Air Ministry Specification B.13/36

Air Ministry Specification B.13/36
Name	Air Ministry Specification B.13/36
Issued	1936
Type	Bomber specification
Origin	United Kingdom
Status	Historical

Air Ministry Specification B.13/36 Air Ministry Specification B.13/36 was a 1936 British requirement for a twin-engined medium bomber, issued as part of pre-Second World War rearmament. It drove design work at companies such as Handley Page, Vickers-Armstrongs, Armstrong Whitworth, Fairey, and Bristol Aeroplane Company and shaped subsequent RAF thinking alongside contemporaneous specifications like Specification B.12/36 and Specification B.1/35. The requirement influenced aircraft that served in campaigns including the Battle of Britain, the North African campaign, and the Defense of Malta.

Background and Purpose

The specification was issued amid political developments such as the Anglo-German Naval Agreement and the rearmament policies promoted by figures in Winston Churchill's political milieu and by officials of the Air Ministry (UK), motivated by lessons from the Spanish Civil War and the Washington Naval Treaty era. Strategic planners from the Royal Air Force's Bomber Command and officers associated with the Chief of the Air Staff sought a design to replace aging types like the Handley Page Heyford and to complement contemporaries such as the Armstrong Whitworth Whitley and Vickers Wellington. International developments — including aircraft demonstrated by Luftwaffe units and procurement programs in France, Italy, and the United States — influenced the ambition for speed, defensive armament, and bombload.

Requirements and Technical Specifications

B.13/36 specified performance targets informed by comparative examples such as the Heinkel He 111, Savoia-Marchetti SM.79, and Douglas DB-7. Required attributes included a specified maximum speed comparable to twin-engined designs seen in Focke-Wulf Fw 200 reports, a service ceiling influenced by operations over the North Sea, and a range sufficient for sorties to targets similar to strategic options intersecting with bases like RAF Scampton and RAF Lossiemouth. Structural and systems criteria referenced innovations appearing on types like the Bristol Blenheim, Avro Anson, and Fairey Battle; priorities included a stressed-skin fuselage, retractable undercarriage, powered turrets akin to those on Short Sunderland prototypes, and provisions for navigation equipment analogous to that used on Handley Page Halifax trials. The specification mandated defensive armament and bomb bay configurations to accommodate payloads comparable to prewar doctrines practiced by Bomber Command squadrons such as No. 3 Squadron RAF and No. 10 Squadron RAF.

Competitors and Submitted Designs

Manufacturers responding to B.13/36 produced proposals alongside designs submitted to concurrent specifications like Specification F.7/35. Key firms included Handley Page, whose concepts were developed in parallel with work on the Handley Page Harrow and earlier Heyford derivatives; Vickers-Armstrongs proposed concepts related to the Wellington lineage; Armstrong Whitworth advanced ideas informed by the Whitley; Fairey Aviation submitted designs reflecting experience from the Battle production; and Bristol Aeroplane Company presented proposals building on the Blenheim program. Smaller firms and experimental bureaus associated with de Havilland and Westland Aircraft examined alternative arrangements, while independent design teams referenced practices from Svenska Aeroplan Aktiebolaget exchanges and displays at airshows featuring the Dornier Do 17 and Junkers Ju 88.

Evaluation, Trials, and Selection

Flight trials and assessments were conducted at test centres including Royal Aircraft Establishment, Aeroplane and Armament Experimental Establishment, and RAF stations such as RAF Martlesham Heath and RAF Farnborough. Evaluation panels included representation from Air Ministry, various RAF commands, and engineering figures associated with Sir Kingsley Wood's procurement offices. Performance was compared against contemporaries including the Heinkel He 115 reports and captured data from Mediterranean operations like the Battle of Taranto. The selection process weighed production scalability as demonstrated by companies like Short Brothers and Boulton Paul, supply-chain considerations involving Rolls-Royce and Bristol Aeroplane Company engine divisions, and the anticipated efficacy in theatres such as the Western Desert campaign. Political and industrial lobbying by directors like those at Vickers and Armstrong Whitworth also influenced adjudication, as did export interest from governments including Australia and Canada.

Impact on British Aircraft Development

B.13/36 accelerated design trends toward geodetic and monocoque structures seen in later Vickers Wellington production runs and encouraged integration of equipment types later standardized across RAF inventories, such as turrets by Boulton Paul and navigation aids developed at RAE Farnborough. It informed material allocation strategies coordinated with Ministry of Aircraft Production policies and intersected with research by engineers connected to Frank Whittle and early jet propulsion studies at Power Jets. Manufacturing practices adopted from the program influenced dispersed production strategies used by firms like Bristol and Hawker and operational doctrines refined by RAF Coastal Command and RAF Bomber Command.

Operational Use and Service History

Aircraft that originated directly or indirectly from designs developed for B.13/36 entered service with squadrons engaged in operations over the English Channel, the North Atlantic, and the Mediterranean theatre. Units flying derived types operated from bases such as RAF Scampton, RAF Waddington, and RAF Boscombe Down and participated in missions including strategic bombing raids linked to the Combined Bomber Offensive and tactical operations supporting the North African campaign and the Italian Campaign (World War II). Survivors from production runs underwent postwar conversion for uses in training units like No. 1 Flying Training School and in civil roles examined by operators including British European Airways and manufacturers such as Short Brothers and Harland.

Category:Royal Air Force specifications