Gyroplane Training 
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Web by: Rebel Systems Training Days April 7 - 22 2001 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 May 26 - June 2 2001 April 1 - 11 2002 |
Day 9 Forecast for today is again not good, so it might be a theory day. Roger mentioned that the aerodynamics theory was the first to be done, so that should be good. Forecast - gusting 40 knots and rain. It's already 15 gusting 25, and going up. Ok, so theory it is. First stop the powered rotor of the helicopter. The main difference here is the air enters the rotor disc from above. New terms were introduced, like the angle of attack being the angle between the chord and the resultant air flow, and the pitch being the angle between the chord and the rotor disc plane, and how an airfoil section works by faster air over the upper surface lowering the air pressure causing a differential with that on the lower surface.
From there we moved onto the autorotative force and how the rotor system driving itself around can be explained by looking at a vector diagram of the forces acting on the rotor, and once resolved found some motive force left over which provided the rotor torque. This was that left over from the lift/drag vector, to axis of rotation ie rotor thrust line.
We then moved on to an analysis of the autorotative force spanwise along the blade and how near the root it was stalled, the center section providing the driving, autorotative force, and the outer section being the driven section. We also explored ways of extending the autorotative force further to the rotor tip by twisting the blade nearer the tip so the pitch angle was reduced as in Dragon Wings, and/or reducing the chord length as typified by sailplanes which greatly reduces tip vortices as the air pressures above and below the rotor try to equalise.
Then for a look at the teetering effect. Causes being the differential lift caused by the advancing and retreating blade, such that the advancing blade rises, and in so doing its angle of attach diminishes so reducing the lift. This results in the rising blade finding a point of equilibrium and rising no further. The same is true of the retreating blade, except it goes down due to lowering lift. It is interesting to note that the maximum teeter is for/aft, and the maximum rate of change of teeter is left/right. Maximum flap angle is also at the front diminishing as it retreats.
This afternoon is beginning to brighten up. Wind has dropped to 10 knots, gusting 15 so the front looks like it has past. A few hours more, into this evening and things should have settled to allow us to make use of it. We'll see! We then have lunch, followed by the gyroplane technical theory paper. Both Neil and myself pass that. I have a dispensation from all the other papers as I took them for my triking PPL, so I'm done with the papers now. Had to give a talk on differing aurorotative forces acting on a rotor to finish off the theory. (Chris likened that to the Muppet show!). Got that signed off now. Phew! Unfortunately the wind is building again so we pass on flying and end the day early. Tomorrow is to try out my new found feet, takeoffs, engine offs. Hopefully on the single seat soon! As an aside, a Chinook flew in. They are BIG.
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