#### Jean Claude

##### Junior Member

- Joined
- Jan 2, 2009

- Messages
- 2,204

- Location
- Centre FRANCE

- Aircraft
- I piloted gliders C800, Bijave, C 310, airplanes Piper J3 , PA 28, Jodel D117, DR 220, Cessna 150, C

- Total Flight Time
- About 500 h (FW + ultra light)

Let me evaluate very roughly the possibility of takeoff with no run by pitch setting jump:The total mass of the current rotor of Michel is 40 kilograms, each composite blade weighs 10 kgs

Assuming the rotor pitch is adjusted abruptly to lift the weight of the gyrocopter in hover, the time during which the rotor energy due to overspeed will be available depends on the average power input:

For an 8 x 0.2 m rotor the power input is about 20 kW (IGE) at 450 rpm, while the stored energy is 0.5* I *(ΩMax^2 - Ω min^2) or

**50 kJ**if I = 100 kg.m2, Ω Max = 47 rd/s, Ω min = 35 rd/s

So t = Estored / Pabsorbed = 50 kJ / 20 kW =

**2.5 s**

If the horizontal speed required to hold the level is assumed to be Vmin at rrpm min and the propeller thrust (2000 N) gives an average horizontal acceleration of 6.5 m/s2 on the 300 kg mass, the forward speed will have reached VH = 6.5 m/s2 * 2.5 s =

**16 m/s**just required when the rrpm will have decayed to that of the autorotation (Ωmin). The flight can then continue in full autorotation.

In this scenario, there is not really a jump, but a continuous slope from the stop.

A small jump is possible if we take into account the transient increase in lift due to the more slow progression of induced velocity.

But I not knows make.