The Hawker Horsley was a single engine biplane bomber designed in the 1920s and was the last all-wooden design to be built by Hawker Aircraft.
In August 1923, the Air Ministry issued Specification 26/23, calling for a single-engine landplane day bomber to replace the RAF’s Fairey Fawns. Hawker accordingly submitted their proposal for a two-bay, staggered biplane of unequal span and of equal chord, with the lower wing being of narrow chord.
Initially named Kingston, this was amended to Hawker Horsley shortly after as 'Horsley Towers' was the name of the home of Company Chairman Sir Thomas Sopwith.
The outer wings of the new bomber were swept and its blunt-nosed front fuselage was of rectangular section, housing a pilot and bomb-aimer/gunner in tandem. It also featured adjacent cockpits to the rear of the cut-out trailing edge of the upper wing and unusually it was fitted with dual rear controls.
Powered by a 650 hp Rolls-Royce Condor III engine, the prototype (J7511) incorporated two engine-coolant radiators fitted to the sides of the fuselage, some 6ft (1·8m) aft of the engine. These fuselage-mounted radiators were however found to be unsatisfactory and they were quickly replaced with a more conventional single 'chin' type radiator.
Although the Hawker Company was well advanced in its use, design and development of metal construction in its aircraft, the two prototypes Horsleys and at least 10 of the early production Horsley Mk Is were all made of wood and these represented the last of the company machines to be constructed in this manner. Later Horsley aircraft incorporated part-metal construction methods and by the end of production the type was in fact an all-metal structure.
The first prototype was almost ready in December 1924 when it was damaged in an accident, delaying its first flight until March 1925 when Hawker Test Pilot F.P. Raynham took the aircraft aloft for the first time at Brooklands.
In early May 1925, the second aircraft (J7511) was delivered to the Aeroplane & Armament Experimental Establishment at Martlesham Heath where it was assessed by the pilots of No 22 Sqn, alongside its competitors which included the Bristol Berkeley, the Handley Page Handcross and the Westland Yeovil. During the trials it became apparent that none of these contenders were able to meet the requirements of the demanding specification. However, it was the Horsley that was felt to be the most promising of the bunch.
During July 1925, the prototype was sent to No 11 Sqn for Service Trials but again 'judgement was reserved' as it appeared that the actual Ministry specification was in fact flawed.
As a result, the Specification regarding the required military load requirement was revised and the new Specification 23/25 was issued instead. Happily for Hawkers, the Horsley still met these revised requirements as well as those later set down for Specification 24/25 which called for a torpedo-bomber variant.
In December 1925, the second Horsley prototype (J7721) made its first flight in the hands of P.W.S (George) Bulman, this example incorporating a much greater use of metal in its construction.
Another new Specification (22/25) was then issued to cover the further development of the Horsley and in March 1926 an order was placed for 38 aircraft and calling for the first ten to be of the wooden MkI variety with the remainder being of mixed wood and metal construction - these latter aircraft being designated as Horsley Mk IIs.
The Horsley entered RAF service with No 11 (Bomber) Sqn at Netheravon in January 1927 and No 100 Sqn received its examples shortly afterwards. The new bomber was a considerable advance on the Fairey Fawn (which it replaced) as it was able to carry three times the Fawn’s bombload over much greater distances.
Both squadrons demonstrated their new mounts at The 1927 RAF Display at Hendon and the type was later used to fly non-stop from the UK to India in May of that year (during which one aircraft was reportedly forced down into the Persian Gulf having flown 3,420 miles / 5,500km in just 34½ hrs. This was declared an unofficial record as it was surpassed only a few hours later by Charles Lindbergh and his solo 3,590 mile Trans-Atlantic flight in the Spirit of St Louis.
By 1928, the Horsley was serving with four RAF squadrons — Nos 11, 15, 33 and 100 as well as operating with the Anti-aircraft Co-operation Flight at Biggin Hill.
In the meantime, the tenth production Horsley Mk II (J8006) had been modified to carry a 2,100lb (950kg) torpedo and flew for the first time in August 1926. During January 1927, it was sent to the Torpedo Development Flight at Gosport for evaluation and at the end of that year an order was placed for 12 torpedo-bombers. This variant entered RAF service with the Coast Defence Torpedo Flight (renamed No 36 Sqn) in August 1928.
Further orders for all-metal torpedo-bombers (sometimes erroneously designated Mk IIIs) were placed and in total some 128 Horsleys were built for the RAF before they retired the type during 1934–35.
With good manoeuvrability and excellent endurance, the Horsley was much in demand as an engine testbed during the mid-1920s with the first prototype (J7511) being used for development work with the Rolls-Royce Condor, Eagle and H.10, and Napier Lion engines.
In 1927, Specification 17/27 was issued to Hawker to cover the conversion of the Horsley from its standard Condor engine to an Armstrong Siddeley Leopard 14-cylinder air-cooled radial unit. A Horsley Mk II (J8620) was also converted and it was much used for the testing of the Leopard engine, although the Condor remained the standard for the RAF’s Horsleys.
Other engines tested on Horsleys included Germany’s Junkers Jumo and most importantly Rolls-Royce’s early Merlin variants.
The first prototype was adapted as one of two Horsleys equipped with floats, tested by the Marine Aeroplane Experimental Establishment at Felixstowe. Although it underwent testing it was never actually adopted by the Royal Navy, nor was is ever used in service as a floatplane.
Several Horsleys were converted into target-tugs by the addition of a cable-drum and winch, fitted to the port side of the fuselage beside the rear cockpit.
The aircraft also caught the attention of the Greek Naval Air Service who ordered a total of six Mk IIs. Five of these were used as torpedo-bombers whilst the remaining machine was used as a VIP transport aircraft.
The Greeks were not the only ones who could see the potential of the Horsley and following the successful installation of an Armstrong Siddeley Leopard into a Mk II (J8620), the Danish government placed an order for two Leopard-powered machines. This variant, which could be fitted with interchangeable land or float undercarriages and was named Dantorp in Danish service. It was initially intended for the type to be built under licence at the Danish Naval Dockyard factory in Copenhagen.
Of composite wood and metal construction, the two Dantorps were given serials 201 and 202 and incorporated accommodation for a third crew member between the pilot and observer/gunner. 201 made its maiden flight on 19th September 1932 at Brooklands and in the summer of 1934, one of the Dantorps flew from Copenhagen to the Faroe Islands (a distance of some 1,000 miles - 1,610km) in just nine hours.
Although the Dantorps were much used, a lack of funding precluded the intended manufacture of the type under licence and only two were ever built.
In total 124 Hawker Horsley aircraft were built in various marks including the 2 Dnatorps and 6 for the Hellenic Naval Air Service. The last reamining Horsley was used as a Merlin Testbed at the Royal Aircraft Establishment at Farnborough, flying for the last time on 7th March 1938.
Variants & Numbers
|Prototypes||Two aircraft: J7511, J7721 Condor III|
|Horsley Mk I||Wooden construction. 1 x 650 hp Rolls-Royce Condor IIIA engine. About ten aircraft built from initial production batch of 38.|
|Horsley Mk II||Of mixed wood and metal construction. 1 x 665 hp Rolls-Royce Condor IIIA. Late-production batch of all-metal construction, erroneously referred to as “Mk IIIs”. Approximately 28 of the initial production batch of 38 aircraft. Further batches totalling around 90 aircraft for the RAF.|
|Greek Horsley||Six aircraft for the Hellenic Naval Air Service with Condor IIIA delivered in 1928.|
|Horsley testbeds||Various testbeds were flown (including J7511, J8003, J8620, J8611 and S1436) with the following: 670 hp Rolls-Royce Condor III; 665 hp Rolls-Royce Condor IIIA; 690 hp Condor IIIB; 480 hp Condor C.1 (compression-ignition); 810 hp Rolls-Royce Buzzard I; 880 hp Buzzard III; 810 hp Rolls-Royce H.10; 580 hp Napier Lion V; 765 hp Armstrong Siddeley Leopard I; 800 hp Leopard II; 805 hp Leopard III; 800 hp Leopard IIIA; 930–1025 hp Rolls-Royce P.V.12 Merlin C, E, F and G|
|Dantorp||Danish three-seat torpedo-bomber version. Two built. Mixed wood and metal construction. Initially fitted with 1 x 800 hp Armstrong Siddeley Leopard II, but both delivered with 805 hp Leopard IIIA|
|Total Built||Around 138 aircraft: 2 prototypes, 10 Horsley I, 118 Horsley II, 6 Greek Horsley, 2 Dantorp.|
|Powerplant||1 x 665 hp Rolls-Royce Condor IIIA V12 liquid-cooled piston engine driving a 14ft 6in-diameter Watts two-bladed wooden propeller (Horsley Mk II)|
|Maximum weight||Mk II bomber: 7,800lb. Mk II torpedo-bomber: 9,270lb|
|Capacity||1 x pilot; 1 x bomb-aimer/gunner|
|Armament||1 x fixed forward-firing Vickers gun; 1 x Lewis gun in bomb-aimer/gunner’s position; 1,500lb bombload or 1 x 2,100lb torpedo|
|Maximum speed||Mk II bomber: 125 mph at 6,000ft. Mk II torpedo-bomber: 118 mph at 5,000ft|