Blackburn Perth from Above |
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The Blackburn Perth was the largest biplane flying boat to see service with the RAF, and replaced the Blackburn Iris with No.209 Squadron, but wasn’t as successful as the Iris and had a very short service life.
During its life the Iris had evolved from the wooden Iris I with Condor III engines to the metal Iris V with Rolls-Royce Buzzard engines. The last Iris V had been built with a larger nose that allowed it to carry a 37mm Coventry Ordnance Works quick firing cannon, and this aircraft was effectively the prototype of the Perth.
The Perth was designed by J.D. Rennie to Air Ministry Specification 20/32. Like the Iris V it had an all metal structure, with a metal covered lower hull. The hull was wider than on the Iris – 12ft 6in instead of 11ft 0.5in – to give it more buoyancy. The hull was covered with Alclad, aluminium coated duralumin, which was more resistant to corrosion than unprotected duralumin.
The wings were built with duralumin box spars and ribs and were fabric covered. A walkway was built along the lower wing to allow engineers to reach the engines. It was a three bay biplane wing. Power was provided by three Rolls-Royce IIMS engines in streamlined nacelles carried between the wings. The central engine was carried on short struts, while the outer engines were carried directly on the wing struts. It had a biplane tail, with a larger upper horizontal surface. There was also a rear gunner’s position at the very tip of the tail.
Internally the aircraft had six compartments. The bow compartment carried the 37mm anti-shipping Coventry Ordnance Works cannon, a bomb sight, bomb controls, a compass, mooring hear, an anchor, chain lockers, parachute storage and a .303 Lewis gun that could replace the cannon. Next was the pilot’s cockpit, now an enclosed cabin with two pilots sitting side by side. Behind that was the navigator’s compartment. Next came the first of two wardrooms, then the engineer’s station, and finally the second wardroom.
Each engine was a self contained unit with its own radiators, starters and oil. Three 575 gallon fuel tanks were carried below the upper wing, giving a maximum range of 1,500 miles. Any fuel tank could feed any engine.
A total of only four Perths were ordered, three in the first batch and one extra. The first aircraft made its maiden flight on 11 October 1933. The second aircraft was the first to enter service with No.209 Squadron, arriving in January 1934. The third aircraft followed in February, with the delayed first aircraft coming in May. The Perths were used to patrol over the Irish Sea but had a short service career. They were first grounded on 8 October 1934 because of concerns about their tail units. Flying resumed from 6-27 November 1934, but the tails were then removed and sent to Blackburn at Brough to be modified. The squadron used the prototypes of the London, Scapa and Short R.24/31 flying boats while the Perth was away. The Perths returned to service in July-August 1935, but one was then lost on 14 September while attempting to take off in heavy seas off Stornoway. The surviving two aircraft were struck off charge in 1936.
The fourth and final Perth was delivered in April 1934 and went to the MAEE at Felixstowe for experiments. It was officially transferred to that unit in May 1936. However it was badly damaged in a landing and struck off charge on 2 February 1938.
Engine: Three Rolls-Royce Buzzard IIMS engines
Power: 825hp each
Crew: 5
Span: 97ft 0in
Length: 70ft
Height: 26ft 5.5in
Empty weight: 20,927lb
All-up weight: 32,500lb (38,000 overload)
Max speed: 132mph at sea level
Climb Rate: 800ft/ min
Service ceiling: 11,500ft
Range: 898 miles at 109mph
Endurance: 898 miles normal, 1,500 miles maximum range
Armament: One 37mm COW rapid firing cannon, three .303in machine guns
Bomb load: Two 520lb, four 230lb or eight 20lb bombs