DISCOVERY 



cases the screws are visually made to revol\-e in opposite 

 directions, for otherwise the whole machine would simply 

 be turned on its axis when the engine is started. 



To the first class belongs the helicopter designed by 

 a Spaniard named Pateras Pescara, with which trials 

 have taken place at the Four Winds Aerodrome near 

 Madrid, in the presence of officers appointed by the 

 Aeronautical Department of the French Government. 

 The machine, which has actually left the ground, 

 though details of the flight are lacking, consists of 

 what is to outward appearance a motor-car from which 

 rises a vertical shaft. On the shaft are the two lifting 

 screws, each of which consists of four arms in the form 

 of small biplane surfaces. The chief feature of this 

 machine is that each arm of the screws appears to be 

 of ordinar\' aeroplane wing form, which one would 

 not have thought likely to be efficient w'hen following 

 a rotary path through the air. Details of the span 

 and engine power of this machine are imfortunately 

 lacking, as are particulars of the mechanical design, 

 although it is imderstood that the lifting screws can 

 be swivelled for horizontal motion. 



A promising American helicopter is the Crocher- 

 Hewitt, the screws of which are 51 feet in diameter. 

 Each screw consists of two tubular steel amis, at the 

 extremities of which are the four blades made up of 

 ribs riveted across the steel tube and covered with 

 aluminium sheeting. Horizontal motion in this design 

 is obtained partly by tilting the screws and partly 

 by altering the position of small auxiliary surfaces, and 

 utilising the down draught from the screws on these 

 surfaces to drive the machine in the required direction. 

 Two 100 h.p. motors are fitted. 



Lieutenant Petroczy and Professor Karmen have 

 produced in Austria a helicopter which is not designed 

 for horizontal motion, but is intended to replace an 

 observation balloon, as it is less vulnerable to attack 

 from hostile aeroplanes and a smaller target for artil- 

 lery'. It is flown on a wire from the ground, and the 

 observers sit in an armoured turret above the screws. 

 The main framework consists of three horizontal 

 frames, on which are carried the three 120 h.p. Le 

 Rhone engines, which provide the motive power. 

 Shafts from the three engines drive through bevel 

 gearing two vertical shafts, one revolving inside the 

 other, on which are carried the wooden two-bladed 

 screws, each of which is 20 feet in diameter. This 

 machine has made numerous ascents, and is said to have 

 reached a height of 300 feet or more. 



Of helicopters with the lifting screws working on 

 separate axes, perhaps the best known is that of 

 M. Damblanc, who lead a paper on the theory of 

 his machine before the Royal Aeronautical Society 

 in 1920.^ This machine has an ordinary aeroplane 



' Aeronautical Journal, voi. x.xv, No. 121. 



fuselage, with rudder and elevators, while in place of 

 the wings are two four-bladed lifting screws of special 

 design, somewhat reminiscent in shape of a clover- 

 leaf. These screws, which are rotatable in order to 

 obtain horizontal motion, are driven from two separate 

 Le Rhone 120 h.p. engines. For safety of descent in 

 case of engine failure, the angle at which the blades 

 meet the air can be varied at the will of the pilot. 



Observer and 

 Macfiine-Gun Turret 



DI.\GR.\JDI.\TIC SKETCHES OF THE K.^RJIEXPETROCZV 

 HEUCOPTER. 



Another American helicopter, belonging to a different 

 school from the Crocher-Hewitt, is the Leinwerer- 

 Curtiss, which again has an aeroplane fuselage with a 

 rudder, but no elevator. The means of sustentation 

 selected here consists of four three-bladed propellers, 

 arranged on a somewhat novel plan. They are placed 

 in pairs on each side of the fuselage, each pair being 

 mounted at opposite ends of a massive arm containing 

 at its centre the gearing from which the drive is 

 received from the engine in the fuselage. The arms 



