The AD Scout (later known as the Sparrow) was designed by Harris Booth of the British Admiralty's Air Department as a fighter aircraft to defend Britain from Zeppelin bombers during World War I.
This aircraft was an unconventional heavily-staggered, single-bay biplane, built to meet an Admiralty requirement for a fighter built from commercially obtainable materials and which could be armed with the Davis two-pounder quick-fire recoilless gun. The gun was mounted in the bottom of a short, single-seat nacelle, the top longerons were bolted directly to the main spars of the upper wing. The A.D. Scout was powered by a 100 hp Gnôme Monosoupape rotary engine driving a 9 ft pusher airscrew. The pilot had a excelent view in nearly every direction. A twin-rudder tail was attached by four booms, and it was provided with an extremely narrow-track "pogo stick" type undercarriage.
Four prototype aircraft were ordered in 1915. Two aircraft, (serial numbers 1452 and 1453) built by Hewlett and Blondeau Ltd of Leagrave, Beds. The remaining two (serial numbers 1536 and 1537) were built by Blackburn Aeroplane & Motor Company.
The four prototypes were all delivered to RNAS Chingford. The test trials flown by pilots of the Royal Naval Air Service were less than favorable. They proved the aircraft to be seriously overweight, fragile, sluggish, and difficult to handle, even on the ground. Due to the fact the Sparrow was considerably over-weight and difficult to handle in the air, all of the examples were scrapped.
The Vickers E.F.B.7 was a prototype British fighter aircraft of the First World War. A twin-engined biplane, the E.F.B.7 was unsuccessful, only a single example being built.
In August 1914, following the outbreak of the First World War, the British pioneer aircraft designer Howard Flanders was hired by Vickers Limited as an aircraft designer, with his first job to design a fighting aircraft to carry a Vickers 1 pounder (37 mm) cannon. (This was not the well-known pom-pom, but a smaller and lighter long recoil cannon firing less powerful ammunition.) Flanders produced a twin engined development of his earlier Flanders B.2 single-engined biplane, the E.F.B.7 (Experimental Fighting Biplane No.7).
The E.F.B.7 was a two-bay biplane with a steel-tube structure with plywood and fabic covering. It had unstaggered wings, with the upper wings of much greater (i.e. 22 ft (6.7 m)) span than the lower ones. It was powered by two tractor Gnôme Monosoupape rotary engines mounted between the wings. The gunner was sat in a large cockpit in the nose of the aircraft, with a rotating mount for the cannon and an armoured floor claimed to be bulletproof, while the pilot sat in a cockpit behind the wings, so that the pilot and gunner could not communicate.
The E.F.B.7 first flew in August 1915, being passed to the Central Flying School for testing. Sometime early in its career, it was fitted with large cowlings to catch oil from the engines. An order for a further twelve aircraft was placed on 20 August 1915, which were to have a modified fuselage allowing the pilot to sit closer to the gunner, and owing to a shortage of Monosoupapes, powered by two 80 hp (60 kW) Renault 80 hp air-cooled V8 engines. The first prototype was modified to this form, becoming the E.F.B.7A. Performance with these less powerful engines was much poorer, however, and the production orders were cancelled on 16 February 1916 before any more were completed.
The Vickers E.F.B.8 was a prototype British twin-engined fighter of the First World War. It was abandoned after only one aircraft was built, single engined fighters being considered to have superior manoeuvrability.
In autumn 1915, as well as the big, cannon armed, Vickers E.F.B.7, Vickers were working on the design of a second twin-engined fighter, the E.F.B.8 (Experimental Fighting Biplane No. 8). This design, which was assigned to Rex Pierson was for a smaller, machine gun armed fighter. With twice the power of Vickers' single-engined pusher Vickers F.B.5 Gunbus, which, while possessing an effective armament, was far too slow, the E.F.B.8 was hoped to have adequate performance. Like the E.F.B.7, the E.F.B.8 was a two-bay biplane with a steel-tube structure with plywood and fabic covering, and powered by two tractor Gnôme Monosoupape rotary engines mounted between the wings. It was however, much more compact, with a wingspan 20 ft less and 500 lb (230 kg) lighter. The gunner, armed with a single Lewis gun was sat in the nose, while the pilot again like the E.F.B.7. sat under the trailing edge of the wings, remote from the gunner and hindering co-operation between them in battle.
The E.F.B.8 flew in November 1915, demonstrating good performance, being the fastest twin engined aircraft of 1915, although not as good as expected. It was not considered manoeuvrable enough for use as a fighter, and with the prospect of better performing single engined fighters with synchronised guns, was rejected for production. The experience designing it proved useful to Pierson, however, when two years later, he came to develop the Vickers Vimy bomber, much larger but of similar layout.