The Blackburn M.1/30 (B-3) was a two man carrier torpedo bomber that reached the prototype stage, and helped test out some of the features of the Blackburn Shark, which was ordered into production in significant numbers.
The M.1/30 was designed in response to Air Ministry specification M.1/30, which called for a large single-bay, folding wing, deck landing torpedo bomber. Three companies were given contracts to build prototypes, for the Blackburn M.1/30, Vickers Type 207 and Handley Page HP 46.
Blackburn already had a great deal of experience with torpedo bombers. Their Blackburn Ripon entered service with the Fleet Air Arm in 1930, having made its maiden flight in 1926. In 1928 they had produced a design for a 50ft biplane powered by a Rolls-Royce F.XII engine in response to Specification M.5/28, and they based the new M.1/30 on that design.
The new design was somewhat similar to the metal Ripon III and had unequal span wings with raked wing struts. It had a crew of two (pilot and observer/ gunner). There was a small bombing position for the observer under the pilot’s cockpit. The fuselage was built around a fabric covered steel tube framework. The fabric covered wing spars were made of stainless steel strips and the ribs were also steel. They folded back from the point where the rear spar reached the fuselage. It was powered by a 825hp Rolls-Royce Buzzard IIIMS twelve-cylinder water cooled supercharged engine mounted in a streamlined cowling. The radiators were carried under the lower wing roots. It used a divided undercarriage, which left a gap for the torpedo to be carried under the fuselage.
The Blackburn prototype, serial number S1640, carried out its first engine runs on 18 February 1932 and made its maiden flight on 8 March 1932. It was tested by an RAE pilot on 31 August. On 29 January 1933 it moved from Blackburn’s factory at Brough to the A&AEE at Martlesham, where it was later lost in an accident. By this point a new specification, S.15/33, had been issued, calling for a torpedo-spotter-reconnaissance aircraft. This new specification led to the Blackburn Shark, which made its maiden flight on 24 August 1933, and to the more famous Fairey Swordfish. As a result there was no official interest in the M.1/30.
This didn’t stop Blackburn building a second prototype, to a modified design. This aircraft was known as the M.1/30A, and also as the B-3. The main change was the use of an all-metal semi-monocoque fuselage. It also had smaller wings, reducing the total wing area by 70sq ft. It could carry a dedicated gunner as well as the observer and pilot. The fuselage was divided into watertight compartments, which greatly improved its buoyancy. Fuel was carried in a fuel compartment that filled the space between the pilot’s cockpit and the front watertight compartment. This was made of stainless steal with riveted and soldered joints to make it fuel tight, then divided into three by bulkheads, to produce a 135 gallon main tank, 100 gallon rear tank and a 22 gallon gravity tank above them which was used to provide fuel to the engine. Each tank had a large manhole for inspection and repair. It was armed with a fixed forward firing Vickers Mk II machine gun, and a flexibly mounted .303in Mk III Lewis gun at the rear. It could carry four 550lb, 520lb or 500lb bombs, eight 250lb bombs or eight 20lb bombs on racks under the wings or one 1,900lb Mk VIII or Mk X or 18in K Type torpedo between the undercarriage legs.
The M.1/30A made its maiden flight on 24 February 1933. It went to Martlesham on 2 March but had to be returned to Blackburn for repairs, before returning to Martlesham on 14 March. In tests it performed well, but didn’t quite reach the requirements of the original M.1/30 specification. The new fuel tank was criticised for being dangerously vulnerable to enemy fire or damage. However the sealed watertight fuselage did impress, and the Air Ministry purchased the aircraft in May 1933, with the military serial number K3591. In June it was placed on display in the New Types Park at the Hendon RAF Display, then at the SBAC Show.
By this point the Air Ministry had already decided to purchase the Blackburn Shark, which used the same flotation system. On 25 January 1934 the M.1/30A was transferred to the Marine Aircraft Experimental Establishment at Felixstowe where it was used for ditching trials. On 30 April, after the trials were over, it was returned to Blackburn for studies into the impact of salt water corrosion. Soon afterwards the first order for the Shark was placed.
Blackburn B.3 M.1/30A
Engine: Rolls-Royce Buzzard IIIMS
Span: 49ft 6in (upper), 42ft 0in (lower)
Length: 39ft 10in
Height: 14ft 7in
Empty weight: 5,853lb
All-up weight: 10,393lb
Max speed: 142mph at sea level, 130mph at 10,000ft
Climb Rate: 35min 45sec to 12,000ft
Service ceiling: 12,000ft
Range: 750 miles
Armament: fixed forward firing Vickers Mk II machine gun, and a flexibly mounted .303in Mk III Lewis
Bomb load: four 550lb, 520lb or 500lb bombs, eight 250lb bombs or eight 20lb bombs on racks under the wings or one 1,900lb Mk VIII or Mk X or 18in K Type torpedo