The Art of the Helicopter John Watkinson - Karatunov.net

348 The Art of the Helicopter
were unsuitable. Once the true helicopter was developed, the gyroplane could not compete
and its market contracted dramatically. The basic problem is that the rotating
wings introduce some of the high stress, the mechanical complexity and the high maintenance
regime of the helicopter, for which there is no compensating ability to hover.
In gyroplanes having pusher propellers, the visibility from the cockpit is truly excellent.
It has had some success as a recreational machine and in applications such as aerial
photography where slow stable flight is an advantage, but has effectively been eclipsed
by the helicopter.
The gyroplane rotor experiences the same advancing/retreating and gyroscopic phenomena
as the helicopter, in fact most of these were first discovered in the gyroplane.
One does, however, tire of reading quite erroneous descriptions of how Juan de la
Cierva’s machines rolled over because of the lift difference between advancing and
retreating blades. It is well established that the lift difference between advancing and
retreating blades may result in a roll couple, but this is subject to the gyroscopic phase
lagof90 ◦ that results in flapback. Clearly the advancing/retreating asymmetry was not
the origin of de la Cierva’s difficulty.
Figure 9.1 shows that de la Cierva’s early machines were basically aeroplanes having
conventional aircraft controls but with a rotor added. The early rotors were hingeless
and acted like gyroscopes. The problem was simply that when the conventional elevator
was operated, a pitching moment was applied, but the rotor would precess this into a
roll. Equally the operation of the ailerons would result in a rolling moment that would
precess into a pitching motion. This was not a novel phenomenon; some World War
I aircraft having rotary engines were notoriously gyroscopic and displayed precession
whereby use of the elevator would cause an amount of yaw.
Fig. 9.1 An early de la Cierva autogyro having wings and aircraft-type control surfaces.