High Speed Blade Flap would be my guess. [so shoot me for speculating so shamelessly, I dont care
Statistically it is evident that the following is true:#1 cause of gyro accidents:
Flying into Wires#2 cause of gyro accidents:
Flying behind the power-curve (too low too slow)#3 cause of gyro accidents:
Rotor mismanagement on the ground
Fatality probability is higher the lower the number above.
Gyro's all essentially behave the same, no matter what the make or model. This is not about a specific manufacturer or configuration. All gyro's will experience the same given the same circumstances.
From the FAA rotorwing handbook:
On a gyroplane with a semi-rigid, teeter-head rotor system,
blade flap may develop if too much airflow passes
through the rotor system while it is operating at too low
r.p.m. This is most often the result of taxiing too fast
for a given rotor speed. Unequal lift acting on the
advancing and retreating blades can cause the blades to
teeter to the maximum allowed by the rotor head
design. The blades then hit the teeter stops, creating a
vibration that may be felt in the cyclic control. The frequency
of the vibration corresponds to the speed of the
rotor, with the blades hitting the stops twice during
each revolution. If the flapping is not controlled, the
situation can grow worse as the blades begin to flex and bend."
The higher the speed the more violent the flap. At 60mph the average gyro's rotor speed should be around 350+. Any less angle of attack to lift the machine off the ground at that speed is very risky. Remember gyroscopic-precession will happen 90deg later. In a counter-clockwise rotation system, high speed blade-flap will probably result in a roll-over to the left (I think).
"Decreasing the rotor disc angle of attack with forward cyclic (stick full forward) can reduce the excessive amount of airflow causing the blade flap. This also allows greater clearance between the rotor blades and the surface behind the gyroplane, minimizing the chances of a blade striking the ground."
This is basic stuff actually. If you understand the aerodynamics it can't happen to you. You wouldn't jump off a cliff with a half inflated para-glider wing would you? Open the 'chute' with the stick back, balance , hold, then take off safely.
Question 10 in our Student Pilot Licence
10. When rotor flap is experienced, what can be done to prevent it from continuing or getting worse?
a) Stick back, power off and hit the brakes
b) Stick forward increase power and apply rotor brake
c) Stick forward, cut power and hit the brakes
The answer has to be right before the student officially commences with his training. If he doesn't get it by the time he wants to start training, he should go play golf.
The value of practicing wheel balancing during instruction cannot be over-supported and should form part of the taxiing syllabus.
If you play a game with yourself and lose a point every time the nose wheel touches down after initial lift off, or the tail wheel drags, then you can begin to score your own ability. The same applies on landing. If your attitude and airspeed are right for the round-out & hold-off, the main wheels will touch first, steering with pedal to remain on the line you hold the nose off until the stick is full back and the nose-wheel 'plops' down on its own. You will be stationary by then. 10 points.
Stick forward, no angle of attack, no danger of further blade flap.
Perfect safe landing.
Try it and lets fly safer!