摘要 :
Discussed here are computations of drag or negative traction of geared down supporting propellers in the downward vertical glide of a helicopter. By means of Frounde's Theory, the maximum value of the drag of a windmill is calcula...
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Discussed here are computations of drag or negative traction of geared down supporting propellers in the downward vertical glide of a helicopter. By means of Frounde's Theory, the maximum value of the drag of a windmill is calculated. For wooden propellers, the author finds that the difference between the drag and the weight is proportional to the number of blades and is larger for propellers of small diameter; thus it is 25 kg. for a six blade propeller with a diameter of 2 m. 50. The author notes that if we are to adopt large propellers, we must have recourse to a different method of construction, resulting in large dimension propellers much lighter than those made of wood. In discussing insufficient drag, the author notes that the question of the drag of geared down supporting propellers can only be decided by experiment.
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摘要 :
Helicopter geometrical configurations, means of control, and general design features are introduced. Characteristics of the helicopter which differ from those of fixed wing aircraft are described.
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There has been a standing need for small portable strap-on backpack helicopters. This paper describes the steps leading to the design and construction of a working prototype. The prototype has a single rotor blade 12 feet long bal...
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There has been a standing need for small portable strap-on backpack helicopters. This paper describes the steps leading to the design and construction of a working prototype. The prototype has a single rotor blade 12 feet long balanced by a 4 foot spar supporting two counter rotating propellers. A belt power transmission system drives the propellers from a small two-stroke gasoline engine located at the center of rotation of the rotor. The device straps onto the pilot's back, and the pilots's legs act as the landing gear. Empty weight of the machine is 75 pounds and it can lift a total of 270 pounds. Performance figures are calculated to be: Top speed - 48 mph, cruise speed - 38 mph, maximum rate of climb - 420 ft/min., minimum rate of descent (power off) -9.4 ft/sec, and fuel consumption - 1.5 gal/hr. Recommendations for future designs are given in the paper. (Author)
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Langley Research Center has done extensive research into the effectiveness of tail boom strakes on conventional tail rotor helicopters. (A strake is a "spoiler" whose purpose is to alter the airflow around an aerodynamic body.) By...
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Langley Research Center has done extensive research into the effectiveness of tail boom strakes on conventional tail rotor helicopters. (A strake is a "spoiler" whose purpose is to alter the airflow around an aerodynamic body.) By placing strakes on a tail boom, the air loading can be changed, thrust and power requirements of the tail rotor can be reduced, and helicopter low speed flight handling qualities are improved. This research led to the incorporation of tail boom strakes on three production-type commercial helicopters manufactured by McDonnell Douglas Helicopter Company.
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Descriptions are given of two captured helicopters, one driven by electric power, the other by a gasoline engine. An account is given of flight tests of the gasoline powered vehicle. After 15 successful flight tests, the gasoline ...
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Descriptions are given of two captured helicopters, one driven by electric power, the other by a gasoline engine. An account is given of flight tests of the gasoline powered vehicle. After 15 successful flight tests, the gasoline powered vehicle crashed due to the insufficient thrust. Also discussed here are the applications of helicopters for military observations, for meteorological work, and for carrying radio antennas.
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Application of theories presented in Volume I, as well as special methods of procedures applicable to performance prediction is illustrated first, on an example of the conventional helicopter described in Chapter I, and then winge...
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Application of theories presented in Volume I, as well as special methods of procedures applicable to performance prediction is illustrated first, on an example of the conventional helicopter described in Chapter I, and then winged and tandem configurations. Chapter II deals with performance prediction of conventional helicopters in hover and vertical ascent. In Chapter III, various approaches to performance prediction in forward translation are presented. Chapter IV deal with performance problems previously discussed in Chapters II and III; only this time, a wing is added to the baseline configuration, and both aircraft are compared with respect to their performance. In Chapter V, this comparison is extended to a tandem. Appendices on methods for estimating performance guarantees and growth of aircraft concludes this volume.
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The research and technology demonstration requirements to achieve emergency-power capability for a civil helicopter are documented. The goal for emergency power is the ability to hover with one engine inoperative, transition to mi...
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The research and technology demonstration requirements to achieve emergency-power capability for a civil helicopter are documented. The goal for emergency power is the ability to hover with one engine inoperative, transition to minimum-power forward flight, and continue to a safe landing where emergency power may or may not be required. The best method to obtain emergency power is to augment the basic engine power by increasing the engine's speed and turbine-inlet temperature, combined with water-alcohol injection at the engine inlet. Other methods, including turbine boost power and flywheel energy, offer potential for obtaining emergency power for minimum time durations. Costs and schedules are estimated for a research and development program to bring emergency power through a hardware-demonstration test. Interaction of engine emergency-power capability with other helicopter systems is examined.
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