J.Davilla, A.Soltan French Aircraft of the First World War (Flying Machines)

SPAD 11

  The SPAD family of fighters had proved to be an outstanding success and so it was perhaps natural that Bechereau would have turned his attention to producing a two-seat fighter to meet the C2 specification. This aircraft, which received the STAe designation SPAD 11 (presumably the SPAD 6, 8, 9, and 10 designations had been assigned to the SPAD projects mentioned above), was developed in parallel with the SPAD 7.
  The SPAD 11 appeared in many ways to be a scale-up of the basic SPAD 7 layout. It was a two-bay biplane with sweepback and positive stagger but without dihedral, and powered by a 220-hp Hispano-Suiza 8Bc. There were cutouts in the lower wings to improve the crew's downward view. Rib spacing was 190 mm in the upper wing and 175 mm in the lower. The wing trailing edge was made from metal wire. Ailerons were on the upper wing only. The fuselage had four longerons with a rectangular cross-section. A trap-door was located in the floor behind the observer/gunner's cockpit. The tailplane was attached to the upper longeron at zero degrees incidence; both sides were cambered. The Hispano-Suiza engine was attached to the fuselage on engine bearers connected to the longerons by transverse wooden supports braced by aluminum fittings. The pressurized fuel tank held 140 liters and there was a gravity tank in the upper wing. The oil tank held 15 liters and was located on the fuselage floor behind the engine. The annular radiator in front of the engine was connected to a reservoir next to the front spar of the upper wing. The aircraft had dual controls, and the observers cockpit could hold up to six ammunition drums. The pilot had a forward-firing Vickers machine gun and the gunner had a single Lewis gun on a ring mounting. A bomb load of 70 kg could be carried.
  Aircraft SPA 6049 with a loaded weight of 1,167.5 kg, a Hispano-Suiza 8Ee engine, and Ratmanoff H.R.1 propeller had the following performance during STAe testing on 25 October 1917: maximum speed 181 km/h at 2,000 m; 177 km/h at 3,000 m; 168 km/h at 4,000 m; climb to 500 m in 1 min. 35 sec.; 1,000 m in 3 min. 25 sec.; 2,000 m in 7 min. 35 sec.; 3,000 m in 12 min. 30 sec.; and 4,000 m in 17 min. 30 seconds.
  An evaluation of the SPAD 11 published 28 November 1917 stated that the aircraft's performance was inadequate for a two-seat fighter and was described as comparable to the SPAD SA series. It was hoped that fitting the SPAD 11 with a Lorraine engine could salvage the program. The Hispano-Suiza engines were noted as being out of service two out of every three days.
  Furthermore, it was decided that the SPAD 11's handling qualities were unacceptable for a fighter and therefore could not meet the requirements of the C2 category. At the time, the army cooperation squadrons were beginning to realize that the A.R.1s and Sopwith 1 1/2 1A2 Strutters were obsolescent. The class A2 requirement was initiated by the STAe as a result and it was decided to procure the SPAD 11 as an army cooperation machine along with the Salmson 2 and Breguet 14.
  Because of production difficulties with the Hispano-Suiza engines, as well as an explosion that heavily damaged the Bernard factory at Courneuve, production of the SPAD 11 was greatly delayed. In October 1917 complaints were being made about problems with the control system. Specifically, the aircraft was noted to be tiring to fly and difficult to control because it was tail heavy and lacked maneuverability. Worse, it stalled easily, often ending up in a spin. Despite these glaring problems, it was decided that the A.R.1s and Sopwith 1 1/2 Strutters had to be replaced and the SPAD 11 had the virtue of being a more modern design that was readily available.
  A night fighter version of the SPAD 11 was designed. It had a searchlight mounted in similar fashion to the pulpit of the SPAD A series. Designated the SPAD 11 Cn2, only a single example was built.
  Difficulties with the Hispano-Suiza engine led the SPAD firm to fit a 220-hp Renault to a SPAD 11. It has been reported that the performance with this engine was inferior to the standard production versions. At least one SPAD 11 was fitted with a 310-hp Hispano-Suiza 8Fb with a Rateau supercharger. It was designated SPAD 11 CE.
  Although it was inferior to the Breguet 14 A2 and Salmson 2 A2, 1,000 SPAD 11s were built. There were still 85 SPAD 11s at the front in October 1918.


Operational Service

  Problems with the SPAD 11 continued after it entered service. A GQG memo dated 9 January 1918 suggested that repairs of the Hispano-Suiza engines were frequently required and Adjudant Foidit visited the SPA-Bi units to ensure that the repairs were done correctly. A memo of 11 July 1918 noted that the SPAD 11's oil coolers were deficient and required repair or replacement. It was also reported that month that the tail skids were weak and needed to be reinforced. The modifications, suggested by Adjudant Girardon of SPA-Bi 266, enabled the skid to better withstand the shock of landing and also helped to keep the plane straight during takeoff and landing. A less serious problem was the gun mount. When the plane was flown as a single-seater pilots were warned to lock the turret in place or it would swivel violently in flight. A GQG memo dated 27 June 1918 noted that in the field some of the SPAD 11s required modifications to the rigging.
  SPAD 11s were gradually withdrawn from service during the first months of 1918. They were replaced by SPAD 16s with 240-hp Lorraine engines or, in a few cases, Breguet 14 A2s.


Foreign Service

Belgium
  SPAD 11s were acquired by the Belgian Air Service in 1918. These served with the 4th Escadrille d'Observation at Hondschoote, 5th Escadrille d'Observation at Houtem (along with Breguet 14 A2s), 6th Escadrille d'Observation at Houtem, and with the Escadrille Royale. The SPAD 11s were retired from service in 1921.

Japan
  At least one SPAD 11 was purchased by the Japanese in April 1918. It was used as a trainer by the army aerial reconnaissance corps based at Shimoshizu.

Russia
  At least one SPAD 11 was used by the RKKVF as late as 1923. It served with the 2nd Otdel'nyi Istrebitel'nyi Aviaotryad.

United States
  The American Expeditionary Force acquired 35 SPAD 11s in 1918. They were supplied to the 1st and 90th Aero Squadrons.
  The 1st Aero Squadron received 18 SPAD 11s in February 1918. They were reported to be troublesome to maintain and apparently most of the difficulties were attributed to the 220-hp Hispano-Suiza engines. On 1 May 1918 there were 14 SPAD 11s on strength with the 1st Aero Squadron. They were replaced beginning in June by the far more successful Salmson 2s.
  The 90th Aero Squadron had a few SPAD 11s on strength but these were apparently replaced by Sopwith 1 1/2 Strutters (!) by May 1918.

Uruguay
  A few SPAD 11s were acquired by the Uruguayan air service after the First World War ended.


SPAD 11 Two-Seat Reconnaissance Aircraft with 220-hp Hispano-Suiza 8Bc
   Wing span 11.24m; length 7.80m; height 2.50 m; wing area 30 sq. m
   Empty weight 679 kg; loaded weight 1035 kg
   Maximum speed: 185 km/h at sea level; 172 km/h at 4,000 m; climb to 2,000 m in 7.5 minutes; climb to 3,000 m in 12.6 minutes; climb to 4,000 m in 17 minutes; ceiling 6300 m; endurance 2.25 hours
   Armament: one fixed, synchronized 7.7-mm Vickers machine gun fired by the pilot and one 7.7-mm Lewis gun mounted on a ring stand fired by the observer, and 70 kg of bombs
   Approximately 1,000 built

W.Green, G.Swanborough The Complete Book of Fighters

SPAD S.XI France

   The basic SPAD S.XI was intended by Louis Bechereau as a two-seat fighter. When the prototype appeared in September 1916, it was clearly descended from the S.VII, but it had conventional two-bay interplane bracing for its longer wings, which were staggered and featured sweepback. Powered by a 220 hp Hispano-Suiza 8Bc eight-cylinder water-cooled Vee-type engine, the S.XI was found to possess extremely sensitive handling qualities and was deemed unsuited for the fighter role. It was adopted as a Corps d'Armee reconnaissance aircraft, however, entering production as the S.XI A2. It proved a dismal failure in service, largely for reasons unassociated with the basic design, yet 1,000 examples were produced. In an attempt to create a two-seat night fighter, one of these was experimentally fitted with a frontal searchlight as the S.XI Cn2. The mounting of the searchlight ahead of the propeller clearly drew on SPAD’s earlier experience in mounting the forward nacelle of the Type A series. It may be assumed that the S.XI Cn2 proved unsuccessful under test as only one example was completed. The following data are for the S.XI A2, but those for the Cn2 version can be assumed to have been similar.

Max speed, 112 mph (180 km/h).
Time to 9,845 ft (3 000 m), 12.6 min.
Endurance, 2.25 hrs.
Empty weight, 1,497 lb (679 kg).
Loaded weight, 2,282 lb (1035 kg).
Span, 36 ft 9 1/3 in (11,21 m).
Length, 25 ft 8 2/3 in (7,84 m).
Height, 9 ft 2 1/4 in (2,80 m).
Wing area, 322.93 sq ft (30,00 m2).

G.Swanborough, P.Bowers United States Military Aircraft Since 1909 (Putnam)

SPAD 11A-2 and 16 A-2

   The Spad 11 and 16 were fast two-seat reconnaissance types developed from the Spad VII. Retaining the same short nose of the single seater made it necessary to sweep back the wings of the two seater for balance purposes. Thirty-five 11A-2s were procured, and have erroneously been referred to ever since as Spad 112 because the caption on the most-used photo released by the Office of Public Information in World War I inadvertently left the letter A and the dash out of the designation 11 A-2. The Model 16, of which there were six in the A.E.F. was an identical airframe with a 250-h.p. direct drive Lorraine engine.

Журнал Flight

Flight, May 16, 1918.

THE SPAD TWO-SEATER.
200 H.P. HISPANO-SUIZA ENGINE.

   THE following particulars and illustrations, apparently from an official report on the Spad two-seater, are published in Flugsport of April 10th :-
   The Spad two-seater, which is shown in the accompanying illustrations, is marked B 6006, and is built under licence in July, 1917, by the Aircraft Works of Ad. Bernard in La Courneuve (Seine). In general design and in constructional details it resembles the single-seaters, but does not have the divided inner interplane struts usually found on these. It is built as an ordinary two-strutter. The spars of the lower wings are braced to the under-carriage from the point of attachment of the inner pair of struts. The upper wing, which runs right through, has a span of 11.22 metres, and a chord of 1.53 metres, while the lower wing has a span of 10.90 metres and a chord of 1.43 metres. The gap is 1.335 metres and the stagger 0.4 metre. There is no dihedral angle, but both upper and lower wings are swept back, the angle being 174°. In order to give a better view, the lower wings have been cut away near the body, and the upper wing has a cut-out portion in the centre. The two spars are placed closer together than those of the lower wing, and the interplane struts converge somewhat upwards. The angle of incidence of the upper plane is 2.8° in the centre, and 2.5° at the tip, while the lower plane has a uniform angle of 1.5°. The lift wires are in duplicate, and in order to reduce head resistance, the space between them is filled up with strips of wood. The landing wires are single. A drift cable runs, from the junction of the inner interplane strut to the upper front spar, to the point of attachment of the front under-carriage strut. The interplane struts, which are of streamline section, are made of wood. Their fittings are attached to a steel tube carried inside the strut.
   The spacing of the ribs is 190 mm. in the top wing and 175 mm. in the lower wing. Between the ribs there are false ribs on the upper surface running from leading edge to front spar. The fabric is tacked to some more strongly constructed ribs, and is, in addition, stitched to ribs and to the wire forming the trailing edge. On the under surface, near the trailing edge, there are eyelets which serve to equalise the pressure and to drain any moisture out of the wing. Wing and body covering are painted a yellowish white.
   Non-balanced ailerons are hinged to false spars in the upper plane. They are operated by means of pull and push rods which rest in the lower plane behind the rear spars, and the movement of which is transmitted through cranks at the lower ends of the outer struts, to vertical struts pivotted to the lower surface of the aileron.
   The body, which is of the usual construction, with four longerons, is rounded off top and bottom by formers and stringers. The longerons have a rectangular section, while the vertical and horizontal body struts are spindled out to an I section, and are reinforced by plywood. A trap-door in the floor behind the observer's cockpit provides access to the interior of the body.
   The stabilising and control surfaces are of the usual Spad type. The tail plane, which runs right across the body, and has both sides cambered, is attached to the upper longeron at an angle of incidence of 0°. To its trailing edge, the divided elevator is hinged by means of a steel tube. In order to reduce resistance, the cranks are placed in the centre inside the body and vertical fin.
   The machine is provided with dual control. For operating the ailerons, the movement of the control shaft is transmitted by means of a lever, to a rocker supported in a partition between pilot's and observer's cockpits. The rods - which rest in the bottom wing - engage with a downward projection of this rocker. The observer's control lever is in the form of a telescopic tube, whose upper part is forced upwards by a spiral spring, or pressed down when not in use, and held in position by a bayonet joint. When extended, its length measured from the pivotting point is 53 centimetres, and when telescoped it measures 36 centimetres. The rudder bar in the observer's cockpit can be covered over with detachable covers, to guard against accidental use. The V form under-carriage struts are made up of several layers of wood glued together, and the whole covered with fabric. Diagonal bracing is employed in both front and rear bays. The two stub axles rest between two cross tubes covered with fabric, and move in slots in the struts. The travel is 125 mm. The VEE type Hispano-Suiza engine, which develops about 200 h.p. at 2,000 r.p.m., rests on engine bearers which are connected up to the body longerons by means of transverse supports of three-ply wood, and angle pieces pressed out of aluminium. The two-bladed air screw is geared down, by means of gearing incorporated with the engine in the ratio 4:3. The exhaust gases are carried away by collectors on each side of the body extending to behind the pilot's seat.
   A pressure petrol tank with a capacity of 140 litres forms the pilot's seat, while a gravity tank holding 10 litres is mounted in the upper wing, between the spars. The oil tank, which holds 15 litres, rests on the floor of the body behind the engine. The bottom of the oil tank has pressed on it ribs for cooling the oil. The fuel capacity is sufficient for a flight of about 2 hours' duration.
   The radiator, which is provided with shutters, forms the nose of the fuselage. A reservoir connected with the radiator is built into the upper wing in front of the front spar. Any steam or excess water is carried off underneath the body by means of an overflow and a pipe.
   The pilot's seat, which as in all Spad aeroplanes is kept very narrow, is separated from the engine by a linen curtain. In front of it is a wind screen divided into three parts and framed in aluminium.
   Of instruments, &c, there are as follows:
   On the right: The starter and the hand operated air pump. In the centre: Two switches, one three-way cock for pressure tank and connecting up with either hand or motor air pump, one three-way cock handle for turning on or off the petrol from tank to carburettor, one tap for turning the motor air pump off from the pressure tank, one manometer, and the revs, indicator.
   On the left: The gas lever, lever for regulating the mixture, and lever for operating the radiator shutters. There is no provision made for advancing or retarding the magneto. The instruments are to a certain extent badly arranged. Thus the revs, indicator is placed with its dial horizontal and so that the pilot sees the figures upside down.
   In the observer's seat are, in addition to the dual controls, two switches, one gas lever, and one lever for regulating the mixture, so that, apart from the petrol controls, the observer can look after the engine. Wireless installation is not fitted, although antennae wires are provided in the body.
   The armament consists of a fixed Vickers machine gun mounted above the body, for the pilot. The gun is operated by a push-rod from the right hand cam shaft. The trigger is on the control lever. The observer is armed with two Lewis machine guns coupled together. Six ammunition drums can be carried in the observer's cockpit, suitable brackets being provided.
   The weight of the machine empty, but including the cooling water, was ascertained to be 765 kg. A notice on the rudder gives they useful load (poids utile) as 255 kg. and the fuel weight (poids combustible) as 120 kg. This gives a total weight of 1,140 kg., so that the weight per sq. m. (the area is 29.8 sq. m.) is 1140/298 = 38.5 kg., and the weight per h.p. is 1140/200 = 5.7 kg.

Item Weights.
   Kg.
Motor 225.0
Cooling water 33.0
Wings 167.9
Elevator and rudder 19.9
Body, &c. 319.2
Total 765

Loading.
   Kg.
Pilot and observer 170.0
Armament .. 81.5
Instruments, &c. 3.5
Fuel 120.0
Total 375

Unit weight of wings
   167.9/29.8 = 5.64 kg./sq. m.