Page 22 - Build Your Own Quadcopter_ Power Up Your Designs with the Parallax Elev-8

chapter 1

Introduction to

Quadcopters

A Brief History of Multirotor Helicopters

The multirotor helicopter also known as a quadrotor or quadcopter is equipped with four
rotors to create lift. It is a true helicopter in that lift force is created by narrow-chord
horizontally rotating air foils. The quadcopter design has been in existence since the 1920s
when an early manned version named the De Bothezat helicopter was built and successfully
flown. First developed and prototyped under a U.S. Army contract, the De Bothezat helicopter
is pictured in Figure 1.1.
It first flew in October 1922 at what is now known as Wright Field in Dayton, Ohio.
The helicopter actually started with six rotors, but eventually two were deemed
unnecessary and were eliminated. It made more than 100 flights over a period of years but
never flew more than 5 meters into the air and never with any lateral movement. This was
due to the complexity and difficulty of simply trying to maintain level flight, never mind
moving in a lateral direction. This lateral movement control was to be the bane of multirotor
helicopters until the invention and use of computer-assisted flight-control systems that
would lessen the pilot workload. The U.S. Army eventually lost interest in the De Bothezat
project and discontinued it in the early 1930s, after spending more than $200,000 on
the program.
Helicopter development languished, at least in the United States, from the early 1930s to
the mid 1940s. With the ending of World War II, development work did resume, but the
focus was on more conventional designs that employed a main rotor with a tail rotor or the
use of coaxial main rotors. The armed forces that initially funded helicopter development
apparently believed that any possible advantages of using quad rotors were far outweighed
by their complexity and ill-mannered flight characteristics.
The U.S. Army eventually developed and successfully fielded a heavy-lift, tandem-rotor
helicopter named the Chinook, model CH-47, which despite being designed in the 1960s, is
still in wide use today. It has undergone many updates and upgrades to keep it fully
compatible with today’s environment.
The U.S. Department of Defense also sponsored the development and production of a
hybrid, dual-tilt-rotor aircraft named the Osprey, model V-22. It takes off and lands as a dual
rotor helicopter, but flies as a traditional airplane with the wings tilted to a level position
while it is operating in cruise mode. Figure 1.2 is a picture of the pilot’s station in the V-22,
showing all the incredible technology available to the pilot.

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