Pre rotation

[steveh]

Hi there, Newbie here. Just getting interested in gyros.

Question.

Gyro pre rotators spin up the rotors to enable a shorter take off run. Why don't they spin the rotors up to an RPM sufficient to enable vertical take off, or at least just get the aircraft off the ground so that no take off run is required ?

Thanks.

[RossM]

Hi Steve, and welcome.
Gyro's do not have a tail rotor like a helicopter to stop them from spinning around

[RickE]

Hi there, Newbie here. Just getting interested in gyros.

Question.

Gyro pre rotators spin up the rotors to enable a shorter take off run. Why don't they spin the rotors up to an RPM sufficient to enable vertical take off, or at least just get the aircraft off the ground so that no take off run is required ?

Thanks.

Welcome Steveh,

Gyros are unique aircraft which unlike helicopters have fixed pitch rotor blades and require air flow through the rotor system from underneath in order to keep the unpowered rotor spinning and create lift.
There are some gyros that have collective type control which are able to change rotor pitch for a short time enabling them to get airborne before moving forward.
We can land and takeoff vertically, we just have to wait for a day with 25-30 knots of constant "breeze"

[steveh]

Thanks gents,

So do those gyros with collective pitch have powered rotors ? If so how do they cancel the torque of the rotor ?

[Tim]

When the collective is set to zero lift the weight of the gyro stops it spinning while the rotors are spun up to a tad over flying speed The rotor drive (torque) is then disconnected before the pitch is increased.

[steveh]

Got it, thanks.

[tonydenton]

I washed my rotars on sunday after a fly and thought I should dry them before I put their PJ sleeves on that ross's lovely wife mariann made for me . so without the prop running I spun them up using the pre rotator . very interesting to see the iniatal schock engagement and load on the mast area. something you don't normally see when your sitting in the seat with the engine running. something that gives you a bit more respect especially for the higher turning ones. obviously mine just engages the starter motor pre rotar and is not a soft start. back in one of the magazines rossco [ the original rossco that never crossed to the dark side like another rossco on the forum ] showed how he did a test of torque. [ you should remember it TIMMY ] I couldn't help thinking how clever the test was and how he come up with the idea. says a lot about the man.
and me too because I liked it and can still remember it . I wish he would answer his e-mails thou.