One of the weirdest looking airplanes ever to take flight.
The Dunne biplane, constructed in England by Short Brothers to the design of Lieut. J. W. Dunne, was very solidly built and presented a very unusual appearance. In the numerous flights made in 1910 at Eastchurch, Isle of Sheppey, exceptional stability was exhibited by this biplane. Since its outstanding features were the absence of the usual elevation and direction rudders, and the curious shape of the main cell, it excited a great deal of interest and comment. It was even rumored that the British army had experimented in secret with a prototype of this machine.
Top Speed: n.a.
Engine: 50 horse-power, 4-cylinder Green
Wingspan: 46 feet
Weight: 1,700 pounds
Specifications from “Monoplanes and Biplanes,” by Grover Loening, 1911
The Frame
The construction of the main cell is of the usual wooden and wire frame, canvas-covered type. At the centre there is built in a skiff-like body 18 feet long containing the motor, seat, controlling levers, radiator, etc.
The Main Wings
The conspicuous feature of this machine is the employment of the dihedral principle, laterally, transversely, and longitudinally. The general aspect of the main planes are evident from the accompanying scale diagrams. The greatest fore and aft direction is constituted by the wings themselves. The incidence of the tips is much less than the incidence at the center. In flight the angle is very low indeed, and is certainly negative at the ends. The camber of the ribs is a very interesting feature. At the center the ribs have their greatest depth of camber far to the front, with a long straight portion to the rear. But at the ends the ribs are curved so that the greatest depth of camber is about at the center. The theory involved in this type of construction is very interesting, and indicates that by making use of the variations in position of the center of pressure a semi-automatic balance is obtained. The planes are 6 feet apart, 6 feet in depth, and spread 20 feet 4 inches longitudinally and 46 feet laterally. The total area is 527 square feet.
Elevation.-At the rear ends of each plane are hinged flaps, each 7 1/2 feet wide and 12 1/2 square feet in area, controlled by a left-hand and a right-hand lever. They are so connected that when the right-hand lever is pulled back, and the left-hand lever pushed forward, then the left ailerons arc pulled down, lifting up that side and the right ones are turned up. When both levers are pulled back together, both flaps are turned up, and since they are to the rear of the center of support, the entire machine will be turned up for ascent. Direction.-When steering to the right, for example, the right lever is drawn back and the left pushed forward, thus pulling up the right flap and pulling down the left. The angle of incidence of the ends is always negative. There fore turning up the right flap increases still further the negative incident angle, and consequently greatly increases the negative drift, thus causing the right side of the machine to slow down, at the same time as it is depressed. But since the flaps are at the rear of the center of gravity, and since turning up the right flaps causes this end to sink (like the tail of a Bleriot, for example), there is a tendency for the entire machine to ascend. To counteract this, the left lever is pushed over, thus increasing the lift on this end and decreasing the negative incident angle. This now results in a decrease of drift on this side, and causes the machine to “skew” around faster and to “bank” with the right down and the left up.
Roll Control
The character of the planes on this biplane give it practically an automatic transverse equilibrium, so that there is no distinct and separate manner of controlling lin- lateral inclination of the machine. The manner in which this aeroplane is artificially inclined when making turns, however, has already been described.
Keel
The end panels of the main cell are covered-in, giving a vertical keel at each side, which aids materially in the various movements for equilibrium and holds the machine to its course, preventing any skidding sideways, etc.
Propulsion
Two wooden propellers are mounted on a frame built out on either side of the central body. These propellers are 7 feet in diameter. 7 1/2 feet pitch, and rotate at 660 r.p.m. They are driven by chains from a 50 horse-power four-cylinder Green engine, and are rotated in the same direction. To counteract the torque resulting from this, a weight is fixed on one end of the machine. This is not a very good provision.
Landing Gear
The landing gear is similar to the old Voisin type, and consists of two rubber-tired wheels mounted on a steel-tube chassis fitted with coiled steel springs at the front and a single wheel and skid at the rear.
Weight, Speed, Loading and Aspect Ratio
The total weight in flight is about 1,700 pounds, 34 pounds are lifted per horse-power, and 3.2 per square foot of surface. The aspect ratio, considering the actual width of the planes, is 9 to 1, and considering the projected span of 46 feet. is 7.6 to 1