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Helicopter Society (AHS) International STEM Committee: Free to Distribute with Attribution History of Rotorcraft

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Helicopter Society (AHS) International STEM Committee: Free to Distribute with Attribution History of Rotorcraft History and Overview of Rotating Wing Aircraft Photo by Paolo Rosa Produced by the American Helicopter Society (AHS) International STEM Committee: www.vtol.org/stem Free to distribute with attribution History of Rotorcraft • Definition of Rotorcraft – Any flying machine using rotating wings to provide lift, propulsion, and control that enable vertical flight and hover Rotating wings provide propulsion, Rotating wings provide lift, but negligible lift and control. propulsion, control at same time. History of Rotorcraft • Two key configurations developed in parallel – Autogiro • Close to helicopter, uses many of same mechanical feature • Cannot hover • Unpowered rotor – Helicopter • Powered rotor • Many configurations have been developed • Autogiros flew first! – Autogiro innovations enabled development of first helicopters Autogyro – How it Works Lift Unpowered Rotor that Spins Due to Wind Blowing Through Rotor Like a Wind Turbine Relative Wind No Need for Anti-Torque Since Not Driven Thrust By an Engine Fixed to the Fuselage Control Surfaces Autogyro – How it Works Kind of like parasailing, except rotor provides lift in addition to drag. Helicopter – How it Works • Powered Rotor • Equal and opposite torque applied to rotor acts on fuselage Tail Rotor Rotor Thrust Thrust Main Rotor Drive Shaft Tail Boom Cockpit Tail Rotor Engine, Fuel, Landing Skids Transmission, etc. Controls Helicopter – Need for Anti-Torque • Engine fixed on body – exerts torque on rotor shaft – Rotor shaft exerts equal and opposite torque on body • Many configurations created around anti-torque problem – Autogyros, tip jets, tip propellers, tandem helicopters, tilt wings, tilt rotors, synchcopter -T T Basic Rotor Controls Flap and Lag Hinges Pitch Bearing Rotor Pitch Link Control Servos Swashplate Red = Rotating Blue = Fixed Basic Rotor Controls • Cyclic control – Changes pitch sinusoidally of all blades around azimuth angle (blade rotation angle) – Accomplished by tilting swashplate side to side on gimbal • Collective Control – Increases/decreases pitch on all blades at all azimuthal locations – Accomplished by moving swashplate up and down rotor shaft Blade azimuth angle ψ Key Problems in Early Rotorcraft Development • Understanding basic aerodynamics of vertical flight – Amount of power to produce fixed amount of lift was unknown – First significant application of aerodynamic theory to helicopter rotors came about in the early 1920s • Lack of a suitable engine – Not until the mid-1920s that engines with sufficient power and with high power to weight ratios suitable for vertical flight became widely available • Minimizing weight – Early engines made of case iron – too heavy! – Aluminum not cheap enough for use on aircraft until 1920 Key Problems in Early Rotorcraft Development • Counteracting rotor torque reaction – Tail rotor to counter torque reaction and provide directional control not used on most early designs – Igor Sikorsky was the first to successfully use the tail rotor in the single rotor helicopter configuration we know today. • Providing stability and control – Primary concern was to devise a means of defeating the unequal lift produced on the blades advancing into and retreating from the relative wind when in forward flight – Problems overcome only with articulated rotor and cyclic pitch control • Conquering high vibrations – Vibration was source of many mechanical failures of the rotor and airframe – Reflected an insufficient understanding of the dynamic and aerodynamic behavior of rotating-wings History of Rotorcraft Early Concepts Chinese Top – 400 B.C. Early Concepts DaVinci - 1493 • Leonardo da Vinci credited with first idea for vertical flight • Oversized Archimedes water screw • Airscrew consisted of platform with metal helical screw • Propellers made of starched linen, frame made of wire • Just a sketch Enabling Devices Lomonosov - 1754 • Russian, Mikhail V. Lomonosov • Very first self-propelled model of a lifting airscrew flown • Coaxial rotor system, spring-driven device • Flown freely and climbed to good altitude • Intended for lifting thermometers and other instruments into the air Enabling Devices Phillips – 1840’s, D’Amecourt – 1860’s • Horatio Phillips, 1840’s • Constructed first steam driven vertical flight machine • Steam generated by mini-boiler ejected at blade tips • First time rotorcraft flew under engine power • Ponton D’Amecourt, 1860’s • Also designed, built, and flew a a number of small steam powered helicopter models • Coaxial rotors • Pictured on right Enabling Devices Bright - 1859 • Henry Bright, Englishman • First helicopter patent granted by the British Patent Office • Two counter-rotating coaxial two-bladed rotors • Mounted on a vertical shaft Enabling Devices Achenbach - 1874 • Wilheim Achenbach, German • Single rotor concept • First side thrusting tail rotor to counteract main rotor torque Enabling Devices Forlanini - 1878 • Enrico Forlanini, Italian • Steam driven helicopter model, dual counter-rotating propellers • Forced superheated steam to a high pressure in a small metal sphere • Flew 40 ft for 20 sec Early Contraptions Cornu - 1907 • Paul Cornu, French Bicycle Maker • Vertical flight machine carried human off ground for the first time • Dual rotor, 24 HP gas engine, belt-driven Early Contraptions Breguet - 1907 • Louis and Jacques Breguet, French Scientists • Quad-Rotor gyroplane, 40-hp engine, • Briefly carried a pilot off the ground Early Contraptions Sikorsky - 1909 • Igor Sikorsky, Russian • Prototype coaxial nonpiloted helicopter • Did not fly due to vibration problems and lack of power Early Contraptions Yurev - 1912 • B.N. Yuriev, Russian • Developed single main rotor helicopter • Included collective pitch, cyclic pitch, and tail rotor • Aircraft never flew properly due to lack of power Early Contraptions Ellehammer - 1914 • Jacob Ellehammer, Danish • Coaxial rotor helicopter • Short blades attached to 2 large circular aluminum rings • Top ring like a parachute for failures • Aircraft made short hops off the ground Early Contraptions Petroczy – 1920 • Stephan Petroczy, Austrian, assisted by Theodore Von Karman • Build and flew coaxial rotor helicopter • Pilot-Observer positioned over the rotors, inflated bags for landing gear • Powered by 3 rotary engines • Machine only flew tethered to ground Early Contraptions Berliner – 1909 to 1920 • Emile and Henry Berliner, father and son from United States • Developed coaxial and side-by-side rotor helicopters • First to observe power required decreases when entering forward flight • Side-by-side aircraft: twisted rotor blades • Side-by-side aircraft control: Differential shaft tilt, wings in slipstream Early Contraptions Brennan – 1920 • Louis Brennan, English • Single 2 bladed rotor • Rotor driven by propellers on blade tips (no anti-torque needed)‏ • Control achieved with servo flaps inboard on rotor • Machine flew successfully inside a balloon shed, crashed on Flight 7 Early Contraptions Pescara – 1920’s • Raul Pescara, Argentinan working in spain and france • Coaxial helicopter with biplane-type rotors • First to use cyclic blade pitch • Aircraft achieved short uncontrolled flights Early Contraptions Von Baumhauer – 1924 • A.G. Von Baumhauer, Dutch • Single main rotor helicopter • Collective pitch, cyclic pitch • See-saw teetering rotor • Main and tail rotors not connected – difficult directional control • Machine made several short semi-controlled hops off ground Autogyro – First Flight - 1923 • Juan de la Cierva, Spaniard • Hinged Blades, standard fixed wing aircraft controls in rotor slipstream • Low speed control difficult, lack of dynamic pressure • Required about a 50 ft ground run Autogyro – Cyclic Pitch - 1931 • E. Burke Wilford, American • First rigid rotor to fly • First to use cyclic blade pitch Autogyro – Direct Control - 1932 • Juan de la Cierva, Britain • Rotor mounted so shaft can be tilted for control • Led to elimination of ailerons and stub wings. Autogyro – Coming Back • Jay Carter, United States • “Personal Air Vehicle” • 2-bladed rotor, pusher propeller, tip weights on blades for jump take-off • Rotor slowed in forward flight for reduced drag Early Helicopters Bothezat – 1922 • Georges de Bothezat, United States • Quad-rotor, 6 bladed rotors • Controlled by collective, differential collective, and cyclic pitch • Called the “Flying Octopus” • Flew many times successfully at low altitude and low speed Early Helicopters Oemichen – 1924 • Etienne Oemichen, French • Quad-rotor Helicopter • Won FAI award for the first helicopter to fly a 1 km standard circuit • Stable and somewhat maneuverable machine Early Helicopters d’Ascanio – 1930 • Corradino d’Ascanio, Italy • Built and flew successful coaxial helicopter • Two bladed rotors, flapping hinges, collective and cyclic pitch • Servo tab control on blades • Small propellers on fuselage used for additional pitch control Early Helicopters Bleeker – 1930 • Maitland Bleeker, United States • 4-Bladed single rotor helicopter • Followed work of Brennan, rotor powered By props on blade tips • Servo tab control on blades Early Helicopters Florine – 1933 • Nicolas Florine, Belgium • Built and flew one of the first tandem rotor helicopters • Rotors spun in same direction, but tilted differentially for anti-torque • Flew for 9 minutes to an altitude of 15 ft Early Helicopters Focke – 1936 • Henrich Focke, German • Built and flew successful side-by-side rotor helicopter • Three bladed rotors, flap and lag hinges • Longitudinal control via swashplate on rotors • Lateral control via differential
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