Pre-rotate before entering runway

MonkeyClaw

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What's the deal with pre-rotating before going onto the runway? I thought it was common practice in some countries to get the rotor moving before entering the runway for takeoff. I know there are some busy airports where it would be very useful. At the same time, I'm not a big fan of taxiing around much with spinning rotors if it can be avoided.
 

WaspAir

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Most tower controllers can handle a short delay while in "line up and wait" condition while you spin up, if informed in advance of that request.
 

MonkeyClaw

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I'm thinking more about busy, uncontrolled airports. My home airport will sometimes have multiple people in the pattern and waiting for departure. To add to the fun, calm wind departure runway is 21 while calm wind landing is 03 (due to a sloped runway).
 

Vance

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In my opinion the reason many pilot's operating handbooks (POH) advocate for stopping on the centerline to pre-rotate is because it reduces the complexity of the pre-rotation and takeoff.

Because the takeoff is a common phase of flight for gyroplane mishaps reducing the complexity and task saturation is a positive thing.

The down side of stopping on the runway to pre-rotate at a non towered airport is you are stopped on the runway with your back to traffic and a gyroplane on the runway is a difficult thing for landing traffic to see.

Gyroplanes are uncommon so it is likely other pilots in the pattern have no idea what you are going to do when you announce “delay on runway for pre-rotation” as part of your lining up for takeoff radio call.

The down side of pre-rotating on the roll with an engine driven pre-rotator is you have to be careful to manage your throttle as you line up for takeoff and it is hard to focus properly on the pre-rotation goals while you are managing a moving aircraft.

If I am instructing in my clients aircraft; I follow the POH for that gyroplane.

I prefer to pre-rotate on the roll at non towered airports.
 

BEN S

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I had a meeting with the tower chief and described the situation prior to using the runway. It has worked out well even if it means waiting for a bit for other traffic.
When I am at an untowered airport, I line up with my wheels all the way to one side of the runway and a little cattywompus (technical term) so I can see whats coming. Stay on the comms and rotate up the blades. Only once did I have a 172 land (technically an incursion but were all friends here) the look on the pilots face let me know he realized what hed done! gyros a re small and manuervable and your life is at stake, don't let "conformity pidgeon hole you into doing something that can hurt you.
 

BEN S

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It's technical, you wouldn't understand.....;)
 

JETLAG03

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I suspect that spinning the rotors to 50-60rrpm for the taxi on grass reduces the stress on the rotor blades bouncing up and down and also adds another level of stability due to the gyroscopic effect of the disc. I am fortunate, if I choose to enter the runway and pre-rotate from zero our traffic is so low that a delay of 60 seconds normally causes no issues
 
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GyroCFI

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in the J-2 you were supposed to pre-rotate to 150 RPM IIRC when taxiing over grass/unimproved runways.
 

Doug Riley

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I try to inform FW pilots who might be using the runway at the same time as me about my operating needs. I bring it up at the morning pilots' briefings at flyins, for example. The "special needs" I announce include (1) the delay caused by prespinning, (2) my close-in patterns, and (3) very steep approaches.

(#3 has caused more trouble than anything else; I've had fast FW planes do their finals UNDER me and land in FRONT of me while I'm on short final in a gyro. They are watching the numbers and don't look ABOVE them for something descending steeply toward the same spot. I've developed the habit of frequently turning around and looking behind me, up the "10-mile final" glide slope when on final. Many fixed-wingers turn final in the next county over.

I always prerotate at idle power before rolling away from the startup area (unless airport or flyin rules prohibit this). It's easier on the blades. I taxi at this low RRPM to the end of the runway and pull off the taxiway/runway. IOW, I don't prespin while sitting on the active, or at downwind end of the taxiway. If a FW plane is taxiing for takeoff behind me, I will radio or wave for him/her to go ahead, if desired. I only roll onto the active when I've achieved my target RRPM -- at least 180 RRPM and over 200 if possible.

With prerotator engaged, ground steering is strongly biased by the torque; when in a gyro with non-unitized steering, I switch to rudder ASAP.
 

DavePA11

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In the Sportcopter M912 I was not able to taxi while prerotating since the nose of the gyro would tend to pull in opposite direction so I had to go onto runway and then pre-rotate.

I also saw an accident where a gyro started to pre-rotate before entering the runway and lost control where applied too much power.

I think it’s safer to taxi on the runway then pre-rotate, but depends on the capabilities of the gyro and pilot.
 

Tyger

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when in a gyro with non-unitized steering, I switch to rudder ASAP.
Doug: Can you explain what you mean in a bit more detail? "Unitized"?
Dave: Can you describe what exactly happened in the accident you saw?

I always prerotate to 100 rpm, with stick all the way forward, before entering the runway. After about 100, it's safe for me to tilt the rotor all the way back, at which point I really want to be facing into the wind. Once on the runway, with any significant wind, it spins up to 220 pretty quickly, and that is usually the rpm where I start my takeoff roll.
 
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Doug Riley

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Tyger: On the earlier Bensens and on Dominators (to name two I've owned), there are separate ground-steering and rudder controls. On the Bensen, the ground steering was via a simple steering bar attached to the nosewheel fork. You could steer with your heels, or drop your feet down to the bar and steer with your toes. Either way, you had to select the moment when you switched to rudder steering. That's what I meant by "non-unitized."

On the Dom, ground steering did not connect to the nosewheel; rather, it was differential braking on the mains. The (separate) brake pedals could be either heel brakes or toe brakes (my tandem had toes in front and heels in back). Again, you had to pick the moment when you switched to rudder steering.

Some people found the Bensen steering bar to be backwards (push right, go left) -- even though the steering "sense" was the same as bike handlebars. Others found the extra workload on the pilot (determining when to switch steering controls) objectionable. So Bensen came out with what he called "unitized" nosewheel and rudder steering. The link from the pedals to the nosewheel was soft enough that (one hoped) the nosewheel would straighten out when it touched the ground if you landed while holding hard rudder in a slip.

If the "unitizing" link was just a wee bit too stiff, the gyro could swerve when you touched the nosewheel down with rudder applied, resulting in a capsize. I had a close call or two under these circumstances on my Air Command, which came with spring-linked unitized steering.

I went back to the separate-control setup for my personal Gyrobee, although the plans call for unitizing links.

There's no doubt that the separate-controls version requires more practice. In my opinion, though, it's worth it, both in prerotating and in crosswind landings. I mastered the Bensen version by go-karting my gyro around without blades for hours, probably annoying my neighbors greatly.
 

Tyger

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Thanks for the explanation. My nosewheel is linked to my rudder. Even coming in with a lot of crosswind (and thus rudder), the castered nosewheel straightens out as soon as it touches. I keep a light touch on the pedals and when it touches I just let them push my feet where they need to go. I have never had any problems with swerving, happily.

As far as prerotating, I don't usually do that while moving, except while crossing the hold-short line to line up (as discussed previously), but on occasion I have got it spinning while taxiing, and I have not noticed any special steering issues from so doing. I can imagine how this could be trickier with differential steering and a free nosewheel, however.
 

Doug Riley

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Right, a gentle spin-up while taxiing (say, at idle or just above ) will not affect steering much, if at all. Taxiing with blades turning is a grass-strip habit that I've simply carried over to paved strips. On really smooth pavement, it isn't necessary, though.

Where the steering gets more challenging is in a prerotator-engaged takeoff run, with coal duly poured on. The Wunderlich, RFD/Dominator hydraulic, and the Butterfly Metro-launch prespinners all allow this type of takeoff. Between the torque and the fact that the nosewheel is getting light, rudder steering is essential at this phase. The Bendix will drop when airflow overtakes the prerotator, or you can release the clutch at a time of your own choosing -- be ready for a power surge as the engine offloads.

I've done this type of takeoff in the Air Command, with unitized steering. I don't recall any steering issues. The steer-swerve issues on the that gyro arose in cross-wind landings. Feet-light-on-pedals sounds like a good precaution when landing with unitized pedal steering.
 

WaspAir

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If you try to taxi an A&S 18A with the spinup clutch engaged, you will make amusing little circles on the ramp for everyone's entertainment, and get nowhere near your destination.
 

Doug Riley

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Yes, but that A&S has one monster prerotator! Our weed-whackers deliver a few horses at most. That's why keeping them engaged during at least the initial phase of the takeoff run pays dividends.
 

WaspAir

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I went through that little dance while in the back seat (no spin up controls there) with none other than John Potter flying from the front (4000 hours in type at the time). We had a good laugh after he suffered a moment of puzzlement as to why he couldn't taxi straight, until he finally noticed that the glowing clutch button was crying out to be pressed (the depitch, rotor brake, and clutch buttons are all internally illuminated when active). It was a useful reminder about checklists/panel flow being a good idea even for the most experienced of pilots.
 
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