RB3 Perth

The RAF's largest biplane flying boat.
Blackburn Perth K3580 air to air front stbd An air-to-air photograph of the first Blackburn Perth K3580.
The Blackburn 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 Iris (described separately) 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, and is RAF’s largest biplane flying boat to see service.
Power was provided by three 825hp Rolls-Royce Buzzard II engines with the outer engines 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 with these being streamlined into the wing leading edge above each engine.
The all-metal hull was skinned in Alclad and incorporated two steps in its bottom surface. Accommodation was provided for up to five crew and a range of internal equipment including an auxiliary power supply for electrical services, air compressor, fuelling pump, life belts, dinghy, galley equipment, radio and navigation equipment, toilet and sleeping berths.
Blackburn Perth K 3581 prob Plymouth The second Blackburn Perth K3581, believed to be at its Mount Batten base at Plymouth.
The five crew roles were Captain, Second pilot / Navigator, Bow-gunner / Bomb-aimer, Midships gunner / Wireless operator and Rear-gunner / Engineer.
A 37 mm Coventry Ordnance Works (COW) automatic cannon was fitted in the Bow-gunner’s position and this was supplemented by three machine guns in bow, dorsal and tail positions. A maximum bomb payload of 2,000 lb could be carried. The 37 mm cannon was intended for anti-ship use, firing 1.5 lb shells at 100 rounds per minute.
The two pilots sat side-by-side in an enclosed cockpit. Patrol endurance was around 4.5 hours and the aircraft had a maximum still air range was 1,500 miles. Fuel could be cross-fed from any tank to any engine and all fuel piping and control cocks were mounted external to the hull.
A total of four Blackburn Perth aircraft were built, the first aircraft (K3580) being flown for the first time on 11th October 1933 before being delivered to Felixstowe for trials on 10th November.
The second aircraft (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 Perth’s were used by 209 Sqn for patrols over the Irish Sea operating from either Plymouth or from an outstation at Stranraer.
Blackburn RB3A Perth K4011 1934 A 1934 air-to-air photograph of the fourth and final Blackburn Perth K4011.
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 at Felixstowe until it was struck off charge on 2nd February 1938.

Variants & Numbers Built

RB3A Perth                 Three aircraft K3580 – K3582 used by 209 Sqn RAF. One aircraft K4011 used by Marine Aircraft Experimental Establishment, Felixstowe
Total production Four aircraft


Powerplant Three 825 hp Rolls-Royce Buzzard IIMS engines
Span 97 ft 0 in
Maximum Weight 32,500 lb (overload weight 38,000 lb)
Capacity & Armament Five crew; one forward-firing 37 mm COW automatic cannon, three defensive Lewis guns, up to 2,000 lb bomb load. 
Maximum Speed 132 mph sea level, 126 mph at 5,000 ft
Econ cruise speed 109 mph
Range  Normal 898 miles, maximum 1,500 miles


No Blackburn Perth aircraft survive.