Flight, August 10, 1916.
THE NEW WRIGHT TRACTOR BIPLANE - TYPE L.
IN general appearance the new Wright tractor does not present anything startling, but follows fairly closely along standard lines. It is designed to combine a fair speed range with reasonable power and low purchase price and cost of upkeep. Its lines do not impress one as being particularly pleasing, and it would appear to have been quite possible to have improved these, considerably without necessarily increasing the cost. However, according to reports the machine flies very well, and after all that is the main consideration.
The main planes are of a totally different section from that of the older Wrights, but no dimensions of the new wing section are available. The top wing is built up in three sections, and the lower in two, the end sections being interchangeable. Bracing is effected by solid wires, all the lift wires being in duplicate. No turnbuckles are employed, the ends of the wires being formed with eyes, securely soldered, which loop over hook plates under the ends of the struts. Instead of having the body struts run to the top rails of the body, as is standard practice on this side, they are connected at the top to a centre section, and at the bottom to a short length of wing secured to the sides of the body. In this way the outer sections of the wings arc easily detachable for purposes of transport. The inter-plane struts are of spruce, streamlined, and fit into sockets with their ends. By taking out a small bolt which runs through the strut and its fatting the struts are slipped out, releasing the wires from the hook-plates. The main wing spars are of spruce, as are also the ribs, which are of I section.
The tail consists of a semi-circular fixed stabiliser, non-lifting, to which the elevator flaps are hinged.
Lateral equilibrium is maintained by double-acting ailerons cut out of both upper and lower planes, hinged to the rear spars. These have a slight curve, and normally are actual portions of the wings. A spruce spacer strut connects the upper and lower ailerons. The control cables run from the spacer strut-ends over pulleys at the upper and lower extremities of the adjacent plane struts and along the wings to the steering column. The cable from the lower aileron runs to the top of the strut and vice versa. The ample surface of the ailerons insures very easy control. The balanced rudder is operated by cables running into and through the fuselage to the "grip" or lever on the steering wheel. The elevator flaps are operated by cables from the masts through the fuselage to the wheel.
The steering set used is the standard Wright system, in which, it will be remembered, that turning the wheel right or left operates the ailerons; rocking the wheel and its supporting column fore and aft operates the elevators. An aluminium hand lever turns the rudder with very little pressure. Gripping the wheel and the lever at the same time in one hand causes the rudder to turn simultaneously with the operation of the ailerons, otherwise the ailerons may be operated entirely independently. The aileron and rudder cables end in short chains which run over sprockets on the steering column. The aileron sprocket is rigidly attached to the axis of the steering wheel. The rudder sprocket is free on the same shaft. Gripping the rudder lever with the wheel in one hand obviously rotates the two sprockets simultaneously.
The fuselage is of usual box girder construction, strongly braced. The nose is covered with aluminium, with very large doors to give access to the motor. The remainder is covered with linen, doped, painted grey and varnished. The deck is of veneer, linen covered. The body tapers to a vertical knife edge at the rear. The rudder is hinged to the rearmost strut of the fuselage. Where control cables pass into the fuselage brass eyelets are used. In the fuselage no bolts pass through the rails, a special fitting obviating this practice. The longitudinal rails are ash, and the struts are spruce. The pilot sits in a comfortable scat under the trailing edge of the upper wing.
In front of him is a dash with petrol gauge, clock, aneroid, pressure gauge and speed indicator mounted thereon. Pressure in the tank is maintained by hand pump. The engine may be primed from the seat. The right foot operates the throttle pedal, and the left pedal takes care of the magneto advance. Between the two is a magneto cut-out button.
On a strut is fastened the Wright Incidence Indicator which gives at all times the angle of the chord of the planes with respect to the air currents through which the machine is flying, and is entirely independent of gravity.
The motor is the latest Wright, six cylinders, 4 3/8 ins. by 4 5/8 ins. bore and stroke, rated at 70 h.p. The tractor screw, of high pitch, is mounted on a short shaft, which forms part of the Wright flexible drive. The engine shaft has a light flywheel keyed to it. Concentric with this is a steel disc, to which the propeller shaft is keyed. Eight stud bolts project from the disc and the flywheel respectively, and over each pair of studs is a short but very heavy endless rubber band. These bands transmit the full power of the motor to the propeller, and absorb vibration and sudden strains on propeller or engine shaft. The petrol tank is to the rear of the motor, enclosed in the fuselage. The entire engine is covered in by the fuselage, the exhaust pipes sticking through holes in the deck. A flat tube radiator is on either side of the nose of the fuselage, and these are quickly demountable by unfastening retaining straps which hold them to plates attached to the framing. The hose connections can be quickly taken off.
The chassis is very simple. The axle is a steel tube, and the weight of the machine is taken by rubber band shock absorbers. The wire wheels are fitted with aluminium discs; the chassis struts are of ash.
Span is 29 ft.; gap, 5 ft. 9 ins.; chord, 6 ft.; area main planes, 334 sq. ft.; length over all, 24 ft.; weight empty, 850 lbs. A useful load of 650 lbs. may be carried, including 12 gallons of fuel for 2 hours' flying, water, oil, pilot, &c. The gross weight per square foot, including ailerons, is 4.5 lbs.