Flight, November 1932
Boulton & Paul, Ltd.
When the British Air Ministry issued a specification for a mailplane more than a year ago, it was stipulated that to be adopted the machine must carry a
mail load of 1,000 lb. (454 kg.) over a distance of 1,000 miles (1 610 km.) at a cruising speed of at least 150 m.p.h. (241 km./h.). The Boulton & Paul P.64, which was the design selected, has an estimated cruising speed of 172 m.p.h. (275 km./h.), a maximum speed at 5,000 ft. of 195 m.p.h. (314 km./h.) and a range, with normal tanks, of 1,250 miles (2 000 km.).
The P.64 carries a crew of two, and is capable of level flight on one engine at 5,000 ft. (1 525 m.). At a cruising speed of 150 m.p.h. the engines are throttled down to approximately half of their power, under which conditions they should be singularly free from breakdown.
The undercarriage has been very carefully designed, and calculations showed that the extra fuel to be carried to overcome the undercarriage drag is less than would be the extra weight of a retractable undercarriage. A fixed undercarriage was, therefore, chosen.
Structurally the P.64 is similar to other Boulton & Paul machines, and is of all-metal construction. The two engines with which it will be equipped are Bristol Pegasus I M.2. They are mounted high in the gap, and are provided with Boulton & Paul Townend drag-reducing cowlings.
The cabin for pilot and navigator is in the nose of the fuselage. Behind it is the wireless and navigation compartment, and aft of that again the mail compartment.
The principal data relating to the Boulton & Paul Mailplane are :-
Length o.a. 42 ft. 6 in. (13,3 m.)
Wing span 54 ft. (16,45 m.)
Wing area 756 sq. ft. (70 m.2)
Tare weight 6,125 lb. (2 780 kg.)
Disposable load 4,375 lb. (1 990 kg.)
Gross weight 10,500 lb. (4 770 kg.)
Absolute ceiling 25,000 ft. (7 620 m.)
The Boulton & Paul P.64 in original form, at Mousehold. The Handley Page slats can be seen open.
Boulton & Paul "Mail Carrier"
This view of the Boulton & Paul P.64 shows its clean lines in spite of strut- and wire-bracing.
The P.64 after having fins fitted to the tailplane.
The P.64 on a test flight, with the original tail unit.
The Air Ministry Mail Carrier under construction by Boulton & Paul, Ltd.