The Hawker Horsley was a rare example of a bomber produced by Hawker, and was the last wooden aircraft to be produced by them before the introduction of their famous metal construction system.
The Horsley was designed by George Carter and Sydney Camm in response to Air Ministry Specification 26/23, which called for a fairly standard medium bomber, but with a metal framework in place of the wooden frames then in use on most British military aircraft. Hawker were thus operating at a double disadvantage - not only had they no experience of building a successful bomber, they also had no experience of working in metal.
The Horsley was an orthodox aircraft, with a larger upper wing and smaller lower wing. At this early stage in its design it was an entirely wooden aircraft, and this reflected a serious argument within the Hawker management that ended with Carter leaving the company to join Short Brothers to design a wooden racing seaplane. The Air Ministry approved the construction of a wooden prototype for the Horsley, but on the understanding that production aircraft would use metal. The original aircraft could carry one 550lb bomb under the fuselage (later increased to 1,000lb) and two 230lb bombs under the wings.
The Horsley was originally to be called the Hawker Kingston, but it was renamed in honour of 'Horsley Towers', a house owned by Harry Hawker, the test pilot who had helped form the company after the collapse of Sopwiths, before being killing in an aircraft crash. The name change had been made before the first prototype, J7511, made its maiden flight in March 1925.
Camm was responsible for the design of the second prototype, J7721. This aircraft had hand-built metal wings, and was designed with a new bomber specification, 23/25 and a torpedo-bomber specification, 24/25, in mind. The bomber specification increased the maximum size of a single bomb to 1,500lb, the torpedo-bomber specification to 2,150lb and later 2,800lb. In March 1926 the Air Ministry placed an order for thirty aircraft - 10 Mk Is, based on the all wooden first prototype and 20 Mk IIs, based on the second prototype. All thirty were to be complete by the end of 1927.
The first squadron to receive the Horsley was No.100 (Bomber) Squadron, which began to convert in August 1926. It was followed by No.11 Squadron in mid-1927 and by a re-formed No.33 Squadron in 1929. No.504 (County of Nottingham) Squadron of the Special Reserve also used the Horsley, from 1929 until February 1934.
In 1926 Horsley J8006 was modified to carry a 2,069lb torpedo, and at the end of 1927 Hawker was given a contract to produce the first twelve all-metal torpedo-bombers (followed by two orders for 18 aircraft). These aircraft were still officially Mk.IIs, although they are sometimes referred to as the Mk.III. The first of the production aircraft went to the Coast Defence Torpedo Flight in August 1928, and two months later this was renamed as No.36 (Torpedo Bomber) Squadron. After two years in Britain the squadron and its aircraft were moved to Singapore, where it operated its Horsleys until they were replaced by the Vickers Vildebeest in 1935. No.100 Squadron replaced No.36 as a home-based torpedo-bomber squadron, before itself converting to the Vildebeest prior to a move to Singapore. The torpedo carrying Horsley was sold in small numbers to Denmark as the Dantorp, while six standard Horsley IIs were sold to Greece.
A Horsley very briefly held the world long distance record. On 20 May 1927 Flt Lt Roderick Carr took off on the first of three attempts to fly to India. He was eventually forced down in the Persian Gulf, but by then he had flown 3,420 miles, beating the previous record. Unfortunately for Carr, a few hours later, on 22 May, Charles Lindbergh landed in Paris after his famous Atlantic crossing, setting a new record of 3,590 miles.
The Horsley's greatest contribution was probably as an engine test bed. The original prototype was used by Rolls Royce to test versions of the Condor, as well as the Eagle VIII and H.10, then by Napier to test the Lion. Later aircraft flew with the Armstrong Siddeley Leopard, Rolls-Royce Buzzard and even the Junkers Jumo! The most important trials were carried out by aircraft S1436 and J8611, which between 1934 and 1937 were used for flight trials of the Rolls Royce Merlin 'C', 'E', 'F' and 'G', and the Merlin X, later used in the Whitley V and Halifax bombers.
Horsley Mk II
Engine: Rolls-Royce Condor IIIA
Wing span: 56ft 5 ¾ in
Length: 38ft 10in
Height: 13ft 8in
Empty Weight: 4,760lb (4,957lb for torpedo bomber)
Loaded: 7,800lb (9,270lb for torpedo bomber)
Max Speed: 125mph at 6,000ft
Service Ceiling: 14,000ft
Armament: One fixed forward firing Vickers gun and one flexibly mounted Lewis gun
Bomb-load: One 1,500lb, one 1,100lb or two 550lb bombs or a combination of light bombs on a No.I Mk III F skeleton tubular bomb rack
Torpedo-load: One Admiralty Type VI or VIII torpedo