The Royal Aircraft Factory S.E.5 was a British biplane fighter aircraft of the First World War. Although the first examples reached the Western Front before the Sopwith Camel and it had a much better overall performance, problems with its Hispano-Suiza engine, particularly the geared-output H-S 8B-powered versions, meant that there was a chronic shortage of S.E.5s until well into 1918 and fewer squadrons were equipped with the type than with the Sopwith fighter. Together with the Camel, the S.E.5 was instrumental in regaining allied air superiority in mid-1917 and maintaining it for the rest of the war, ensuring there was no repetition of “Bloody April” 1917 when losses in the Royal Flying Corps were much heavier than in the Luftstreitkräfte.
Design and development
The S.E.5 (Scout Experimental 5) was designed by Henry P. Folland, John Kenworthy and Major Frank Goodden of the Royal Aircraft Factory in Farnborough. It was built around the new 150 hp (112 kW) Hispano-Suiza 8a V8 engine that, while providing excellent performance, was initially under-developed and unreliable. The first of three prototypes flew on 22 November 1916. The first two prototypes were lost in crashes (the first killing the chief test pilot at the Royal Aircraft Factory, Major F. W. Goodden on 28 January 1917) due to a weakness in their wing design. The third prototype underwent modification before production commenced; the S.E.5 was known in service as an exceptionally strong aircraft which could be dived at very high speed – the squarer wings also gave much improved lateral control at low airspeeds.
Like the other significant Royal Aircraft Factory aircraft of the war (B.E.2, F.E.2 and R.E.8) the S.E.5 was inherently stable, making it an excellent gunnery platform, but it was also quite manoeverable. It was one of the fastest aircraft of the war at 138 mph (222 km/h), equal at least in speed to the SPAD S.XIII and faster than any standard German type of the period.
While the S.E.5 was not as agile and effective in a tight dog fight as the Camel it was much easier and safer to fly, particularly for novice pilots. The S.E.5 had one synchronised .303-in Vickers machine gun to the Camel’s two, but it also had a wing-mounted Lewis gun on a Foster mounting, which enabled the pilot to fire at an enemy aircraft from below as well as providing two guns firing forward. This was much appreciated by the pilots of the first S.E.5 squadrons as the new hydraulic-link “C.C.” synchronising gear for the Vickers was unreliable at first. The Vickers gun was mounted on the forward left dorsal surface of the fuselage with the breech inside the cockpit. The cockpit was set amidships, making it difficult to see over the long front fuselage, but otherwise visibility was good. Perhaps its greatest advantage over the Camel was its superior performance at altitude, making it a much better match for the Fokker D.VII when that fighter arrived at the front.
Only 77 original S.E.5 aircraft were built before production settled on the improved S.E.5a. The S.E.5a differed from late production examples of the S.E.5 only in the type of engine installed – a geared 200 hp Hispano-Suiza 8b, often turning a large clockwise-rotation four-bladed propeller, replacing the 150 hp model. In total 5,265 S.E.5s were built by six manufacturers: Austin Motors (1,650), Air Navigation and Engineering Company (560), Curtiss (1), Martinsyde (258), the Royal Aircraft Factory (200), Vickers (2,164) and Wolseley Motors Limited (431). A few were converted as two-seat trainers and there were plans for Curtiss to build 1,000 S.E.5s in the United States but only one was completed before the end of the war. At first, airframe construction outstripped the very limited supply of French-built Hispano-Suiza engines and squadrons earmarked to receive the new fighter had to soldier on with Airco DH 5s and Nieuport 24s until early 1918. The troublesome geared “-8b” model was prone to have serious gear reduction system problems, sometimes with the propeller (and even the entire gearbox on a very few occasions) separating from the engine and airframe in flight, a problem shared with the similarly-powered Sopwith Dolphin.
The introduction of the 200 hp (149 kW) Wolseley Viper, a high-compression, direct drive version of the Hispano-Suiza 8a made under licence by Wolseley Motors Limited, solved the S.E.5a’s engine problems and was adopted as the standard powerplant.
About 38 of the Austin-built S.E.5as were assigned to the American Expeditionary Force with the 25th Aero Squadron getting its aircraft (mostly armed only with the fuselage-mounted Vickers gun) at the very end of the war.
The S.E.5b was a variant of the S.E.5 with a streamlined nose and wings of unequal span and chord. The single example, a converted S.E.5a, first flew in early April 1918. It had a spinner on the propeller and a retractable underslung radiator. The S.E.5b was not a true sesquiplane – as the lower wing had two spars. Its performance was little better than the S.E.5a – the increased drag from the large upper wing seems to have cancelled out any benefit from the better streamlined nose. The S.E.5b was not considered for production; probably it was always intended mainly as a research aeroplane. In January 1919 it was tested with standard S.E.5a wings and in this form survived as a research aircraft into the early twenties.
The S.E.5 entered service with No. 56 Squadron RFC in March 1917, although the squadron did not deploy to the Western Front until the following month, among other reasons so that the very large and unpopular “greenhouse” windscreens could be replaced with small rectangular screens of conventional design. Pilots also disliked the original high seating position, designed to improve vision over the upper wing, preferring to sit lower (and more comfortably) in the cockpit. The squadron flew its first patrol with the S.E.5 on 22 April. While pilots, some of whom were initially disappointed with the S.E.5, quickly came to appreciate its strength and fine flying qualities, it was universally held to be under-powered and the more powerful S.E.5a began to replace the S.E.5 in June.
At this time 56 Squadron was still the only unit flying the new fighter; in fact it was the only operational unit to be fully equipped with the initial 150 hp S.E.5 – all other S.E.5 squadrons officially used the 200 hp S.E.5a from the outset – although a few S.E.5s were issued to other squadrons due to an acute shortage of the S.E.5a. This shortage resulted in a very slow initial build up of new S.E.5a squadrons, and lasted well into 1918. Once the Wolseley Viper powered model became plentiful many more units re-equipped, until by the end of the war the type was employed by 21 British Empire squadrons as well as two U.S. units. Many of the top Allied aces flew this fighter including Billy Bishop, Andrew Beauchamp-Proctor, Edward Mannock and James McCudden. Legendary British ace Albert Ball was initially disparaging of the S.E.5 but in the end claimed 11 of his 44 victories flying it. McCudden wrote of the S.E.5 “It was very fine to be in a machine that was faster than the Huns, and to know that one could run away just as things got too hot.”
Sholto Douglas who commanded No. 84 Squadron RFC which was initially equipped with the S.E.5a, listed the type’s qualities as:
- Comfortable, with a good all-round view.
- Retaining its performance and manoeuvrability at high level
- Steady and quick to gather speed in the dive.
- Capable of a very fine zoom.
- Useful in both offence and defence.
- Strong in design and construction.
- Possessing a reliable engine.
Some S.E.5s remained in RAF service after the Armistice, but began to be withdrawn soon afterwards. The type continued in service for a time in Australia and Canada, and in 1921 a Viper-engined S.E.5a was taken to Japan by the British Aviation Mission to the Imperial Japanese Navy.
A number of machines found roles in civilian flying after the war. The first use of skywriting for advertising was on 30 May 1922, when Cyril Turner, a former RAF officer, spelt out “London Daily Mail” in black smoke from an S.E.5a at the Epsom Derby. Others were used for air racing; an example won the Morris Cup race in 1927.
First production version. Single-seat fighter biplane, powered by a 150 hp (112 kW) Hispano-Suiza 8a piston engine.
Improved production version, powered by a 200 hp (149 kW) Hispano-Suiza 8b V-8 or 200 hp (149 kW) Wolseley Viper piston engine.
Experimental prototype, with semi-sequiplane wings, streamlined nose and retractable radiator.
S.E.5a assembled from spare parts by American company Eberhart Aeroplane, 180 hp Wright-Hispano E engine and plywood covered fuselages, about 60 built.