Armstrong Whitworth Albemarle

Background The origins of the Albemarle can be traced back to the mid-1930s and the issuing of Specification B.9/38 by the British Air Ministry. This sought a twin-engine medium bomber of wood and metal construction, without the use of any light alloys, in order that the aircraft could be readily built by less experienced manufacturers from outside the aircraft industry. Furthermore, the envisioned aircraft had to be engineered in a manner that would allow it to be divided into relatively compact subsections, all of which had to fit on to a standard Queen Mary trailer to facilitate the adoption of a dispersed manufacturing strategy. Several aircraft manufacturing firms, including Armstrong Whitworth, Bristol and de Havilland, were approached to produce designs to meet the specification. Bristol proposed two designs – a conventional undercarriage and an wingspan capable of 300 mph and a tricycle undercarriage design with span with a maximum speed of . Both designs, known as the Type 155, used two Bristol Hercules engines. The rival Armstrong Whitworth AW.41 design used a tricycle undercarriage and was built up of sub-sections to ease manufacture by firms without aircraft construction experience. Furthermore, according to aviation author Oliver Tapper, the brief was a relatively difficult one for any company to fulfil. A number of modifications were made to the design during this late stage of development, including the extensive redesign of the aircraft's structure by Lloyd at Coventry. The Albemarle's production run was principally undertaken by A.W. Hawksley Ltd of Gloucester, a subsidiary of the Gloster Aircraft Company, which was specifically formed to construct the Albemarle. Amongst the companies that were subcontracted were MG Cars, to produce the forward fuselage, Rover, which constructed the wing centre section, and Harris Lebus, which built the tailplane units. Production of the Albemarle was terminated during December 1944, by which point 602 aircraft had been completed. ==Design==

The Armstrong Whitworth Albemarle was a mid-wing cantilever monoplane with twin fins and rudders. The fuselage was built in three primary sections; the structure being composed of unstressed plywood over a steel tube frame, including four circular steel longerons; most elements were bolted together via gusset plates. The structure was intentionally divided in order that it might readily permit individual sections to be removed and replaced in the event of battle damage being sustained. The centre section of the wing was a single piece that ran through the fuselage, being built around a steel tube girder; it formed the attachment points for the central and nose fuselage sections, as well as the engines, main undercarriage legs, and extension wings. Aside from a portion of the leading edge that used light alloys, the majority of the wing was covered in plywood. The extension wings were almost entirely made of wood, save for the bracing of the two spars by steel tubing; the Frise-type ailerons and tailplane were also composed of wood. The Albemarle featured a Lockheed-designed hydraulically-operated, retractable tricycle undercarriage, the main wheels retracting back into the engine nacelles, and the nose wheel retracting backwards into the front fuselage, while the tail wheel was fixed in position, albeit semi-concealed by a "bumper" configuration. It was one of the particularly notable design features of the Albemarle, according to Tapper, it was the first British-built aircraft with a retractable nose-wheel to be built in quantity for the Royal Air Force. A fairing forward of the turret automatically retracted as the turret rotated to fire forwards. The original bomber configuration of the Albemarle required a crew of six including two gunners; one in the four-gun dorsal turret and one in a manually operated twin-gun ventral turret but only the first 32 aircraft, the Mk I Series I, were produced in such a configuration. As a bomber, the Albemarle was commonly considered to be inferior to several other aircraft already in RAF service, such as the Vickers Wellington; according to aviation author Ray Williams, the type was only used ever used as a bomber on two occasions. ==Operational history==

Ambitions to use Albemarle in the bomber role were dropped almost immediately upon the type reaching service; this was due to it not representing an improvement over current medium bombers (such as the Vickers Wellington) and possessing inferior performance to the new generation four-engined heavy bombers that were also about to enter service with the RAF. However, the aircraft was considered to be suitable for general reconnaissance and transport duties, and thus was re-orientated towards such missions. During training, one aircraft was lost with no survivors. The first RAF squadron to operate the Albemarle was No. 295 at RAF Harwell in January 1943. The pinnacle of the aircraft's career was a series of operations for D-Day, on the night of 5/6 June 1944: 295 and 296 Squadrons sent aircraft to Normandy with the pathfinder force, and 295 Squadron claimed to be the first squadron to drop Allied airborne troops over Normandy. On 6 June 1944, four Albemarle squadrons and the operational training unit sent aircraft during Operation Tonga; 296 Squadron used 19 aircraft to tow Airspeed Horsas; 295 Squadron towed 21 Horsas, although it lost six in transit; 570 Squadron sent 22 aircraft with ten towing gliders; and 42 OTU used four aircraft. For Operation Mallard on 7 June 1944, the squadrons towed 220 Horsas and 30 Hamilcars to Normandy. On 17 September 1944, during Operation Market Garden at Arnhem, 54 Horsas and two Waco Hadrian gliders were towed to the Netherlands by 28 Albemarles of 296 and 297 squadrons; 45 aircraft were sent the following day towing gliders. Of the 602 aircraft delivered, 17 were lost on operations and 81 lost in accidents. The final RAF unit to operate the Albemarle was the Heavy Glider Conversion Unit, which replaced its examples with Handley Page Halifaxes during February 1946, at which point the type was formally retired from all operational units. ==Variants==

Over the course of its production life, a number of variants of the Albemarle were built: • ST Mk I – 99 aircraft • GT Mk I – 69 • ST Mk II – 99 • Mk III – One prototype only. • Mk IV – One prototype only. • ST Mk V – 49 • ST Mk VI – 133 • GT Mk VI – 117 Most Marks were divided into "Series" to distinguish differences in equipment. The ST Mk I Series 1 (eight aircraft) had the four gun turret replaced with hand-operated twin-guns under a sliding hood. As a special transport, a loading door was fitted on the starboard side and the rear fuel tank was removed. ==Operators==

; • Twelve aircraft were exported to the Soviet Union (two more lost in transit). • Transport arm of 1st Air Division, later 10th Guards Air division (to 1944); naval air units until retirement in 1945. ; Royal Air Force • No. 161 Squadron RAF – Albemarle I from October 1942 to April 1943 at RAF Tempsford. • No. 271 Squadron RAF operated one aircraft at Doncaster between October 1942 and April 1943. • No. 295 Squadron RAF – Albemarle I from November 1943 to July 1944 at RAF Hurn and then RAF Harwell. Albemarle II from October 1943 to July 1944 at RAF Hurn and then RAF Harwell. Albemarle V from April 1944 to July 1944 at RAF Harwell. • No. 296 Squadron RAF – Albemarle I from January 1943 to October 1944 at RAF Hurn, RAF Stoney Cross including operations in North Africa. Albemarle II from November 1943 to October 1944 at RAF Hurn and then RAF Brize Norton. Albemarle V from April 1944 to October 1944 at RAF Brize Norton. Albemarle VI from August 1944 to October 1944 at RAF Brize Norton. • No. 297 Squadron RAF – Albemarle I from July 1943 to December 1944 at RAF Thruxton, RAF Stoney Cross and then RAF Brize Norton. Albemarle II from February 1943 to December 1944 at RAF Stoney Cross and then RAF Brize Norton. Albemarle V from April 1944 to December 1944 at RAF Brize Norton. Albemarle VI from July 1944 to December 1944 at RAF Brize Norton. • No. 511 Squadron RAF – Albemarle I from November 1942 to March 1944 at RAF Lyneham. • No. 570 Squadron RAF – Albemarle I from November 1943 to August 1944 at RAF Hurn and then RAF Harwell. Albemarle II from November 1943 to August 1944 at RAF Hurn and then RAF Harwell. Albemarle V from May 1944 to August 1944 at RAF Harwell. • No. 1404 Flight RAF used three aircraft at RAF St Eval from September 1942 to March 1943 • No. 1406 Flight RAF used two aircraft at RAF Wick from September to October 1942. • No. 13 Operational Training Unit RAF at RAF Finmere (two aircraft between October 1942 and April 1943) • No. 42 Operational Training Unit RAF at RAF Ashbourne from September 1943 to February 1945. • Heavy Glider Conversion Unit at RAF Brize Norton and RAF North Luffenham from January to April 1943 and August 1944 to October 1944 when it became No. 21 Heavy Glider Conversion Unit. • No. 21 Heavy Glider Conversion Unit at RAF Brize Norton from 1944, moved to RAF Elsham Wolds in December 1945 and withdrew the last operational Albemarles in February 1946. • No. 22 Heavy Glider Conversion Unit at RAF Keevil and RAF Blakehill from October 1944 to November 1945. • No. 23 Heavy Glider Conversion Unit at RAF Peplow from October to December 1944. • No. 3 Glider Training School operated eight Albemarles at RAF Exeter between January and August 1945. • No. 301 Ferry Training Unit operated four Albemarles at RAF Lyneham from November 1942 to April 1943. • No. 305 Ferry Training Unit bases at RAF Errol from January 1943 to train Soviet Air Force crews, disbanded in April 1944. • Torpedo Development Unit at Gosport used one aircraft between April and September 1942 • Telecommunications Flying Unit at RAF Defford used one aircraft during May 1943, • Airborne Forces Experimental Establishment at RAF Ringway and RAF Sherburn-in-Elmet between May 1942 and October 1944. • Coastal Command Development Unit used two aircraft at RAF Tain between September and December 1942. • Central Gunnery School at RAF Sutton Bridge used one aircraft between September and November 1942. • Bomber Development Unit used three aircraft at RAF Gransden Lodge between August and November 1942. • Operation Refresher Training Unit at RAF Hampstead Norris from May 1944 to February 1945 Aircraft were also operated for tests and trials by aircraft companies, the Royal Aircraft Establishment, and Aeroplane and Armament Experimental Establishment. One was operated by De Havilland Propellers for research into reversing propellers. ==Specifications (ST Mk I)==