Cranwell CLA.4

The Cranwell Light Aeroplane (CLA) club was formed in 1923 by staff and students at the RAF College Cranwell. The students came from No.4 Apprentices Wing and one of their lecturers, Flt-Lt Nicholas Comper became chief designer of the three aircraft produced by the club as well as one, the CLA.1 that was not completed. The last of the series, the CLA.4 was designed to compete in the 1926 Lympne Light Aeroplane Trials. Two were built for this competition, one to be powered by a Bristol Cherub engine and the other by the new Pobjoy P. Unfortunately, the latter engine failed its own trials not long before the Lympne event and only the Cherub powered aircraft took part. In the case of the CLA.4, the upper wing had a span of 80% of the lower and 83% of its chord. The wings were straight, unswept and of constant chord apart from at the rounded tips, with ailerons on the lower wings only. The CLA.4 was a single bay biplane with inward leaning single wide chord interplane struts with wide, faired roots. Two pairs of centre section struts held the upper wing well clear of the fuselage; the absence of stagger made wing-folding easy. Like much of the rest of the aircraft, the wings were of fabric covered wood. The fuselage was built up on four longerons, spruce at the rear where they were linked into a tapering Warren girder, and ash ahead of the rear cockpit where more traditional wire braced rectangular forms were used. It was topped with a standard rounded decking. The two open cockpits were placed at the leading and trailing upper wing edges and fitted with dual controls. The flat twin Bristol Cherub III was mounted on a steel plate and smoothly partially cowled to a neatly pointed nose, but with the cylinder heads exposed for cooling. At the rear of the fuselage the fin and tailplane were fabric covered metal structures, though the generous control surfaces were wood framed. Fin and rudder together formed a shape not unlike that of many de Havilland aircraft though more rounded and unbalanced. The main undercarriage was built from a pair of steel V-shaped tubes bearing a single axle and rubber cord shock absorbers. ==Operational history==

Two CLA.4s were built for the Lympne trials, the Cherub powered G-EBPB, entry no.12 and the Pobjoy powered G-EBPC. no.11. The latter was withdrawn because of the Pobjoy problems and was one of three withdrawals before the start on 10 September, leaving 13 competitors. On the following day no.12, flown by Nick Comper making it the last CLA.4 to fly. During this period it was re-engined with a more powerful 55 hp Viele M-5 engine to improve its performance, perhaps to cope with the higher operating altitude of Edmonton. In 1989 Want presented the remains to the Alberta Aviation Museum, Edmonton, where it is being restored to flying condition. In 2001 it was displayed in a half-covered state so its structure could be seen and appreciated but by 2008 was fully covered aft of the engine firewall. Its original Blackburne Thrush is displayed beside it and the other Thrush is now in the Reynolds-Alberta Museum collection. The aircraft has never been registered with the Canadian authorities. ==Naming==

At least some contemporary sources like Flight refer to both the Cranwell built aircraft by the number 4 (or sometimes IV), with no letter suffix. refer to the Cherub powered G-EBPB as a CLA.4A and the other machine as a CLA.4, and later authors use this engine based distinction. They generally agree that G-EBPB is a CLA.4A; but some imply G-EBPB became a CLA.4A when fitted with the Cherub with which it always flew, whereas others continue to use the original CLA.4 name. ==Specifications==