helmet began to feature earphones for radio receivers; still later, as turbo-charging technology permitted higher aircraft operating altitudes, oxygen mask attachments became standard as well. Early eye protection in the form of rubber-framed glass goggles were adopted virtually from the fledgling days of manned flight as the most reasonable way to protect the eyes--especially in open-cockpit machines; this yielded out of necessity, as operating speeds became substantially increased (in jet aircraft), to more substantial, rigid visors intended to protect aircrew from the deadly wind-blast effects of emergency ejection.

 

    Although the crash forces encountered in the early days of aviation were in a sense just as deadly as those created by far more modern high-performance aircraft, little thought was then given to providing a pilot’s head with added protection in the form of semi-rigid shells. Partly this was the result of insufficient materials technology adequate for use in headgear designs, but nevertheless one regularly finds the concerned attempt to provide sturdier, reinforced head protection for aviators in aviation’s earlier years. Several designs (one French, another Italian,  several German) originating in Europe (and many more from other nations including the USA), surfaced in the first two decades of powered flight, consisting mostly of thickly padded and leather reinforced sections added to the upper hemisphere of a conventional soft leather helmet. Other examples are discovered from time to time in studies of flight protection in these early years. In the 30s and 40s, German glider pilot students, for example, sometimes wore substantially reinforced, aluminum-shelled helmets as crash protection in their lightweight sailplanes of the 30s.

 

    In the Second World War, further logarithmic increases in technology brought on by war research resulted in the development of Whittle’s pioneering axial-flow turbojet engine in the West and in similar radial flow designs produced in Germany. Ironically, in the United States, the need for sturdier protective aircrew helmets had been investigated by no less distinguished an investigator than aviation medicine's high-altitude researcher Dr. Harry G. Armstrong  (in 1938) and found 'unnecessary'.

 

"Modified Tanker" helmet used by first P-80 jet pilots,  1946

    However, with the higher speeds permitted by jet engine powered aircraft, more thought was now being given to sparing the pilot from the potential hazards resulting from even greater inertial forces encountered in high-speed flight. Just before the war ended, German aeronautical laboratories had developed a protective helmet design that drew heavily upon then-existing steel shelled flak helmets, using an outer aluminum shell similar to the NSFK glider helmet. Advanced flight helmet studies in penetration resistance and crash-worthiness by Germany’s aeronautical laboratories were in progress when Berlin fell, but again it appears the technology simply had not yet been sufficiently advanced to permit adoption of production standards which truly satisfied the requirements. The closest that these studies got to producing a production hard shell 'crash helmet' for Luftwaffe flyers were steel flak shells that fitted over the soft leather helmet; they were not intended, however to protect aircrew from inertial forces of increasingly higher-speed flight.

   

USN H-2 helmet,  1949

In the post war United States, experimental rocket aircraft testing at the Mojave desert’s famed Muroc Field made it apparent that improvement was sorely needed in aircrew helmet design, as the P-80 Shooting Star, the Bell XS-1, and other experimental high performance projects developed. Although the Air Force aeronautical lab in Dayton was working on standard rigid “crash helmets” for use by aircrew, which would soon come into use, key flight test personnel such as Col. Albert Boyd and Bell Aircraft’s ‘Slick’ Goodlin were adopting their own early expressions of rigid crash protective helmets. In some cases, these were borrowed directly from sportscar racing and occasionally a helmet was home-made (as in the possibly apocryphal story wherein Chuck Yeager borrowed an old football helmet and cut holes in it--to allow for earphones to be fitted--for use in his Bell XS-1 flights). There are other examples of privately fabricated or constructed protective helmet designs to be found that were produced at this time and prior to the initiation of standardized military aviation 'crash' helmets, but such specimens are exceedingly rare today in view of the fact that few were saved after they served their purpose.

USAAF P-1 helmet,  1948

  Similarly, when the very first US  Army Air Force jet squadrons of P-80 Shooting Stars were formed after the war's end (1946), members of the new all-jet 412th Fighter Group's squadrons donned US Army tanker helmets that had been especially modified to fit over existing AN-H-15 and A-11 soft helmets. It was apparent that whether officially sanctioned or not, some sort of enhanced head protection was mandated by the new standards of performance that jets ushered into operational reality.

 

   In the late 1947 the first standard USN and USAF production ‘hard hats’ came into use with the development of molded nylon fabric and thermally set phenolic resins technology. The first US Navy hard protective helmet was designated the H-1 and had a distinctive shape which set it apart visually from the first USAF hard shell design, the P-1 (which had been inspired by Dr. Lombard's studies in helmet design at WPAFB's aero-laboratory). Whereas the Air Force abandoned the fabric inner helmet and hard outer shell combination (an experimental prototype designated the P-2), the US Navy, after producing their fully integrated H-1 and H-2 hard helmets, soon reverted to the original concept of using a fabric inner helmet to which a hard helmet shell was added for their later (early 1950s) H-3 and H4 series.

 

USAF P-3 helmet,  1953

  Quite soon after it was adopted, the USAF's P-1

 helmet was upgraded to an improved and modified version called the P-1A, which was in turn followed by the P-1B (this was merely a designated P-1A). An experimental design known as the P-2 was briefly studied (this helmet never entered standard USAF use), the purpose of which was to evaluate the US Navy two-part helmet design (with soft inner helmet and hard external shell) for possible Air Force use. In 1953, the P-3 helmet specification, which was the first USAF effort to provide an externally articulated rigid visor (for windblast protection), was introduced; the P-3 helmet was essentially a P-1A/B type helmet to which a visor was permanently affixed . Both the P-3 and a subsequent P-4 design used an original side-latching, trackless visor design; this was superseded somewhat later by an improved visor design on the P-4A helmet and in 1959 a final specification was called the P-4B (each of the two latter helmets used fiberglass as a basic shell material instead of the fabric/resin shell construction of earlier helmets). The P-4A and P-4B visor were the same, but communications components differed in that the P-4B helmet used an oxygen mask communications cord to link the helmet to the aircraft communications system; this change did away with the so-called "pigtail" cord exiting the helmet at the rear, as found on P-1 through P-4A helmets. Incorporating the same rigid external visor assembly used earlier, the new visor articulation of the P-4A and P-4B helmets did away with the complex and awkward side-latch mechanism and substituted a central track with a release actuator mounted on the upper part of the visor. The new central track visor system was infinitely easier for a pilot to manipulate in flight than the early side-latch design (although still less than fully ideal).

 

USAF P-4B, last model of the P-series,  1959

Changes in helmet communications system components (earphones, com cords, and connectors) continued to be made throughout the 1949 to 1960 period. As each new protective helmet T.O. specification came into standard Air Force use, older helmets still being used were invariably updated to meet the latest technical change (T.O.) requirements. For this reason, most examples of the earliest US Air Force hard-shell crash helmets (such as the P-1, P-1A/P-1B, and P-3) that are found today, are substantially modified and updated and therefore invariably do not reflect their original issue configuration (this is rarely the case with US Navy counterparts). It is not unusual to routinely find early P-1A series helmets that have been fitted with a late-model (central track P-4A type) rigid external visor and corresponding H-143/AIC communications components, which technically updated them to the last P-4B specifications. For this reason , knowledge of the complexities of the official Air Force Technical Orders applicable to the P-series helmets is mandatory if one is to successfully identify and correctly label a particular specimen. (Note: for a capsule summary of the important specifications and changes effected, see the attached appendix, following this article, which provides a useful baseline of basic data).

   

USN APH-5, archetype design for all that followed,  1958

Faced with a need to upgrade naval aviator head protection, the Navy’s Air Crew Equipment Laboratory (ACEL) soon produced (1958) an entirely new design called the APH-5, a bellwether design which basically set the general configurationally standard for subsequent helmets used by all US   military aviation forces from that time onward. By 1960 the US Air force had evaluated and adopted a design based upon the Navy’s APH-5, which was designated the HGU-2/P, and in 1963 the old original P-series helmets had been practically replaced by the new design with its covered external visor (although due to production and distribution delays, the older helmets remained in use well after the new design had been accepted as “standard”). Interestingly, when the early HGU-2/P was introduced it featured the same leather oxygen mask Pull-the-Dot® snap fastener tab system used on the earlier P-series helmets; in the mid-60s, a new oxygen mask retention system, using what were called MD-1 ‘Hardman kits’ (an oxygen mask shell and harness suspension system which utilized notched bayonets and helmet-mounted receivers) initially replaced the long-used Pull-the-Dot® system on Air Force helmets. The Navy used a similar system on its later APH-5 helmets before introducing a modification on its later APH-6 model, which incorporated a newer mask retention system utilizing unique ‘butterfly’ type pinch releases (the Hardman system did not remain in use long, as both services eventually standardized on the presently used ‘Sierra kit’ bayonet type mask receivers). In passing, it should be noted that there were several interim designs explored by both services (although not adopted in large production volumes); these include the interesting US Navy H-5 and the APH-7 helmets, examples of which may still be found, although infrequently. 

 

USN AOH-1 (HGU-20/P),  1966

   One especially interesting concept developed in the 60s period was the so-called 'clam-shell' design. Technically known as the US Air Force HGU-15/P 'Windblast Helmet' (USAF version) and the US Navy AOH-1 / HGU-20/P (US Navy version). Developed as an integrated head protective unit with oxygen breathing system built in, the 'clam-shell' featured a two-part shell that opened and shut like a marine bi-valve's shell. It featured a swivel articulated face visor,  with separate articulated sun-shade, and looked very much like the conventional pressure helmet used during this time (such as the Navy's Mk.IV Full Pressure Helmet Assembly). While the windblast protection afforded by the whole-head clam-shell helmet design in emergency high speed ejection was excellent, there were also aspects of the design that were found to be operationally unsuited (especially for high-G air combat situations). These included substantial weight of the assembly, bearing down disagreeably on the wearer's spine in high negative-G maneuvers and turns, fouling of the chin-piece on parachute harness hardware,  lack of adequate peripheral fields of vision, and lastly, a tendency to leak around the rubber faced seal of the assembly.   Thus, after a year of testing by both services, the 800 or so 'clam-shells' produced were rejected and the design faded temporarily into a dusty corner of history (but reemerging somewhat later in a different form for NASA crews).

 

USAF TLSS helmet,  1985

  One other experimental series of studies of note is the USAF 'TLSS' (Tactical Life Support System) project of the mid-80s, which attempted to combine for the first time all elements of a complete environmental protection package for high-performance aircraft crewmen (these included high-altitude protection, NBC protection, and anti-G protection). While the TLSS system (an ambitious project from the onset that was extensively flight tested at the Edwards Air Force Flight Test Center near Mojave, California) was never adopted as originally designed, the many research advances derived from this important project resulted directly in the consequent operational Combat Edge system in use today, and many other products for current or planned use in the F-22 Raptor Advanced Air Superiority Fighter. Interestingly, much of the precursor research that gave birth to the TLSS system stemmed directly from pioneering RAF aviation medicine studies of the 50s.

 

   From the mid-60s onwards, modifications continued to be made as advances in aircrew protective helmet technology led to new products, incorporating both new materials and new fabrication techniques. These modifications included communications upgrades, twin-visor designs (one clear and one smoked, a feature principally used in bombers, training aircraft, and special applications for protection against bird strikes), the use of new materials in the external shell, and updated oxygen breathing mask systems. In fact, a whole new series of designs has since evolved, making accurate identification of these items more challenging than ever for those recently introduced to the field of modern era aircraft helmet development history. Overall, one of the chief lessons learned from 20 years of research was that for high-G fighter type air-combat situations, two factors were heavily weighted over all others: excellent peripheral visibility and low mass/weight.

USAF Combat Edge prototype,  1988

 

    Complicating things somewhat, the wide range of aircraft life support systems used in US Navy aircraft during the 60s through the 80s resulted in even more complexities in helmet and mask systems, which varied considerably from those meeting US Air Force standards. After years of this extreme variance between Air Force and Navy requirements, a mandated effort was made by the DoD in the late 80s to standardize both services’ life support equipment requirements that to date has been moderately successful, bearing in mind the lessons learned about suitable high-G protection requirements, cited above.

 

    Among the most important advances in recent protective helmet design have been enhancements designed to improve peripheral vision for fighter pilots, attempts to reduce helmet weight to lessen effects of high G-forces on the pilot’s neck, and substantially upgraded oxygen masks and mask retention hardware. Many of these modifications, which are at present reflected in such more advanced assemblies as the US Air Force HGU-55/P and MBU-20/P Combat Edge system (or the US Navy's HGU-68/P and MBU-24/P helmet and mask equivalent system) for enhanced combat maneuvering capability, have literally been forced into being by the need to protect pilots from the physically brutal G forces modern high-performance aircraft are capable of inflicting upon their more fragile human operators. These changes have been prompted by the fact that for the first time ever, modern military jets are being engineered to withstand more Gs that their human pilots are capable of sustaining.

 

 

 

 

Collecting ‘Jet-Age’ Flight Helmets:

 

 

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    Today, one of the most rapidly growing areas of militaria collecting activity is centered on military flight helmets of the modern or ‘jet’ era. Although a few individuals have been collecting flight helmets for many decades, only recently has this special area within general militaria collecting gathered monumental inertia. One of the early precipitating stimuli of this groundswell was the release of the movies ‘TOP GUN’ and Tom Wolfe’s ‘THE RIGHT STUFF.’ Focusing public interest anew on the glamour and glory of modern ‘hot’ military aviation, these films created a surge in the area of collecting of modern aviation memorabilia in general. Subsequently, the relatively recent release of Alan Wise’s and Mike Breuninger’s excellent book, JET AGE FLIGHT HELMETS  (1996) has predictably resulted in a further and massive wave of interest in the collecting of these interesting artifacts of modern military aviation. Although there are some generally overlooked errors in the Wise and Breuninger book, prior to its release there had been no adequate concentrated historical reference upon which to develop a knowledgeable basis for interest in modern flight helmets. JET AGE FLIGHT HELMETS accomplishes this feat in a single substantial tour-de-force of photo-documentation, and the book’s cost ($75) is a small price to pay for such a beautifully illustrated and valuable reference work on a hitherto fore obscure and under-researched subject (Schiffer Publications, Atglen, PA).

 

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    There are, of course, several even more specialized sub-areas within the general field of helmet collecting which bear mentioning. Some aviation headgear specialists limit themselves almost exclusively to high-altitude protection components such as pressure helmets (and their component partial and full pressure suit systems), eschewing anything more than a passing interest in helmets used in ordinary (or non-high altitude) aircraft operations. As this is a very specialized area of interest and subsequent to a recent wave of increased interest in such things by modern aviation militaria collectors, the spectacular costs associated with collecting of these items have recently soared beyond the reach of most individuals of ordinary means.

 

    Regrettably, this same broadened awareness of military flight helmet collecting in general has had some substantial impact upon availability and cost of the more common helmet artifacts among collectors. For one thing, prices have begun to increase to absurd levels for otherwise relatively ordinary items (due to lessened supply and enhanced demand). For another, more than a few people advertising themselves as being in the business of authoritatively selling aviation memorabilia are now asking unrealistically high prices for items they actually lack any real authoritative knowledge of. Although there are specialists such as Wise, Breuninger (there actually two Breuningers, both brothers), Wilson, Gilliam, Daugherty, Norris, LeBeau, Patterson, Mattson, and a few others who have true expertise in these areas, many others lack basic understanding of the technical variations frequently found in early military flight helmets, which constitute the basis of their distinctive model identification. This insufficiency of technical knowledge is reflected in their advertising and pricing of some items far beyond their true worth.

 

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NASA LEH helmet (Launch-Entry), dev. from HGU-20/P, 1984

    An excellent example of this is found in the misidentification of some early jet-age helmets (particularly USAF P-series types) by some aviation memorabilia dealers. As mentioned earlier, the early P series helmets which remained in use after newer types ‘came into standard’ were regularly updated to meet the latest Air Force TO Standard specs. Consequently, what is commonly advertised as being a P-1A helmet by an unknowledgeable dealer may actually bear little factual resemblance to the original “as issued P-1A helmet” that the knowledgeable collector is seeking, due to the possible addition of a P-4 type external visor, bayonet mask receivers, upgraded communications sets, or possibly even a P-4/P-4 type helmet suspension harness fitted to a P-1A shell. The only method by which one encounters true “as issued” original-specification P-1A helmets these days is when they have come from personal effects saved by a family which had a member on active duty in the Air Force at the time when the helmet was issued and who kept it when he left the service (shortly after it was issued or before it had been affected by T.O changes). As such, and usually painted in colorful squadron markings, these helmets when found today constitute a fascinating ‘time-warp anomaly’ discovery that makes them extremely valuable finds to the knowledgeable early flight helmet tyro.

 

  Care must also be exercised in buying helmets sight-unseen through mail order businesses unless the seller is known personally, as attempts to ‘rebuild’ or restore helmets purely for resale profit potential can occasionally be encountered in instances wherein a somewhat less than completely honest dealer attempts to sell a ‘restored’ item as an original. There is, unfortunately, no substitute for a visual, hands-on inspection of any helmet one is interested in, with reference to type, condition and originality, unless the dealer’s reputation is well established. Still another 'market-induced' practice that has come into being recently, is the practice by some of buying old flight helmet shells and 'restoring' or 'rebuilding' them with new or surplus components.  While some of these efforts are exceptional, there are far too many that are inaccurate, less than expertly crafted, and in some cases, completely incorrect. The careful and knowledgeable collector takes great pains to learn as much as possible about the history of aircrew life support equipment so as to be adequately prepared to spot these 'phony' restorations and avoid them when they are clearly overpriced.

 

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Special NBC modified HGU-15/P "clam-shell", , one of only 16 made, 1974

   A further effect prompted by the recently enhanced interest in military flight helmet collecting is price gouging, resulting from increased demand for an increasingly smaller number of items. Perhaps the best example of this is the current asking price for an HGU-15/P or HGU-20/P “clam-shell” Aviator’s Integrated Oxygen Helmet (AOH-1). Originally produced in limited quantities by Robertshaw Controls (with sub-contractor Sabre Industries) in the mid-60s, not many years ago few individuals actually knew much about this very unique and interesting helmet, let alone were willing to pay almost any price to obtain one. Operationally tested by both the US Air Force and the US Navy as an advanced design which provided enhanced wind-blast protection and eliminated the need for a discrete oxygen mask, the AOH-1 design was found to be too cumbersome and visually restrictive for naval combat use and was ultimately retired after a short period of trial applications in USAF F104s, F105s, and USN F4B Phantom,  A-4 Skyhawks, and A-7 Corsair II aircraft. Much later (early 80s), the same design was revived by NASA and issued to flight crews of the first STS space shuttle missions (up to and including the ill-fated Challenger mission in 1986) as an LEH crash protective helmet (known as the Launch & Entry Helmet, it was adopted virtually unmodified from the Navy’s HGU-20/P except for the addition of a second microphone and a Kevlar shell). Original specimens of the HGU-15/P (USAF version, also known as the Windblast or Mach 2 Helmet) and the HGU-20/P (US Navy version) were once available for as little as several hundred dollars. All variants of this design have come to be popularly known as “the clamshell,” a term which originated during the original development program in the 60s, and which is not to be confused with the early USAF K-1 “split-shell” pressure helmet. Today, excellent examples used in either service routinely bring prices in excess of several thousand dollars! Surviving specimens of the 16 HGU-15/P helmets that were specially modified as NBC protective assemblies in an experimental Air Force chemical/biological defense project (which began in April of 68 and ended in June of 70) can command as much $4000 or more.

 

 

The Future Of Flight Helmet Collecting :

 

    As this is being written, existing stocks of many of the earlier jet-age flight helmets are in the process of being depleted and disappearing. Some, such as original, unmodified examples of the early USAF HGU-2/P have become increasingly rare (most were attired during the Vietnam war, unfortunately, and thus early HGU-2/P examples remain one of the rarer finds today), and others, such as the fascinating HGU-15/P-20/P “clam-shell”, are now beyond the reach of all but the most serious and/or fanatical collectors (mea culpa!). Still, the history of these interesting artifacts of the jet age is richly rewarding both to those who are interested in the history of aeronautical protection equipment and to those who collect aeronautical memorabilia.

 

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Chinese TK-4A pressure helmet,  early 1990s

    This is especially so now that many foreign jet-age helmets of other nations (many formerly hostile enemies of the US) are currently finding their way into this country and comparisons between foreign and US design approaches are revealing interesting advances in the evolution of aircrew protection technology which the US did not instigate or even fully consider! Examples of this are found in Russian (formerly Soviet) aircrew helmets (ZSh-5 and ZSh-7) which featured visors that automatically actuated upon ejection, and in occipital air bladders which served both to help combat negative G effects (termed “G-Loc”, or “Gravity-induced Loss of Consciousness”) and hold oxygen masks more firmly to the face during high-G maneuvering. In both areas, Russia pioneered development of the technology which is today considered mandatory for enhanced safety in advanced fighter operations. The use of a snap-strap secured hard visor, such as found on the current US Air Force HGU-55/P helmet, was actually introduced by the French at a much earlier date! The interesting and somewhat hard to find Chinese TK-4A pressure helmet is another unusual design that combines features of several different design approaches; bringing to mind older helmets such as the US MA-2 and English Taylor E pressure helmets,    the TK-4A also resembles more modern pressure helmets such as the USAF HGU-8/P and the HGU-20/P  in certain aspects.

 

    If asked to make a personal list of the most sought after and scarce jet age US aircrew helmets today, I would have to include all the early US Navy helmets (H-1 through H-5), all the early USAF helmets (from original P-1 through P-3), the early USAF Pressure helmets (including the K-1, MA-2, HGK-13, etc.), clearly the 'clam-shells' (especially the very rare USAF HGU-15/P 'Windblast Helmet'  and NASA LEH versions), the TLSS helmet and the HGU-51/P F-111 NBC helmet.

 

    With authentic, original examples of older jet-age helmets starting to become scarce, collectors must be especially watchful for unscrupulous individuals advertising helmets for sale, at great cost, as “genuine” that have been ‘built-up’ (or put together from parts and pieces, not infrequently inaccurately). Most reputable dealers take pains to be honest in their business, but there are a notable few who take grossly unwarranted liberties in this manner. As always, caveat emptor!

 

    On-line auction houses such as eBay have had both a positive and negative effect on this area of collecting; while prices for examples offered frequently grow way out of proportion to their actual value to a knowledgeable expert, a plus side is that many, many interesting specimens come to light that would otherwise not become known about.

 

    Hopefully, however, reason, a sense of proportion, and a spirit of fairness shall prevail as retail business and commercial speculation in the growing hobby of collecting aircrew protective helmets heats up, driving flight helmet prices unrealistically higher in a continuing cost escalation to the hypoxemic sub-stratospheric heights wherein such items were originally intended to protect their wearers!

 

Photo and audio credits:

    Thanks to NASA, Lockheed-Martin Skunk Works, and Trey Turner III of Check-6 Aviation for photographs used in this article, along with the author’s. Audio track courtesy of James Charles Kaelin http://www.earthstation1.com/

 

 

A History Of USAF P-Series Flight Helmet Development

 

Of all the so-called 'hard' or 'jet-era' protective flight helmets produced in the United States since the introduction of enhanced protection requirements (which were prompted by the use of the new turbojet engine to power military aircraft), the most interesting to me have always been the very first USAF designs from about 1948 through approximately 1964.

These were the P-series helmets and they constituted the first American Air Force attempts to provide standardized cranial protection from crash and cockpit movement injury for pilots and aircrew flying the new, fast, jet-propelled airplanes that were entering service from about 1945 onwards.

When the National Defense Act of 1947 resulted in (among other things) the emergence of the US Air Force as a separate service, the requirement for a pilot's protective military flight helmet had already been issued under the aegis of the Army Air Forces command and a design finalized. US jet aircraft, notably the P-80 Shooting Star (the first standard production American combat jet aircraft generated in large numbers), had been flying since about mid-1945. Just as the pilots of these aircraft lacked adequate head protection, necessitated by the higher performance of their machines, so too did the aircraft themselves lack any sort of vestigial provision for rapid, safe emergency egress (ejection seat systems), other than the traditional 'bail-out' over the side of a stricken craft.

Prior to the institution of a standard protective helmet design for use by all high performance aircraft crews, a number of unofficial and innovative designs were used by the earliest jet aviators—particularly by the pilots of the new Lockheed P-80A Shooting Star squadrons, whose personnel devised interim cockpit "bump protection" in 1946 by using the rigid fiber shells from WWII ‘tank crew’ helmets as an outer shell over existing soft AN-H-15 (summer), A-11 (winter), and A-10 (summer) flying helmets.

US Army Air Force Specification number 3277, drawing number 47R3184, resulted in the very first hard protective flight helmet, designated the "Type P-1 Flying Helmet". This was the result of Technical Order (TO) 13-1-37 / WF-(A)-O-17 Dec 1948, originating from Wright Field’s aeronautical laboratory. At about the same time, the first ejection seat systems were being introduced into jet aircraft; it is interesting to note that Army Air Force air research and development investigators had actually been concerned with and were actively looking into the pressing problem of how to exit a high performance aircraft safely, somewhat in advance of parallel concerns about protecting the head of jet fighter and bomber aircrewmen who flew the machines. Further, no less an authority on aviation medicine and flight physiology than the US Army Air Corps’ Dr. Harry Armstrong had much earlier (late 30s) investigated the possible benefits of rigid protective helmets for aircrewmen and found them ‘impracticable’.

Over the next 15 years (from about 1947) the original Type P-1 Flying Helmet (substantially based on pioneering studies done by Dr. Lombard of Northrop Aviation) gradually evolved into its final configuration (known as the Type P-4B), a process that is best understood by modest familiarization with a profusion of complex Technical Orders (T.O.) that accompanied the updated specifications. Just how these changes regulated identification of P-series helmets will be briefly discussed here, in hopes that this will enable those who are fascinated by modern protective flight headgear to more readily understand and identify the different P-series helmets that were our first US Air Force 'hard' protective aircrew helmets.

[One final note: Although an earlier type designated helmet was frequently upgraded to a subsequent specification, new production helmets manufactured at the precise moment a specification was in force were also given the same 'current type designation'. Thus, a type designation could be borne equally by both an older helmet (through T.O. upgrading) and a new one, by virtue of simply being a newly manufactured unit built to current specifications. This fact has created endless amounts of confusion, as regards positively and correctly identifying a particular P-series helmet today, and it is the chief reason why so many factors must be considered in deciding what designation a P-series helmet should properly bear in a chronological history.]

 

The Type P-1 Flying Helmet

This first hard protective helmet, the forebear of all US protective flight helmets today, came about as per the Wright Field Aircrew specification referenced above. Identified as Stock Number 8300-396400, this helmet was not intended to enable a pilot to survive a crash as much as to provide head protection within the close confines of the jet fighter (and bomber) cockpit. Thus, "crash-helmet" is a misnomer and actually somewhat misleading. "Hard-hat" and "brain-bucket" were terms in favor among US pilots for these items, while "bone-dome" was a distinctly British (RAF) term in use as the first hard helmets came into service on both sides of the Atlantic (the very first RAF rigid protective helmet was the Mk.I, which was worn with the RAF type "G" soft communications helmet underneath). There were many other slang terms for these items of 'personal equipment' that were somewhat less polite and the new helmets were at first not readily accepted by all air crews, who sometimes found them awkward to wear, visually restrictive, and uncomfortable to get used to. [There is at least one authenticated report of a pilot removing his early hard hat and using it to relieve himself, rather than leave the controls of a multi-engine type aircraft.]

The US Army Air Force Type P-1 Flying Helmet (for as such it was first known) was constructed of pressure and heat molded laminated cotton duck fabric that had been saturated with phenol-resin (essentially similar to "Bakelite"). It was produced in one shell size (based closely upon the original "Lombard helmet" design) and used an internal head suspension sling of then-conventional design (similar to that used in Army infantry helmet liners and tanker crew helmets), consisting of a leather and cotton sling that could be adjusted through the use of laces at the rear to accommodate just about any size head. [Anecdotally, it is interesting to note that a study performed by the RAF in the 1950s found that pilots of fast, high performance (fighter) aircraft tended to have smaller head sizes than those who flew slower, multi-engine (bomber and transport) machines. We will stop short of engaging in any speculation about the size of the cranium in relation to the size of the pilot's ego, but the possibilities for formulating idle hypotheses are fascinating!]

The P-1 shell was issued in semi-gloss, off-white color paint, although it was not unusual to find them painted to suit the wearer's whims, with colorful personalized or squadron markings. The P-1 head-suspension sling crown pad was imprinted in white with "Army Air Forces" (this was very soon thereafter changed to "US Air Forces", and later "U.S. Air Force", when the service became independent of the US Army in late 1947). While I have no absolute evidence that the earliest P-1 helmets were issued with a decalcomania on the outer forehead segment of the hard-shell (as in the manner of the "US Air Forces" decal found on the subsequent P-1A), my resources indicate that many did feature a decalcomania of the traditional Army Air (Corps) Force winged star on a blue circular field (not unlike that used later, but without the lettering). Numerous photos and images from this period appear to provide evidence of this fact. The early P-1 head sling was identified by a woven black label that read "Sling Assembly for helmet, Pilot's Protective, Type P-1, Drawing no. 47D3185, Contract no. W33-038-AC1947S-(19413)". A manufacturer's name appeared in the last line and as per usual there were a number of primary subcontractors who produced the sling (among them Switlik Parachute Company, The Selby Shoe Company, The Bates Company, & the Joseph Beugelson Company). The P-1 head sling enabled a wide range of sizing adjustment, from about 6½ through 7¾, in use with the standard single size hard outer shell.

The P-1 type sling, initially made of leather and OD cotton fabric, was later made of leather and nylon fabric (starting with subsequent TO versions of the P-1: P-1A/P-1B). Standard military white parachute riser cord was used to attach the sling to the hard shell and this is identified in the P-1 TO as being "Cord, Nylon, Type III, Spec no. AN-C-63", from which the inner core strands had been removed. The Type P-1 helmet did not have a fixed (riveted) chin strap as did later upgraded versions, but instead could be secured to the head if the wearer desired, through use of a chin cup that snapped onto the lowest of the snaps on the oxygen mask mounting tabs. Invariably, when an A-14 or A-13A mask was worn with the helmet, the mask itself served as a head securing mechanism. There was no nape strap on the P-1 helmet (as with P-1A/P-1B). Further, photographs we have seen of the original P-1 helmet show it to have a black rubber edge roll that is distinctively different from that fitted to the P-1A/P-1B helmet; this is substantiated by examination of actual surviving specimens. The P-1 helmet also had black-finished leather oxygen mask tabs, positioned on either side of the front face opening, each tab fitted with three screw-threaded snaps for securing either the A-14 Demand Oxygen Mask or the A-13A (later MS22001) Pressure Demand Oxygen Mask; later P-helmets used brown-finished leather tabs and had light tan rubber edge rolls of a slightly different construction that did not protrude through the edge of the beading. A paper specification label was fixed to the inside of the hard shell in the area where a nape strap would later be added (in compliance with the P-1A TO).

The Type P-1 Flying Helmet used the Type HS-33 and HS-38 headsets initially, which featured the same kapok-filled, chamois leather covered earphone cushions found in all existing soft (leather or fabric) flying helmets , although the cushion attachment method differed from that used in the later P-1A TO upgrade. Active radio communications elements of the earliest original P-1 initially consisted of the standard AN-1-B (WWII type) electromagnetic earphone receivers, identical to that in use on all soft fabric and leather US Army Air Forces flying helmets from WWII onwards. Somewhat later, the P-1 headset specification was changed to HS-38, and then to HS-38A, incorporating slight modification and different earphone elements.

One important feature of the original P-1 helmet is found in the original manner of attaching the HS-38 headset cushions. The P-1 helmet initially used a system of earphone mounting retainer 'flaps'. These leather flaps were situated above and below the earphone hard-rubber holders on each side of the helmet and the cushions were secured in place with these flaps. This system proved less efficient than desired in actual flight use and in the subsequent P-1A design, earphone pads were attached via lacing at top (to the head sling harness) and bottom (to the bottom left and right hard shell). The original US stock numbers for the HS-38 and HS-38A headsets used in the P-1 helmet (and also in the subsequent P-1A) were "Electric Headset, 1790-207625000 or 1790-207625500" and "Electric Headset, 1790-207626000". Naturally, the P-1 featured the typical U75/U communications connector at the end of its 'pigtail' com cord, exiting from the rear of the helmet shell, as did all helmets of that early period.

The P-1 helmet, in its original, non-TO-updated issue configuration, is today among the 'rarest of the rare', and examples that are still able to be found have inevitably been upgraded to later specifications. Most have long since disappeared as they suffered structural failures in flight use and were taken out of service to be destroyed. Only a very few examples are now to be found and these were usually kept by the families of pilots to whom they were issued and whom had left the Air Force before the P-1A specifications were introduced. In terms of rarity, the Army Air Force Type P-1 Flying Helmet is on par with the original US Navy hard-hat design, the H-1 (also very few surviving examples are to be found today).

Although the P-1 specification (3277) is dated 1948, quantities of the new helmet were very limited at first and thus it was in short supply among US Air Force flying personnel at the onset, when introduced; photographs may be seen of P-80 pilots who were still occasionally wearing the soft tan AN-H-15 & A-10 summer flight helmets, or the brown leather A-11 well, into the 50s (this was especially true for training applications, particularly in propeller-driven aircraft such as the T-6, the P-51, where the soft fabric helmets continued in standard use for many years). As might well be understood, the first P-1 hard hat issue was prioritized for first-line, high performance, jet fighter aircraft crews. Before many of the helmets had been issued, however, the P-1 was upgraded to newer P-1A specifications and therefore there were not great numbers of the original, unmodified design manufactured (we are presently uncertain of specific numbers produced). By the time the Korean War began, the P-1A specification had been issued and most of the hard helmets used by US Air Force personnel when that war began were either originally manufactured as P-1As or had already been upgraded to P-1A specs. Of additional interest from a historical standpoint is evidence (Col. Ralph Parr, quoted in the new book "Hot Shots: An Oral History of Air Force Combat Pilots of the Korean War", ISBN 0-688-16455-2) that demonstrates the scarcity of these original hard-shell protective helmets at the onset of the Korean "Police Action". Col. Parr states that in early June of 1951, as he entered active Korean combat in the new F-86 Sabre, he was using a "broken helmet" (presumably a P-1) that was held together with duct tape; he further states that these helmets were so scarce that several of the pilots in his squadron flew wearing the type of plastic football helmet that were in use in the early 50s by college football players (that the pilots themselves had brought over to Korea, or had sent to them from the US by relatives). This probably ties in to a later decision to "reissue" the P-1A, which led to the P-1B type re-designation, after it was found that the older helmets were still needed by aircrews, among whom there was a scarcity of these items at the onset of the war.

 

The Type P-1A Flying Helmet

The P-1 helmet, while it provided pilot basic protection, was far from perfectly configured for comfort and functional adequacy. As mentioned earlier, the 'flap attachment' provision for securing headset earphone receivers was shown to be somewhat less than desirable. Further, the lack of a secure chinstrap was another shortcoming. The forces encountered in high speed ACM (aerial combat maneuvering) required that the helmet remain fixed in place without skipping out of proper adjustment on the head. Further, with the adoption of ejection systems in the new jets, properly helmet retention and positioning was even more of a pressing requirement. Several steps were therefore taken to address these shortcomings with the introduction of a riveted (permanently secured) chin strap that went under the chin, rather than around it. Additionally, it was shown that an additional strap, fitted so that it ran crossways behind the cranial occiput, helped considerably to maintain proper helmet adjustment for the wearer. At this time, rubber framed goggles of the B-8 type were commonly used with the P-1 to provide eye protection. Modifications taken to the basic P-1 shell included the addition of a fixed chin-strap, addition of a nape-strap, attachment of the HS-38 headset with Nylon cord (Type I, spec No. AN-C-63) at the top of the cushion assembly to the head harness and at the bottom to the helmet shell itself. A final modification involved upgrading of the oxygen mask leather attachment tabs, through removal of the original black finished tabs that protruded through the black helmet edgeroll, and replacement with light brown finished leather tabs secured to the inside of the helmet shell. The headset receivers and communications plug (AN-1-B receivers and U-75/U plug) remained initially unchanged.

A P-1 helmet, thus modified, was specified as the P-1A. As was the usual practice, any older P-1s in use when the new spec came into 'standard' were upgraded to the newer specification, but any new units manufactured during this period were produced already incorporating these improvements into the new stock. Whereas the P-1 shell was made in one size that accommodated all heads, via adjustment of the head harness sling, the P-1A helmet shell was made in two sizes (small and large). This was an important innovation that made a proper, comfortable fit more readily achieved. The head harness slings used in each of the two shells again permitted more precise adjustment. Finally, a unique identifying characteristic of an original P-1 upgraded to P-1A specifications is a cross-hatched lacing of the front lateral edgeroll, where the edgeroll was sewn shut with heavy duty light colored thread after the original protruding mask suspension tabs had been removed and replaced.

 

The Type P-1B Flying Helmet

The type P-1B Flying Helmet specification was created through a change in designation nomenclature only and the P-1A and P-1B helmets are otherwise identical in all respects. This came about as a result of a rescinded decision to take the P-1A out of standard service when the P-3 helmet was introduced; when demands of the new war in Korea required more and more of the aircrew protective helmets, and in the face of a critical shortage of these items, the P-1A was reintroduced into standard use with the designation P-1B (reference earlier remarks made by Colonel Ralph Parr of the 18th Fighter Wing--F-86 Sabre, Korea).

 

The Type P-2 Flying Helmet

Although conclusive historical research has not yet been completed on this designation, the Type P-2 Flying Helmet appears to have been a limited, non-standard research prototype design developed by Wright-Patterson Aeronautical Labs as a 'proof of concept' application of the new US Navy approach of utilizing a soft fabric (nylon) helmet to hold the communications headset under a hard outer protective shell. The Navy experimented with this idea and replaced its original H-1 helmet (and the subsequent H-2, which was somewhat similar) with the new H-3 design (using this concept) that consisted of a two-component (soft inner/hard outer) assembly (the Navy H-3 was in turn replaced by a slightly modified version known as the H-4, before the original integrated assembly approach was again adopted in the short-lived H-5 integrated helmet, a design used briefly by the Navy before standardization of  the APH-5 in the late 50s). The USAF P-2 design, of which only a single somewhat indistinct photograph is known (to me personally) to exist, shows a hard P-1 type white phenol resin impregnated cotton duck shell used over a conventional USAAF type A-10 khaki poplin flying helmet. Presumably, the headset is identical to that used with the A-10/AN-H-15 and the photograph referred to shows an A-13A/MS22001 type mask in use that is attached to leather oxygen mask tabs of the type used in the P-1 series helmets. Otherwise, the outer rigid shell features the same conventional design leather/nylon head suspension sling, fitted so as to accommodated the slightly extra protrusive bulk of the inner A-10 helmet. Although to this date, these facts have not yet been confirmed to me officially (research on the mysterious "P-2" in still underway), these hypotheses appear to be reasonably certain. Seemingly, the Air Force found that the Navy concept was unsuited for Air Force use and the original one-component, integrated design of the P-1A was kept and simply updated on a continual basis, until about 1959, when the new HGU-2/P helmet was introduced. [Of interest is the fact that the RAF initially also used a two-part helmet design in their Mk.I, which paralleled the US Navy’s originally rigid helmet approach.] Note that the photo image appearing above left of a P-2 helmet, is a reconstruction of the P-2 design based on photographic evidence, as no actual P-2 specimens are known to exist today.

 

The Type P-3 Flying Helmet

In 1950, a further modification was undertaken to add wind-blast protection to the P-1 style helmet. With improvements in aircraft ejection seat capabilities, pilots no longer dared attempt a manual 'bail-out' over the side of a stricken aircraft. Speeds and performance capabilities were simply too great to insure aircrew survival in such situations. The old B-8, rubber framed goggles were thus replaced by a new rigid, side-latch actuated external visor assembly. Rubber goggles tended to be blown off of the helmet in an ejection and the new visor assembly, while still far from perfect, went a great way towards helping insure helmet and mask retention against the effects of severe wind-blast that were routinely encountered in an emergency ejection at high speed. This early rigid, vertically articulated visor had two secure positions--full up or full down and secured. It used a unique sort of ratcheted pivot mechanism with each one of the two latches securing to a pinned triangular mounting plate positioned roughly at about the area of the helmet's temple, on both sides. Springs were used to pull the helmet visor into the full-up position when it was lifted free of the temple pins by positive forward and upward hand motion. This visor assembly was designated the PN 51C3632 assembly. Of central interest is the fact that any P-1 helmet (P-1A or P-1B) to which this rigid visor assembly was added, automatically became specified as a P-3 helmet. The P-3 was otherwise identical in all respects to the P-1A and P-1B helmets. As before, all older P-1A/B helmets were upgraded to the new type designation as circumstances permitted and helmets manufactured after the TO change came into force were produced with the assembly at the factory.

An item that is worth noting in passing is that due to the constraints of the Korean War on supplies in the combat areas, repairs to the headset cushion assemblies of P-1 and P-3 type helmets were frequently made using salvaged or cut-out kapok-filled chamois leather-covered cushion 'doughnuts' removed from AN-H-15 and A-10 type fabric helmets. Although the cushions were not absolutely identical in every respect to those used in the rigid P-series units, they were nearly so, and this explains the discovery of what appear to be AN-H-15 & A-10 type units fitted to early P series helmets that were used in and around Korea, from 1951 through 1953. For this reason it is therefore not technically 'incorrect' to replace old, worn-out P-helmet earphone cushions with AN-H-15 and A-10 type units today, when 'restoring' these early items of headgear. There was, after all, an expedient historical and practical precedent for the practice!

Because of its superior wind-blast protection, and also because of its additional sun-glare protective function, the Type P-3 Flying Helmet was mandated for use in all high-speed, high performance jet fighters and bombers. Somewhat later (in 1955 or thereabouts), a slight modification of the basic 'side-latch' rigid external visor was adopted. The differences between the early version and the later version are not readily apparent until two helmets fitted with each version are compared side by side. The principal modification was two-fold: the protrusive 'tab' located at the top of the visor mounting bar was done away with and the length of the side latch securing arm was slightly lengthened. In the case of the latter modification, this small change permitted the visor to swing up completely out of the peripheral visual area of the pilot's face, whereas the original ratchet-securing articulation permitted part of the lower lens on both sides to slightly obscure the upper periphery of the pilot's field of view. It is important to note that the rigid shaded visor lens used with the P-3 type side-latched visor came in three sizes (small, medium, and large); the size was determined as being equal to the distance between the top center of the visor and its lower nose-bridge point and had nothing to do with the curvilinear lateral measurement of the visor lens itself (as has been sometimes assumed). The correct visor size for a wearer was established with a ruler, after the correct mask had been fitted to the helmet. The visor mounting bar assembly was referred to in official T.O. references as the visor "yoke".

Other small changes that were incorporated into all the P-helmets at various times in the early to mid 50s included replacement of the original riveted chin-strap with a slightly modified one, addition of a chamois-covered, wool-cushioned pad to the helmet's chin-strap, replacement of the leather oxygen mask attachment tabs with ones that made the snaps more accessible, and introduction of a slightly newer head-harness sling. Overall, however, the P-1A through P-3 helmets were virtually identical for the most part and only the new rigid external visor distinguished the P-1 series from the P-3 series helmet, for all practical purposes. All the early P-series helmets including the P-1 through the P-3 helmets used the HS-33. HS-38, and HS-38A communications headset assemblies (AN-AIC-1, with ANB-H-1 earphone receivers) , with their characteristic chamois-covered, kapok-filled earphone cushions, and type U-75/U connector plug. The next major upgrade would come about with the introduction of the Type P-4 Flying Helmet specification in late 1955. [Of interest is the fact that chin straps found on early versions of the P-1A helmet—especially original P-1 helmets upgraded to P-1A standards--included olive drab cotton duck variants, as well as the white cotton duck straps that are more common.]

 

The Type P-4 Flying Helmet

The USAF Type P-4 Flying Helmet specification came about with the need to make helmet headset communications and oxygen mask dynamic microphone compatible with new aircraft intercommunications sets of the AN AIC-10 standard. The year of 1955 saw a number of upgrades undertaken to modify the P-series flying helmets. In early 1955 all earlier type P-series helmets (P-1A/P-1B, and P-3 helmets) were updated with the new H-75/AIC headset. Originally, the A-13A/MS22001 masks had used, as did the A-14A mask, the ANB-M-C1 carbon element microphone. With the introduction of newer noise-canceling dynamic microphones (M-32/AIC mask microphone assembly and the boom-type M-33/AIC assemblies that were used through the early Vietnam period), the new H-75/AIC headset system was added to the earlier P-series helmets (the earlier HS-38 headsets and ANB-M-C1 microphones were not compatible with the new aircraft communications systems coming into use). Unlike the original HS-38 type earphone cushion design, the new earphone cushions used more modern cushioning material (open cell foam rubber, protected by a black 'Hypalon' external skin). More importantly, the new system did away with the original and simple system of using sponge rubber half-rings to custom adjust the HS-38 kapok-filled chamois cushions to the pilot's ears. The new earphone cushion assemblies were spring mounted and tethered to short nylon strings which protruded through the lateral helmet walls to be secured over a rubber lock-nut and snubber bar. A type U-93/U com connector was fitted to the helmet communications 'pigtail'. Shortly thereafter (in July 1955), a slightly modified H-75A/AIC headset replaced the H-75/AIC assembly (TO 14P3-4-508). All helmets modified accordingly with the new communications assembly were type-specified to the new P-4 designation.

In 1955, all P-series helmets were officially upgraded to the new P-4 type specification, which called for the replacement of earlier headsets with the H-75B/AIC assembly. An earlier P-3 helmet, thus updated, became designated as a Type P-4 Flying Helmet. P-4 helmets, newly assembled were delivered directly from production runs with the new headset assembly. All T.O. updated   P-4 helmets still kept their early, original heat/pressure molded, phenolic-resin saturated cotton duck shell. However, all newly manufactured P-4 helmets made to spec Mil-7328A  were produced with new fiberglass shells. As before, the new headset used a rear exiting 'pigtail' communications cord, but the com connector was designated Type U-93/U. Also, in keeping with the earlier P-1A/P-1B system, the P-4 helmet was made in two sizes (small and large) only. A type JJ-055 microphone connector was an important feature of the new headset specification, the adoption of which required use of a slightly larger rubber 'boot' that was stitched to the left rear area of the helmet shell to replace the older connector and boot (this is simple way of determining at a quick glance whether an early P-series helmet has been TO upgraded to later P-4 type specifications; an original HS-38 type mic. connector would feature the smaller elongated "U" type rubber connector boot).

At about this time(1954-55), due to all the TO changes that appear to have been introduced to the P-series helmets, an already somewhat confused type designation system becomes slightly more so. Another change resulted in P-1A/P-1B helmets used without the side-latch visor assembly being re-designated the MB-4 helmet. It is important to note that the MB-4 configuration (which was otherwise identical to the P-4, except that it lacked the rigid external visor) was apparently intended for use in non-high performance aircraft, such as slower, multi-crewed bombers, transports, and utility aircraft, in which the extra protection of a wind-blast visor was not needed and in which the protruding mechanism itself might pose needless range-of-motion encumbrances on a crew flight deck or within a flight station. Here, the confusion increases further, as the external visor assembly was frequently added to the MB-4 designated helmets arising from individual pilot preference, although the rigid wind-blast visor was not standard to the MB-4 specification. Thus, surviving specimens of both the MB-4 and the P-4 can both be found today with the visor assembly...a situation which has created some consternation on the part of helmet collectors, flightgear archeologists, and life support historians. However, despite this apparent incongruity, the MB-4 and P-4 helmets were given mutually distinct PNs and other identifying nomenclatural numbers, according to the TOs. TO 14P3-4-508 dated 11 Jul 55 specifies that "...any P-1A/P-1B helmet updated with the newer H-75/AIC headset system (and lacking the visor) will be designated as Helmet, Flying, Type MB-4", whereas "...any P-3 updated to the (new communications) specification will be thereafter designated as Helmet, Flying Type P-4". One final observation here is of interest. The TO also specified that any helmet thus modified or updated would have the original helmet shell identification tag covered with a new, self adhering tag identifying the assembly by its updated type. Although some helmets treated accordingly will still have this added tag in place, in some cases it has been removed by collectors interested in learning what the original shell label specified. (Unfortunately, the label has not been placed back on the shell in compliance with the strictest spirit of authenticity, in many cases.)

Thus, all the early P-series helmets including the basic rigid helmet and suspension systems of the P-1, P-1A/P-1B, P-3, P-4, and MB-4, were essentially identical to each other, with only small, technical differences in communications assemblies, subcomponent items, visors, and accessory parts variations.

 

The Type P-4A Flying Helmet

In June of 1957, a new type visor yoke assembly was retrofitted to all earlier P-4 helmets. This consisted of the new visor mechanism that, while quite similar to the original rigid external visor assembly in superficial appearance, did away with the side latching design in favor of a tracked visor securing system actuated by grasping a central rubber knob and pulling the visor down into position. Two positions were permitted, full up and full down just as in the original design, but the new knob actuation was grossly simpler and somewhat easier for a pilot to accomplish quickly and positively. This new assembly was fitted to all external visor equipped P-helmets in place of the side-latch design, and there were two yoke sizes (small/PN 51C3632-1, and large/PN 51C3632-2) and three visor sizes (small, medium, and large). The P-4A specification was applied to all P-4 helmets thus retrofitted, but newly assembled P-4A helmets made use of the new fiberglass shell material that replaced the earlier phenol resin and molded cotton duck material.

T.O. 14P3-4-1 dated 30 Apr 57 states that "…with the exception of the new center-track actuated rigid external visor, type MB-4 and type P-4A helmets are identical" (although the MB-4 sometimes had the visor added by bomber crews that used them, as before). Further improvements to newly manufactured P-4A helmets included the incorporation of ensolite type sponge pads lining the internal surface of the new fiberglass shell at front, rear, and crown (replacing the original, older sponge rubber used in early P-series helmets). As before, the headset used remained either the H-75A/AIC or H-75B/AIC specification, but the communications "pigtail" ended in the U-93A connector (similar to the U-93). A further additional change that was instituted with introduction of the new P-4A TO specification was inclusion of an additional shell size: Extra-Large. The USAF PNs for the P-4A shells were as follows: Helmet, Flying, Type P-4A, Small, PN 56D3508-1; Helmet, Flying, Type P-4A, Large, PN 56D3508-2; Helmet, Flying, Type P-4A, Extra-Large, PN 56D3508-3. MB-4 helmets were, of course, originally P-1A/P-1Bs, and their PNs were: Helmet, Flying, Type MB-4, Small, PN 54D3733-1, and Helmet, Flying, Type MB-4, Large, PN 54D3733-2. Visors for the three P-4A shell sizes were: Visor, Small, PN 51D3643-3; Visor, Medium, PN 51D3643-2; and Visor, Large, PN 51D3643-1.

 

The Type P-4BFlying Helmet

In 1959, a final TO P-helmet specification was issued that consisted principally of a change in the headset communications cord assembly. The P-4B helmet specification did away with the helmet communications 'pigtail' cord and substituted a new helmet cord assembly designated CX-4708/AIC. This allowed the entire earphone and mask microphone communications system to be integrated into the aircraft radio and intercom systems via the oxygen mask communications cord H-149/AIC. The active earphone receivers were updated to H79/AIC specs and the previously used, spring-loaded earphone cushion assemblies were done away with. Instead, in what would appear a "retrograde progressive" move, the earphone cushions were again secured to the rigid helmet shell at upper and lower sections in a manner not unlike the attachment system used in the P-1A/P-1B helmet. Foam pads were again used to adjust the cushions to the pilot's ears. This system would also be used in the following, new generation helmet (the HGU-2/P), before a return to a slightly different type of spring loaded ear cup would return in the even later HGU-2A/P helmet.

The reason given for replacement of the helicoiled "top hat" spring-loaded earphone system in the P-4A was that some crew had apparently sustained severe injury in crash situations involving a crushing lateral impact on the helmet; in certain instances, it was found that the metallic spring units could actually be driven into the cranium, resulting in non-survivable head injuries to the temporal skull.

While older P-4A helmets were updated in the field to the new P-4B specs, newly manufactured stock featured all of these refinements directly from the factory run. The external rigid visor was unchanged from that used on the P-4A. Newly manufactured P-4B helmets had no plug-filled circular orifice at the rear of the shell (where a former com cord pigtail exited); older P-4A helmets that had been updated by squadron personal equipment/life support techs featured a black rubber plug in this area. As before, the JJ-055 mic. connector jack (outlet on pilot’s left) was used in the helmet earphone loom.

The early H-149/AIC oxygen mask communications cord, originally used with the late model P-helmets (B) and with the first of the HGU-2/P helmets that replaced the P-series, was superseded by the more recent CX-4707/AIC series oxygen mask communications cords (these last specification cords are still in use today in slightly updated configurations). [It is not altogether uncommon to find that a P-4A specification helmet was occasionally ‘created’ simply by cutting and removing the ‘pigtail’ communications cord, a modification which resulted in the functional equivalent of the new P-4B wiring loom!]

 

P-Series Visors

 

The P-Series 1st, 2nd, & 3rd Model Visor

As far as the P-series visors go, there are actually three definitive variations in the P-series evolution. The VERY early (original) P-series visors (1st and 2nd design) featured several characteristic design details that subtly set them off from the third and definitive refinement. Both of these early visors were successive evolutions of what I have come to term the "side-latch" visor, in that they lacked a center track (as found in the final design) and secured in an up-position by spring activated auto-retraction and down through the positive engagement of the short "J" arms (on the lateral aspects of the visor bar) onto the pins protruding from the temporal helmet visor-mount fixtures. The differences between the initial 'side-latch' visor and the successive version are to be found in 1) the protruding square metal flange that was located at the very top rear of the visor bar, and in 2) the short throw of the lateral "J" arms (about 1", versus 1&1/4" on the succeeding version). The short throw of the "J" arms was found to result in the protrusion of the lower visor edges in the upper peripheral field of the pilot's vision; this constituted a slight, but significant visual distraction--not something, as the popularity of the much later HGU-55/P helmet and the HGU-33/P cutaway visor-cover has borne out, that pilot's welcome in hot air-combat mixers. Further, this protuberant upward thrusting square flange on the visor bar, although intended to serve as a convenient gripping point for visor actuation by hand, was found to snag on things (such as parachute riser shrouds) and also scratched canopies. The second version of this original P-series visor came with this protuberant flange removed (close examination of one such visor bar will reveal only a short stub, where the flange used to be); furthermore, longer "J" arms on the side-latching mechanism (about a quarter of an inch, but enough to do the job quite effectively) allowed the retracted visor to secure in the open-position much higher on the helmet's forehead section--this removing the offending lower visor field's peripheral distraction up and away from the pilot's fields of vision. In the field, the early visor bars were frequently modified with addition of the longer "J" arms and the upward thrusting "grip" flange was filed off to a nub. [There were also two distinctly different, although superficially similar appearing helmet mounted attachment plates upon which the visors articulated. Very few of the earliest type, with a top pivot extension (rather than a bottom pivot, as found on the last type plate), are today found and almost all examples found on surviving early helmet specimens are of the second type.]

[One observation is salient here. The very first short-J arm side-latch visors featured a curious circular perforation pattern in the external yoke bow. This may be clearly seen in some of the earliest images shown in Air Force technical publications. The reason for this unique pattern of holes in the outer visor yoke is uncertain at this time, but subsequent to this appearance, the later yoke bows are noted to all be uniformly constructed of smooth metal (aluminum).]

The third and final P-series visor design used the new "center-track system", which is common to most P-4A and P-4B helmets (the early side-latch visors were used only on P-1A, P1-B, P-3, and P-4 helmets). It retained the familiar springs on both sides for full up visor placement (auto-retraction, once unsecured), but relied for securing in full down positioning on insertion of the visor's spring steel mounted and rubber knobbed ball-pin into a small square recess on the lower end of the track. Interestingly, this track was sometimes modified by the addition of additional holes spaced a short distance apart along the lower length of the track, so that variable positions of retraction could be achieved.

Lacking springs for positive self-retraction, the TOPTEX system used a variation of the center track idea but relied on friction alone to allow variable positioning of the visor to allow the pilot to adjust its shading effect. Arguably the USAF spring-actuated, side-latching visor system came into use first, but it is entirely possible that the later improved USAF center-track visor system (P-4A & P-4B) was inspired by the TOPTEX center track system. (Practically speaking, both the original USAF side-latch system and the TOPTEX center-track system came into being at roughly the same time, as nearly as I am able to determine.)

There were many complaints about the original side-latch visor from pilots; most reflected the fact that the visor was found to be somewhat difficult to engage and disengage the J-arms with a one-handed motion. As the aluminum corroded and gained a small layer of aluminum oxide on the J-arms and as the visor bar got knocked slightly out of true in the course of use, this difficulty became more pronounced. Further, if the "J" arms were not correctly positioned by personal equipment people to facilitate easy actuation of the "J" arm engagement, after addition of the new visor to older helmets, this would also enhance the recalcitrance of the visor to engage and disengage smoothly. These were common complaints about the original side-latch visor system.

While the later center-track system removed this problem, the old P-series visors were never an optimal design to begin with; further research into the matter by aircrew lab ergonometric engineers would have probably resulted in a better design, but concerns with the Korean War tended to divert attention away from "minor" problems such as this that were deemed less important than the greater overall concerns of that period.

In the broad and critical view of hindsight, the first P-helmet hard external visors were a simple and practically useful innovation for protection of aircrew against ejection air blast and canopy bird-strike effects. They were, however, still marginal in the greater and final assessment of their usefulness, when compared to their drawbacks, snagging tendencies, and user-deployment awkwardness. It remained till later, with the development of the HGU-2/P & APH-5 type visor, that a marginally better design came into use, although it is interesting to note that even today, with all the advancements in aircrew protective equipment that have been made since 1950, the perfect flight helmet visor design has YET to be perfected!

[A final bit of information bears recounting here: the original USAF side-latching visor system was used in a few instances on US Navy H-3 and H-4 helmet shells, when Navy pilots found the hard external visor system preferable to use of the old rubber-framed B-8 goggles in extreme wind-blast situation (such as in ejections, which were a new concern prompted by increasing jet aircraft performance parameters). There are no known or recorded instances, however, where the later USAF type center-track visor system was ever used on a US Navy helmet. ]

 

P-Series Oxygen Mask Attachments

The very first P-series oxygen mask attachment system used leather tabs (equipped with three internally threaded snaps), one on each side of the helmet’s frontal face area. On the P-1 helmet they were installed so that they protruded through the black rubber edgeroll material. Any older P-series helmet found today in that condition (or with the equally distinctive cross-stitched repair of these two edgeroll areas) is an original P-1 specimen. Starting with the P-1A, the old black tabs were removed and new (but very similar) brown leather finished leather tabs (also fitted with three screw-snaps) were installed. In subsequent up-grade modifications, these tabs, which fitted closer to the helmet than in later

 versions, were replaced by tabs that extended a bit further out from the helmet shell edge (allowing easier access to the snaps). In about 1958 a new bayonet type mask receiver made of polished metal was installed on some late model P-series helmets. This kit, made by the Hardman Tool Company and known as the MD-1 Kit, used a characteristic ratcheted bayonet sometimes known as "the Christmas tree". Both the US Air Force and the US Navy used this kit on their helmets, along with a fiberglass or plastic MS22001 oxygen mask suspension cup fitted with straps to the bayonets (the leather tabs were removed when this kit was

installed on the helmet). Shortly after introduction of the Hardman kit, an even newer mask suspension receiver & bayonet system was introduced by the Sierra Engineering Company of California, which is still in use today (known appropriately enough as the "Sierra Kit"). This kit used a bayonet that was initially of a single, straight blade type that took a single strap, although later modifications featured a two-strap design. The Hardman kit was typically seen in use with the MS22001 type masks, whereas the Sierra kit was more commonly seen in use with the newer MBU-5/P hard-shell mask that was introduced in late 1958/early 1959.

 Both the P-4A and field-updated P-4B helmets were initially fitted with the original leather snap-tabs for oxygen mask attachment, but the last examples of the late model P-4B helmet actually came from the Gentex and Consolidated Controls Company production lines (both major contractors for the last model P-4B helmet) with the Sierra kit already installed (the Air Force standardized this kit for oxygen mask attachment). To the right is illustrated a somewhat rare modification of the original snap-tab to facilitate use of a short bayonet type receiver; this set-up is occasionally found, but is uncommon.

 

 

P-Series Head Harness Slings

The Head harness slings used in P-series helmets were initially identified as to the specific specification of the helmet they were used in. That is, a P-1A head harness sling is labeled as such (Head Harness, Type P-1A", etc.). Staring with the P-1A or thereabouts, the straps were made of sage green nylon instead of OD canvas duck. This was true for all helmets in the P-series, although late in the 1950s a generic head harness sling was produced that was simply labeled "Head Harness, P-helmet, Universal" (although still marked for the correct size helmet to be used with and featuring the standard sage green nylon straps).

The earliest head harness slings (such as found in the original P-1 helmet) had olive drab cotton duck straps joining the leather sweat band to the leather crown pad. This P-1 leather crown pad found in the original (earliest) P-1 helmets is marked with an "Army Air Forces" stamp. This was later briefly changed to "US Air Forces", and in its final form (from about the P-1A onwards), with "U.S. Air Force" stamped in white permanent ink.

The earliest P-1 shells featured a simple Winged Star roundel (or "meatball") on the front exterior of the shell. Starting with the P-1A, this had added to it the words "U.S. Air Forces" in black lettering (some also appear to have lettering in white), and still later to simply "U.S. Air Force" (only in black lettering). These characteristics are frequently covered by or hidden under colorful helmet paint and personalized decorations that were typical of Korean War vintage helmets.

 

A final word: This history does not claim to be a definitive history of the P-helmet development story, but it is based upon a collection of documentation from a wide range of sources that include official USAF technical reports and orders, personal statements from former military personnel involved with life support activities, and other similarly collected material.

  AEOLUS AEROSPACE

 

 

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02/10/2014

 

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