R23X class airship

R23X class
R27 during her brief career in the summer of 1918
Role	Naval patrol airship
National origin	United Kingdom
Manufacturer	Beardmore (R27) Armstrong-Whitworth (R29)
First flight	29 May 1918
Primary user	RNAS / RAF
Number built	2
Developed from	23 class airship

The British R23X class of rigid airships were developed during World War I using the experiences gained from the 23 class, but only two of the planned four R23X class were built: R27 and R29. Both were completed mid-1918, but just two-and-a-half months after entering service R27 was destroyed by fire in a hangar; while R29 went on to become the most successful British wartime rigid airship, being the only one to meet enemy action, as well as the only one to sink a submarine.

The Vickers-designed 23 class rigid airships, which were basically "stretched" and modified versions of the No. 9 design, were never used in combat; however, the four ships in the class provided many hours of valuable training for British airship crews and experimental data for designers and engineers, and some radical changes and refinements were consequently incorporated into the design of the R23X class. Originally four R23X class were planned, R27 to R30 consecutively, but the programme was re-evaluated following the forced landing of L 33 in Little Wigborough, Essex, on 24 September 1916. British engineers gained a valuable insight into the state of German rigid airship design and technology when they examined the virtually intact Zeppelin, and it was subsequently decided to cancel R28 and R30 in order to concentrate resources on an improved design, the new R33 class.

Redesigned bow and stern sections increased the gas capacity slightly for a corresponding increase in lift, but a more radical measure was the removal of the external keel corridor from the R23X design. Not contributing significantly to the strength of the hull, the keel's main function was to distribute the weight of the fuel tanks, ballast bags and other heavy items, as well as to allow the crew to travel between the cars, and its removal effected a considerable reduction in weight together with improved manoeuvrability. Instead, the various loads were concentrated at the bulkheads and suspended from the radial wiring that maintained the shape of the hull. The gas-bags were shaped to accommodate a new internal corridor, created by the provision of inverted "U"-shaped ribs above the two lowest longitudinal members, which also allowed access to the fuel tanks and ballast. An improved system of pipes linking the fuel tanks enabled faster refuelling, and could be used to jettison fuel in an emergency. However, as with earlier designs, doped linen was used for the hull's outer covering; and being absorbent, just a few hours of rain could add around a ton of water to the weight.

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