Aviator168-aircraft
Active Member
Just curious. Anyone here studied the translational lift generated by a gyroplane rotor system. Like percent of total lift attributed to the forward motion of the gyroplane.
What about during a vertical descent in which a gyroplane has no forward speed?100% of the lift generated by a gyro rotor in level flight is due to the deflection of the 'relative wind' downwards. Here's a drawing due to Jean Claude:
View attachment 1155826
That's an special case. The rotor is powered by the relative wind blowing from below the disk, and the rotor does indeed produce a certain amount of lift, that has the same value and opposite direction as the weight of the gyro. Hence, the machine falls at a constant velocity...What about during a vertical descent in which a gyroplane has no forward speed?
It is enough to consider the speed in relation to the upstream infinite, and the angle of the disc in relation to this speed.
For example in vertical descent at Vz =-10 m/s, we have Vupstream= +10 m/s and A.o.A = 90 degrees.
This case can be treated like any "forward" flight.
Of course since the drag is always the force opposite to this speed and the lift is always the force perpendicular, then in vertical descent, it is the drag that will oppose to the weight, while the lift will be zero
The blades of a gyroplane rotor work exactly the same way as the wings of a glider. Both lift and force to spin the rotor, as well as drag are produced.It is enough to consider the speed in relation to the upstream infinite, and the angle of the disc in relation to this speed.
For example in vertical descent at Vz =-10 m/s, we have Vupstream= +10 m/s and A.o.A = 90 degrees.
This case can be treated like any "forward" flight.
Of course since the drag is always the force opposite to this speed and the lift is always the force perpendicular, then in vertical descent, it is the drag that will oppose to the weight, while the lift will be zero
The blades of a gyroplane rotor work exactly the same way as the wings of a glider. Both lift and force to spin the rotor, as well as drag are produced.
XXavier,
I do not agree verticle descent is a special case. The rotor works exactly the same way regardless of whichever direction the gyroplane is flying in.
If you do a blade element analysis, everything is the same and what is changing are the environmental parameters. Better yet, put the rotor into a CFD simulation, and you can see how autorotation works. Need to stop looking at the rotor as a disk.
In my opinion a gyroplane does not experience the effect of translational lift because a gyroplane does not takeoff from a hover.Just curious. Anyone here studied the translational lift generated by a gyroplane rotor system. Like percent of total lift attributed to the forward motion of the gyroplane.
If you send me your e-mail address, I can send you my calculation file of a rotor in forward flight with 11 elements per blade and 24 azimuth positionsIf you do a blade element analysis, everything is the same and what is changing are the environmental parameters. Better yet, put the rotor into a CFD simulation, and you can see how autorotation works. Need to stop looking at the rotor as a disk.
Xavier,
Due to the high forward speed the environmental parameters of the rotor are very similar to those of a solid disk i.e lift mainly due to deflection, as showed in this sketches.
But the difference with the solid disk becomes progressively more pronounced as the angle of attack increases, due to the thrust due to slow down of the airflow through the rotor.
Only beyond 70 degree, the slowdown flares the air flow so much that a certain discontinuity appears.
View attachment 1155996
Yes XXavier. One cannot simply look at the rotor as a disk. You can have a rotor with more than 2 blades but still, have the same disk area. I took the data of Cavalon at gross weight. If the rotor is considered a flat plate, descending from 3000 ft, the vertical descent rate is more than 2000ft/m.I believe that the disk behaves like thrust-generating element, and not as a drag-generating parachute. Yes, I know that the drag coefficients are similar, but disk and parachute are essentially different. In my opinion...
Hope you don't mean SPIN as the way a fixed wing does.Generally speaking I do not do zero airspeed vertical descents in a Cavalon during training because all of the Cavalons I have flown (7) will spin in a zero airspeed vertical descent.
A T-10 parachute descents at about 1400ft/minuteOnce, years ago, I made a couple of tests of vertical autorotation with an ELA, but got scared and gave up when passing the 1000 ft/min mark, more or less. The gyro yawed perceptibly, too. The 'terminal velocity' for a pilot-only ELA is probably 1500 ft/min...
I fully agree with this, and this is the reason why the maximum lift coefficient of the rotor relatively to the swept disk area is much higher than that of a solid disk in forward flight.I believe that the disk behaves like thrust-generating element, and not as a drag-generating parachute. Yes, I know that the drag coefficients are similar, but disk and parachute are essentially different. In my opinion...