| S.XIII | |
|---|---|
 SPAD S.XIII in the markings ofCapt. Eddie Rickenbacker, U.S.94th Aero Squadron at theNational Museum of the U.S. Air Force in Ohio. | |
| General information | |
| Type | Biplane fighter |
| National origin | France |
| Manufacturer | SPAD |
| Designer | Louis Béchéreau |
| Primary users | Aéronautique Militaire |
| Number built | 8,472[1] |
| History | |
| First flight | 4 April 1917[2] |
TheSPAD S.XIII is a Frenchbiplanefighter aircraft of theFirst World War, developed bySociété Pour L'Aviation et ses Dérivés (SPAD) from the earlier and highly successfulSPAD S.VII.
During early 1917, the French designerLouis Béchereau, spurred by the approaching obsolescence of the S.VII, decided to develop two new fighter aircraft, theS.XII and the S.XIII, both using a powerful new geared version of the successfulHispano-Suiza 8A engine. The cannon armament of the S.XII was unpopular, but the S.XIII proved to be one of the most capable fighters of the war, as well as one of the most-produced, with 8,472 built and orders for around 10,000 more cancelled at theArmistice.[1]
By the end of the First World War, the S.XIII had equipped virtually every fighter squadron of theAéronautique Militaire. In addition, theUnited States Army Air Service also procured the type in bulk during the conflict, and some replaced or supplemented S.VIIs in theRoyal Flying Corps (RFC), pending the arrival ofSopwith Dolphins. It proved popular with its pilots, and numerousaces from various nations flew the S.XIII. Following theArmistice of 11 November 1918, which marked the end of the First World War, surplus S.XIIIs were sold to both civil and military operators throughout the world.
The origins of the SPAD S.XIII lies in the performance of its predecessor, theSPAD S.VII, a single-seat fighter aircraft powered by a 110 kW (150 hp) direct driveHispano-Suiza 8A water-cooledV-8 engine and armed with a singlesynchronisedVickers machine gun. The type had good performance for the time, and entered service with the FrenchAéronautique Militaire during August 1916.[3] By early 1917, however, the S.VII had been surpassed by the latest German fighters such as theAlbatros D.III.[4]
More capable German fighters soon resulted in a shift in aerial supremacy towards theCentral Powers, which led to calls for better aircraft.[5] Frenchflying aceGeorges Guynemer personally lobbied for an improved S.VII, telling the SPAD's designerLouis Béchereau that "The 150 hp SPAD is not a match for theHalberstadt ... More speed is needed."[6] A quick solution to the problem was to increase the compression ratio of the Hispano-Suiza engine, which increased its power to 130 kW (170 hp) to significantly improve performance, allowing the SPAD S.VII to remain competitive for the time being.[7]
Hispano-Suiza were already in the process of developing a more powerful geared version of the 8A engine,[4] and this engine was chosen by Béchereau to power two developed versions of the S.VII. The BritishRoyal Aircraft Factory S.E.5a andSopwith Dolphin fighters would also be powered by the same engine.[5]
The first of Béchereau's designs to fly with the new, reduction gear HS.8B engine design series was theS.XII in itsHS.8BeC (or "HS-38") version, which was armed with an unusual 37 mm (1.457 in) cannon that fired through thepropeller shaft. However, this aircraft only saw limited use, having been rapidly followed into production by the more conventionally armed S.XIII, which was deemed to be a preferable configuration by several French pilots and officials.[8] Aviation author C.F. Andrews has claimed that a large portion of the credit for the S.XIII lies with Marc Birkigt, the designer of the engine, who had chosen to introduce various innovative features upon it, such as monoblocaluminium cylinders, which were furnished with screwed-insteel liners, which improved its performance.[9]
The SPAD S.XIII flew for the first time on 4 April 1917.[10][11] An early distinguishing feature of the S.XIII – as with the SPAD S.XII – was that its similarly geared HS.8Be V8 engine had a left-handed propeller, which rotating in the opposite rotation to the earlier, direct-drive HS.8A-powered S.VII. Early on, similarly to the BritishSopwith Dolphin also powered with HS.8B-series geared V8s, problems were encountered with the gearing, however, Béchereau persisted with the engine, which soon became fairly reliable.[11] Production was ramped up almost immediately after the first flight. Within months of its first flight, the S.XIII had not only entered service with theAéronautique Militaire, but had proven itself to be a successful fighter.[11]
The SPAD S.XIII was a single-engine biplane fighter aircraft. In terms of its construction, it shared a similar configuration and layout to the earlier S.VII,[nb 1] featuring a mainly wooden structure with afabric covering.[12] It was however generally larger and heavier than its predecessor. Other changes were made to theailerons, the rounded tips of the tailplanes, the bulkier cowling accommodating the gear-drive Hispano-Suiza 8B engine, and enlargedfin andrudder with a curved trailing edge.[11] The S.XIII was armed with a pair of forward-mounted Vickers machine guns with 400 rounds per gun, which replaced the single gun of the earlier aircraft.[10]
The S.XIII featured relatively conventional construction, that being a wire-braced biplane with a box-shaped fuselage and a nose-mounted engine, except for its interposed wing struts located halfway along the wing span, which gave the fighter the appearance of being a double-bay aircraft instead of a single-bay.[13] This change prevented the landing brace wires from whipping and chafing during flight. Otherwise, it had an orthodox structure, comprising wooden members attached to metal joint fixtures.[13] The fuselage consisted of four square-sectionlongerons, with wooden struts and cross-members while braced with heavy-gaugepiano wire. Wire cable was used for the flying and landing wires.[14]
To enable a two-hour endurance, the S.XIII was fitted with several underbelly fuel tanks held within the forward fuselage area which fed into the main service tank in the upper wing center section with an engine-driven pump.[15] Similar pumps were used for supplying pressurisedoil and water circulation between the engine'sradiator and a header tank was housed within the upper wing. The circular nose radiator incorporated verticalVenetian-styleblinds to regulate engine temperatures.[12]
The upper wing was made in one piece, with hollow box-section short spars that connected withlinen-wrappedscarf joints, Andrews claims that long runs of spruce were difficult to obtain.[14] Plywood webs and spruce capping strips, internally braced with piano wire, formed the airfoil. The upper wing was fitted with ailerons, actuated by the pilot via a series of tubular pushrods that ran vertical directly beneath the ailerons, with external, 90° bellcranks mounted on top of the lower wings.[15] The lower wing had spruceleading edges and wire-cabletrailing edges, while the surfaces were fabric-covered and treated withaircraft dope to produce a scalloped effect.[14]
While the forward Vickers machine guns were standard, they were not always available. As a result of a shortage during the last months of the war, several American S.XIII squadrons replaced Vickers .303 machine guns with the lighter 11.34 kg (25.0 lb).30/06-calibre Marlin Rockwell M1917 and M1918 aircraft machine guns,[16][17] saving some 7 kg (15 lb)[18] over the Vickers' 30 kg (66 lb), for the guns alone. By the end of the war, about half of American S.XIIIs had been converted.
The powerplant of the S.XIII was a geared Hispano-Suiza engine, at first a 8Ba providing 150 kW (200 hp),[10] but in later aircraft a high-compression 8Bc or 8Be delivering 160 kW (210 hp) was often used.[19] These improvements produced a notable improvement in flight and combat performance.[11] It was faster than its main contemporaries, the BritishSopwith Camel and the German Fokker D.VII, and its higher power-to-weight ratio gave it a good rate of climb. The SPAD was renowned for its speed and strength in a dive, although the maneuverability of the type was relatively poor and the aircraft was difficult to control at low speeds, needing to be landed with power on, unlike contemporary fighters like theNieuport 27 which could be landed with power off.[11]
The geared engines proved to be unreliable, suffering from vibration and poor lubrication. This severely affected serviceability, with it being claimed in November 1917 that the Spad S.XIII was "incapable of giving dependable service". Even in April 1918, an official report stated that two-thirds of the 150 kW (200 hp) SPADs were out of use at any one time due to engine problems.[20] At least one American observer believed at the time that the French were giving the American SPAD XIII squadrons lower-quality engines from their least favored manufacturers while keeping the best for themselves.[citation needed] The reliability issues were an acceptable price to pay for improved performance, however,[21] improved build quality and changes to the engine improved serviceability.[22]
At the beginning of 1918 the Aviation Militaire issued a requirement for a more powerful fighter, in a C1 (Chasseur single-seat) specification. SPAD responded by fitting the 220 kW (300 hp) Hispano-Suiza 8Fb in the SPAD XIII airframe. The structure was strengthened and improved aerodynamically, retaining the dimensions of the SPAD XIII. TwentySPAD XVII fighters were built and issued to units withGC 12 (Les Cigones).
Deliveries to theArmée de l'Air commenced During May 1917, only one month following the type's first flight.[23] The new aircraft quickly became an important element in the French plans for its fighter force, being expected to replace the SPAD S.VII as well as remaining Nieuport fighters in front line service.
However the slow rate of deliveries disrupted these forecasts and by the end of March 1918, only 764 of the planned 2,230 had been delivered.[24]
Eventually, the S.XIII equipped nearly every French fighter squadron, 74escadrilles, during the First World War.[25] At the end of the war, plans were underway to replace the S.XIII with several fighter types powered by the 220 kW (300 hp) Hispano-Suiza 8F, such as theNieuport-Delage NiD 29, theSPAD S.XX and the Sopwith Dolphin II.[26] These plans lapsed following the signing of theArmistice of 11 November 1918, which ended the First World War and the SPAD S.XIII remained in French service as a fighter aircraft until 1923,[16] with Nieuport-Delage NiD 29 deliveries being delayed until 1920.
The S.XIII was flown by numerous famous French fighter pilots such asRene Fonck (the highest scoring Allied ace, with 75 victories),Georges Guynemer (54 victories), andCharles Nungesser (45 victories), and also by the leading Italian aceFrancesco Baracca (34 victories).[27] Aces of theUnited States Army Air Service who flew the S.XIII includeEddie Rickenbacker (the United States' leading First World War ace with 26 victories) andFrank Luke (18 victories). Andrews attributes the S.XIII's natural stability, which made it a steady gun platform, as the key for its success.[28]
Other Allied forces were quick to adopt the new fighter as well and the SPAD XIII equipped 15 of the 16 operational USAAS pursuit squadrons by the Armistice. Prior to the United States entry into the war, American volunteers flying with the Allies had been flying the type.[29] Nearly half of the 893 purchased by the United States were still in service by 1920. In the United States, some S.XIIIs were re-engined with 130 kW (170 hp) Wright-Hispano engines and used to prepare pilots for the newThomas-Morse MB-3 fighter (which used SPAD-type wings) in 1922. The Wright-Hispano engines were unable to matching the performance of the original powerplant.[29]
During December 1917,No.23 SquadronRoyal Flying Corps (RFC) equipped with the SPAD S.XIII and retaining them until April 1918 when it re-equipped with the Dolphin, whileNo. 19 Squadron (equipped with the earlier S.VII) also operated at least one S.XIII for a time.[30] The type was used as an interim fighter while awaiting delivery of British-built aircraft.[29]
In his memoir Sagittarius Rising,Cecil Lewis described an aerial competition between himself and a SPAD flown by Guynemer, and Lewis in an SE5, "Their speeds were almost identical, but the high-compression Spad climbed quicker. After the race was over, Guynemeyer and I held a demonstration combat over the aerodrome. Again I was badly worsted. Guynemeyer was all over me. In his hands the Spad was a marvel of flexibility. In the first minute I should have been shot down a dozen times".[31]
The S.XIII was also acquired by Italy for theCorpo Aeronautico Militare.[29] Italian pilots expressed a preference for another French-built fighter, theHanriot HD.1, which was more maneuverable but less powerful. Belgium also operated the S.XIII and one Belgian ace, Edmond Thieffry, came to prominence while piloting the type.[29] After the end of the war, the S.XIII was also exported, including to Japan, Poland andCzechoslovakia.[citation needed]
Data from French Aircraft of the First World War[44]
General characteristics
Performance
Armament
Related development
Aircraft of comparable role, configuration, and era
