ROTORS turning or static whilst taxiing ??

JETLAG03

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Jul 6, 2019
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france
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300+ flexwing (pendulaire) newly trained on gyrocopter ((autogire)100h)
Hi Folks.

I often spin my rotors up to 50rrpm (ish) when taxiing on grass for the runway thinking that slowly spinning blades suffer less than those at rest when taxiing. Am I mis-informed and if so why??

phil (de fer)
 
I taxi for takeoff with my rotor fore and aft, brake on, and the stick can jerk around quite a bit when going over bumpy turf. After landing, though, the rotor is spinning while I taxi off (there's no actual distinction between runway and taxiway at my home field) and I don't get those same kind of jerks till the rotor gets below about 100 rpm (I cannot read rotor rpm after I put the rotor brake on). I'm rather more worried about stresses on the hub than on the blades themselves, though.
I think my composite rotors are fairly heavy compared to extruded aluminum, though, so my experience may not be typical.
 
I taxi with my blades turning about 65 RPM. The RPM is settable since it is electric. I think the blades turning is less harmful on the bearings since there is no brinelling. Brinelling is when the bearing balls are hammered on exactly the same spot on the bearing race over and over which would be the case if the blades were attached and locked while getting hit by bumps in the road. Taxiing with the blades locked is similar, but generally less impact and less duration than over the road travel as I see it.
 
I have heard that with the rotors turning and some lift being produced, the blades flex less than stationary ones will over rough ground, the bearings suffer less, and, part of their weight is being supported by the lift being generated.
 
A slowly rotating rotor during taxi can catch breezes easier and result in flapping....we had someone knock a tail off due to a gust...rotor was probably 50-60 rpm. Can be done....must use extreme caution.
 
100 RRPM is the minimum to taxi with rotor blades spinning, otherwise they can flex when you hit a bump (we operate on a grass strip). If less than 100, we stop, wait for rotors to stop turning, then taxi with stick full forward.
 
I taxi for takeoff with my rotor fore and aft, brake on, and the stick can jerk around quite a bit when going over bumpy turf. After landing, though, the rotor is spinning while I taxi off (there's no actual distinction between runway and taxiway at my home field) and I don't get those same kind of jerks till the rotor gets below about 100 rpm (I cannot read rotor rpm after I put the rotor brake on). I'm rather more worried about stresses on the hub than on the blades themselves, though.
I think my composite rotors are fairly heavy compared to extruded aluminum, though, so my experience may not be typical.
Mine are resin
 
On any ramp where there could be people or ground vehicles, I would advise blades not turning for safety, regardless of the bearing issue. My practice has been to pull off the runway, stop, and do a configuration clean-up (reset transponder, apply rotor brake, adjust mixture, etc, much like pulling off to retract flaps on a fixed wing) before continuing to parking. Likewise, on the way out, I don't start blades turning before reaching the run-up area.

If you fly out of a pasture, such concerns might not apply.
 
There are cases for both taxiing with a stationary rotor, and for with one in motion.

Perhaps an example that one one technique may not suit all situations, and that a good pilot assesses, understands, and can sensibly, and safely, adapt to cope with prevailing circumstances.
 
On any ramp where there could be people or ground vehicles, I would advise blades not turning for safety, regardless of the bearing issue. My practice has been to pull off the runway, stop, and do a configuration clean-up (reset transponder, apply rotor brake, adjust mixture, etc, much like pulling off to retract flaps on a fixed wing) before continuing to parking. Likewise, on the way out, I don't start blades turning before reaching the run-up area.

If you fly out of a pasture, such concerns might not apply.
I agree... and it's only on bumpy "pasture" taxiways that it bears consideration, IMO.
 
I keep them spinning at the RRPM I can get with prerotator engaged just at idle engine RPM. I typically fly from grass; not all of it smooth. I don't care for the look of static blades bending wildly as I taxi over the bumps. Even a little centrifugal stiffening helps. You must remain aware of the wind direction and speed to avoid (OK, minimize) flapping and hard contacts with the teeter stops.

At flyins, stopping the rotor before entering the apron area is typically mandatory. That's understandable.
 
Once I am clear of people and other machines, I spin up the blades to 100 or more RRPM and taxi to the end of the runway with the blades spinning.

You have to be mindful of RRPM not to flap the blades, but oftentimes by the time I reach the runway the blades are well above the speed needed for further prerotation and I can just turn onto the runway and take off.
 
Exactly! You can even air-taxi a light gyro on your back-taxi run if conditions are right and the natives are friendly. Saves time and wear on the prerotator.
 
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