By Rob Coppinger in London
New design requirements for gyroplane blades are expected to emerge from a UK Civil Aviation Authority-funded three-year rotor behaviour research project at the University of Glasgow. The CAA decided to fund the research when a study of the 200 gyroplane-related fatalities since 1966 found a possible common cause – powered pitch-over.
The work began in mid-2005 and an early conclusion is that blade pitch changes due to unbalanced aerodynamic and mass centres can cause uncontrolled rotor acceleration or a dramatic loss of speed. In particular, excessive blade tip mass appears to cause the blade to pitch down and create a runaway acceleration. Aft blade mass can also cause an oscillatory divergence, which causes a sudden blade slow-down.
New design requirements could define blade stiffness and mass balance parameters as the research is beginning to show that some combinations are more vulnerable to pitch instability. Modelling so far has examined blade elastic and mechanical degrees of freedom with simplified aerodynamics.
Source: Flight International
