Here Comes The Iris

Review

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The R.B.1, codenamed ‘Iris’ was the first flying boat design and development project encompassed by the Yorkshire-based Blackburn Aeroplane and Motor Corporation, Ltd. The design of the Iris-I was the direct result of the Royal Air Force (RAF) desire to fill its maritime reconnaissance arm with a long range platform. A pre-design specification request was delivered to Blackburn in early 1925.

Only one year after the specification, the company was able to produce a workable aircraft fully loaded. On the morning of June 26th, 1926, the first prototype, R.B.1-I took to the air in its maiden flight. The Iris-I was an all wooden, three engine flying boat that utilized a distinctive biplane tail elevator on its upper plane and three rudders. The aircraft needed a five men flight crew. The two pilots sat on a side-by-side, open cockpit in the top front of the fuselage. The rest of the crew also sat in an open cockpit placed in the rear area, behind the wing structure.

Following a brief evaluation period, engineers at Blackburn decided to replace the provisional wooden hull for an all metal one. There are also some minor modifications performed on the Iris-I’s three Rolls Royce Condor IIIB piston engines. The resulting type was called model R.B.1A-II. It employed a more powerful power plant, the same RR Condor engines, but with an augmented in-line fuel distribution mechanism.

Overall, five versions of the Iris were produced between 1926 and the fall of 1932. All types employed the same airframe profile. Versions I through III were fitted with a Rolls Royce Condor engine, while IV utilized an Armstrong Siddeley Leopard III radial piston engines and type V carried three Rolls Royce Buzzard II MS piston motors. The final three produced Iris (III, IV and V) made it to full operational status, with the RAF’s 209 Squadron, in early 1930. At the time of their deployment, the Iris had the distinction of being the largest operational flying boat in the world.

Despite a very good service record, the Iris is most famously remembered by a lone flight. In September 28th, 1928, British Under Secretary of State for Air, Sir Philip Sassoon, took a 15,929km flight on an Iris-II. Sassoon and his party took off from Felixstowe and flew to Karachi to inspect RAF’s units deployed in the Island of Malta, Iraq and Egypt. The whole inspection flight took sixteen days, an impressive achievement for those times.

Power Plant: Three Rolls Royce 570hp Condor Engines (other variants are described above)
Wingspan: 29.57m
Length 20.54
Height: 7.77m
Total Wing Area: 207.07m(2)
Maximum Take off Weight: 13,376kg
Top Speed: 190kph
Serviceable Ceiling: 3,230m
Operational Range: 1,287km
Climb Rate: 184m per minute

An article by Raul Colon: rcolonfrias@yahoo.com