The Blackburn Aircraft Company R.B.3A Perth was a large, three-engine flying boat, developed against Air Ministry Specification 20/32 which called for a replacement for the Blackburn RB1 Iris which it replaced it in RAF service.

The three-bay biplane featured wings of 97 ft span and was of all metal construction with a fabric covering. It was and still is RAF’s largest biplane flying boat to see service.

Power was provided by three 825hp Rolls-Royce Buzzard II engines, with the outer unitss mounted on the inner inter-plane struts, with a central pylon supporting the middle engine. Each engine was fed by its own 575 gallon fuel tank, these having been streamlined into the wing leading edge above each engine.

The all-metal hull was skinned in Alclad (corrosion-resistant aluminium) and incorporated two steps in its bottom surface. Accommodation was provided for up to five crew plus a wide range of internal equipment including an auxiliary power supply (APU) for electrical services, an air compressor, a fuelling pump, life belts and dinghy plus galley, radio and navigation equipment. Finally and most importantly it included a toilet and sleeping berths.

The five crew roles were Captain, Second pilot / Navigator, Bow-gunner / Bomb-aimer, Midships gunner / Wireless operator and Rear-gunner / Engineer. The two pilots sat side-by-side, in an enclosed cockpit.

A 37 mm Coventry Ordnance Works (COW) automatic cannon was fitted in the Bow-gunner’s position, which was supplemented by three machine guns in bow, dorsal and tail positions. The 37 mm cannon was intended for anti-ship use, firing 1.5 lb shells at 100 rounds per minute whilst a maximum bomb payload of 2,000 lb could be carried.

Patrol endurance was around 4.5 hours and the aircraft had a maximum still air range of around 1,500 miles. Fuel supplies could be cross-fed from any tank, to any engine via fuel pumps, piping and control cocks which were mounted external to the hull.

A total of four Blackburn R.B.3A Perth aircraft were built, the first aircraft (K3580) being flown for the first time on 11th October 1933, before being delivered to Marine Aircraft Experimental Establishment (MAEE) at Felixstowe for trials on 10th November.

The second Blackburn R.B.3A Perth (K3581) flew on 5th January 1934, being handed over at once to the RAF and flown non-stop to 209 Sqn’s Mount Batten base, at Plymouth. The third aircraft (K3582) was delivered a month later.

The first aircraft (K3580) was lost in an accident off Stornoway in September 1935 whilst the other two aircraft were struck off charge during 1936.

The Blackburn R.B.3A Perth’s were used by 209 Sqn for patrols over the Irish Sea, operating from either Plymouth, or from an outstation at Stranraer.

A fourth aircraft (K4011) was flown on 16th April 1934, and had two (rather than three) fuel tanks. This aircraft spent its service career at the Marine Aircraft Experimental Establishment (MAEE) at Felixstowe, until it was struck off charge on 2nd February 1938.
Specifications
General characteristics
Crew: 5
Length: 70 ft 0 in (21.34 m)
Wingspan: 97 ft 0 in (29.57 m)
Height: 26 ft 5.5 in (8.065 m)
Wing area: 2,461 sq ft (228.6 m2)
Empty weight: 20,927 lb (9,492 kg)
Gross weight: 32,500 lb (14,742 kg)
Max takeoff weight: 38,000 lb (17,237 kg)
Powerplant: 3 × Rolls-Royce Buzzard II MS V-12 water-cooled piston engines, 825 hp (615 kW) each
Propellers: 2-bladed fixed-pitch propellers
Performance
Maximum speed: 132 mph (212 km/h, 115 kn)
Cruise speed: 109 mph (175 km/h, 95 kn)
Range: 1,300 mi (2,100 km, 1,100 nmi)
Service ceiling: 11,500 ft (3,500 m)
Rate of climb: 800 ft/min (4.1 m/s)
Wing loading: 13.2 lb/sq ft (64 kg/m2)
Power/mass: 0.076 hp/lb (0.125 kW/kg)
Armament
Guns:

1 × C.O.W 37 mm (1.46 in) automatic cannon in bow
3 × .303 in (7.7 mm) Lewis guns in bow, amidships and tail positions

Bombs:

Up to 2,000 lb (907 kg) bombs












Text from here - https://www.baesystems.com/en/heritage/blackburn-rb3-perth