. Discovery. Science. 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-ca
. Discovery. Science. 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 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 targe
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