Juan de la Cierva, a Spanish aeronautical enthusiast and engineer, participated in a design competition to develop a bomber for the Spanish military in 1921. His design (a tri-engine bomber) stalled and crashed during an early test flight.
De la Cierva, troubled by this stall phenomenon, spent considerable time applying his mind to the development of an aircraft that could fly safely at low airspeed.
He determined that the only way to eliminate any chance of stalling would be to allow the wing to move independently of the rest of the aircraft . . . his research and early experimentation resulted in a radically new concept – a rotating wing positioned above the fuselage and allowed to rotate freely in the oncoming airflow.
By 1923, his ongoing development efforts resulted in the first successful rotorcraft flight.
De la Cierva named his invention the ‘Autogiro.’
Cierva C-3 Autogiro
The names Gyroplane, gyrocopter & autogyro (or autogiro), all refer to this specific type of rotary-wing aircraft, which obtain lift (to overcome gravity) from air-driven, ‘auto-rotating’ rotors, while thrust (forward propulsion) is delivered by means of engine-driven propellers.
As stated, the fixed-pitch rotor of the gyroplane functions in an autorotative state. It is driven by a continuous flow of air moving, from the front, through the rearward-tilted rotor and then downwards behind the aircraft, as it is propelled forward through the air by the engine driven propeller.
The rotor blades are manufactured according to a specific airfoil profile and mounted at a specific blade-angle, so that the rotor disc not only generates sufficient lift (the ‘driven’ region of the disc) to oppose the aircraft weight but, via the horizontal component of this lift generated by each blade, it also generates a rotational impetus (the ‘driving’ region of the rotor-disc), which always keeps the rotor turning at the right and proper RPM.
The teetering action of the typical contemporary gyroplane rotor allows the blades to ‘see-saw’ up and down during the rotational cycle, thereby automatically compensating for asymmetry of lift – i.e. the different lift force generated by the advancing and retreating sides of the rotor-disc as the gyroplane flies through the air.
The control system is used to tilt the rotor disc in any direction in order to turn, climb or descend.
In contrast, a helicopter remains in the air by driving air, from above, down through the engine-driven, variable-pitch rotor system. The rotor disc is tilted forward to obtain forward propulsion, or in any direction in order to manoeuvre.
Gyroplane lift & propulsion
Helicopter lift & propulsion
Because of the way lift and thrust are generated, a gyroplane is simpler and safer to operate and maintain than a helicopter (and many fixed-wing aircraft.) Since the gyroplane rotor auto-rotates, there is no need for the complex transmission system and anti-torque device (e.g. tail rotor) found on helicopters, making the gyroplane a more stable flying platform.
Helicopters displace air downwards through their engine-driven rotor which gives them the ability to hover, but this single advantage of helicopters is offset by the many drawbacks associated with the complication and expense of the fully-articulated, powered rotor systems required . . . the ability to hover is necessary in only a very limited number of situations (i.e. rescue or sling-load work) in any event!
If the engine should fail, a helicopter must perform a difficult and time-critical transition to autorotation while, should the same unfortunate circumstances befall the gyroplane, one would merely remain in the autorotative state and easily manoeuvre the aircraft into a safe forced-landing in any available (very!) small, clear area.
Gyroplane lift & propulsion