FAQs
FAQs
Frequently Asked Questions

1. Who invented the helicopter?
2. When was the first helicopter flight?
3. If Igor Sikorsky did not invent the helicopter, then why is he important?
4. Is helicopter development driven by the military or commercial interests?
5. Is helicopter flying more dangerous than fixed wing flight?
6. What is the difference between a helicopter and a gyroplane?
7. What is the difference between an Autogiro, an autogyro and a gyroplane?
8. What was the first use of armed helicopters?
9. When was the word "ROTOR" first used for the helicopters?


FREQUENTLY ASKED QUESTIONS

1. Who invented the helicopter?

The short answer is that no one person can claim credit for the helicopter in the manner that the Wright brothers did so for the airplane.  However, certain individuals have played key roles.  Juan de la Cierva, with the development of the Autogiro, provided many of core technologies of rotary wing flight.  Many of those associated with gyroplane development deserve credit for making rotary wing flight practical, such as Bennett, Pitcairn, Larsen, Kellett, Prewitt and Hafner.  Henrich Focke, operating under the auspices of the Third Reich, did much to promote the helicopter.  In the United States, Igor Sikorsky’s perseverance in adapting Autogiro technology resulted in the adoption of the single main rotor helicopter as the conventional configuration.  Many types of helicopters had particular pioneers behind their origin, such as Arthur Young and Bart Kelly with the teetering (semi-rigid) rotor and Frank Piasecki with the tandem rotor.       

2.When was the first helicopter flight?

The first substantive attempts to fly a helicopter carrying a human occurred in 1907.  In France, Louis Breguet and Charles Richet claimed a flight in August or September, while Paul Cornu claimed one in November.  Neither machine possessed a viable control system and despite initial claims, no evidence exists to substantiate a sustained, controlled hover and engineering analysis of the designs make any such claims of flight highly dubious.  Photographic evidence exists of a Dane, Jens Christian Ellehammer, who flew a helicopter for the first time on September 12, 1908 in Copenhagen, Denmark.  However, he had to have an assistant stabilize for pilot Erik Hildes-Heim.  In the United States, the first conclusively document instance of an assistant-stabilized “flight” occurred in June 1920 at College Park, Maryland with a coaxial helicopter developed by Emil Berliner and his son, Henry (who was the pilot).  The first conclusively documented instance of an undocumented helicopter free flight occurred on January 11, 1922 at Issy-les-Moulineaux, France with the Pescara 1S, developed and flown by the Spaniard, Marquis Raoul Pateras Pescara.  The design featured collective and cyclic control and provision for autorotation.  Pescara’s follow-ons to the 1S achieved flights with altitudes of more than 20 feet and durations of several minutes, but ultimately, the ungainly coaxial biplane rotor design and complex blade warping system of control, combined with high vibrations and heavy control loads to create an unstable and ultimately impractical design. 

3. If Igor Sikorsky did not invent the helicopter, then why is he important?

Sikorsky’s genius lay in building on the significant body of work done in the development of the Autogiro and adapting into a utilitarian form.  Perhaps his greatest accomplishment was in his skills as a showman in selling the helicopter to the military, whose wartime resources were critical in establishing the helicopter industry, and to the general public, whose fascination with Sikorsky’s helicopters encouraged many engineers, inventors and investors to pursue helicopter development.  Sikorsky also oversaw a series of crucial developments that made his products the predominant operational types in military and commercial service from World War II through the Korean War and which ensured that even as competitors took on greater market shares, Sikorsky was well positioned to be a leading manufacturer for decades to come.

4. Is helicopter development driven by the military or commercial interests?

Military spending on rotorcraft development has typically outpaced commercial investment by a factor of about ten-to-one since the end of World War II.  This is in spite of the fact that today, far more civil rotorcraft are produced than military rotorcraft.  Highly specialized platforms like the Osprey tiltotor and complex subsystems account for this discrepancy. 

5. Is helicopter flying more dangerous than fixed wing flight?

Accident rates have typically been higher in helicopters than in comparably purposed airplanes.  The reason has less to do with greater mechanical complexity or difficulty of control than with the nature of the helicopter’s operating environment.  Routine helicopter operations, such as sightseeing have an excellent safety record, but the utilitarian nature of the helicopter means that it is often called upon in extreme situations and is required to operate in environments that would typically be unsuitable for normal operations.  By operating in close proximity to the ground, unseen hazards such as wires and towers can pose significant risks to helicopters that are not experienced by airplanes operating out of carefully constructed airport environments.  Likewise, brownouts due to dust or sand and dynamic rollovers due to terrain increase the accident rate of helicopters relative to airplanes.  Numerous safety initiatives are underway to improve visual cues to pilots in low visibility conditions and enhance situational awareness.  These technical solutions hold great promise in reducing operational accidents, while improved training regimens are creating better pilots.

6. What is the difference between a helicopter and a gyroplane?

During conventional flight, an engine continuously drives a helicopter’s rotor to provide lift, whereas a gyroplane features a free-wheeling rotor that windmills in rotation (autorotation) as a relative airflow transitions upwards through it.  Without forward motion relative to the surrounding air, the gyroplane’s rotor will not maintain its rotation and will descend.  This means that gyroplanes cannot hover or climb vertically.  Some gyroplanes have provision for providing power to the rotor to “prerotate” it so that it has sufficient rpm to facilitate autorotation when beginning the takeoff role and some have the capability to overspeed the rotor on the ground for a “jump takeoff” when pitch is suddenly increased on the rotorblades, causing a short burst of lift.  However, power cannot be provided to the gyroplane rotor in flight without some means in place to offset torque.

7. What is the difference between an Autogiro, an autogyro and a gyroplane?

Gyroplane refers to a class of rotary wing aircraft that depend primarily upon an autorotating rotor for lift (though not necessarily for control, stability or propulsion).  Autogiro (always with a capital “A”) is a proprietary term for Cierva and Cierva-licensed gyroplanes while autogyro refers to gyroplanes of the Cierva-type configuration that may or may not be Cierva products.   


8. What was the first use of armed helicopters?

As early as 1940, the U.S. Army Air Corps explored the question of flexible machine gun mounts for self defense.  The German Focke-Achgelis Fa 223 likewise incorporated a machine gun in the nose to ward off potential fighter attacks, though there is no anecdotal evidence that such an arrangement had to be used.  The U.S. Army Air Corps experimented with mounting depth bombs on the R-4, R-5 and R-6 series helicopters during World War II, but given payload limitations and severe changes in the center-of-gravity when released, this provision was never implemented on operational aircraft.  At least one WWII-era account exists of a crew chief arriving in a landing zone on a Sikorsky R-6 and firing into a suspected Japanese position with a carbine.  At the end of the war, a U.S. Army Airborne Board evaluated the use of a 57mm recoilless rifle mounted on an R-6.  The back-blast damaged the helicopter and the experiment was discontinued.  The U.S. Marine Corps experimented with Korea saw the extensive use of small arms being fired from the helicopter to suppress hostile fire during personnel pick-ups in hostile territory, against suspected guerilla positions and against floating mines.  The U.S. Navy did experiment with machine gun mounts for use against aquatic mines.  The first use of fixed offensive armament on helicopters came in the Algerian Insurgency (1954-1962), where French Forces used Bell 47Gs, Sikorsky H-19s, H-34s and Vertol H-21s with a wide range of armament, including 7.62 mm, .30 cal, .50 cal machine guns, 20mm cannon and 57mm recoilless rifles as well as 2.75 in rocket pods.  Another significant innovation was the use of the SS-11 surface-to-surface guided anti-tank missile in the airborne role where it was used aboard the Sud-Est Alouette II.

9. When was the word "ROTOR" first used for the helicopters?

A good question, and one that was fun to research.  Like many things in
the primary phases of rotary wing development, the answer seems to lie
with Cierva and the Autogiro.  "Propellers" and "air screws" were used
almost exclusively in rotary wing patents until 1931, when "rotor" and
"rotor blades" start to appear.  Of course, "propeller" was a fairly
accurate description of most helicopter airfoils until Cierva, though
exceptions, such as Pescara, also use the term in their patents.  The
initial use of rotor was almost exclusively in connection with autogyro
patents.  In Cierva's patents filed before the summer of 1929, he never
used "propeller" or "air screw" to define a rotor, but rather used
"rotative wings" and "rotating wings" to describe this construction.  A
survey of other literature shows that by the time Pitcairn started
marketing Autogiros in 1931, "rotor" was in standard use.  An official
report on the Cierva C.19, dated 1930 also uses "rotor" as standard
terminology.  My suspicion is that as Cierva and his licensees began
preparing to market Autogiros commercially they wished to get away from
the popular labeling of "windmills" in press accounts, which made them
seem archaic.  "Rotorcraft" and rotors seemed to have fit with their
desire to portray the Autogiro as a piece of modernity.  There was no
pressing need from the pure helicopter community to rename their lifting
mechanism as they were not saddled with the "windmill" moniker.  By
1935, "rotor" seems to have been in frequent, if not common, use, even
among those applying for helicopter patents, though this was by no means
universal.  By 1938 and Focke's patent application, "rotor" seems to
have been the preferred term, even for helicopters.  Of course, by this
point, "propeller" and "air screw" were no longer accurate definitions
the airfoils on what were truly rotating wing aircraft.

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