Blackburn B.25 Roc
Swayed by the RAF's enthusiasm, the Royal Navy invited Blackburn to design a naval turret fighter based on the Skua, issuing Specification O.30/35 on December 31,1935. The Skua's maiden flightvwas still more than a year away, but the Air Ministry ordered 136 Rocs to production standard “off the drawing board" and without prototypes.
The design was similar to the production Skua, modified to accept a Boulton Paul Type-A Mk 11 electrically-driven turret. The centre of the cockpit, which in the Skua contained the main fuel tanks, became a space for the gunner to operate the radio.
Retractable fairings in front of and behind the turret could be lowered to allow it to rotate freely. The Skua's central bomb recess was deleted, but wing racks for two 2501b bombs were added. To avoid the Skua's lowspeed instability the Roc's wing panels gained 2 degrees dihedral, doing away with the upturned tips.
Blackburn was too busy with Skua and Botha work, so the production order went to Boulton Paul. Blackburn subsidiary General Aircraft built the tail units.
Both the Skua and the Roc were of all-metal stressed-skin construction, with external plating flush-riveted to longitudinal stringers over transverse frames. The fuselage was built in two sections. The main fuselage ran from the firewall at the nose to a point just ahead of the fin, while the detachable rear fuselage incorporated the fin and tailplane mountings. The fuselage had a hollow in the upper surface containing a liferaft, and the cover was faired in with the top of the rear fuselage. The raft was accessed by pulling a D-ring on a cord in the rear cockpit, which rarely worked as advertised.
Along most of its length the fuselage was of circular section, but under and immediately aft of the wings triangular-section fillets joined the mainplanes to the fuselage, giving a complex cross-section. Two watertight compartments were built in. The cockpit was watertight up to the coaming and was enclosed by a long framed glazing with a steep windscreen. Two of the fuselage frames in the cockpit area extended to the top of the cockpit to prevent crushing if the aircraft overturned.
The glass was unarmoured initially, although from July 1940 armoured glass was added to the windscreen front panel. The standard RAF blind-flying panel formed the centre of the instrument panel; the gunsight was a Mk II reflector unit.
Two 200gal non-self-sealing fuel tanks were installed in the middle of the cockpit on either side, while a small tank for starting the engine was mounted in the forward fuselage.
The rear gun was mounted on a Fairey pillar, and lowered into a recess in the rear fuselage when not in use. The glazing enclosing the rear cockpit could be swivelled back into the canopy when the gun was to be used.
Rather than a seat, the Observer or Telegraphist Air Gunner(TAG) had only a thinly rubber-padded bench atop the bomb recess. To keep the TAG in place during diving and other violent manoeuvres a "g-string" was bolted to the floor, and the occupant could attach this to his harness. A bar could also be attached across the rear cockpit to give added support.
The production Skua II and Roc I had a cartridge-started Bristol Perseus XII nine-cylincler sleeve valve moderately-supercharged air-cooled radial engine giving 745 b.h.p. maximum climbing for 30min and 905 b.h.p. in level flight for 5min. Cooling gills at the rear of the cowling could be opened to provide greater flow of air. The engine was mounted on a two-bay tubular steel structure and fully cowled. An exhaust collector ring fed into a single tube discharging to starboard. The three-bladed, two-pitch de Havilland propeller was hydraulically operated.
The wings comprised three main sections; a centre section and two outer panels. The outer panels could be manually folded back along the fuselage for stowage of the aircraft in carrier hangars. The wings were based on two box-girder spars, on to which were attached the latch pin fittings that locked the wings in place when unfolded. The ailerons were fabric-covered. The all-metal flaps, of aerofoil section, were operated by hydraulic jack rams. The flap was arranged so that the leading edge moved aft as the flap was extended. At full extent the flap was vertical and the leading edge had moved through approximately 16 of the chord of the flap.
The tailplane was a two-spar structure similar to the wings, with a fabric-covered mass balanced elevator. The fin, which was detachable, was set forward of the tailplane to avoid the airflow being blanketed in a spin and at low speeds. The rudder was fabric-covered and horn balanced. Trim tabs on elevators and rudder could be controlled from the cockpit.
The undercarriage consisted of two retractable main units and a non-retractable tailwheel. The main units were oleo-pneumatic struts mounted on the outer edges of the centre section. The undercarriage legs and all the hydraulic retraction gear were located in the centre section, but folded outwards into the outer mainplanes. The tailwheel was fixed and later modified with an anti-shimmy device that could lock it straight or leave it free.
The Skua and Roc were equipped with an RT1110 Wireless Telegraphy (W/T) set consisting of a 1082 Receiver and a 1083 Transmitter. The W/T used an overhead aerial, but to make best use of the high-frequency equipment a trailing aerial could be wound out by the TAG or Observer. Communication was only by Morse code, but the transmitter was also used as an amplifier to provide intercom between the front and rear cockpit, a vast improvement on the Gosport tubes of previous FAA aircraft.
Communication between aircraft in flight was basic or non-existent. The W/T set was tuned laboriously by fitting pairs of plugs (twenty pairs, one red plug and one green) into sockets, more or less by trial and error until the correct coil for a particular frequency was reached. In the Skua this equipment was situated at the rear of the cockpit; in the Roc it was repositioned in the central space between the turret and the pilot's cockpit.
The Roc had no fixed forward facing weapons. The Boulton Paul power turret was fitted with four belt-fed Browning 0.303in machine-guns, fired by a control stick operated by the gunner.
The Roc was essentially similar to the Skua, but with its shape and construction altered as necessary for the role of turret fighter. The changes needed to instal this device mainly affected the rear fuselage. The body aft of the centre section was widened slightly. Instead of having the Skua's complex underbody shape, the Roc was flat underneath and a hatch was incorporated to provide an escape route for the gunner.
The centre cockpit housed a small "radio room", so fuel storage was relocated to the wings. The central section of canopy automatically retracted to allow the turret to traverse clearly, as did a plywood fairing aft of the turret. The fairings were pneumatic, powered by a pump run off the engine. Pressure could run down if the turret was revolved too much, the fairings becoming stuck until the pressure had built up again.
The pilot's cockpit was largely similar to that of the Skua. Control of the turret guns could be transferred to the pilot with the turret facing forward.
The wings were similar to those of the Skua but had greater dihedral and no upturned tips.
The first production Roc M k 1, L3057, made its maiden flight on December 23,1938, piloted by Blackburn test pilot Fit Lt H.J. Wilson. It remained at Brough for contractor's trials until March 1939, when the A&AEE took it for handling tests. Stalling speed was rather higher than that of the Skua, but handling was better. However, if the turret was used over-exuberantly the air pressure system operating the fairings would run down, preventing full turret movement until pressure was restored. While L3059joined the A&AEE test programme, the second Roc, L3058, was used for turret tests.
The Admiralty thought Roc floatplanes could be used for fleet defence, so when handling trials were largely complete, in November 1939, L3057 and L3059 were fitted with floats at Dumbarton. Tests at the Marine Aircraft Experimental Establishment at Helensburgh showed that the floats degraded directional stability, and L3059 crashed on December 3. As a result L3057 was given a much deeper ventral fin. Although L3060 and L3074 were also converted, the poor performance was evident and further trials scheduled for June 1940 were cancelled. Even so, L3074 retained its floats and was used as a target tug in this form.
Rocs entered service in late 1939. They were never allotted their own squadrons, but were issued to existing Skua units to operate alongside their stablemates. Small numbers, typically three or four, were later operated by Nos 800, 801, 803 and 806 Sqns, FAA.
The first combat work undertaken by Rocs was with 803 Sqn, protecting the fleet anchorage at Scapa Flow. Early in the war this target was tempting for German bombers, and RAF fighter squadrons were not available, so 803 Sqn moved to Wick in October 1939.
The Roc's shortcomings quickly became apparent. After October 18 the Luftwaffe rarely approached Scapa Flow, confining its attacks mainly to transport convoys and warships in the North Sea. Increasingly, 803 Sqn was called upon to deal with flying-boats shadowing warships of the Home Fleet, and civilian shipping under attack. The squadron was divided into sections of three, usually comprising two Skuas and one Roc. As the aircraft were frequently required at longer range, the Rocs were said by 803 Sqn's CO, Lt-Cdr D.R.F. Cambell, to be "a constant hindrance" ' He described an occasion when the C-in-C of the Home Fleet requested fighter assistance 210 miles from Wick. Two sections were on standby but only the four Skuas could cover the distance, reducing the squadron's strength by a third.
Blackburn was developing a long-range fuel tank for the Roc, but it was not ready for Service use. In January 1940 Cambell wrote to the Admiral Commanding Orkney and Shetlands, requesting that the four Rocs be replaced by Skuas, but was strongly opposed by the Naval Air Division (NAD) of the Admiralty, which was desperate to gain experience in tactics for the turret fighters. Even the C-in-C Home Fleet, Admiral Forbes, favoured 803 retaining Rocs.
Even Cambell said that the Roc could be considered "slightly superior” to the Skua. Forbes noted that with its "excellent multi-gun turret" the Roc was "more than slightly superior to the Skua; it offers the only chance of effective action against an enemy aircraft of equal or superior performance". The concept still had quite a few supporters, Forbes, in a letter to the secretary of the Admiralty in February 1940, suggested that all future FAA fighters should be of the turret fighter type. Nevertheless, in March 1940 the Rocs were replaced by Skuas. It had been decided that all aircraft in the Scapa Flow area must have identification friend or foe (IFF) to avoid "friendly fire" incidents, but the Roc's cockpit had no space for the equipment. So the Rocs had to be withdrawn from the region. Ironically, the Luftwaffe chose this moment for a concerted attack on the fleet anchorage, and in the ensuing five days of air raids a Roc made the type's first combat claim, a Heinkel He 111 damaged.
On April 8 Germany invaded neutral Norway and the RN was hurriedly required to respond. The early strikes were carried out by Skuas, the only aircraft with the range and accuracy to attack targets in Norway. Both Glorious and Ark Royal were training their Swordfish squadrons in the Mediterranean, and their Skua and Roc units were disembarked. Furious left for the combat zone in such a hurry that 801 Sqn was left behind at Evanton. Therefore, until Glorious and Ark Royal returned, the FAA’s Rocs were unable to contribute.
A nonentity in Norway On April 20 Ark Royal and Glorious, under Vice-Admiral Wells, embarked their fighter squadrons and set out to join the Norway Campaign Task Force. Ark Royal's fighter squadrons took Rocs as well as Skuas; 801 Sqn had three and 800 Sqn two. On Glorious, 803 Sqn was now exclusively a Skua unit, although it was the only squadron with any Roc combat experience.
Most missions in support of the ground forces needed every bit of the Skua's endurance, so Rocs were limited to providing combat air patrols (CAP) over the task force. Roy Stevens, an 800 Sqn armourer, remarked: "When the Rocs were ranged, you knew there was a raid coming! "
Rocs had about twice the endurance of the Gloster Sea Gladiators with which they shared CAP duty, but while the Gladiators had the speed and rate of climb to make interceptions, Rocs struggled to catch even the slowest shadowing seaplanes. Furthermore, on the few occasions when a Roc was able to bring its guns to bear, lowering the fairings and swinging the four Brownings into the airflow usually reduced the hapless fighter's speed enough to allow the prey to escape. The Rocs made little impact during the campaign, and one 800 Sqn armourer summed up their contribution to the Norwegian campaign as "bloody useless".
The higher echelons in the RN pushed the squadrons hard to make the Roc work. But an almost symbiotic co-operation between pilot and gunner was required, as the latter had to tell the pilot where to place the aircraft. Pilots were often officers, and gunners were enlisted men, expected to speak only when spoken to. The Admiralty requested that a second-line squadron be tasked with investigating the best tactical use of the Roc, with particular emphasis on co-operation between the pilot and gunner. This job was given to 759 Sqn at Eastleigh, but it seems little was done before the Roc was withdrawn from service.
The fourth Skua and Roc squadron, 806, had been formed in February 1940 and blooded over Norway with a number of long range strike missions from Orkney, flying Skuas. The squadron transferred to RAF Coastal Command control and flew to Manston in May, and then to Detling, to help cover the Allied withdrawal from France. On May 29 two Skuas and a Roc flown by Midshipman Day, RNVR, with Naval Airman Newton as his gunner, were patrolling the French coast. They saw a gaggle of Junkers Ju 88s about to bomb some ships, intent on their targets and flying slowly. Performing as intended for once, the Roc drew alongside a Ju 88 and a broadside of Brownings sent the bomber crashing inflames. It was the only confirmed kill ever scored by a Roc.
At the end of May 806 Sqn was replaced at Detling by 801 Sqn, which then became the closest thing to a Roc squadron when it exchanged some of its Skuas for the Rocs from 800 and 806 Sqns. Endurance was less important over the Channel, so the Skuas were kept for the squadrons still fighting in Norway.
From early in the morning on June 2 numerous patrols were flown over the ships ferrying troops back from France, the Skuas and Rocs joining RAF Hudsons and Blenheims. On the following day therewere hardly any German aircraft over the Channel and the squadron Operations Records Book states: "Nothing to report". The three Skuas and three Rocs patrolled at 4,000ft around the North Foreland and saw nothing; the evacuation was all but over. However, the Battle of France raged on and Channel convoys were now even more vulnerable. The Roc's work was to continue.
The next mission for 801 Sqn, escorting convoys, did not take place unti1June 9. Similar missions were flown on the 11th and 12th, the convoys being hard to locate because of poor visibility. While part of the squadron searched in vain for convoys, the rest attacked E-boats in Boulogne Harbour.
At around 1235hr Skuas and Rocs dive-bombed the harbour where the E-boats were moored and strafed the boats themselves. On returning to Detling the flight commander suggested another attack with the addition of 201b bombs in Light Series carriers, so at 1525hr the Flight of five aircraft took off again. The E-boats had been moved across the harbour, but were no less vulnerable. The aircraft dropped three 2501b bombs and 40 x 201b bombs. One E-boat suffered several direct hits and two others were damaged.
More convoy and reconnaissance missions followed, plus further strikes against German positions. On June 20 four Skuas and five Rocs of 801 Sqn were despatched to bomb heavy gun emplacements for a large battery being installed at Cap Blanc Nez.
Apparently the lessons of the recent past had been learned (a disastrous attack on the Scharnhorst in Norway had taken place only the previous week), and fighter escort was on hand. At 1440hr the squadron attacked from the sea in line astern. Diving to 1,000ft before dropping their bombs, they caught the defences off guard, but by the time the third sub-flight had winged-over into the dive the anti-aircraft artillery batteries were firing. Sub- Lieutenant Day and Naval Airman Berry's Roc was hit as it dived, and plunged into the sea wreathed in black smoke. The others scored four direct hits and a number of near misses.
Shortly afterwards 801 Sqn was released by Coastal Command and returned to Hatston. It soon re-equipped with Skuas, and the Roc's front-line career ended. Various trials had not yet been completed, so swiftly did the end come. The second wave of floatplane trials was cancelled, and the long-range tank never saw Service use. In December 1940 the Admiralty decreed that trials on tactical use of the Roc were no longer required. The Roc had outlived its usefulness. It continued in second-line service as a target tug and gunnery trainer, and the last was phased out in 1943.
Engine: Bristol Perseus XII, 893 hp / 675kW
Length: 35 ft 7 in / 10.85 m
Height: 12 ft 1 in / 3.68 m
Wingspan: 45.997 ft / 14.02 m
Wing area: 310.003 sq.ft. / 28.8 sq.m
Max take off weight: 7951.2 lb / 3606.0 kg
Weight empty: 6125.5 lb / 2778.0 kg
Max speed: 194 kt / 359 km/h / 223 mph
Cruising speed: 117 kt / 217 km/h / 135 mph
Service ceiling: 17995 ft / 5485 m
Wing load: 25.63 lb/sq.ft / 125.0 kg/sq.m
Range: 704 nm / 1304 km
Armament: 4x cal.303 MG (7.7mm)