D-TYPE, FIRST PATTERN
Type D, first pattern, tropical flying helmet
Stores Ref. No. 22C/581-584
The Type D flying helmet was basically a “tropical version” of the Type C using the same construction pattern. Intended for the use in warm climates like the Mediterranean, North Africa and Middle East it was made of heavy khaki colored cotton lined with satin. The main additional feature was a quilted, round shaped neck flap to protect the wearer from the sun.
A brown felt lining was applied across the brow and on the chin strap.
Appearing as early as 1942 the first version of the Type D came unwired, with the earphones to be inserted when needed into sewn-on black rubber receptacles. The inside of the helmet featured padded chamois or satin “donuts” for wearing comfort and noise reduction.
Provision for attaching oxygen masks (or as in warmer climates more frequently: microphone carriers, i.e. oxygen masks or derivates thereof without oxygen tubes, as missions were generally flown at lower altitudes where no oxygen supply was needed) initially consisted of female and male snap fasteners to fit all available masks, as Types D, E, E* and G.
Like its predecessor, the Type D underwent various modifications during production, resulting in differences in materials and fittings.
MK VII flying goggles
Stores Ref. No. 22C/826
Some characteristics were similar to its predecessor, like heavy frames, nuts and bolts, split lenses and flip down sun shield. Anyway, the result consisting of three sections of brass for the frames which were painted in various shades of “blue”, was now more streamlined and replaced the cumbersome ear-loops with a more practical leather strap with spring fastenings and rear adjustment buckle.
The polarized flip shield was often discarded as considered superfluous while too fragile and/or cumbersome (imagine yourself under the closed perspex canopy of a Spitfire Mk.Vb/Trop or a Hurricane Mk.II/Trop ...).
Later production batches of the Mk VII were equipped with improved goggle straps made of elaticized webbing of the type used on oxygen mask harnesses.
Type E oxygen mask
Stores Ref. No. 6D/473
The Type E, which underwent various modifications and improvements right after its appearance, represents the first British designed oxygen mask to part with the continuous flow oxygen system and finally introducing the much more economical and reliable “economizer” demand system.
Representing a real breakthrough in British aviation medicine the new type of mask had to provide a secure seal over the wearer's face, a feat impossible to achieve with the predecessor, the Type D mask.
Initial and trial models featured thin rubber tubes like those used with the Type D, various materials were tested and used for lining, insulation and prevention of skin irritations caused by the untreated rubber. Initial attachment devices like leather straps, C-shaped leather handles (see picture on the left) or Bennet buckles were other features which were soon considered inadequate. Last but not least production of the mask needed a vast amount of hand-labour slowing down mass production.
The introduction of the third version of the mask with improved harness assembly, which is represented by this specimen, mitigated some of the issues. It retained the uncovered rubber body which was now lined with chamois and designated with the stores Ref. No. 6D/473. An adequately wide oxygen inlet valve protruding from the chin funnel accepted the corrugated breathing tube (6D/528) which was fitted with a Mk IV bayonet connector (6D/526) and a crocodile clothing clip.
This mask is equipped with a Type 26 electro-magnetic microphone (10A/12570).
While being a vast improvement over the Type D mask, the Type E still had its important shortcomings. The two-way valve was prone to freezing and blocking when the warm and moist exhaled air came in contact with the cold, dry oxygen, thus interrupting the flow of the latter, leading to hypoxia and if not detected in time, to suffocation.
Another problem was that during combat maneuvers and by consequence high “G” loads the mask could not be held in place by the leather strap arrangement. This represented a serious issue especially for fighter pilots who saw their oxygen supply all of a sudden cut off.
Thus, final solutions still had to be found.
Hi/lo impedance switch (Stores Ref. No. 10A/13163)
Early USAAF aircraft were fitted with low impedance radios for which the R-14 was designed (identified by the black plug). This was found to be incompatible with British radios which used high-impedence radios, which is why the RAF issued those cords with high-low impedance switch boxes for crews flying in American lend-lease aircraft.