STATUS: Retired, Out-of-Service
MANUFACTURER(S): Blackburn Aircraft - UK
OPERATORS: United Kingdom
LENGTH: 35.60 feet (10.85 meters)
WIDTH: 45.93 feet (14 meters)
HEIGHT: 12.14 feet (3.7 meters)
WEIGHT (EMPTY): 6,140 pounds (2,785 kilograms)
WEIGHT (MTOW): 7,970 pounds (3,615 kilograms)
ENGINE: 1 x Bristol Perseus XII air-cooled radial piston engine developing 890 horsepower and driving a three-bladed propeller unit at the nose.
SPEED (MAX): 224 miles-per-hour (360 kilometers-per-hour; 194 knots)
RANGE: 811 miles (1,305 kilometers; 705 nautical miles)
CEILING: 18,045 feet (5,500 meters; 3.42 miles)
RATE-OF-CLIMB: 1,500 meters (457 meters-per-minute)
Detailing the development and operational history of the Blackburn Roc (B-25) Navy Dive Bomber / Fighter Aircraft.
Entry last updated on 10/24/2017.
Authored by Staff Writer. Content ©www.MilitaryFactory.com.
Born from the Blackburn B-24 "Skua" of 1938 (detailed elsewhere on this site), the Blackburn B-25 "Roc" was a direct offshoot developed as a naval-minded "turret fighter". As its classification would suggest, the aircraft was given a fully-powered (single-seat) turret carrying a battery of machine guns for which to engage enemy fighters with, similar in form and function to the classic, and better-remembered, Boulton Paul "Defiant" platform of World War 2 (1939-1945). Introduced in 1939, just 136 of the Roc aircraft were produced in all for the design proved as inherently limited as its original.
In late December of 1935, the British Air Ministry revealed Specification O.30/35 to cover a new single-engine, two-seat naval fighter armed with a turret over the rear dorsal position to equip the Royal Navy's Fleet Air Arm (FAA). Blackburn Aircraft was already at work on their all-modern, land-based B-24 design (the "Skua") which featured monoplane wings, a traditional tail unit and trail-dragger undercarriage, and seated its crew of two in tandem under an enclosed canopy fitting. To expedite a possible contender to Specification O.35/35, the Skua was offered by Blackburn Aircraft as the base form for the new turret fighter and the Air Ministry, seeing its potential, contracted for two prototypes. This design would compete against Boulton Paul's own "P.85" which was a navalized variant of its land-based Defiant.
The new Blackburn aircraft, designated "B-25" and ultimately named "Roc" after a mythical bird, was just as conventional as its original design. The engine was fitted to the nose, the crew of two over center and tail using a single vertical plane. The wing mainplanes were low and set slightly ahead of midships. The undercarriage was of the same tail-dragger arrangement and retractable into the design. Some chief changes to the naval-minded aircraft included reinforcement of various members and folding wings to better handle carrier-based operation and storage. All-metal construction was used along with an enclosed cockpit, retractable undercarriage and monoplane wings - all regarded as notable features of then-modern aircraft.
The Bristol Perseus air-cooled radial piston engine was selected to power the type and to this was fitted a three-bladed propeller unit in "puller" arrangement at the nose.
The turret, the heart-and-soul of this new fighter, was the same power-operated model from the Boulton Paul Defiant series - the component manufactured by Boulton Paul itself. This weapon system carried 4 x 0.303 caliber medium machine guns and offered a good "punch" against modern aircraft. As a traversable installation, the gunner could engage with all four guns along any side of the aircraft - conceivably an excellent quality for a fighter to be able to train its armament against an unsuspecting foe. Beyond this, the Roc retained the Skuas dive bombing capability and could be equipped with 2 x 250lb conventional drop bombs and rely on dive brakes to retard its descend during attack actions.
In need of modern aircraft, the Air Ministry moved ahead with this potential Blackburn offering and contracted for 136 examples of the type. However, Blackburn's existing, ongoing commitments meant that rival Boulton Paul was charged with the Roc's production. This led to a first-flight of a prototype aircraft on December 23rd, 1938 which revealed good control but an underpowered airframe as the aircraft was only able to achieve near 220 mile-per-hour top speeds. This poor early showing quickly doomed the Roc program but the aircraft on order were allowed to be completed lest production lines be disrupted.
Fleet Air Arm (FAA) squadrons 800 and 803 were the first to be issued the Roc in late 1939. In practice, the series was not well-liked by its crews who generally preferred the slightly better Skua. However, the Roc was available and all manner of aircraft were needed in the fighter against the Axis powers so the series pressed on to war, taking part in the Norwegian Campaign against German in April-June 1940. Despite their underperforming nature, the Rocs were used in air defense roles against more nimble enemy fighter platforms and, of course, suffered mightily. During the evacuation of Dunkirk, Rocs provided limited air cover to retreating Allied forces attempting to leave France for the relative safety of Britain. They tended to fare better as dive bombers and were also used in this regard against German targets in and around France and Belgium for their part in the war.
With their combat usefulness all but spent, Rocs ended their days as target tugs and Search And Rescue (SAR) platforms. The line soldiered on into late-1944 before being given up for good. In all, some twenty-seven Fleet Air Arm squadrons equipped with the Blackburn Roc and three Royal Air Force squadrons followed suit.
As completed, the aircraft sported an overall length of 35.6 feet, held a wingspan of 46 feet and featured a height of 12 feet. Empty weight was 6,120lb against an MTOW of 8,000lb. Power was from a Bristol Perseus XII air-cooled radial piston engine developing 890 horsepower, propelling the aircraft to speeds of 223 miles per hour (cruising generally done near 135 miles per hour). Its service ceiling reached 18,000 feet and rate-of-climb was 1,500 feet-per-minute. Range was out to 810 miles.
One notable variant planned for the Roc series was a floatplane derivative which saw the base design removed of its wheeled undercarriage and fitted with water-running floats and related equipment instead. A prototype of this form was completed. This design, too, was underpowered and performed poorly in testing. The prototype crashed in December of 1939 which forced revisions but the entire idea was ultimately dropped.
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Our Data Modules allow for quick visual reference when comparing a single entry against contemporary designs. Areas covered include general ratings, speed assessments, and relative ranges based on distances between major cities.
Relative Maximum Speed Rating
This entry's maximum listed speed (224mph).
Graph average of 225 miles-per-hour.
Graph showcases the Blackburn Roc's operational range (on internal fuel) when compared to distances between major cities.
Useful in showcasing the era cross-over of particular aircraft/aerospace designs.
Unit Production Comparison
Comm. Market HI*: 44,000 units
Military Market HI**: 36,183 units
* Commercial Market High belongs to Cessna 172.
** Military Market High belongs to Ilyushin Il-2.