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.’
Gyroplanes enjoyed initial popularity before a shift in focus towards helicopter development, necessitated by the onset of WWII, resulted in limited development and war-time service for gyroplanes.
During the 1950’s, the popularity of gyroplanes was revived by Dr. Igor Bensen, following the development of his B-7 & B-8 model ‘gyrocopters,’ building-plans of which were published in “Popular Mechanics” at that time.
Cierva C-3 Autogiro
Gyroplane, gyrocopter & autogyro (or autogiro), all refer to this specific type of rotary-wing aircraft, which obtains lift (to overcome gravity) from an air-driven, ‘auto-rotating’ rotor, while thrust (forward propulsion) is delivered by means of an engine-driven propeller.
The fixed-pitch rotor of the gyroplane is driven to auto-rotate by a continuous flow of air moving, from the front, through the rearward-tilted rotor. This air is then deflected downwards behind the aircraft as it is propelled forward through the air by an 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 (in the ‘driven’ region of the disc) to oppose the aircraft weight but, also, via the horizontal component of this lift produced by each blade, generates a rotational impetus (in the ‘driving’ region of the rotor-disc). This ensures that the rotor is always rotating at the required flight RPM.
The teetering action of the gyroplane ‘rigid-rotor’ system, allows the blades to ‘flap’ up and down during the rotational cycle, thereby automatically compensating for asymmetry of lift – i.e. the teetering action accommodates 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 slightly adjust the rotor disc angle 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 in order to generate lift. The asymmetry of lift is compensated for by a complex, ‘swash-plate’ controlled, variable, collective-pitch mechanism which must adjust the individual blade pitch-angle, according to the rotor-blade’s position in the disc-azimuth.
The rotor disc must be tilted forward to obtain the thrust required to move forward and, simultaneously, in the lateral direction required to manoeuvre as desired.
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 (i.e. tail rotor) found on helicopters, making the gyroplane more economical to purchase, operate and maintain.
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 complexity 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 . . . should the same unfortunate circumstances befall the gyroplane, one would merely continue in the autorotative state while easily manoeuvering the aircraft into a safe forced-landing – even at low-level! Alternatively, if height permits, one may simply select a forced landing field while maintaining a slow, controlled vertical descent until correctly positioned on the required final glide-approach path. Thereafter, forward speed is regained as the rotorcraft is flown down this glide-slope onto the selected forced-landing area required.
Should the pilot mis-calculate or mis-manage the forced-landing, the robust uTe construction methods and materials are able to provide credible protection from any low-energy crash-landing which may result!
Robust Construction Features