The Helicopter:A Hundred Years of Hovering

Chinese Bamboo Helicopters (circa 400 B.C.)

For many Westerners, the myth of Icarus, the boy who flew too close to the sun on manmade wings, represents the dreams and the dangers of flight. But a century before the earliest mentions of Icarus in ancient Greece, Chinese children were already playing with

kites and spinning bamboo propellers. While the kites had religious significance, and rockets became favored by the military, the flying propellers remained mainly toys. Children sent them aloft by spinning the central stick between their palms.

LEONARDO DA VINCI'S VITE AEREA — THE AERIAL SCREW (1483 TO 1486)

Trade from the Far East resulted in the Chinese toys reaching Europe in the early Renaissance, likely inspiring Leonardo da Vinci (1452-1519) to create a drawing called the Aerial Screw. "I believe that if this screw device is well-manufactured, that is, if it is made of linen cloth, the pores of which have been closed with starch, and if the device is promptly reversed, the screw will engage its gear when in the air and it

will rise up on high," da Vinci wrote in a note next to the drawing, according to the National Museum of Science and Technology in Milan, Italy.

AERIAL SCREW IS FLIGHTLESS (1483 TO 1486)

Leonardo da Vinci drew a number of designs for flying machines, including ornithopters, which mimic bird flight, and the Aerial Screw. The designs assumed, incorrectly, that one or more human pilots could generate enough power

to lift the machine into the sky. While the design indicates that four men could turn the screw using a pumping action, the machines would never have been able to generate enough lift to get off the ground, according to experts.

MIKHAIL LOMONOSOV'S AERODYNAMIC (1754)

Three centuries passed before another major milestone in vertical flight appeared. Looking for a way to loft meteorological instruments into the air, noted Russian scientist Mikhail Lomonosov designed a model that used two propellers rotating in opposite directions on the same axis. The coaxial design offsets the torque created by a single propeller -- a situation that would have caused the device to spin in the opposite direction of

the propeller blade. Lomonosov demonstrated a model powered by a clock spring to the Russian Academy of Sciences in July 1754. Questions remain whether the device managed to lift itself during the demonstration or whether it was supported by a string

LAUNOY AND BIENVENU RECREATE HELICOPTER TOY

(1784)

Naturalist Christian de Launoy and his mechanic Bienvenu,

about whom very little is known, presented a coaxial model of a simple helicopter powered by

the tension in a bow. "When the bow has been bent by winding the cord, and the axle placed in the desired direction of height -- say vertically, for instance -- the machine is released," the pair told the French Academy of

Sciences in 1784.

SIR GEORGE CAYLEY, FATHER OF AVIATION, DESIGNS

GLIDER (1799)

While reports of gliders appeared in China (fifth century B.C.) and Moorish Spain (A.D. 875 A.D.), Cayley is widely

recognized for discovering the four principle forces of flight -- weight, lift,

drag and thrust -- and their relationship. The baronet also

designed a familiar-looking airplane -- consisting of a single wing, rear

stabilizers and a vertical fin. He used the design to create the first glider to

have a well-documented manned flight. A full-scale model of the glider

-- or "governable parachute," as it was called -- carried one of Cayley's

employees aloft in 1853.

CAYLEY'S "AERIAL CARRIAGE“ (1843)

Sir George Cayley searched for a way to propel his heavier-than-air

vehicles. He tried to create a rudimentary engine fueled with

gunpowder, but the invention did not work reliably. He decided to design around his lack of success

with engine power by revisiting da Vinci's ideas of a human-powered

machines. He came up with the concept of the "Aerial Carriage" in 1843, consisting of four umbrella-like propellers that would rotate for lift, but it never successfully

hovered or flew

CALL THEM "HELICOPTERES“ (1863)

One vertical-flight enthusiast, Gustave Vicomte de Ponton

d’Amécourt, designed a model flying machine using coaxial

propellers and a coiled spring for propulsion. While that model could fly, another version using a steam

engine had failed. Ponton d'Amecourt called his machines

"helicopteres," a word derived from the Greek adjective for "spiral" and the noun "pteron," meaning "wing."

Ponton d'Amecourt and his group of enthusiasts inspired Jules Verne

to add helicopters to his stories.

THOMAS ALVA EDISON FAILS WITH HELICOPTERS (1880)

Inventors who focused on helicopters during the latter half of the 19th century were stymied by the lack of powerful, but lightweight, engines to turn their helicopters' rotors. Among the early engineers, Thomas Edison was the first American to attempt to further the study of helicopters by focusing on the engines. The inventor -- known for successfully creating the long-lasting light bulb and the phonograph -- tried

to power his models with an early internal-combustion engine that used guncotton for fuel, but an explosion in his lab convinced him to switch to an electric engine. He concluded, however, that the design required higher-performing rotors.

JULES VERNE DEPICTS THE ALBATROSS FLYING SHIP (1886)

The push to create heavier-than-air vehicles caught the imagination of many 19th-century citizens, among them the famous writer Jules Verne. In his book, Robur-le-Conquérant (or Robur, the Conqueror), published in 1886, Verne envisioned a flying ship named the Albatross that could fly through the air by using 37 helicopter-like propellers.

Robur uses the ship to launch attacks against his enemies.

WRIGHT BROTHERS FLY AT KITTY HAWK (1903)

Wilbur and Orville Wright designed and built the first airplane to attain powered flight, four years before the first helicopter inventors could claim such a feat for vertical flight. The self-trained engineers steadily improved the

design, from a kite in 1899 to three gliders and then three powered airplanes in 1903, 1904 and 1905. By their final flight, they had improved the design to the point that extended flights, fully controlled by the pilot, were possible.

THE BRÉGUET-RICHET GYROPLANE NO. 1 (1907)

Brothers Louis and Jacques Bréguet began work on their version of a helicopter in 1905 under the tutelage of Professor Charles Richet. In late summer 1907 -- sources vary on whether it was Aug. 24 or Sept. 29 -- the machine achieved its first vertical ascent, hovering off

the ground for two minutes. However, the craft -- christened Gyroplane No. 1 -- needed four men to steady it, as the primitive helicopter lacked any way to control its flight. The craft had a 45-horsepower engine, just powerful enough to hover.

PAUL CORNU, INVENTOR AND ENGINEER (1907)

Like the Wright Brothers, Paul Cornu was a bicycle maker and engineer. Born in 1881 in Glos-la-Ferrière, France, to a family of 13 children, Cornu had an interest in inventing and drawing early in life. He worked with his father in the family transport company, but because of Cornu's

interests, the business eventually transitioned to bicycle design and repair. In the early 1900s, Cornu had his eye on winning the Deutsch-Archdeacon award -- the X Prize of its day -- a purse of 50,000 francs funded by two Parisians for the first heavier-than-air vehicle to complete a

1-kilometer circuit.

PAUL CORNU: FIRST TO HOVER? (1907)

Using 100 francs borrowed from friends, Cornu built a life-sized version of a 25-pound helicopter model that he successfully flew in 1906. On Nov. 13, 1907, Cornu's twin-rotor craft flew for about 20 seconds, rising about one foot (0.3 meter) off the ground. The vehicle's rotors

were mounted outrigger-style on either side of the steel-frame-and-wire contraption. A 24-horsepower engine powered the propellers. Cornu's helicopter had no effective way to control its flight, a fact that led engineers to abandon the design after a few flights.

FIRST MANNED FLIGHT IN THE UNITED STATES (1908)

Emile Berliner, who created the gramophone (disc-record player) and founded the Victor Talking Machine Co., was also an avid

helicopter inventor. Berliner created a 36-horsepower engine and used

two of them on a platform designed by John Newton Williams. The craft reportedly lifted both men about 3

feet off the ground, but likely had to be steadied. Berliner, went on to

build several other helicopters, and also suggested the use of an

auxiliary tail rotor -- a standard feature of helicopters today -- to

stabilize flight.

JUAN DE LA CIERVA (1920’s,)

Born in 1895, Juan de la Cierva is credited with pioneering many of the

necessary systems for controllable helicopter flight. In 1920, the 25-year-old Spanish engineer started work on a strange mechanical manticore: an

airplane with the wings replaced by a non-powered propeller. By 1923, his latest aircraft -- called Autogiro No. 4 -- flew a 4-kilometer circuit around

Madrid. Ironically, the Spanish engineer questioned whether

helicopters could ever be successful, as he believed they were too

complicated to fly reliably. De la Cierva died on Dec. 9, 1936, when his plane

crashed on takeoff from London.

DE LA CIERVA'S FLIGHT (1923)

As helicopter historians begin to question the veracity of Paul Cornu's achievement in 1907, de la Cierva's flights in 1923 are increasingly considered to be the start of the helicopter era. Despite the strange configuration of the autogiro, de la Cierva pioneered the use of hinged rotor blades to stop the vehicle from tilting, as well as creating workable controls for lateral motion and pitch and

yaw. On Jan. 17, 1923, de la Cierva took his first flight in Autogiro No. 4, considered to be the first controlled helicopter flight.

BERLINER HELICOPTER, MODEL NO. 5 (1924)

Following Emile Berliner's nervous breakdown in 1914, son Henry Berliner continued to work on helicopters. The Berliners created a coaxial helicopter in 1920 that managed to move forward several yards, representing the first manned, controlled helicopter flight in the

United States. In 1924, the pair's research culminated in a hybrid helicopter that used the fuselage of a Neuport 23 biplane and wing-mounted rotors to create a vehicle that could move at about 40 mph, rise to an altitude of 15 feet and turn with a radius of 150 feet. The craft

was demonstrated in front of Navy officials and the press on Feb. 24, 1924.

HEINRICH FOCKE AND THE FA-61 (1937)

Born in Bremen, Germany, in 1890, Heinrich Focke in 1923 founded the Focke-Wulf airplane company, which manufactured most of Germany's aircraft during World War II. He also began working on helicopters in the 1930s. After being ousted from his previous company

by the shareholders, Focke, along with German engineer Gerd Achgelis, set up another company, Focke-Achgelis, which focused on helicopters. Together, they created an aircraft -- the Fa-61, also known as the Focke-Wulf 61 -- that looked superficially like Cierva's autogiro,

but had powered rotors rather than a propeller that rotated with the relative wind created by forward motion.

IGOR SIKORSKY, FATHER OF HELICOPTERS

Born in Kiev, Russia (now Ukraine) on May 25, 1889, Igor Ivanovich Sikorsky became interested in flight at an early age. Both parents were physicians, giving Sikorsky the scientific grounding that he needed to develop aircraft

ideas inspired by Leonardo da Vinci and Jules Verne. At age 12, he built his first flying model of a helicopter.

SIKORSKY'S VS-300 (1939)

In 1938, United Aircraft -- which had bought Sikorsky's company -- granted him permission to create an experimental helicopter design. Eschewing the coaxial rotors that had been used up to that point, Sikorsky used a single three-bladed main rotor and a two-bladed vertical rotor on the tail to offset torque. On Sept. 14, 1939, Sikorsky

himself took the prototype on its first flight. The helicopter, known as the VS-300, hovered several times, but was tethered to the ground. Originally dubbed "Igor's Nightmare" by Sikorsky's mechanics because of the problems trying to reduce the helicopter's vibrations, the aircraft made its first free flight in May 1940. A year later, it

went on to break the world helicopter endurance record -- previously held by the Focke-Achgelis Fa-61 -- by staying airborne for 1 hour, 32 minutes, 26.1 seconds.

PLATT-LEPAGE XR-1 (1941)

The design of the Focke-Achgelis Fa-61 inspired two American engineers, W. Laurence LePage and Haviland H. Platt, to design a helicopter with a rotor on either side, designated the XR-1. Driven by the German's lead in helicopter technology, Congress passed a bill assigning $2 million to jump-start helicopter

research in America. The helicopter was piloted around a test circuit on June 9, 1941, reaching speeds nearing 100 mph. A number of problems plagued the XR-1: The helicopter was hard to control and suffered from severe vibrations (a problem that plagued other contemporary aircraft), and the design had

poor visibility of what lay beneath the aircraft. The latter was resolved by covering the nose in Plexiglas, a feature still used today in many helicopters.

FOCKE-ACHGELIS FA 330A (1942)

When the Battle for the Atlantic turned against the Nazis in World War II, the German Navy asked Focke to create a surveillance craft that could be deployed quickly from submarines, so that German U-boats, which had to patrol areas of the ocean far from coastlines, could detect

possible convoy targets and Allied patrols. Focke came up with the Fa 330, a gyro kite that didn't have an engine but would be towed by German U-boats. The aircraft flew high enough to boost the scouting range, had excellent stability and could quickly separate from the

submarine in the case of an emergency or an attack on the U-boat.

IGOR SIKORSKY'S XR-4 (1942)

Based on his success with the VS-300, the U.S. Army Air Corps gave Sikorsky a $50,000 contract in December 1940 to build an easily manufactured version of the aircraft. Sikorsky demonstrated his new aircraft, designated the XR-4, in January 1942. Eventually, the XR-4

would be used in amphibious and shipboard operations as well as rescue missions. The U.S. and British military bought dozens of the XR-4 series. With the helicopter, Sikorsky established himself as a leading innovator in helicopter design by the end of World War II. The XR-4 is

considered America's first production helicopter.

FRANK N. PIASECKI AND THE PV-2 (1943)

Born in Philadelphia in 1919, Frank Piasecki earned degrees in both mechanical and aeronautical engineering by age 20. In 1940, Piasecki cut his teeth in the helicopter-design world when he worked on the Army Air Corps' first

contracted helicopter, the Platt-LePage XR-1. In 1943, to solve problems he witnessed in the XR-1, Piasecki developed and flew the PV-2.

HEINKEL WESPE "WASP" EARLY VTOL DESIGN (1944)

With the air superiority of the German Luftwaffe being eroded in 1943, the

Nazi military commanders looked for ways to solve two problems: improving

defenses to restore its command of the air, and design aircraft which

would not be hobbled by the bombing of its airfield. A proposed solution

included a vertical rocket plane, the Bachem Ba 349, but also a design for an aircraft, the Henkel Wespe, that

could take off vertically using a large central rotor, a design known as a

coleopter ("sheath-winged"). Originally conceived in 1944, the Wespe -- and its sister design, the

Lerche II ("Lark II") -- were never built.

LARRY BELL AND THE UH-47 (1947)

Larry Bell founded Bell Aircraft in 1935, but his company was struggling by the beginning of World War II, and Bell decided to start investing in helicopter design. The Bell Model 30 first flew in December 1942, but both the 30 and its successor, the Model 42, failed to sell well. Bell rethought the design, adding seating for two and a more powerful engine, and christened the result -- finished in 1947 -- the Model 47. The

helicopter sold very well in the commercial market, and military interest soon followed. During the Korean War, the H-13 -- as it was designated by the military -- evacuated more than 15,000 wounded.

PIASECKI'S "FLYING BANANA" (1947)

Driven by the need to increase the carrying capacity of the helicopter, and criticism that it hadn't made good use of the innovative machine, the U.S. Navy funded a number of designers who had not signed contracts with the Army Air Corps. , Piasecki's company received a contract from the Navy in 1944 to build what at the time was the

world's largest helicopter. Piasecki used his experience with the XR-1, which he noticed flew better sideways than forward, and his success in developing the dynamically balanced rotor on the PV-2, to develop a design with tandem fore and aft rotors. The result was the XHRP-X "Dogship," which was also called the "Flying Banana" because of its shape. It first flew in 1945 and had over three times the payload of any other helicopter flying, satisfying the Navy’s requirement for a minimum 1,800-pound useful

payload. The XHRP-X went into production in 1947.

STANLEY HILLER, AVIATION ENTREPRENEUR

Born in November 1924, Stanley Hiller had the entrepreneurial gene. By the time he was 16, he'd established Hiller Industries to build model-car kits. But less than a year later, he switched to airplane parts as World War II heated up, and earned his first million. Hiller became a top defense contractor, supplying the military with several versions of his aircraft and developing some less-conventional designs, including the Hornet, Rotorcycle and the Flying Platform. With his popular UH-12, which the U.S. military used in Korea and Vietnam, he also became the first American manufacturer to figure out how to produce helicopters without reliance on

government funds. Civilian versions of the craft were used by ranchers, police departments and the media. Hiller died in 2006.

HILLER'S HORNET, A HELICOPTER WITH RAMJET (1950)

In 1948, following French innovations in the use of ramjets on aircraft, Stanley Hiller began to experiment with mounting the simple jets on the tips of a helicopter's main rotor blade. Hiller aimed to manufacture

the helicopters for $5,000, making personal ramjet-powered helicopters practical and affordable.

LOCKHEED AND CONVAIR GET CONTRACTS TO BUILD

VTOL (1951)

Using designs captured from the Germans, the U.S. Air Force and Navy crafted two

design studies in 1947 for creating a fixed-wing vertical-takeoff-and-landing, or VTOL, aircraft. The goal of the project was to build a fighter that could protect convoys but not require a large landing area. In May 1951, both Lockheed and Convair won contracts to build prototypes of the aircraft, which

resembled squat fighter planes standing on their tails. The Navy, however, gave Convair the only engine rated for vertical takeoffs

and landings, allowing its aircraft -- the XFY-1 Pogo -- to make several vertical ascents

and multiple transitions to horizontal flight. The Lockheed XFV-1 used a less-powerful engine and never made a vertical takeoff,

but was fitted with landing gear and made 32 horizontal flights.

KAMAN K-225 PERFORMS LOOP (1953)

Engineer Charles Kaman improved on another German design, Anton Flettner's Al-232, a helicopter that used two coaxial blades to fly. Dubbed a "synchropter," the aircraft saw limited used by the Germans during World War II. Kaman took the design and modified it in many ways, but most significantly, he added a jet-turbine

engine, replacing the old reciprocating piston engines used by previous helicopters. The addition of the turbine engine made the Kaman K-225, and future helicopters, safer, more reliable and easier to maintain. Turbine engines also increased performance, allowing the Kaman K-225 to successfully fly through an intentional loop in

March 1953. The design, however, had a significant flaw: It moved at only three-quarters of the speed of contemporary rotorcraft.

THE SEGWAY OF HELICOPTERS (1955)

In addition to vertical takeoff and landing, a number of other innovative helicopter designs appeared during the 1950s. Among the most radical was a flying platform that used the pilot's natural balancing reflexes to control direction, a technology known as kinesthetic control and made popular most recently by the Segway Personal

Transporter. The idea was first suggested by engineer Charles Zimmerman, who called it the "flying shoes."

BELL UH-1H (THE "HUEY") FLIES (1956)

Designated by the Army as the HU-1H -- thus the nickname "Huey" -- and later designated the UH-1H, the helicopter became a veritable Swiss Army knife: ferrying the wounded, troops and cargo around Vietnam for all branches of the military. The helicopter also changed the

way that troops were mobilized for quick assaults on military targets. Nearly 900,000 wounded were transported by helicopter in the Vietnam War, 50 times more than the Korean War. (M.A.S.H. -- a dark comedy set during the Korean War -- used the Huey in the title credits,

even though the helicopter had not been built at the time of the conflict.)

PIASECKI'S FLYING JEEP (1958)

The U.S. Army awarded Piasecki Aircraft a contract in 1957 to develop a fast, low-flying aircraft that could act as a "flying jeep." Piasecki's design, which first flew in October 1958, used a fore and aft rotor to create a vehicle that could travel at over 60 mph and at an altitude of about 2,500 feet. The second version of the flying jeep, or AirGeep as Piasecki called it, could fly at over 80 mph and carry five people. Both versions of the AirGeep were true flying cars, not hovercraft, as they did not rely

on so-called positive ground-effect forces to keep them aloft. They did, however, each have powered wheels for maneuvering on the ground. They were also very stable and could be used as weapons platforms. Yet, the Army eventually scuttled the project in favor of more-conventional battlefield helicopter designs.

SIKORSKY "BLACK HAWK" HELICOPTER (1976)

The U.S. Army requested a new design for a utility transport helicopter in 1972. It granted the contract to Sikorsky for its S-70 family of helicopters in December 1976. Designated by the Army as the UH-60 "Black Hawk," the helicopter has a unique flattened appearance because of the requirement that

it fit in the transport hold of a C-130 Hercules cargo plane without removing the rotors. The helicopter has a number of interesting safety features, including a crash-resistant cabin, landing gear that can cushion a hard landing, and two engines, either of which can keep the aircraft aloft on its own.

Today, the Black Hawk is the most popular helicopter in the U.S. military, with more than 2,400 in use, according to the Smithsonian Institution.

HUGHES "APACHE" HELICOPTER (1982)

The U.S. Army requested proposals in 1972 for a helicopter gunship whose form was dictated less by the Vietnam War and more by the perceived need to destroy Soviet tanks. Nearly a decade later, the Pentagon granted the contract to aircraft-maker Hughes to build the

AH-64 "Apache" helicopter. The development of the Apache was controversial, because it cost far more than previous contracts. During the 1991 Persian Gulf War, the helicopter performed well as both a tank killer and fast-assault vehicle.

BELL-BOEING V-22 "OSPREY" TILTROTOR CRAFT (1989)

The joint U.S. military services began development in 1981 of a hybrid helicopter and airplane that could carry more and move faster than a typical helicopter. The V-22 Osprey used tilting rotors to vertically take off and then move to horizontal flight, where it would use its airplane-like

aerodynamics to move faster and lift more. Full-scale development began in 1986 with Bell Helicopter and Boeing working on different parts of the hybrid helicopter, known as a tiltrotor aircraft. Although the Osprey completed its first successful test in March 1989, the Pentagon only signed off

on production for the aircraft in 2005. Like the Apache program, the project's high costs and long development time has opened it to criticism.

HUMMINGBIRD HOVERS (2006)

Using concepts pioneered by early VTOL aircraft, aeronautical engineer Philip Carter is designing a plane intended to excel at acrobatics. The inventor says on his website that that the plane, dubbed the Hummingbird, will be able to

perform maneuvers impossible for other aircraft -- including the ability to hover like a hummingbird. A radio-controlled model of the plane flew in 2006.

HOVER CAR, MOLLER INTERNATIONAL

Dreams of a personal sky car continue to lure inventors. One engineer, Paul Moller, has designed three vehicles that he claims could fit the bill. Moller plans to sell the M400 Skycar, a tricked-out cherry-red VTOL vehicle, for $500,000 -- about the price of a high-performance helicopter. The saucer-like M200 hovercraft sells for $90,000 to $450,000,

but is based on older technology

FLYING WINDMILL FOR ENERGY PRODUCTION

The concepts embodied by Cierva's autogiro continue to appear today. One startup, Sky WindPower, believes that a four-rotor tethered windmill could be lofted 15,000 feet into the air and both keep itself airborne and generate power using the more predictable winds in the

high atmosphere. Bryan Roberts, the inventor of the airborne windmill and a professor at the University of Technology in Sydney, has designed a wind-powered generator that weighs 1,100 pounds and uses four 35-foot rotors. Roberts believes that a flock of 200 such

windmills could provide as much electricity as the United States' most productive nuclear reactor.

How does a helicopter actually fly?The answer is … aerodynamics!

What Is Aerodynamics?Aerodynamics is the way air moves around things. The rules of aerodynamics explain how an airplane is able to fly. Anything that moves through air reacts to aerodynamics. A rocket blasting off the launch pad

and a kite in the sky react to aerodynamics. Aerodynamics even acts on cars, since air flows around cars.

What Is Lift?

Lift is the push that lets something move up. It is the force that is the opposite of weight. Everything that flies must have lift. For an aircraft to move upward, it must have more lift than weight. A hot air balloon has lift because the hot air inside is

lighter than the air around it. Hot air rises and carries the balloon with it. A helicopter’s lift comes from the rotor blades at the top of the helicopter. Their motion through the air moves the helicopter upward. Lift for an airplane comes from its wings.

What Is Thrust?

Thrust is the force that is the opposite of drag. Thrust is the push that moves something forward. For an aircraft to keep moving forward, it must have more thrust than drag. A small airplane might get its thrust from a propeller. A

larger airplane might get its thrust from jet engines. A glider does not have thrust. It can only fly until the drag causes it to slow down and land.

What Is Drag?

Drag is a force that tries to slow something down. It makes it hard for an object to move. It is harder to walk or run through water than through air. That is because water causes more drag than air. The shape of an object also

changes the amount of drag. Most round surfaces have less drag than flat ones. Narrow surfaces usually have less drag than wide ones. The more air that hits a surface, the more drag it makes.

What Is Weight?

Everything on Earth has weight. This force comes from gravity pulling down on objects. To fly, an aircraft needs something to push it in the opposite direction from gravity. The weight of an object controls how

strong the push has to be. A kite needs a lot less upward push than a jumbo jet does.

References

http://www.nasa.gov/audience/forstudents/k-4/stories/what-is-aerodynamics-k4.html

http://www.wired.com/science/discoveries/multimedia/2007/11/gallery_helicopter?currentPage=1&slideView=4

http://howthingsfly.si.edu/forces-flight