Avro Lancaster B.VI

The B.VI was an attempt to push the Lancaster higher. Nine aircraft were converted from B.IIIs with two-stage supercharged Merlin 85 and 87 engines, annular cowlings similar to those of the Avro Lincoln and three-bladed paddle propellers. At a take-off weight of 65,000 lb (29,000 kg) it reached 504 km/h at 5,500 m with a service ceiling of 8,700 m, and climbed to 8,500 m in 44.8 minutes. In June 1944 one was dived to an indicated 350 mph, equivalent to Mach 0.72 at 7,600 m.

The nose and dorsal turrets were removed and faired over. The aircraft went to Pathfinder units — Nos. 7, 83, 405 (RCAF) and 635 Squadrons — often in the master bomber role, apart from two retained by Rolls-Royce for engine testing. The two-stage Merlins proved troublesome: ground crews disliked their rough running and tendency to surge and hunt, a fault caused by variations in the fuel-air mixture that damaged the engine over time. The mark was withdrawn from operations in November 1944 and the survivors passed to Rolls-Royce, the Royal Aircraft Establishment and the Bomb Ballistics Unit for experimental work.