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18th of June, 1926

95 years ago, on this day in aviation history the Blackburn Iris I made its first flight from the factory at Brough (Yorkshire, England). The Balckburn Iris I was a three-engined bi-plane and was build according to the Specification R.14/24 of the British Air Ministry. Both wings (wood and metal construction with fabric covering) were of equal span and had ailerons on both lower and upper wings. The fuselage had a stepped V bottom that gave excellent water handling qualities. The tail was unconventional, with two horizontal tail surfaces and three fins and rudders. It was a long-range reconnaissance aircraft for the RAF, they were operated by the No. 209 Squadron. the crew of 5 consisted of

  • 2 pilots, side by side in the cockpit in front of the wing

  • forward and aft gunner

  • fuselage gunner

Only five aircraft were built for and used by the RAF besides the single prototype

  • R.B.1 / Iris I Prototype, Wooden hull. Three 650 hp (485 kW) Rolls-Royce Condor III V-12 piston engines.

  • R.B.1A / Iris II It was found that the wooden hull of the IRIS 1 was absorbing up to several hundreds of pounds of water. To counter this the Iris II had a metal hull. Three 675 hp (503 kW) Rolls-Royce Condor IIIA V-12 piston engines.

  • R.B.1B / Iris III (4 built) First flight 21st of November 1929 5 Seat all-metal hull and metal wing structure, covered by fabric Three 675 hp (503 kW) Rolls-Royce Condor IIIB V-12 piston engines.

  • R.B.1C / Iris IV Conversion of the Iris II. Three 800 hp (600 kW) Armstrong Siddeley Leopard III radial piston engines

  • R.B.1D / Iris V Final variant. Three Iris Mk IIIs were fitted with 825 hp (615 kW) Rolls-Royce Buzzard IIMS piston engines

Some specifications of the Iris III:

Crew: 5

Length: 67 ft 4.75 in (20.5423 m)

Wingspan: 97 ft 0 in (29.57 m)

Height: 25 ft 6 in (7.77 m)

Wing area: 2,461 sq ft (228.6 m2)

Empty weight: 19,301 lb (8,755 kg)

Max takeoff weight: 29,489 lb (13,376 kg)

Fuel capacity: 906 imp gal (1,088 US gal; 4,119 l) in 3 tanks above each engine

Powerplant: 3 × Rolls-Royce Condor IIIB V-12 water-cooled piston engines, 675 hp (503 kW) each

Propellers: 4-bladed fixed-pitch propellers

Maximum speed: 118 mph (190 km/h, 103 kn)

Endurance: 4 hours 54 minutes

Service ceiling: 10,600 ft (3,200 m) [22]

Rate of climb: 630 ft/min (3.2 m/s)

Wing loading: 11.8 lb/sq ft (58 kg/m2)

Power/mass: 0.0699 hp/lb (0.1149 kW/kg)

Guns: 3 × .303 in (7.7 mm) Lewis guns, 1 mounted forward and two aft in open cockpits

Bombs: Up to 2,000 lb (910 kg) of bombs

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