Flight, November 1923

NEW AMERICAN NIGHT FLYING MAIL 'PLANES

A LITTLE while back the U.S. Air Mail Service issued tenders for a certain number of aeroplanes designed specially to meet the various requirements for night mail service. As a result three types of machines have already materialised, one from each of three well-known American aircraft constructors - the Aeromarine Plane and Motor Co., of Keyport, N.J., the Curtiss Aeroplane and Motor Co., of Garden City, N.Y., and the Glenn L. Martin Co., of Cleveland. We give below brief descriptions of these three machines, together with illustrations. It may be mentioned that these machines are intended for use on the "night section" of the New York-San Francisco air mail service, that is, the section between Chicago and Cheyenne.
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   The Curtiss Night Mail 'Plane. - This machine is a tractor biplane of the "one-and-a-half-strutter" type, employing the U.S.A. 27 wing curve and fitted with a Curtiss 160 h.p. C.-6 engine. A feature of the wing arrangement is the construction of the upper centre section. This is metal, and contains the fuel tank, and on which are mounted the Curtiss wing type radiators. The advantages claimed for this arrangement are low head resistance, due to the use of wing type radiators, reliability of fuel system on account of the use of gravity feed entirely with consequent elimination of fuel pump trouble, and the desirable feature of having the petrol outside the fuselage. This centre section is carried above the fuselage by a pair of N struts.
   Top and bottom planes are of equal span and chord, and have a slight sweep back and a dihedral angle, and ailerons are fitted to the top planes only.
   The fuselage is of the usual rectangular section girder construction of wood. The pilot is located aft of the main planes, and between his cockpit and the engine is a roomy compartment, with easily opened hinged cover, for mails. Loading and unloading the latter is greatly facilitated by covering the top surface of each lower wing, alongside the fuselage, with strong veneer, and thus providing a safe walkway.
   Another important feature of the Curtiss machine is the employment of a Reed duralumin airscrew of high efficiency, manufactured by the Curtiss Co. It is claimed for this airscrew that it cannot be injured in flying through rain or hail.
   Searchlights are mounted on the tips of the lower plane, for use in night landing, the wiring for these lights being carried in aluminium conduits within the wings.
   One of the most noteworthy features of this machine, which makes it particularly adaptable to mail service, is its great economy of operation. Although the specifications under which the machine was designed only call for a mail load of 300 lbs., the efficiency of the machine has proved such that 500 lbs. of mail has satisfactorily been carried in flying trials. Credit for this is said to be due largely to the use of the C.-6 engine, giving its 163 h.p. with an economy of fuel consumption which provides a flight range of 3i hrs. or 360 miles full throttle, or 5 hrs. - 425 miles, at cruising speed.
   Characteristics of Curtiss Night Mail 'Plane :- Span, 33 ft.; chord, 6 ft.; gap, 6 ft.; o.a. length, 26 ft. 11 ins.; height, 10 ft. 3 ins.; area, 364.8 sq. ft.; sweep-back, 5°; dihedral angle, 1 1/2°; incidence, 2°; weight empty, 1,704 lbs.; weight laden, 2,524 lbs.; loading/sq. ft., 6.9 lbs.; loading/h.p., 15-5 lbs.; speed range, 44-106 m.p.h.; climb, 5,600 ft. in 10 mins. (800 ft./min.); ceiling, 14,000 ft.
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