THE DE HAVILLAND D.H.4 was a two-seater fighter-reconnaissance day-bomber. Three different types of engines were fitted to this aircraft. With the most powerful one, a 360 horse-power Rolls-Royce Eagle, the aircraft had a higher ceiling than any other British aeroplane of 1918, except the Le Rhone Camel and the Martinsyde F.4, both of which were single-seater fighters.
WHEN considering many of the Great War types of aeroplanes, we must allow for the overlapping of their duties. Aeroplanes designed primarily for fighting were sometimes used for bombing or reconnaissance; this applied even to single-seaters. Reconnaissance aeroplanes were used also for fighting, bombing and artillery and infantry cooperation.
There were two main types of reconnaissance aeroplanes, fighter-reconnaissance types attached to armies, and corps-reconnaissance types attached to army corps. Fighter-reconnaissance aeroplanes were the eyes of the H.Q. staffs; corps-reconnaissance types were mainly used for artillery and infantry cooperation. Fighter-reconnaissance aeroplanes had to fight their way when necessary and nearly always flew in formation. The corps-reconnaissance aeroplanes were expected to fight only in self-defence, and flew singly as a rule.
The sole duty of the rear gunner of the corps-reconnaissance aeroplane was to keep a lookout and to be ready to shoot if enemy aeroplanes attacked; the corps-reconnaissance pilot flew the aeroplane, observed the effect of the ground firing and maintained wireless communication.
Royal Flying Corps aeroplanes were used for reconnaissance from the beginning of the war. At that time there was no other duty for their aeroplanes to perform. Types then in use - such as the B.E. and the Bleriot - were described in the first chapter of this series. The first machine specifically built for R.F.C. reconnaissance duties in the war was the Vickers F.B.9 (1915-16), better known as the Vickers Fighter or “Gun-Bus”. Its official classification was fighter-reconnaissance, and it was described on page 618 in the chapter on fighters. Almost contemporary was the De Havilland 1a fighter-reconnaissance two-seater (1915-17), described on the same page. These two aeroplanes were included in the chapter on fighters, because they were the earliest aeroplanes designed and built for that specific purpose, in addition to the duty of reconnaissance.
The B.E.2c (1914-17) was a two-seater double-bay tractor biplane. It had the 90 horse-power R.A.F.1a engine and a four-bladed airscrew, and it was used for corps-reconnaissance work. It was used also for home defence. Description and performance are given in the first chapter of this series (page 505). Its dimensions were: span 37 feet, chord 5 ft 6-in, gap 6 ft 3¼-in, stagger 2 feet, incidence 4 degrees 9 minutes, dihedral 3½ degrees, length 27 ft 3-in, height 11 ft 1½-in, wheel track 5 ft 9¾-in. In the later model with the R.A.F. 1a engine the R.A.F.14 wing section was used. The earlier model fitted with the 70 horse-power Renault engine, one of which flew to France in August 1914, had the R.A.F.6 wing section and an incidence of 3½ degrees. Other dimensions were identical.
The F.E.2b (1915-17), designed at the Royal Aircraft Factory, was fitted first with the 120 horse-power and later with the 160 horse-power six-cylinder vertical water-cooled Beardmore engine and was classified as a fighter-reconnaissance and night-bomber aeroplane. It was a two-seater pusher; the crew was carried in a nacelle which projected in front of the wings, with the observer in the extreme nose. It carried two guns, a movable Lewis gun mounted in the nose of the nacelle and operated by the observer, and a fixed Vickers gun firing forward under the control of the pilot. The speed with the 120 horse-power Beardmore was 73 miles an hour at 6,500 feet and 72 miles an hour at 10,000 feet; with the 160 horse-power Beardmore the performance was 81 miles an hour at 6,500 feet and 76 miles an hour at 10,000 feet. These speeds were obtained by the F.E.2b as a fighter-reconnaissance type without bombs. Duration was 3½ hours; service ceilings were 9,000 feet and 11,000 feet. The 120 horsepower F.E.2b was used by Nos. 6, 18, 22, 23, 25 and 100 Squadrons of the R.F.C. The 160 horse-power F.E.2b was used by Nos. 18, 20, 22, 23, 25, 38, 58, 83, 100, 101, 102, 148 and 149 Squadrons of the R.F.C. The dimensions were: span, first model 47 ft 9-in, second model 50 ft 1-in, chord 5 ft 6-in, gap 6 ft 3½-in, incidence 3½ degrees, sweep back 8½-in at outer struts, stagger nil, dihedral 4 degrees, length 32 ft 10-in, height 12 ft 7½-in. The first model had the R.A.F.6 wing section with an incidence of 3½ degrees, and the second model had the R.A.F.14 wing section with an incidence of 4 degrees 10 minutes.
A FOUR-BLADED PROPELLER was fitted to the B.E.2c, a two-seater double-bay tractor biplane. This aircraft was used for corps-reconnaissance work and also for home defence When fitted with an R.A.F. 1a engine the aircraft could reach 72 miles an hour at 6,500 feet, and had a service ceiling of 10,000 feet One of the earlier models, fitted with a Renault engine, is shown in this photograph.
The B.E.2e (1916-17) was similar to the B.E.2c in general characteristics, but was designed as a single-bay biplane with extensions on the upper wings, giving unequal spans to the top and bottom wings. Fitted with the 90 horse-power R.A.F. 1a engine, it was used for corps-reconnaissance duties in 1916-17. The speed was 82 miles an hour at 6,500 feet and 75 miles an hour at 10,000 feet, duration 3¼ hours and service ceiling 11,000 feet. It was used by Nos. 2, 4, 5, 6, 7, 8, 9, 10, 12, 13, 15, 16, 34, 42, 52 and 53 Squadrons of the R.F.C. In 1918 it was the principal aeroplane used in the R.A.F. School of Wireless Instruction.
The F.E.2d (1916-17) fighter-reconnaissance two-seater pusher aeroplane was similar in general characteristics to the F.E.2b. It was fitted with the 250 horse-power Rolls-Royce 12-cylinder V water-cooled Falcon engine. The first of these aeroplanes to be sent to France lost its way over the Channel on June 30, 1916, and landed behind the German lines. The F.E.2d was used on the Western Front for some twelve months and put up a remarkable performance as a fighter. Formations of the machines on reconnaissance fought their own way across the lines and back again. When attacked by enemy scouts, they adopted a defensive formation by making a circle, each machine covering the tail of the one in front. Any enemy aeroplane attacking this formation could be shot at by several F.E.s simultaneously. The speed was 93 miles an hour at 6,500 feet and 88 miles an hour at 10,000 feet. Duration was 3 hours and service ceiling 16,500 feet. The service ceiling is the height at which an aeroplane’s rate of climb at full throttle and at the best climbing angle falls to 100 feet per minute. It is distinct from the absolute ceiling, the maximum height to which any given aeroplane can climb at full throttle. Between the service and absolute ceilings manoeuvre becomes virtually impossible, because the margin of lift is small and the speed range restricted. For these reasons the service ceiling represents the greatest height at which an aeroplane can usefully carry out military duties, even though it is not the greatest height it can attain. The F.E.2d was used by Nos. 20 and 57 Squadrons, R.F.C.
The Morane Parasol (1916-17), a two-seater tractor monoplane of French design, was fitted with the 80 horsepower and later the 110 horse-power Le Rhone rotary engine. As its name implies, the Parasol was a monoplane with the wing raised above the fuselage by struts. The wing was externally braced. The machine had no fixed tail-plane; the complete tailplane was a movable surface which acted as the elevator. It was delicate on fore and aft control. It was used as a corps-reconnaissance aeroplane, and its speed with the 110 horse-power engine was 96 miles an hour at 6,500 feet. Its duration was 2½ hours and service ceiling 15,000 feet. It was used by R.F.C. Squadrons Nos. 1, 3 and 60.
The Nieuport Two-Seater (1916-17) was a tractor aircraft of sesquiplane design with V struts between the wings. This aeroplane, of French design, was used in the R.F.C. for corps-reconnaissance duties. It was unstable and heavy on the controls. Fitted with the 110 horse-power Clerget rotary engine, it had a speed of 91 miles an hour at 6,500 feet. The duration was 3 hours and the service ceiling 13,000 feet. It was used by No. 46 Squadron of the R.F.C., and after it had been withdrawn from active service it was used as a stop-gap by No. 45 Squadron during delays in the delivery of Sopwith 1½-Strutters. Dimensions: span (upper) 29 ft. 7½-in, span (lower) 26 feet, chord (upper) 6 feet, chord (lower) approximately 3 feet, incidence (upper) 3½ degrees, incidence (lower) 4 degrees, left lower wing tip 5 degrees, stagger (at root) 2 ft 10½-in, (at struts) 2 ft 10⅞-in, dihedral (upper) nil, (lower) 2 degrees, sweep back 2 degrees 45 minutes, length 23 ft 11¼-in, height 8 ft 10-in.
The Sopwith 1½-Strutter (1916-17) was fitted first with the 110 horse-power and later with the 130 horse-power Clerget rotary engine. It was made in two types, a fighter-reconnaissance two-seater and a day-bomber single-seater. The former type was used by both the R.N.A.S. and the R.F.C.
From the autumn of 1916 until the summer of 1917 the fighter-reconnaissance type was used for army work in France, making long reconnaissance and photo-graphic-reconnaissance flights far over the territory occupied by the German armies. The squadrons had to fight their own way. In 1917 their losses were heavy. One fixed, synchronized Vickers gun was mounted in the centre of the top of the fuselage, and was operated by the pilot through the Ross interrupter gear which fired the gun slowly, there being a long interval between rounds. The observer had one Lewis gun mounted on a Scarff ring. Fuel tanks were situated between pilot’s and observer’s cockpits. Speed was 100 miles an hour at 6,500 feet, 97 miles an hour at 10,000 feet and 87 miles an hour at 15,000 feet. Duration was 3§ hours and service ceiling 15,500 feet. These aeroplanes were used by No. 8 Squadron, R.N.A.S., and by Nos. 43, 45 and 70 Squadrons of the R.F.C.
The day-bomber 1½-Strutter was used by the R.N.A.S. only. A number of the day-bomber type were collected at Luxeuil in October 1916 for the projected R.N.A.S. independent bombing force. They had a speed of 102 miles an hour at 6,500 feet and 98 miles an hour at 10,000 feet. The service ceiling was 13,000 feet.
Dimensions: span 33 ft 6-in, chord 5 ft 6-in, gap 5 ft 4¾-in, stagger 24-in, incidence 2 degrees 10 minutes, dihedral 2 degrees 23 minutes, length 25 ft 3-in, height 10 ft 3-in.
The R.E.8 (1916-18) was a two-seater tractor biplane fitted with the 150 horse-power R.A.F. 4a twelve-cylinder V stationary air-cooled engine. Both aeroplane and engine were designed at the Royal Aircraft Factory, Farnborough. The R.E.8 had single-bay wings with considerable extensions to the upper plane. It carried a synchronized Vickers gun on the left side of the fuselage outside the pilot’s cockpit, and a Lewis gun on a Scarff ring for the rear gunner. Classified as a corps-reconnaissance type, it replaced the earlier B.E. series. Its main duty was artillery cooperation, which consisted to a great extent of trench and counter-battery shoots, and photography. The speed was 102 miles an hour at 6,500 feet and 96 miles an hour at 10,000 feet. Duration was 4½ hours and the service ceiling 13,000 feet. It was used by Nos. 4, 5, 6, 7, 9, 12, 13, 15, 16, 21, 34, 42, 52, 53 and 59 Squadrons of the R.F.C.
Dimensions: span (upper) 42 ft 7-in, (lower) 32 ft 7½-in, chord 5 ft 6-in, stagger 24-in, incidence 4 degrees, dihedral 3½ degrees, length 27 ft 10½-in, height 11 ft 4½-in, tail span 14 feet.
The Armstrong Whitworth F.K.8 (1917-18) two-seater tractor biplane was a corps-reconnaissance type fitted first with the 120 horse-power, and later with the 160 horse-power Beardmore 6-cylinder-in-line, vertical, water-cooled engine. Its duties were similar to those of the R.E.8. With the 120 horse-power engine the speed was 83 miles an hour at 8,000 feet, and the service ceiling was 12,000 feet. With the 160 horse-power engine the speed was 95 miles an hour at 6,500 feet, and 88 miles an hour at 10,000 feet. The service ceiling was 13,000 feet. Duration was 3 hours for both types. They were used by Nos. 2, 8, 10, 35 and 82 Squadrons of the R.F.C.
The De Havilland No. 4 (1917-18), known as the D.H.4, was a two-seater fighter-reconnaissance and day-bomber aeroplane. This tractor biplane was fitted with three different engines of increasing horse-power, and with the last had a higher ceiling than any other British aeroplane of 1918, except the Le Rhone Camel and the Martinsyde F.4, both of which were single-seat fighters.
Almost Immune from Attack
When operating at height, the D.H.4 was virtually immune from the action of hostile aeroplanes. The performances with the different engines were as follows:
200 horse-power R.A.F.3a 12-cylinder V water-cooled engine: speed 120 miles an hour at 6,500 feet, 117 at 10,000 feet and 110 at 15,000 feet. Duration was 4 hours and the service ceiling 19,500 feet. Used by Nos. 18 and 49 Squadrons of the R.F.C.
250 horse-power Rolls-Royce Falcon 12-cylinder V water-cooled engine: speed 117 miles an hour at 6,500 feet, 113 at 10,000 feet and 102 at 15,000 feet. Duration was 3½ hours and the service ceiling 18,000 feet. Used by No. 5 Squadron, R.N.A.S., and Nos. 25, 55 and 57 Squadrons of the R.F.C.
360 horse-power Rolls-Royce Eagle 12-cylinder V water-cooled engine: speed 136 miles an hour at 6,500 feet, 133½ at 10,000 feet, 126 at 15,000 feet and 122½ miles an hour at 16,500 feet. Duration was 3¾ hours and the service ceiling 23,000 feet.
One synchronized Vickers gun was mounted centrally on top of the fuselage in front of the pilot’s cockpit, and a Lewis gun was mounted on a Scarff ring for the observer. The fuel tanks were situated between the two cockpits. Dimensions: span 42 ft 4½-in, chord 5 ft 6-in, gap 6 feet, stagger 12-in, incidence 3 degrees, dihedral 3 degrees, length 30 ft 2 3/16-in, height 10 ft 1¾-in.
The Bristol Fighter (1917-18) two-seater tractor biplane was colloquially called the “Brisfit”. It was made in two versions. The first model was a fighter-reconnaissance type, fitted with the 250 horse-power Rolls-Royce Falcon 12-cylinder V water-cooled engine. It carried out army-reconnaissance duties and fought its own way in doing so. Speed was 119 miles an hour at 6,500 feet, 113 at 10,000 feet and 105 at 15,000 feet. Duration was 3 hours and the service ceiling 20,000 feet. It was used by R.F.C. Squadrons Nos. 11, 20, 22, 48, 62 and 88 in 1917-18.
The second model was a corps-reconnaissance type, fitted with the 200 horse-power Hispano-Suiza 8-cylinder V water-cooled engine. This type was used only in 1918. Its speed was 105 miles an hour at 10,000 feet and 97½ miles an hour at 15,000 feet. The service ceiling was 19,000 feet. Dimensions: span 39 ft 3-in, chord 5 ft 6-in, stagger 8-in, incidence at centre section 1 degree 42 minutes, length 26 ft 3-in, height 9 ft 5-in.
TWO GUNS WERE FITTED to the Sopwith 1½-Strutter. One gun was mounted in the centre of the top of the fuselage and was operated by the pilot; the other was mounted on a Scarff ring for use by the observer. The 110 horse-power, and later the 130 horse-power, Clerget rotary engine was fitted. The speed was 100 miles an hour at 6,500 feet.