Prototype Optical Sights Respirator

Prototype Optical Sights Respirator R8

Name: Prototype Optical Sights Respirator

Model: R8

Filter Type: No.2 Mk1 or No.2 Mk1

Application: Military

As a result of the Service Respirator No.6 (S6) not being fully compatible with a number of weapons sights, a prototype respirator designed to offer greater compatibility with optical sights was developed in the late 1970s at the Chemical Defence Establishment (CDE). This respirator became known as the Prototype Optical Sights Respirator (R8). The R8 was produced in several variations, all being prototypes for the purpose of user trials and evaluation.

On the 26th of June 1978, a request was made by CDE for a limited evaluation to be undertaken in order to assist in defining the final form of the respirator mold. Trials and evaluation were carried out at the Armoured Trials and Development Unit, the Royal School of Artillery, the Infantry Trials and Development Unit and at Headquarters, Director Army Air Corps. Each of these four establishments took part in a two day trial which was accompanied with a visiting team consisting of personnel from the Chemical Defence Establishment, the Defence Nuclear, Biological and Chemical Centre, and the Army Personnel Research Establishment. The team was tasked with making a comparative evaluation of the R8 and the S6 with selected weapons sights.

The R8 respirators used in these initial trials were made out of plasticised PVC as apposed to natural rubber, which was the material the S6's facepiece was made from. The trial was designed as a three phase programme, consisting of a compatibility assessment, the measurement of the lateral field of view, and a comparative subjective assessment questionnaire.

The R8 fitted with the AFV Conversion Kit and Clansman Respirator Microphone as worn with the AVC Helmet. Photograph sourced from a period document, courtesy of Bovington Tank Museum.

The compatiblity assessment shown that the R8 was more compatible than the S6 with the majority of weapons sights tested, the only case in which the S6 was more found to be more compatible was with the telescopic sight on the Carl Gustaf Recoilless Rifle, which had been modified prior to ensure compatibility with the S6. As well as being an improvement in compatibility with weapons sights, the R8 also showed a good amount of compatibility with helmets already in service, and prototype helmets under development.

The assessment into the lateral field of view when wearing the R8 also shown an improvement upon the S6, in particular with the sights on on Armoured Fighting Vehicles (AFVs). This improvement was associated with the design of the R8, the eyepieces of which were closer to the eye compared to the S6, and the facepiece which allowed the face, and thus the eyes to get closer to to the sight.

The questionnaire was completed by 20 subjects, from the answers provided it was found that the eyepieces of the R8 had a tendancy to fog when used

with weapons sights, and that the general field of view was considerably restricted in comparison to the S6. However, the majority of the subjects found that the R8 was more comfortable than the S6, and was easier than, or no more difficult than, than the S6 to don and doff. Although the R8 was preferred by most subjects for use with sights, the S6 was preferred for general use.

The overall advantages of the R8 over the S6 were; an increase in lateral field of view with sights, ease of adopting the sighting position and a considerable reduction in admittance of extraneous peripheral light to sights, and emission of light from night vision equipment. The features of the R8 which contributed to these advantages included the smaller eyepieces which fitted well with monocular and binocular sights. The absence of a raised eyepiece surround also improved compatibility. The placement of the additional speech transmitter on the side of the facepiece improved the compatibility with boom microphones, the Clansman respirator microphone and most AFV sights as it allowed the face and therefore the eyes to be be brought closer to the sights. This was a significant improvement upon the S6 which required the use of bracket to attach the Clansman Respirator to the outlet valve and speech transmitter. However, the side mounted position of the additional speech transmitter on the R8 interfered with the aiming unit of the Blowpipe surface-to-air missile system. All of the helmets trialed with the R8 were found to be equally, or more compatible with the R8 compared to the S6 since it was of a closer fit to the face, and the buckles on the head harness were closer fitting to the head.

There were however several disadvantages of the R8 when compared to the S6; the general field of view was consierably reduced, a helicopter flight whilst wearing the R8 showed that the reduction in lateral field of view hampered the operational efficiency of the aircrew. As a result, the S6 was preferred for flying duties. Because of a distinct lack of a browline on the R8, the hood of the NBC smock had no reference point and was occassionally drawn across the eyepieces, limiting upward vision. This could be remedied by using the tried and tested "buddy buddy" system of assisting others to don NBC clothing, however slippage of the hood could occur during movement. It was also evident that the R8 was prone to fogging when used with sights, however this may have been a result of the eyepieces being pushed closer towards the eyes in order to achieve the maxiumum field of view.

It was also noted in the report of the trials that some of the findings may have been influenced by the difference between plasticised PVC from which the R8 was made and the natural rubber of the S6. This may have influenced the comfort and fit, and some aspects of compatibility. This difference in materials was noted to be more carefully considered when planning assessments of future prototype respirators.

The initial trial and evaluation concluded that the R8 had an increased lateral field of view through weapon sights, and improved compatibility with weapon sights, helmets and boom microphones. The disadvantages of the R8 are a marked reduction in the general field of view, a tendancy for the hood of the NBC smock to be drawn over the eyepieces, and incompatibility with spectacles.

Whether this initial trial led to further developmental of the R8 is unknown at present, however the design never made it out of the experimental stages so the S6 continued to be used throughout the three services until its replacement in the 1980s by the S10. However, a 1978 dated Nuclear, Biological and Chemical Defence Equipment pamphlet held in the GasMasksUK Collection suggests that the R8 may have made it to a stage where it was considered for actual issue as there is a space allocated within the pamplet which appears to have been reserved for it.

It's also worth noting that one of the other known examples of the R8 held in a private collection feaures a different design of speech transmitter on the side of the facepiece, this is illustrated in one of the photos below. Only three examples of the R8 are currently in private collections, another was previously displayed at Bovington Tank Museum but has since allegedly gone missing following the museums renovation. A handful of others are reportedly held by various MOD establishments throughout the UK.

This article couldn't have been written without the help provided by Sophie Williams and the team at Avon Protection's Wiltshire HQ, and Laura Sweetenham from Bovington Tank Museum, so a big thanks to them.

Below is some data about the R8 held in the GasMasksUK Collection, as well as several extracts from a period document and detailed photographs of both the R8 in the GasMasksUK Collection and the R8 belonging to Mr Aidan Reale-Key.

Date - Facepiece: Nil Manufacturer/Markings - Facepiece: CD 9/54 NI CDE (internally) N (Size)

Filter: Nil Filter: Nil

Head Harness: 5/70 Harness: GD PR565 441

Eyepieces: Nil Eyepieces:

Inhale/Exhale Assembly: Nil Inhale/Exhale Assembly: RCO-77 PR446

The evolution of respirators developed for military use from the First World War until the 1980s, the R8 is shown in between the S6 and S10, despite it never actually being issued. Source Unknown.

The Prototype Optical Sights Respirator R8, illustrated here with the No.2 Mk1 Filter.

Another view showing the additional speech transmitter on the side of the facepiece. Note the provision for, but lack of a date of manufacture beside the lower strap of the head harness.

Another variation of the secondary speech transmitter. Image courtesy of Mr Aidan Reale-Key.

A brief mention of the R8 in the 1978 Nuclear, Biological and Chemical Defence Equipment pamphlet. This suggests that the R8 may very well have almost made it into service.

A sideview of the R8 and the S6, comparing the compatibility of each with the Clansman respirator microphone and two models of AFV helmets. Note the AFV Conversion Kit hose which is shown fitted to the R8, where as the S6 is fitted with the No.1 Mk1 filter. Scan sourced from a period document, courtesy of Bovington Tank Museum.

Diagram showing the R8 and the S6, as used in the initial evaluation. Scan sourced from a period document, courtesy of Bovington Tank Museum.