The Albemarle originated as the Bristol type 155 design to meet an Air Ministry requirement of 1938 for a twin engined bomber. Production was transferred to Armstromg Whitworth when it became clear that the latter had spare design and production capacity. A design team under the supervision of John Lloyd was set the difficult task of taking over another company's creation and adapting it to meet a revised Ministry requirement for a reconnaissance bomber.
The revised Armstrong Whitworth design was very different from the original Bristol concept in detail and construction. The airframe was of mixed composite steel and wood (thereby reducing demand for strategic light alloys). Most of the components were produced by subcontractors (one source mentions almost 1,000 sub contractors even to small companies outside the aircraft industry), with final assembly being made by A.W. Hawksley Ltd.
The Albemarle was the first operational aircraft in RAF service to have a tricycle undercarriage. This was of Lockheed design.
The first of two prototypes flew on 20 March 1940 but proved to be a poor performer as a result of its great structural weight. This machine was destroyed in a crash before the flight of the second prototype in January 1941. The first three aircraft(after considerable delay in establishing production lines)emerged from the factory in December 1941.
The first 32 production aircraft were built as bombers, although they were not used as such. These aircraft were installed with a four-gun Boulton Paul dorsal turret, but weight considerations dictated the removal of this in later aircraft, being replaced by a pair of Vickers 'K' hand operated machine guns. Deliveries to the Royal Air Force began in January 1943 when No.295 Squadron received its first aircraft. By this time the decision had been made to adapt the type as a glider tug and airborne forces transport.
The Albemarle was blooded by No.296 and 297 Squadrons RAF (part of No.38 Wing) operating from North Africa, in the invasion of Sicily in July 1943. On D-Day (6 June 1944) six of No.295 Squadron's Albemarle aircraft. Operating from Harwell, served as pathfinders for the 6th Airborne Division's paratrooper drop over Normandy. In addition four squadrons of the type acted as glider tugs. In September 1944 two Squadrons of Albemarles towed gliders carrying troops of the 1st Airborne Division as a part of the Arnhem operation.
Production ceased in December 1944 after the completion of 602 aircraft. An order for a second batch of 478 machines was canceled. Albemarle deliveries to the RAF consisted of 310 transport aircraft (78 Albemarle ST Mk.I, 99 Albemarle ST Mk.II and 133 Albemarle ST Mk.VI) and 246 glider tugs (80 Albemarle GT MkI, one Albemarle GT MkII, 49 Albemarle GT Mk V, and 117 Albemarle Mk VI ). In addition to these were the original 32 bonbers which were later converted to transport standard, and 10-12 Albemarle transports aircraft which were delivered to the Soviet Air Force from RAF stocks. All Albemarles utilised the same Bristol Hercules XI engine, with the exception of the sole Albemarle Mk IV prototype which was tried with a pair of Wright Double Cyclone radial engines. Albemarle marks mainly differed only in their equipment.
Whilst not a particularly significant type, the Albemarle did perform a useful role and therefore released other types for more vital tasks. In addition, because of Its method of construction and the materials used, production did not unduly disrupt the flow of more important aircraft at a time when these were vital to Britain's survival.
ST Mk I
Machinery Two Bristol Hercules XI 14-cylinder two row radial engines rated at 1,590hp
Armament 2x7.7mm trainable rearward firing dorsal machine guns
Span 23.47 m
Length 18.26 m
Height 4.75 m
Wing Area 74.60 m²
Weight, Empty 10,270 kg
Weight, Loaded 16,556 kg
Weight, Maximum 16,590 kg
Speed, Maximum 426 km/h
Speed, Cruising 274 km/h
Rate of Climb 5.00 m/s
Service Ceiling 5,486 m
Range, Normal 2,092 km
Sources: Aircraft of World War II by Chris Chant (Dempsey-Parr, 1999), World Aircraft Information Files (Aerospace Publishing Peridical).