The Blackburn B-24 Skua was a carrier-based low-wing, two-seater, single-radial engine aircraft by the British aviation company Blackburn Aircraft. It was the first Royal Navy carrier-borne all-metal cantilever monoplane aircraft, as well as the first dive bomber in Fleet Air Arm (FAA) service.Jackson 1968, p. 399. The aircraft took its name from the sea bird which dives on any potential predators that come too close to its nest.
The Skua was designed during the mid-1930s to Specification O.27/34, and was a radical design for the era, combining the functions of a dive bomber and fighter. Its enclosed cockpit and monoplane configuration were obvious shifts from preceding FAA aircraft such as the Hawker Nimrod and Hawker Osprey biplanes. On 9 February 1937, the first prototype performed its maiden flight; it was ordered straight off the drawing board to accelerate its development. In November 1938, the Skua was introduced to FAA service; 33 aircraft were operational by the outbreak of the Second World War.
Early in the war, the Skua was involved in the Norwegian campaign and sank the , the first big warship sunk in war by air attack and by dive-bombers. It was present during the Battles of Narvik, the Dunkirk evacuation and also the early stages of the Mediterranean theatre. While a capable dive bomber, its poor top speed and rate of climb meant it was severely limited as a fighter. Despite this, Fleet Air Arm pilots achieved moderate success with the Skua, scoring numerous aerial victories during the Norwegian and Mediterranean campaigns, with at least one pilot making ace status with five victories. In 1941, the Skua was relegated from frontline operations, but continued to be operated in secondary roles, typically training and target tug duties, as late as March 1945.
Development The origins of the Skua can be traced back to the Air Ministry's issuing of Specification O.27/34, which sought a naval dive bomber whose primary role would be to disable or destroy enemy aircraft carriers with a secondary role as a fighter.Smith 2006, Chapter 1 Blackburn chose to produce its own response under the internal design reference B-24, the design effort was headed by the aeronautical engineer G. E. Petty. Many competing companies also responded, including Avro, Boulton Paul, Hawker and Vickers. Blackburn's submission would emerge as the victor, despite several of the competing proposals adopting similar layouts. Being Blackburn's first dive bomber, the design was occasionally referred to as the D.B.1.
During April 1935, Blackburn received an initial order for a pair of prototypes. On 9 February 1937, the first of these, serial number K5178, performed its maiden flight from the company's facility in Brough, piloted by A. M. Blake. Unusually, it was initially painted in a distinctive grey-and-white colour scheme. On 26 June, the aircraft was first displayed to the public at RAF Hendon, London, and performed an aerial display at RAF Hatfield Woodhouse two days later. Two months later, the Skua name was officially assigned to the type by the Air Ministry.
During the latter part of 1937, the aircraft underwent official handling trials with the Aeroplane and Armament Experimental Establishment (A&AEE) at RAF Martlesham Heath. On 4 May 1938, the second prototype performed its first flight; it differed from the first by having a longer nose. Both of the prototypes would participate in the various tests, including gunnery trials, that were performed at Martlesham up until early 1939. Ditching trials were also undertaken at RAF Gosport.Jackson 1968, pp. 401-402.
Both prototypes were powered by the Bristol Mercury XII radial engine; however, production Skuas were instead powered by the Bristol Perseus XII, largely due to the Mercury engine being prioritised for Bristol Blenheim production. Another change made on production aircraft was the elimination of the wing tip slots, as they were deemed unnecessary after handling tests revealed mild stall characteristics.Jackson 1968, pp. 402-403. Due to the growing urgency for more combat aircraft in the runup to the Second World War, an initial production contract for 190 Skuas was issued in July 1935, effectively being ordered straight from the drawing board. To accelerate production, it was decided to produce the mainplanes at the Olympia Works in Leeds, while a subcontracting arrangement with General Aircraft Limited saw this company build additional fuselages at its Hanworth facility.Jackson 1968, p. 402.
On 28 August 1938, the first production Skua Mk.II, L2867, performed its first flight at Brough, piloted by H. J. Wilson. Both it and the second production aircraft were dispatched to Martlesham to accelerate the last stage of performance trials, which included armament trials. According to the aviation author Aubrey Joseph Jackson, despite the relatively radical nature of the design, relatively few changes were recommended either by the Air Ministry or the engine manufacturer; one of the few modifications requested was the strengthening of the wingtips and a substitute tail oleo.Jackson 1968, p. 403. Almost all of the production run was completed and delivered prior to the end of 1939, 26 Skuas were delivered during the month of July alone. However, due to delays in the overall programme, the Admiralty had also ordered the Fairey Fulmar to perform the same role.Jackson 1968, pp. 403-404.
Design
The Blackburn Skua was configured as a low-wing cantilever monoplane of all-metal construction. Its fuselage drew on the design of the Blackburn Shark, an earlier biplane, making extensive use of flush-riveted Alclad. It was internally divided into two water-tight compartments beneath the pilot's and gunner's cockpits to provide sufficient buoyancy in the event of a forcing landing at sea. For the same reason, the crew compartments were also watertight up to the edges of the cockpit. The fuselage was stressed to withstand catapult-assisted takeoffs and arrested landings aboard aircraft carriers; a hydraulic damping device was incorporated in the hook.
The mainplane, both the structure and covering of which was also composed of Alclad, was built as three separate units. The twin-spar heavy centre section was bolted beneath the fuselage to form the bottom of the watertight compartment. The outer wing panels, which tapered in both plan and thickness, ended in detachable upswept tips and were sealed between the main spars to form additional watertight compartments.Jackson 1968, pp. 399-400. Recesses in the lower surface of the wing accommodated modified Zap flaps that were used to shorten takeoff runs, steepen glides, and limit the aircraft's speed during steep dives. Balanced ailerons were fitted, which used inset hinges with mass balance assistance.Jackson 1968, p. 400.
Considerable design complexity was incurred by the choice to have both a retractable undercarriage and folding wings; the solution drew on the earlier Blackburn Airedale monoplane. When folded, the wings moved back around an inclined hinge housed within the wing, enabling a twist in the movement so that they rest against the fuselage; latch pins were used to secure them in place. The main undercarriage retracted both outwards and upwards into circular wheel wells in the underside of the outer wing panels, the motion being powered by an engine-driven hydraulic pump. The tail wheel unit was fitted with a Dowty-supplied self-centering shock absorber strut and an electrically conductive tyre. Both tailplane and fin were metal-clad cantilever structures that bolted directly onto the rear frames of the fuselage.Jackson 1968, pp. 400-401. Controllable trim tabs and a horn-balanced rudder were fitted, to ensure rapid spin recovery, a portion of the tailplane and the entirety of the fabric-covered elevator was positioned behind the trailing edge of the rudder.
The crew were accommodated beneath an enclosed glazed cockpit enclosure strengthened by two fuselage frames that formed a crash pylon in the event of the aircraft turning over.Jackson 1968, p. 401. It was the Fleet Air Arm's first service monoplane and was a radical departure for a force that was primarily equipped with open-cockpit biplanes such as the Fairey Swordfish. The pilot's position featured a sliding hood and was provided with favourable visibility in most forward-facing directions, while the gunner was seated after of the wing beneath a tilting canopy that could be opened or closed dependent on whether the defensive gun was being operated. This machine gun was stored in a compartment within the rear decking when not in use.
Various key elements of the aircraft were housed between the pilot and gunner's positions. A Wireless compartment was positioned directly behind the pilot. The majority of the fuel was stored in two tanks positioned between the crew members, with a reserve tank in the forward fuselage; the pilot could select for fuel to be drawn from any combination of these tanks via a single selector cock. Just forward of the pilot's instrumentation was a tank for lubricating oil. The aircraft's armament of four fixed, forward-firing 0.303 in Browning machine guns in the wings and a single flexible, rearward-firing .303 in Vickers K machine gun was considered to be effective for the era. For the dive-bombing role, a or bomb was carried on a special swinging "trapeze" crutch under the fuselage (somewhat like that of the Junkers Ju 87), which enabled the bomb to clear the propeller arc on release. Four bombs or eight Cooper bombs could also be carried in racks under each wing.
Its performance as a fighter was compromised by its dual role as a dive bomber. The size of the two-seat aircraft, and the extra strengthening of the air frame required to allow it to withstand the stresses of sustained high-speed dives, meant it was a relatively heavy single-engined aircraft at gross, compared to for the Spitfire Mk1. That was compounded by various features included to suit its naval use, such as an arrester hook, folding wings, a relatively large fuel capacity, watertight compartments, rafts, and a rear gunner/observer. That weight, coupled with the limited power from the Perseus engine, meant the aircraft had a low rate of climb compared to contemporary Japanese Mitsubishi A5M and American Grumman F3F carrier-borne fighters along with the Royal Navy's Gloster Sea Gladiator. The Skua was designed for best performance at low altitude, where its speed was comparable to potential enemy bomber aircraft, and the Skua, with four wing-mounted Browning machine guns, was much better armed than any other nation's pre-war naval fighter, such as the Mitsubishi A5M "Claude" and the Grumman F3F, having only two machine guns each. All those naval fighters compared unfavourably with land-based fighters such as the Messerschmitt Bf 109, which reached at sea level over the Skua's ,.Caygill, Peter. Flying to the Limit Testing WW II Single Engine Fighters. Chapter 4, Paragraph 1. and the Gloster Sea Gladiator's . However the Skua in the fighter role was never intended or envisaged to take on land-based fighters such as the Messerschmitt Bf 109. The Royal Navy and RAF (who at the time its specification was drawn up operated aircraft carrier air wings) only intended the aircraft to take on enemy reconnaissance and bomber aircraft.
The Skua was, however, an effective dive bomber, which was arguably its main intended role. It scored numerous successes as a dive bomber in the Norwegian campaign, sinking and damaging a number of ships, most notably the German cruiser Königsberg on 10 April 1940. Royal Navy test pilot Captain Eric 'Winkle' Brown stated:
Operational history