Aerodynamic of Rotor - Helicopter Flight

Topics: Helicopter, Helicopter rotor, Airfoil Pages: 17 (3577 words) Published: August 13, 2011
HELICOPTER THEORY

Aerodynamics of a Helicopter Rotor in Forward Flight
Introduction

Early History

Modern History

Flapping Hinges

Maximum Speed

Cyclic Control

Momentum Theory

Blade Element Theory

Rotor Wake

Summary

References

Home

Based on a paper originally written
by Doug Jackson
Spring 2000
Introduction:
Even though the design of the modern helicopter was not perfected until the late 1930s, it is arguably one of the earliest ideas for achieving flight, predating the concept of the glider by perhaps as much as two thousand years. Inspired by the flight of birds, even ancient humans dreampt of soaring at high speeds, stopping on a dime, and hovering in place, much like a hummingbird or dragonfly. Yet no one truly appreciated the complexities needed to make that dream become reality, and it took the collected wisdom and patience of a number of notable aviation pioneers over the course of centuries to bring that technology into existence. In this site, we will first explore the history of how the modern helicopter came to be and highlight the great thinkers and designers who made the most significant innovations. Next, we will look at the mechanics of a helicopter rotor in forward flight and introduce the many complex challenges that have to be overcome to make a rotorcraft controllable. We will then discuss the two prevailing analytical theories used by engineers to mathematically describe how a rotor functions before wrapping up with an overview of the wake vortices created by the rotor in flight.

Early Helicopter History
Introduction

Early History

Modern History

Flapping Hinges

Maximum Speed

Cyclic Control

Momentum Theory

Blade Element Theory

Rotor Wake

Summary

References

Home

Early Concepts:
The helicopter is arguably one of the earliest ideas for achieving flight. Over two thousand years ago, the Chinese constructed what are known as Chinese Tops, illustrated below. These simple toys consisted of a propeller attached to a stick that would be spun rapidly through ones hands to spin the propeller and achieve lift. These toys are still common today.

Chinese top [from Gessow and Myers, 1952]
Later, in the 15th Century, famed inventor and artist Leonardo da Vinci designed one of the more aesthetically pleasing concepts for a helicopter, but such a craft was never actually constructed.

Leonardo da Vinci's "Helicopter", 15th Century [from Gessow and Myers, 1952] First Successes:
In England in 1796, Sir George Cayley constructed the first powered models of helicopters that were driven by elastic devices. One of these models, shown below, attained an altitude of ninety feet.

Sir George Cayley's helicopter, 1796 [from Gessow and Myers, 1952] In 1842, almost fifty years after Sir George Cayley, fellow Englishman W. H. Phillips constructed a model helicopter that weighed 20 pounds (9 kg) and was driven by steam. He proposed a full-sized three-propeller machine (one propeller for lift, and two for directional control), but it was never built. In 1878, Enrico Forlanini, an Italian civil engineer, also constructed a steam driven model helicopter that only weighed 7.7 lb (3.5 kg). In 1880, Thomas Edison was the first American to perform any notable research on helicopters. Edison built a test stand and tested several different propellers using an electric motor. He deduced that in order to create a feasible helicopter, he needed a lightweight engine that could produce a large amount of power. Modern Helicopter History

Introduction

Early History

Modern History

Flapping Hinges

Maximum Speed

Cyclic Control

Momentum Theory

Blade Element Theory

Rotor Wake

Summary

References

Home

First Vertical Flight:
The first manned helicopter to rise vertically completely unrestrained was constructed by Paul Cornu, a French mechanic, in 1907. Cornu's helicopter had two...

References: 2. Bramwell, A. R. S. Helicopter Dynamics. New York: Halsted Press, 1976.
3. Gessow, Alfred and Myers, Garry C., Jr
6. Johnson, Wayne. Helicopter Theory. Mineola, NY: Dover Publications, 1980.
7. McCormick, Barnes W
8. Newman, Simon. The Foundations of Helicopter Flight. New York: Halsted Press, 1994.
9. Seddon, J
10. Stepniewski, W. Z. and Keys, C. N. Rotary-Wing Aerodynamics. Mineola, NY: Dover Publications, 1979.
11. _____
12. Young, Raymond A. Helicopter Engineering. New York: Ronald Press Company, 1949.
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