Updated 28 March 08

  MK. 4  SERIES  FLIGHT  HELMETS 

 SPECIFICATIONS  &  SIZES 

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MK.4A Flying Helmets

The MK. 4A Flight Helmet is current Royal Air Force / Royal Navy / Army Air  Corps issue and superseded the MK. 3 series helmet in the 1980`s and is widely used by military and civilian pilots worldwide.  The shell is made of glass fibre impregnated with polyester resin and lined with shock absorbing  expanded polystyrene, the interior is fitted a multi-point adjustable webbing harness system with adjustable independently suspended earcups, all such parts being of bolt fixed assembly allowing easy access and servicing. The helmet has a locking clear inner blast visor and a friction mounted outer tinted visor with a detachable cloth visor cover, avionics consist of twin 300ohm speakers giving an impedance of 150 ohm (1khz) terminating with a 18" downlead (extension leads available) and single pin NATO jackplug. The design of the avionics allow easy fitting of alternative speakers as required. The helmet is fitted with a 2-piece foam backed leather lining which allows easy access to the internal avionics and fittings. Mounting blocks allow the fitting of adjustable hooks for the P or Q type oxygen mask. The 4A has locating holes allowing the fitting of RAF or similar Boom Mikes.

Oxy mask hooks not supplied 

click for info-  Boom Mikes    Oxy-Mask / Mike Wires

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4A Sizing

Determine the basic size required by measuring the maximum length and breadth of the crew member head. The length is measured from the centre of the forehead to the rear and the breadth is measured across the temples. For an accurate measurement calipers should be used. 

Please note it is the purchasers responsibility to determine the correct helmet size and fitting.

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OTHER MK.4 SERIES MARQUES

MK. 4 Flight Helmets

These rare helmets are often confused with the 4A Helmet but are in fact quite different, the Mk. 4 was the first HARD protective helmet produced with a full electronic avionic system which is still used in a modified form on the 4A today, the prototype MK. 4 Helmet was introduced in 1974 and was issued in parallel to the MK. 3 series helmet and was modified into and later issued as the 4A in the early 80`s. The MK. 4 differs from the 4A in several ways, the internal harness adjusters on the MK. 4 are located behind the visor arms as opposed to the rear on the 4A, the MK. 4 has a 1 piece interlaced lining similar to the liner used on the then issue MK.3C. Avionic earcups were of the heavier white colour type as used later on the 4B helmet and the chinstrap assembly was affixed to the outer rim as opposed to the inner on the MK. 4A. P & Q Oxy-Masks were used with a toggle chain adjuster which hooked directly on to the helmet shell, the later issue 4A helmets used adjustable mask hooks that affixed to the helmet and used with P & Q Oxy-masks with non adjustable chains. These MK.4 helmets were issued in limited numbers and the few examples we have seen have had visor modifications allowing the use of the current issue 4A visors and arms, original specifications show the original issue MK.4 helmets used the early MK.3C straight edge visor system which locked on the right side of the helmet, we can only assume that any of these helmets that have survived have all been modified as such. Sizing was the same as the earlier issue MK.1A and G-Type Helmets ie.. Size 1 / 2 / 3 / 4. Avionics are the same specification as the MK.4A Helmet     

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MK. 4B Flight Helmets

These early 80`s issue helmets are similar to the 4A but differ as the helmet shell has flat sides to facilitate the complex but very efficient INFINITE LOCKING dual visor locking system which enabled the visors to be operated  independently and locked in any position, due to the additional weight of this visor system the 4B helmet was primarily used on rotary aircraft. The internal webbing cradle assembly adjusts via the visor mounts on the side as opposed to adjusting at the neck as on the MK.4A and the earcups on these earlier pattern helmets are of a heavier white plastic and are configured through the top of the unit as opposed to the side as on the 4A. The 4B helmet was issued in limited numbers and was not a widely used helmet due to the very complex service procedures. A few of these helmets when serviced were modified and were fitted with the later issue avionics and the LO - PRO lightweight twin visor system as used with the ALPHA Flying Helmet and these became the first 4B / 4L Helmets. This configuration visor system allowed the fitting of a NVG ( Night Vision Goggles) Bracket and allows either visor to be operated and locked up or down independently. Although fitted with oxy-mask mounting blocks these helmets are normally used with a Boom Mike. Avionics are the same specification as the MK.4A Helmet     

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MK. 4B / 4L Flight Helmets

These later issue 4B / 4L helmets have the same internal harness system as the earlier 4B helmet but used the later issue lighter weight 4A avionics and feature the LO - PRO lightweight twin visor system as used with the ALPHA Flying Helmet. The shell on these later marque helmets are fitted with rubber external EARS to eliminate the levers becoming obstructed and  are also configured for use with a NVG bracket. Although fitted with oxy-mask mounting blocks these helmets are normally used with a Boom Mike. Avionics are the same specification as the MK.4A Helmet     

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MK. 4A/D Flight Helmets

The 4A / D is the designation given to the 4A type which allows the fitting of Night Vision Goggles the visible difference being the 3 fitting  holes on the crown of the helmet. The true 4A/D had modified visor arms which allows the visors to sit further back on the helmet allowing the fitting of the NVG but it is common to see the 4A/D with non-NVG visor arms with the upgrade to NVG arms being quite easy. Another variant is where the entire visor system is removed and a single clear GENTEX visor is fitted via straps and stud fittings to facilitate the NVG unit. Avionics are the same specification as the MK.4A Helmet     

click underlines for info

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