British Aircrew Pressure Waistcoat Mk1 and MK1A
Mk1 Stores Ref: 22C/1130 (S) | 22C/1131 (M) | 22C/1132 (L) | 22C/1133 (XL)
Mk1A Stores Ref: 22C/1371 (S) | 22C/1372 (M) | 22c/1373 (L) | 22C/1374 (XL)
For pressure breathing, the J-Type oxygen mask was introduced which created a back-pressure in the oxygen system by applying a sprung flow restriction to the exhalation valve. This pressure in the mask, raises the pressure in the lungs to help the transfer of oxygen into the blood.
To reduce the discomfort casued by pressurising the lungs, a pressure wiastcoat was developed to apply couter-pressure to the outside of the chest.
The pressure waistcoats MK1 and Mk1A are pressureised to the same pressure as the oxygen supply and mask, and therefore also the lungs, thereby balancing the forces on the outside of the body with that being presented inside the body. The waistcoat also acted as an oxygen store, like the economiser, where the bladders would deflate when the wearer breathed in, inflating his lungs siumultaneously. Upon breathing out through the mask's pressure exhalation valve, the chest would shrink, releaving pressure in the waistcoat bladder, upon when it is refilled from the aircraft oxygen supply.
The MK1 is made from rubberized cotton gabardine, and the MK1A ia made from rubberized linen fabric.
Note: To wear a pressure waistcoat under a life jacket, there needs to be provision for connection to the oxygen system. The Mk7 life jacket was manufactured with a square hole to allow the connection of the oxygen supply through to the pressure waistcoat.
RAF/RN AP Resources
AP1182E, Volume 1, Section 4, Chapter 2, Figure 12 (AL59, 1956)
Photograph of the Mk1 / Mk1A pressure breathing waistcoat.
AP1182E, Volume 1, Section 4, Chapter 2, Figure 13 (AL59, 1956)
Exploded diagram of the Mk1 / Mk1A pressure breathing waistcoat.
AP1182E, Volume 1, Section 4, Chapter 2, Figure 1 (AL70, 1958)
Typical AEA of early presure breathing equipment including the J-Type oxygen mask.
The AEA also includes an F-Type helmet, Mk8 goggles, Lightweight Cape Leather gloves, 1952 Pattern boots. The flying suit is too difficult to make out.
AP1182E, Volume 1, Section 4, Chapter 2, Figure 2 (AL59, 1956)
This 1956 dated AP gives a great overview of the J-Type mask conencted to a pressure waistcoat via the connecting box, as part of the AEA.
