P.Lewis The British Fighter since 1912 (Putnam)

The Vickers member of the trio of prototype escort fighter designs was the F.B.11, which appeared also in 1916. The Vickers product showed a far more restrained approach to the problem than its competitors, being basically a straightforward tractor biplane but following the same arrangement for the disposition of the crew of three as that adopted in the Sopwith L.R.T.Tr. The upper gunner was accommodated in his lofty perch above the upper wings in a less shapely nacelle than that of the Sopwith but the Rolls-Royce Mk.1 engine of 250 h.p. was endowed with a neat cowling and radiator installation. None of the proposed escort fighters went into production as the development of synchronizing gears nullified the requirement.

F.Mason The British Fighter since 1912 (Putnam)

Vickers F.B.11

   This large single-engine aeroplane was one of three strange-looking aircraft built to meet a War Office requirement for a long-range escort fighter, with a suggested secondary role as an anti-Zeppelin patrol fighter, the others being the Sopwith L.R.T.Tr and the Armstrong Whitworth F.K.12. High speed performance was not a prerequisite as it was intended that the aircraft should closely accompany bombing aircraft and provide them with all-round gun protection without breaking formation. The need to fire directly forward was therefore of less significance than all-round protection.
   The interpretation of the operational requirement by the three contending manufacturers differed considerably, Howard Flanders at Vickers opting for a single-bay unstaggered biplane, to be powered by one of the new 250hp Rolls-Royce water-cooled in-line engines. Pilot and one gunner were situated in closely-spaced tandem cockpits under the trailing edge of the upper wing, and a second gunner occupied a well-shaped nacelle extending forward from the upper surface of the top wing and supported by a pair of raked struts attached to the fuselage nose. Twin wheels and central skid comprised the undercarriage and, for entry to his cockpit, the nacelle gunner had to ascend a veritable flight of steps up the front port skid strut, up the side of the engine cowling, and on upwards by means of the port front nacelle strut.
   Two F.B.11s were ordered and the first was completed some time in July 1916, several weeks before the Rolls-Royce engine could be delivered, and the first flight of the aircraft, A4814, was considerably delayed until the early autumn. By that time the idea of large escort fighters had been abandoned as bombers of the calibre of the Airco D.H.4 - capable of putting up an effective self-defence - were coming into prospect.


   Type: Single-engine, three-seat, single-bay biplane escort gun carrier.
   Manufacturer: Vickers Ltd (Aviation Department), Knightsbridge, London.
   Powerplant: One 250hp Rolls-Royce Vee-twelve water-cooled in-line engine driving two-blade propeller.
   Dimensions: Span, 51ft 0in; length, 44ft 6in; height, 15ft 8 1/8 in; wing area, 846 sq ft.
   Weights: Tare, 3,340lb; all-up, 4,934lb.
   Performance: Max speed, 98 mph at sea level; climb to 5,000ft, 16 min 30 sec; endurance, 4 1/2 hr.
   Armament: One 0.303in Lewis machine gun on Scarff ring on gunner’s cockpit aft of the pilot’s cockpit, and one Lewis gun on nacelle gunner’s cockpit with all-round field of fire.
   Prototypes: Two, A4814 and A4815 (first flight by A4814 in late September or early October 1916). No production.

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

VICKERS F.B.11 UK

   Designed by Howard Flanders as an airship destroyer, for which purpose it had an elevated gunner’s station, or "fighting top”, mounted on the centre section of the upper wing, the F.B.11 flew in late November 1916. Carrying a crew of three, including two gunners each provided with a 0.303-in (7,7-mm) Lewis gun, the F.B.11 was powered by a 250 hp Rolls-Royce Mk III 12-cylinder water-cooled engine - later to be named Eagle. The F.B.11 proved to be deficient in lateral control and the first prototype eventually crashed and was written off, a second example never being completed as, in the meantime, it had been realised that the entire concept of the large airship destroyer was fundamentally unsound.

Max speed, 96 mph (154 km/h) at 5,000 ft (1525 m), 81 mph (130 km/h) at 10,000 ft (3 050 m).
Time to 5,000 ft (1525 m), 16.5 min.
Ceiling, 11,000 ft (3355 m).
Endurance, 7.5 his.
Empty weight, 3,340 lb (1515 kg).
Loaded weight, 4,934 lb (2238 kg).
Span, 51 ft 0 in (15,54 m).
Length, 43 ft 0 in (13,10 m).
Height, 13 ft 8 in (4,16 m).
Wing area, 845 sq ft (78,50 m2).

J.Bruce British Aeroplanes 1914-1918 (Putnam)

Vickers F.B.11

  THIRD of the three designs to be built to the R.F.C.’s specification for a long-range escort fighter, the Vickers F.B.11 of 1916 was basically a much more conventional aeroplane than its competitors, the Armstrong Whitworth F.K.12 and the Sopwith L.R.T.Tr.
  The F.B.11 was a large tractor biplane powered by a 250 h.p. Rolls-Royce engine. The wings were of equal span and wide gap, and were remarkable for having only a single bay of interplane bracing. The upper centre-section was very wide: it overhung the centre-section struts by an appreciable amount on each side. The outermost portions of the lower wings were braced by additional landing wires from the tops of the interplane struts.
  The engine was enclosed in a clean though somewhat bulky cowling; the radiator was installed behind the engine and within the fuselage. The pilot sat in line with the trailing edges of the wings, and there was a gunner immediately behind him. A second gunner occupied a lofty perch in a small nacelle which was built on to the leading edge of the centre-section and was supported by struts from the forward ends of the upper longerons.
  The undercarriage looked like a massive version of that fitted to the Avro 504. Its strength was necessary, for the F.B.11 was considerably heavier than the larger F.B.7 had been. The tail-unit was of pleasing outline, and was strongly braced by substantial struts.
  The idea of the escort fighter was officially abandoned when it became obvious that aerial warfare was developing along other lines. Vickers themselves hastened its abandonment with their own development of machine-gun interrupter gears.


SPECIFICATION
  Manufacturers: Vickers Ltd. (Aviation Department), Imperial Court, Basil Street, Knightsbridge, London, S.W. The F.B.11 was built at Vickers’ Bexley works.
  Power: 250 h.p. Rolls-Royce.
  Dimensions: Span: 51 ft. Length: 43 ft. Chord: 9 ft. Gap: 9 ft. Stagger: nil. Dihedral: 2°. Incidence: 2°.
  Areas: Wings: upper 440 sq ft, lower 405 sq ft, total 845 sq ft. Ailerons: each 28-25 sq ft. total 113 sq ft. Tailplane: 79-5 sq ft. Elevators: 55-5 sq ft. Fin: 19 sq ft. Rudder: 25 sq ft.
  Weights and Performance: Weight empty: 3,340 lb. Military load: 189 lb. Crew: 540 lb. Fuel and oil: 865 lb. Loaded: 4,934 lb. Maximum speed at 5,000 ft: 96m.p.h.; at 10,000 ft: 815 m.p.h. Climb to 5,000 ft: 16 min 30 sec; to 10,000 ft: 55 min. Ceiling: 11,000 ft. Endurance: 4 1/2 hours.
  Armament: One Lewis machine-gun on Scarff ring-mounting on rear cockpit. The top gunner was similarly armed.
  Serial Numbers: A.4814-A.4815: ordered under Contract No. 87/A/439.

H.King Armament of British Aircraft (Putnam)

F.B.11. Apparently intended primarily for anti-airship duties, though having obvious potential as an escort fighter, this single-engined three-seater of 1916 had two Lewis guns on Scarff ring-mountings. The foremost of these installations was in the nose of a nacelle carried forward from the upper surface of the top wing; the other was immediately behind the pilot, just aft of the wing trailing edges.