W.Green, G.Swanborough The Complete Book of Fighters

CANTILEVER AERO BULLET USA

   The first of two single-seat cantilever sesquiplanes designed by Dr William W Christmas of the Cantilever Aero Company with the assistance of Vincent J Burnelli, and built by the Continental Aircraft Company, was flown for the first time in mid-January 1919. It crashed and was totally destroyed shortly after its first take-off. Initially known as the Scout and subsequently as the Bullet (or Christmas Bullet), it was powered by a 185 hp Liberty 6 six-cylinder water-cooled engine and was primarily of wooden construction. Unusual features included the use of internal rotating torque tubes to operate the ailerons (although conventional cables were fitted at one stage) and a warping tail-plane. The second prototype was powered by a Hall-Scott L-6 six-cylinder water-cooled engine and this also crashed on its first flight in the summer of 1919, development subsequently being abandoned. The following performance data were claimed but are believed exaggerated.

Max speed, 175 mph (282 km/h).
Ceiling, 14,700 ft (4 480 m).
Range, 550 mis (885 km).
Empty weight, 1,820 lb (825 kg).
Loaded weight, 2,100 lb (952,5 kg).
Span, 28 ft 0 in (8,53 m).
Length 21ft 0 in (6,40 m).
Wing area, 170 sq ft (15,79 m2).

Журнал Flight

Flight, February 13, 1919.

THE CHRISTMAS STRUTLESS BIPLANE

   SEVERAL attempts have been made for years by experimenters to perfect an aeroplane with flexible wings, or following closely the flexibility of the wings of a bird. The biplane designed by Dr. W. W. Christmas appears to have met with much success in the structure mentioned, and his theories of flexing wings have shown more practicability than most rigid-wing adherents were apt to believe possible.
   The British and French Governments have manifested considerable interest in this machine, probably because of reports of the great speed accredited to it.
   A most radical departure from what has heretofore been believed to be necessary practice is the entire elimination of struts, cables, and wires in the bracing of the wings, as well as the absence of wiring in the internal structure of the wings. The wing curve is one developed by Dr. Christmas, and is of fairly deep section between the main wing beams, but tapering off sharply aft of the rear beam, and merging into a fiat thin, flexible trailing edge. The effect of the section is to maintain a high angle of incidence as the machine is travelling at low speed, and a low angle as the machine gathers speed, flattening out the wing and presenting very little resistance.
   Upper and lower wings have the same aspect ratio. Upper wing has a thickness of 5 in. Patents are pending on the wing construction, and full details cannot now be given of these features.
   With the wing section used. Dr. Christmas has succeeded in obtaining a 72 per cent, lift on the upper surface, a higher vacuum than found on any other section. Wings are set at an incidence of 3 1/2 degrees.
   As the wings are not braced transversely, flexibility is also obtained in that direction. Puffs of wind or sudden changes of direction, do not sharply affect the machine's progress, for the shock is transmitted only after being partially absorbed by the resiliency of the wings. It would seem that such construction would result in a low factor of safety, but the designer claims a safety factor of seven throughout.
   When at rest on the ground, the wing droops in a negative dihedral of -17 degrees. In flight the wing tips have a range of flexibility of 3 ft.; that is, the wings can assume positive or negative dihedral measuring 18 in. from the horizontal in either direction.
   It has been demonstrated that the wings carry a load no greater than necessary to sustain the machine in flight, and this load is carried regardless of wind puffs or extra strains due to increased wind pressure above or below the wing.
   The principal specifications of the Christmas "Bullet" are as follows :-

Span, upper plane 28 ft.
Span, lower plane 12 ft.
Chord, upper plane 5 ft.
Chord, lower plane 2 ft. 6 in.
Area, upper plane 140 sq. ft.
Area, lower plane 30 sq. ft.
Length overall 21 ft.
Weight, machine empty 1,820 lbs.
Weight, fully loaded 2,100 lbs.
Minimum speed 50-60 m.p.h.
Maximum speed 175 m.p.h.
Cruising radius 550 miles
Ceiling 14,700 ft.

   A Liberty "6" is used, giving 185 h.p. at 1.400 r.p.m.; the machine attains 170 miles at three-quarter throttle. The weight fully loaded is with 50 gallons of gasolene and 5 gallons of oil, sufficient for a sustained flight of three hours.
   The "Bullet" was originally designed as a single seater fighter. The pilot has an unobstructed range of vision, as his eyes are at the level of the upper plane and the lower plane has such a narrow chord that it offers but very little obstruction to vision. Although military necessity does not now demand the adoption of the machine as a fighter, it lends itself admirably to the needs of civilian uses. The planes are readily detachable and are easily set up, as there are no wires to align. When the planes are removed, they can be strapped alongside of the fuselage and the machine then takes up only about one-fifth of the room ordinarily required for storage. The machine can be rigged up ready for flight in 15 minutes.
   All the controls are exceptionally easy in their operation. The tail is flexible, and its efficiency is illustrated by the fact that a 1 in. deflection causes a controlling moment equal to that produced by a rigid flap movement of 4 in.
   The two main tail beams are 1 1/2 in. by 1 3/4 in. laminated spruce. A horizontal V section spruce leading edge is used. The battens are air-seasoned white ash.
   Ackerman spring wheels are used, which cut down resistance and do away with the usual rubber shock absorber cord.
   The principle of radiation is original. Besides the nose radiator of the "Livingston" type, copper mesh screens cover in the sides and top of the fuselage, forward of the wings, and this surface has proven adequate for the Liberty "6." Much of the radiation is thereby effected by skin friction rather than by dead head resistance.
   The propeller was designed by Mr. Caldwell at McCook Field, Dayton, Ohio. It has a 10 ft. 6 in. pitch and is 7 ft. in diameter, designed for a speed of 195 miles an hour, which the machine is expected to make with full power.