On 19 November 1912, the Admiralty placed an order with one of its favoured armaments contractors, Vickers, Son & Maxim, who had opened an aviation department the previous year, for a ‘fighting aeroplane armed with a machine gun’, presumably intending it to be employed in the defence of its shore bases. It seems probable that development of the new machine was already underway at the time of the Admiralty order and that the decision by Vickers to initiate the project had been influenced by the F.E.2.

The new machine designed by A. R. Low was of a pusher configuration and given the type number 18. Its two bay wings were of unequal span and were heavily staggered, the slope of the interplane struts being repeated in those separating the tail booms. Lateral control was by warp and the undercarriage comprised of two wheels mounted on half axles with a central skid. The nacelle had a framework of steel tubing and was covered in aluminium alloy sheeting. Power was provided by a water-cooled V8 Wolseley engine rated at 80 hp and a Vickers belt-fed machine gun was fitted in the nose of the nacelle where it enjoyed a 60 degree cone of fire. The assembled, but as yet untested, machine was exhibited at the Aero Show held at London’s Olympia in February 1913 as the Destroyer, although it would appear that its designers referred to it as the 18. Unfortunately, it proved nose heavy and was wrecked during its first attempt to take off. However, the design had promise and work began on a modified version designated as the 18a.

This variant, almost a complete redesign, had no stagger and its undercarriage was incorporated in twin skids. The nacelle had clear panels in the sides, presumably to improve the view downwards, and power was provided by a 100-hp Gnome rotary engine. Testing by company test pilot Harold Barnwell commenced around October 1913.

A further development designated as the model 18b, without the clear panels to the nacelle and fitted with ailerons on all four wings, was at Brooklands in January 1914 and exhibited at Olympia in March. It was later fitted with a triangular fin. Both 18a and 18b were purchased by the War Office, an order also being placed for a further six examples.

A further development of the basic design—with a new nacelle and with the gun mounted above the cockpit rim thereby increasing its field of fire—was designated as the EFB4 (Experimental Fighting Biplane No. 4) with the previous machines now being regarded retrospectively as EFB1-3. The new machine had the same wings as its predecessor with tubular steel struts and a similar undercarriage (with longer skids) and a modified nacelle and tail surfaces. Following testing, it was delivered to the Admiralty in fulfilment of the original order for a fighting biplane early in 1914 and was given the serial number 32 (in accordance with current practice, the Navy’s type number for the design). During 1914 and early 1915, it was stationed at RNAS Eastchurch to intercept Zeppelins attacking London, but there is no record of any action. It was transferred to No. 2 Squadron RNAS in March 1915 but was replaced shortly afterwards.

EFB5 differed from previous examples with a further modified nacelle and revised fin. Also, the rudder and struts were of spruce instead of steel employed previously. Power remained the 100-hp Gnome Monosoupape rotary engine. Completed by mid-July 1914, it was flown by Harold Barnwell from Joyce Green near the company works at Crayford to Brooklands on 17 July. EFB5 was then flown to Farnborough a few days later for testing by the AID. On 21 July, it was flown by three RFC pilots, Major H. R. M. Brooke-Popham, Capt. R. Cholmondeley and 2 Lt T. O’B. Hubbard, whose opinions were generally favourable, especially regarding the provision of the machine gun. Col. F. H. Sykes, then commanding the RFC, forwarded their three reports to the Director General of Military Aviation with a recommendation that an order be placed. On 25 July, EFB5 was blown over in a high wind and was returned to the workshops to be repaired.

A further development with unequal span wings, EFB6 had no decking between the two seats. Tested at Brooklands on 14 July, it was decided that the EFB5 should be the version adopted for production, its designation changing to Fighting Biplane No. 5 or FB5. Officially named as the Vickers Fighting Biplane, it was dubbed more affectionately as the Vickers Fighter by those who flew it. The name ‘Gunbus’ appears to have been invented by the press and applied indiscriminately to any armed pusher.

In response to demands for aeroplanes to expand the flying services, six machines were delivered after the outbreak of the war. This completed the order placed at the end of 1913 and were allocated the serial numbers 649, 664, 682, 686, 704 and 747. These also included the experimental models FB4 and FB6 with the former becoming 664 and the latter 704. None of these machines went to France although the first machine delivered, 664, was taken on charge on 10 September 1914. This particular FB5 saw action on Christmas Day when it was piloted by 2 Lt M. R. Chidson and took off from Joyce Green to intercept an enemy Friedrichshafen floatplane that was following the course of the River Thames. It was chased out to sea where the FB5’s gunner, Corporal Martin, fired at it and reported that the enemy aircraft has been damaged.

A few weeks later, another FB5 from Joyce Green, flown by Capt. Robert Maxwell Pike—a former naval officer who had trained as a pilot and joined the RFC despite a limp caused by an injured knee—took off in pursuit of a Zeppelin raider, but engine failure cut the mission short. Force landing in the dark, the FB5 hit a dyke and overturned. The resulting crash caused extensive damage to the FB5 although Pike and his gunner, A. M. Shaw, were unhurt. 647 and 682 were assigned to No. 7 Squadron during October 1914 and by the following January, 649 and 664 had been converted to dual control, the former being assigned to No. 11 Squadron during February. 747 was transferred to the RNAS at Dover in February, but was struck off charge by the middle of April.

It is probable that Vickers put the FB5 into production immediately as the design was finalised before the outbreak of war and the first production example was completed during October 1914. It differed from the prototype in having a straight trailing edge to the rudder so that all surfaces were almost rectangular in shape, presumably to simplify production. Orders were placed both by the Admiralty (861–4) and War Office (2340–7) on 14 August 1914 with the War Office placing three further orders, each for twelve machines, over the next few months. Serials assigned to these were 1616–27, 1628–39 and 1640–51. An enlarged rudder with a curved trailing edge was introduced from serial number 1638. Additional machines were ordered with deliveries being almost continuous and manufacture was also under taken by Darracq S.A. in France.

The first Vickers fighter to go to France, 1621, joined No. 2 Squadron on 5 February 1915 and acted as an escort to its reconnaissance machines where it was flown by 2 Lt Chidson. It then took up a similar role with the newly formed No. 16 Squadron a few days later and more machines joined other squadrons on the same piecemeal basis as soon as they became available. 1621 had a fairly brief operational career as it came down behind enemy lines on 2 March and was captured intact. No. 5 Squadron received at total of nine FB5s between February and June 1915, but only had three on strength by the end of that period. It operated one flight of fighters plus two reconnaissance machines the fighters were intended to protect. However, the Vickers were unable to escort the reconnaissance machines due to a disparity in speed, the Vickers proving slower than their unarmed companions and so patrolled the area ahead of their intended operations. Fredrick Powell, then a newly qualified pilot with No. 5 Squadron, recalled:

It was an interesting little aeroplane with a Monosoupape engine which had no throttle. You couldn’t go fast or slow, it only had one speed: flat out. We used to do two-hour patrols. It had petrol for 2½ hours, so that allowed 15 minutes each way to get to the lines.

The Monosoupape engine was far from reliable with those built under licence by Peter Hooker Ltd proving even worse than those manufactured in France and engine failures were common leading to aborted patrols and forced landings. So bad was the situation that Col. Brooke-Popham, then a staff officer in France, complained to the War Office that one Vickers pilot had suffered twenty-two forced landings due to engine failure in thirty flights and demanded an improvement in engine reliability. However, although such an improvement was eventually achieved, the engine never lived down its reputation for unreliability.

A few of the first machines were fitted with a belt-fed Vickers machine gun instead of the lighter drum-fed Lewis that was quickly standardised. Initial problems with the gun mounting resulted in several changes of design, the Vickers No. 2 Mk 1 eventually being adopted. This, however, was far from perfect and several improved variants were developed by squadron engineers in France. The Lewis guns had the barrel cooling jackets removed, reducing their weight as it was considered that the air flow over the weapon would provide sufficient cooling; however, it was not unknown for the barrel to overheat and gunners restricted themselves to ten-round bursts.

In April, No. 7 Squadron flew to France with two flights of R.E.5 bombers and one of Vickers fighters, including 1637 and 1651, adding to the number patrolling over the lines. Other squadrons operated the type, in addition to their other machines, in a similar role. Lt W. Acland of No. 5 Squadron with A. M. Rogers as his observer shot down an enemy machine on 15 May, their Vickers armed with a rifle as well as a machine gun.

The first squadron fully equipped with the FB5 and the RFC’s first ever squadron dedicated solely to aerial fighting was No. 11 that first formed in February 1915. It flew to France on 25 July with eight FB5s in two complete flights, including 1632, 1641, 1643, 1647 and 1650. It received a further three aircraft via the Aircraft Park in a week with the third flight being made up to full strength soon after. By the end of August, the squadron had been issued as replacements with two machines: 5454 and 5455 built by Darracq. The squadron began patrolling its section of the front almost as soon as it arrived in France. Capt. Lionel Rees with Flt Sgt Hargreaves in the front cockpit shot down a Fokker on 17 July despite damage to their own machine.

However, pilots often found that the enemy was disinclined to fight and often being faster than the FB5, simply sped away to avoid combat. This, however, was counted as a success as it freed the skies of enemy machines and allowed the RFC to carry out their duties of reconnaissance, bombing, photography and artillery observation unmolested.

But not all enemy machines refused to fight. On 5 September, another No. 11 Squadron machine flown by 2 Lt Cooper with 2 Lt A. J. Insall as his observer was patrolling near Gommecourt at about 9,000 feet when they spotted an LVG below them. As they dived down in pursuit, the enemy gunner—who occupied the rear cockpit and was equipped with a swivel-mounted machine gun—returned fire. When they grew level, the LVG turned broadside so it could continue to bring its gun to bear. Shots continued to be exchanged in this way until the LVG plunged into a steep dive with black smoke and flames pouring from its exhaust. Indeed, witnesses on the ground confirmed that the LVG was in a steep dive when it ploughed into the ground. Insall later wrote in his account of his part in the war this appreciation of the Vickers FB5 and its noisy rotary engine:

It never pretended to be capable of setting speed or height records. It was quite happy bumbling along above the German Army, booming it its sonorous defiance for all to hear and never evading a trial of strength.

Two days later, a No. 11 Squadron FB5 flown by Capt. Playfair also encountered an LVG; however, it dived away rather than fight. Later the same day, Capt. Darley had a similar experience with an Aviatik, an experience reported several times by other crews over the next few days. Other squadrons had similar experiences although on 29 July, Capt. Reese and Capt. Kennedy from No. 4 Squadron attacked an enemy two-seater that descended into a steep spiral. It returned fire up at the Vickers and hit it in the lower wing damaging both spars, cutting several wires and breaking a rib, although the machine landed successfully.

19 September saw No. 5 Squadron’s Lt F. J. Powell together with A. M. Shaw on patrol to the east of Polygon Wood when they observed an LVG below and dived down to attack. The enemy promptly dived away but they spotted a large twin-engine enemy machine and closed to within 100 yards before opening fire, the enemy returning fire from two separate guns. Shaw’s aim was true as an engine stopped and the enemy machine dived for the ground while trailing black smoke.

On 31 August, Capt. Lionel Rees with Flt Sgt Hargreaves claimed an Albatros CII. On 21 September, they added an Ago C.I to their score and seven days later spotted an enemy two-seater some 2,000 feet below them, and dived to attack. Their opponent turned out to be both faster and superior than the Vickers having two guns to their one; however, they pressed home their attack and were rewarded by seeing it crash just inside the German frontline. Rees was awarded the Military Cross for this action and other similar examples of courage in the face of superior forces, and eventually scored a total of seven victories flying the FB5, the highest score of any pilot of the type. Hargreaves was awarded a Distinguished Conduct Medal for his part in the successes.

26 October saw 5459, a No. 5 Squadron machine flown by the famous actor and pioneer airman, Robert Loraine, dive after an Albatros two-seater. He gave chase from 9,000 feet to just 600 feet with the observer, Lt. the Hon. Eric Lubbock, firing at it and Loraine joining in with a pillar-mounted Lewis gun. The enemy pilot, a corporal, was fatally hit and the machine crashed 20 yards from the frontline held by the Canadians. The observer, Lt Buchholz, who was just 17 years old and wounded in the stomach, was taken prisoner and extensively interrogated, a great deal of useful information being obtained. Both Loraine and Lubbock were awarded the Military Cross for the action. Loraine later dropped a message onto the German aerodrome giving details of the crew’s fate and returning the pilot’s personal effects. Loraine’s was not the only Vickers FB5 armed with a second Lewis machine gun. At least one machine of No. 11 Squadron was similarly equipped, although the task of aiming the swivelling gun while flying the aeroplane meant that the chances of hitting a target was virtually nil.

Capt. Rees scored again on 31 October, claiming an LVG two-seater driven down, his observer on this occasion being Flt Sgt Raymond.

On 7 November 1915, 2 Lt Gilbert Insall of No. 11 Squadron was flying 5074 with AM T. H. Donald in the front seat patrolling the Adinfer-Bapaume area when at 2.30 p.m., they spotted an Aviatik some 1,000 feet above them and Insall immediately climbed to attack. The enemy machine began to move away, trying to lead them into range of an anti-aircraft rocket battery. However, Donald’s shots found their mark and the Aviatik was shot down and landed heavily in a ploughed field. As the crew struggled away from the machine, Insall returned and dropped an incendiary bomb that left the Aviatik wreathed in smoke. Under fire from the ground, the Vickers headed back and crossed the lines at 2,000 feet where it was hit in several places, including the petrol tank. This caused the engine to stop and Insall managed to land about 500 feet behind the lines in the cover of small wood. Although they were unable to observe the aircraft, German artillery began shelling the area. Around 150 shells were fired, fortunately none further damaging the machine and after nightfall, they managed to repair the machine by the light of screened lamps and took off at dawn where they returned to their aerodrome. Insall was awarded the Victoria Cross for his courage but was unable to be invested with the medal as both he and Donald were shot down and captured a week later. Insall managed to escape on his third attempt in August 1917 and returned to active service with No. 51 Squadron.

During the summer of 1915, the enemy introduced the Fokker monoplane fighter armed with a forward firing machine gun. This innovative design changed the nature of aerial combat overnight; however, the Fokker, along with other similar designs, was initially available in very small numbers. Despite the FB5’s obsolescence, the type was obliged to continue in service, to counter the new oppositions as best it could, and on 19 November, the number operating in France increased by the arrival of No. 18 Squadron that was equipped with it. Losses increased and victories became ever more elusive, especially as most enemy machines were faster than the FB5. When during November 1915, a No. 11 Squadron machine courageously attempted to engage a Fokker, the enemy simply sped away in a steep dive.

On 16 March 1916, over a year since the type first entered service in France, Trenchard wrote to the Deputy Director of Military Aeronautics to state that ‘The Vickers Fighters, in their present condition, are now hopelessly outclassed and must be considered as quite out of date.’ Trenchard’s wish was granted and the type was withdrawn from active service from the spring of 1916. A number of machines were reassigned to training units in the UK. No. 18 Squadron exchanged its FB5s for the Royal Aircraft Factory F.E.2b, although No. 11 Squadron soldiered on with their Vickers until July.

The type had made a big impact and lived on in spirit after its withdrawal from the Western Front. When Manfred von Richthofen (The Red Baron) achieved his first victory on 17 September, he claimed that he had shot down an F.E.2b when it was a FB5. Twelve were built under licence in Denmark and were completed around March 1916. Although they saw no action, the Danish FB5s remained in service until 1924, the last of the design to survive.

In an attempt to improve the performance of the fighter, a modified design, the FB9, appeared in late 1915. Slightly smaller than the FB5 with a wingspan of just under 34 feet, it had rounded tips to the wings and tailplane, and was braced by streamlined Rafwires. Like the previous variant, power was provided by the 100-hp Gnome Monosoupape. The nose contour of the nacelle was more streamlined, giving an improved appearance as did the vee undercarriage, similar to that which had replaced the twin-skid version on some later production FB5s. Prototype 7665 was tested by the Central Flying School on 5 January 1916 and was sent to No. 11 Squadron in France for evaluation by service crews the following day. Opinions by pilots were generally favourable although observers were somewhat critical of the reduced leg room afforded by the revised nose contours and of the gun mounting.

7665 appears to have remained with No. 11 Squadron for on 2 April, it was flown by Capt. Champion de Crespigny with 2 Lt J. Hughes-Chamberlain as his observer and attacked a group of five enemy aircraft. One was shot down and a second dived out of control before the FB5 was shot up so badly with the rudder controls inoperative, it crash landed and was struck off charge. A total of ninety-five FB5s were built by Vickers with a further twenty-four built by Darracq, several of which found their way to No. 11 Squadron, the first, 7812, arriving on 19 May. One of these, 7828, scored a combat victory on 1 July 1916 while flown by Lt Moyes and Sgt Glover.

Like the FB5, the FB9 was withdrawn from frontline service by the end of July. Many finished their careers with training units where some were provided with dual controls, the nacelle noses being modified to improve leg room.