P-4
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In the mid-50s, the USAF decided to implement a lower impedance communication system. P-helmets as the P-3 with modification implemented, changed designation to “P-4 Flying Helmet”.
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Unlike the old system which consisted of sponge rubber half-rings between ear pad and helmet shell, the new earphone assemblies were fitted on spring provided mounts called, because of their shape , “Top hats”, tied to short nylon strings which protruded through the helmet shell to be secured over a phenolic resin stud.
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The most visible change implemented to P-4 helmets was the visor yoke that gave the pilot better upwards visibility and carried less risk of snagging between helmet and parachute risers. The J-shaped up lock arms on at each end were longer, allowing the visor to move completely out of the pilot's field-of-view, additionally the visor yoke no longer had the square handle in the middle.
Earphone assembly "Top hats" ( wonder why...);These are of a later model, limitedly rotational adjustable, not possible with early ones as fitted on our helmet.
Pictured is a P-3 "short throw" visor yoke, notice how the visor interferes with the wearer's field of vision.
The JJ-055 microphone connector rubber cover. The two visible holes indicates that the shell was originally a P-3 later converted in P-4.The holes were used to route the cords that secured the HS-38A comm system chamois-covered, kapok-filled ear pads.
Earphone assembly "Top hats" ( wonder why...);These are of a later model, limitedly rotational adjustable, not possible with early ones as fitted on our helmet.