Blackburn Perth

The Blackburn Perth was a British flying boat in service during the interwar period. It was essentially an upgraded Iris, hence the largest flying-boat to serve with the Royal Air Force at the time (and the largest biplane flying boat ever to serve with the RAF).
Design and development.
The Blackburn R.B.3A Perth was designed as a replacement for the earlier Iris to Air Ministry Specification 20/32. Developed from the Iris Mk. V, the Perth first flew in 1933. It differed from the Iris by replacing the Rolls-Royce Condor engines of the Iris by more powerful Rolls-Royce Buzzards and having an enclosed cockpit for the pilots. Unusually, in addition to its normal armament, the Perth was fitted with a Coventry Ordnance Works C.O.W 37 mm (1.46 in) autocannon in its bows.
Four Perths were ordered for service for the RAF.
Operational history.
The Perth entered service with the RAF in January 1934, when the second aircraft was delivered to No. 209 Squadron RAF at RAF Mount Batten Plymouth. Perths remained in service until 1937, being replaced by the Short Singapore and the Saro London. One aircraft was retained by the Marine Aircraft Experimental Establishment until 1938.