de
Havilland DH91 Albatross
Designed by A. E. Hagg to an Air Ministry
specification for a transatlantic mailplane, the de Havilland D.H.91
Albatross was aerodynamically and aesthetically one of the outstanding
commercial aircraft of the pre-war era. Of wooden construction, it
introduced the ply-balsa-ply sandwich fuselage structure later used so
successfully for the Mosquito, and had a one-piece wing similar to that of
the Comet. Powerplant consisted of four de Havilland Gipsy Twelve engines
driving constant-speed propellers, and the landing gear main units were
electrically retractable. The prototype, initially with twin fins mounted
at mid-span on the tail-plane, was flown for the first time at Hatfield on
20th May 1937. Flight test results indicated that the vertical tail
surfaces were unsatisfactory, and the redesigned tail unit incorporated
endplate fins with unbalanced rudders and trim tabs.
Problems with the landing gear retraction system resulted in a wheels-up
landing for the first prototype on 31st March 1938, and a structural
weakness in the rear fuselage was revealed when the second prototype broke
into two a few months later when landing during overload trials. Effective
modifications were soon evolved and the two prototypes were repaired and
used experimentally by Imperial Airways.
However, their 3,330 mile (5359 km) range
made them particularly useful for a shuttle service between the UK and
Iceland, and they were impressed for RAF use with No. 271 Squadron in
September 1940. Five Albatrosses, with reduced capacity, additional cabin
windows and slotted flaps replacing the split trailing-edge flaps, were
delivered to Imperial Airways between October 1938 and June 1939.
Providing accommodation for 22 passengers and a crew of four, they saw
wartime service on the Bristol-Lisbon and Bristol-Shannon routes until,
with their numbers reduced to two by enemy action or accidents, the
survivors were scrapped in September 1943.
Power Plant:
Four 525 h.p. de Havilland Gipsy Twelve series
I Span: 104 ft 8 in Length: 70 ft 0 in Height:
20 ft 2 in Weight (All-Up): 28,500 lb (Mail) 29,500 lb (Passenger)
Max Speed: 213 m.p.h. (Mail) 225 m.p.h. (Passenger) Cruise: 205 m.p.h. (Mail) 210 m.p.h. (Passenger)
Range: 3,230 miles (Mail) 1,040 miles (Passenger) Crew: 4
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