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Aviation History
1947
1947 - 0113.PDF
JANUARY 23RD, I947 FLIGHT 89- Helicopter Operation Some Problems and Their Effect on Design Discussed : The Im~ portance of Reducing Structure Weight THE lecture delivered by Wing Commander ReginaldBrie to the Helicopter Association on January iSthwas largely a plea for making an effort to save structure weight. As an example of how even a very small saving in weight can have a marked "effect on per- formance, he quoted the instance of the C.30 Autogiro, in which the removal of just one gallon of oil, or iolb in weight, prior to a special demonstration, made a great difference to the general handling of the machine. W/C. Brie recalled that it was almost a quarter of a century since Lt. Gomez Spencer, of the Spanish Army, made the first successful Autogiro flight, and thought it would be profitable to look back on the past and try to learn some lessons from it. He paid a warm tribute to the man whose tenacity of purpose and foresight had laid the foundations on which the helicopter now stands, the late Juan de la Cierva. Although it was reasonable to consider the helicopter a logical development of the gyroplane, it did not follow that development had proceeded along entirely rational lines. Whether or not the helicopter was a better type than the gyroplane depended upon the point of view from which they were judged. It was not only more compli- cated mechanically, but also more difficult to fly. No helicopter could be considered safe unless it could land in autorotative flight after a power failure. Autogiro to Helicopter The direct-take-off Autogiro, or, as we used to call it in this journal, the jump-start Autogiro, was a step towards the helicopter take-off without run, but the transition from static to airborne conditions was too abrupt. The '' tower- ing iake-off'' of the Hafner gyroplane provided an accept- able alternative. But the real key to slow-speed flying was the ability to hover in still air. The helicopter had bridged the last remaining gap in the slow-speed range. W/C. Brie grew quite lyrical when contemplating "that gentle levitation clear of the ground ; the effortless pause motionless in space, and the thistledown-like landing on one's own shadow—this is slnw-motion flying in its purest The first Autogiro to be flown in this country was piloted byCapt. Frank Courtney. The rotor was started by a cable wound over a drum. and most elegant form, the practical attainment of which will always be associated with the name of Igor Sikorsky." In attaining this optimum at one end of the perform- ance scale, a penalty had to be paid at the other. No helicopter so far could be landed without power with the facility normal to the Autogiro. The manoeuvres asso- ciated with an autarotational descent and landing at present called for an unusually high degree of skill in pilot- A C.30 fitted with skis. W/C. Brie pleaded for abolition ofthe conventional undercarriage. A Sikorsky R-4 on the after deck of M/V Dagheslan duringtests in Long Island Sound. Brie's sprung platform is just in front of the machine. age. Until disc Joading could be reduced to a more reason- able value an unnecessary hazard was imposed. The too-rapid loss of height due to the high disc load- ing was entirely due to the mechanical complexity and extra structural weight involved in applying continuous power to the rotor system, and was a major part of the penalty paid for the privilege of hovering. By wav of showing that refinements in detail design did not necessarily lead to reduction in structure weight, W/C. Brie gave some data from which lessons might be learned for the future. The data are given in the table. All aircraft were two-seaters, and each incorporated some refinement to improve performance. The lecturer explained the design differences in some detail, but our readers will be able to assess them fairly readily from the data in the table. The analysis showed that the ability to hover had so far proved an expensive luxury. The R-4 helicopter was carrying, by comparison with the C.40, added structure
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