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Aviation History
1956
1956 - 0215.PDF
FLIGHT, 24 February 1956 213 The author (in white hard hat) flying as passenger with Capt. Rochon in the Aerotecnica AC-13 at Torrejon, near Madrid. The airfield is about 2fiOOft above sea level. Capt. Rochon showed h<w the AC-13 could be hovered close to the ground with the collective-pitch lever tree. Turbine and rotor run at constant speed and the throttle is not normally touched after take-off. "Flight" photograph MADE IN SPAIN . . . Rochon found he had 30 seconds to spare before he had to select fully fine collective pitch for an autorotative descent. This is about ten times longer than can normally be expected, and during the 30 sec he had time to consider a further course of action. By the time the AC-13 had descended in autorotation for 320ft, the rotor r.p.m. had dropped by only 30 r.p.m. Capt. Rochon, who flew helicopters in Indo-China, has great confidence in the Aero- t&nica machine. At the time of my visit it had completed 130 hours' flying; after ten hours more the tail outlet was to be altered to allow the first trials in the use erf the anti-torque jet for forward thrust in cruising flight. Further production for Aerotecnica is now being undertaken (Extreme left) Rotor head of the AC-13 Cyclic and collective-pitch changes are made through the spider at the top, and the linkage is arranged to balance the rotor moments. There are neither dampers nor boosters in the control runs. The blades are fully articulated. The anti-torque and directional control system of the Artouste-powered AC-13 helicopter. The bifurcated nozzle is fixed and the final portion of the jet pipe can be swung laterally through the rudder pedal linkage to achieve varying ratios of deflection. The same control linkage moves the two vertical fins for added control in cruising flight and during autorotation. by the E.N.H.A.S.A. company, which is to build six AC-14s complete. In this machine the jet-thrust feature will be fully used and the Artouste II will be mounted above the cabin, like the piston-engine of the AC-12. Extensive soundproofing in the five-passenger cabin will also be included. The first AC-14 should fly diis summer. The following are some quantitative and performance data on the three machines. The AC-12 carries two people and has a three-bladed rotor with a diameter of 27ft lOin. The fuselage is 24ft 2in long and 7ft lOin high. Empty and maximum weights are 1,280 lb and 1,800 lb and the disc loading is 2.5 lb/sq ft. An artist's impression of the five-seater AC-14, the first prototype of which is now being built by E.N.H.A.S.A., the national airscrew com- pany in Madrid. The engine will be a Turbomeca Artouste II giving 350-400 h.p. and mounted above the passenger compartment. Residual thrust will be used in cruising flight to increase forward speed, leaving the movable tail-tins to give all anti-torque and directional control. Engine, rotor and tail rotor r.p.m. are respectively 2,600, 350 and 1,820. The hovering ceiling in standard atmosphere is estimated at 5,800ft with ground efiect, or 2,300ft without. Maximum horizontal speed will be 76 m.p.h. and cruising speed at 80 per cent power 64 m.p.h. The design ceiling in translational flight is 11,700ft and endurance three hours. The AC-13, which has a normal maximum weight of 1,940 lb and carries a useful load of 670 lb, has a rotor diameter of 29ft lOin, a fuselage length of 24ft 8in, a disc loading of 2.7 lb/sq ft and a disc solidity of 0.0468. It demonstrated its high-altitude capabilities last July at the Puerta de Navacerrada (a pass over the Sierras near Madrid), when it took off at maximum weight in an ambient temperature of 25 deg C at an altitude of 6,100ft. In these conditions it climbed to 4,550ft above the take- off point and came down again to land on sloping ground. A rival helicopter powered by tip-jet thrust did not attempt the take-off. The AC-13's hovering ceiling in standard atmosphere is 8,700ft with ground effect or 4,800ft without. The maximum horizontal speed is 112 m.p.h. and cruising speed, at 80 per cent power, 77 m.p.h. Absolute ceiling is 22,000ft. Endurance varies, according to load, between three hours with one occupant and one hour with three occupants. In most respects the estimated performance of the AC-13 has been exceeded in practice, although the machine cannot absorb the whole of the power available from the engine. In the case of the AC-14, the engine power will be absorbed and, as far as load carrying goes, performance will be similar in many respects to that of the S.E. 3130 Alouette II. The AC-14 is expected to weigh 1,210 lb empty and have a maximum weight of 2,640 lb and a useful load of 1,210 lb. Its hovering ceiling will be 11,800ft with ground effect and 7,600ft without. Maxi- mum and cruising speeds will be 95 kt and 68 kt; and the maximum rate of climb and service ceiling will be respectively l,200ft/min and 24,000ft. The reduction gear of the Artouste II will be one designed by Turbomica. The rotor disc area is to be 779.3 sq ft. It is stated that the selling price of the AC-14 will be well under the equivalent of £14,200. From these notes it will be seen that the Aerotecnica heli- copters can claim a number of outstanding features, and their development will be watched with interest. The company is already in touch with some American manufacturers, including Fairchild.
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