Jump take-off vs. rolling take-off

With three bladed jump take off gyros,

With three bladed jump take off gyros,

if the engine quits during the jump or it settles back down during the jump the blades can go out of phase and in a matter of seconds the blades will beat the gyro to pieces. I know of one that did just that.
It was an old Air & Space 18 A gyro. The owner had placed a notice in the cockpit forbidding jumping but one day the owner himself jumped it and at about 3 feet AGL it settled back to the runway and tore itself to pieces .

Marion

Vance,

I think, it is not much different with the Xenon takes-offs,
but Raphael just wants me to be 100% on the safe side.

So we do prerotate to 3000 engine RPM before we start rolling,
the rotor starts pulling up and back quite strong, before you
reach the 75kpm (40knt) Raphael recommends for lift-off,
you have quite to struggle to keep the front wheel down
and keep it rolling in a stable way.

The balance between keeping the rotor loaded (back stick)
and keeping the front wheel down (centre stick) is not that easy.

If you do it wrong, you end up in the air with to low speed or too slow rotor,
both quite unpleasant and potentially catastrophic.

StanFoster said:

In my opinion, if you are in a helicopter hovering at 100 feet at 0 mph, or in a gyro that just did a jump takeoff vertically to 100 feet expending all its extra rotor energy, if either loses an engine, both are in serious trouble. Stan

Click to expand...

Stan,

in a gyroplane jump take off, before you reach 100ft
it will take you a few seconds, during which you are
at full throttle and prop thrust.
It means, at 100ft you should have already app. 20-30knt
ground speed, if you take off into a substantial wind,
it could be even more air speed.

Then you are more on a safe side, than in a hovering helicopter.

I don't think anybody would attempt jump take off without full throttle.

The video of the Carter demonstrator going 100ft straight up and then
back straight down again, was rather to show the G-landing gear function,
not the jump take off, as it should be done.

YouTube - ‪CarterGyro Demonstrator Jump Takeoff Gyrocopter‬‏

On the other hand the PAV videos of jump take-off, show just 30ft jumps,
but at this altitude, they have already a substantial air speed.

YouTube - ‪Carter PAV Phase I Flight Testing Highlights‬‏

Paul, there seems to be significant wind in the first video. That gives you immediate airspeed when you lift off. The jump and the ensuing vertical drop-down landing probably would look a bit different without wind.

-- Chris.

Chris, good point.

Lots of parameters changed . . .
There is a gyro at 100 ft, the pilot is competent, engine went quiet
Now the gyro has three blades . . .
Keeping all the same, what is the discussion about?
Harder to jump? Harder to roll jump?
Still I think it is a matter of choice or need . . .
No skills, no go!
Heron

To me, a gyro equipped with all the necessary stuff to do a jump takeoff, would be a pig. You might as well fly a Cherokee or something.

As a FW pilot I find the rolling gyrocopter take-off a difficult
and dangerous procedure compared to FW.

In the FW you just watch V1, take off, level to Vx and up you go.

Click to expand...

You just encapsulated for me the huge fascination and attraction to gyros. After 40 odd years of aviation in various forms I had now found a machine that was rather like the 'rub your tummy pat your head and recite the alphabet backwards.' It was totally fascinating and a challenge rather than a put-off, and why I then got into gyros.

The next attraction was the agility and high wind tolerance in light sport machines of the gyros.

Yes I was attracted by the Carter demonstrator jumping vertically to 200' but then found out the cost. The rigidity imparted by the rotor tip weights cuts down agility by a considerable degree.

As far as jump/short take off, to my mind Larry Neals Metro launch looks probably the most effective with a normal rotor. Close might probably be the Goped type.

Prerotators on many amateur-built gyros are inadequate. Many of the problems that Paul points out can be eliminated with an adequate prerorator and the simplified technique that it allows.

On a light 2-place gyro, the prerotator should be capable of providing at least 200 RRPM. This puts the rotor past a speed at which flapping is easily achieved.

The aircraft needs brakes that are adequate to hold it against the prop thrust while pre-spinning to 200 RPM.

The prerotator should be designed with an automatic release or overriding clutch (such as those in Bendix drives), that allows the pilot to keep the prerotator engaged during the beginning of the taxi run. This serves two purposes: it increases RRPM quickly as forward airspeed adds to the drive of the prerotator. It also governs the engine, making it run slower even with a high throttle setting. This helps the pilot avoid overrunning his blades and therefore further reduces the chance of blade flap.

I am surprised to hear of expensive, cabin-class 2-place gyros that have 125 RPM prerotators. Of course you can fly with these units (or with hand-spinup, for that matter), but they are not game-changers the way a more powerful prespin is.

As I see it, the biggest downfall of the normal pre-rotators is the added torque required due to the positive pitched blades.
With the rotor system I'm using, setting the 0012 blades to stay at 0° pitch for spin-up and rotating to a positive pitch during rollout is not a problem.
Changing blade pitch is a problem when using the Bensen rotor system but I can't see where it is insurmountable….especially when it would be so beneficial to start a single place rollout at 300+ rotor rpm.

http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=14427


The link above is for an RC motor but it seems like the current designs of brushless DC motors has really evolved. Would something like the above be compatible for a prerotator drive and if so what could rrpm could one expect on something like a SportCopter Vortex?

Paul, your over complicating things.
Once youv dun it a few times its no more demanding than walkn.


Manual collective feed instead of a preset 'flick a switch/leaver' to change to autorotion pitch will give you much better control over how fast you burn up inertia and how high you jump for a vto gyro. Also gives more options at the flair.

Synchronized jumping:

YouTube - ‪Two Gyros - Jump Takeoff‬‏

I personally have no experience with a jump takeoff Gyro, but I have talked to Larry Neal about it and he has a lot of experience with it. He is currently the chief test pilot for the Carter PAV. While he thinks jump takeoffs are fun and can add some capability to a Gyro, he also feels like they add complexity to the take off, and require a lot more skill to successfully accomplish.

That is why he designed his Gyros with the Metro Launch pre-rotator. It is a powerful pre-rotator that takes the rotors to near flying speed (about 300 rrpm) before you ever start your forward roll. This eliminates the danger of blade flap and shortens the takeoff roll to about 100 feet (in calm air). He has automated the process to make it very simple and reduce the chance of pilot error. He feels is is the best compromise and it sure makes sense to me.

The windsock can be see at 1.24 in the video.

"Per FAA standards referenced below, a 15-knot (28 km/h; 17 mph) wind will fully extend the properly functioning windsock. A 3-knot (5.6 km/h; 3.5 mph) breeze will cause the properly functioning windsock to orient itself according to the wind."

How effective are jump takeoffs at gross weight and zero wind speed?


Dave

Doug Barker, the Metro-Launch is one of a couple brands of prerotator that meet the criteria I was ranting about earlier. It (and they) don't require collective pitch. That keeps things simple both mechanically and operationally. They do require good brakes, though.

I have not found the torque unmanageable when keeping a strong prerotator engaged during the takeoff run -- although the torque certainly makes itself known. You need rudder, but a well-designed rudder is quite effective with the throttle up where it needs to be anyway to run the prespin.

Thanks all of you for your interesting remarks.

Birdy is probably right, this is beginners trouble,
should be gone soon...

At the beginning of commercial airline operations, it was thought that pilots couldn’t fly unless they could feel the wind in their faces.

The first airliners had the passengers in an encolsed cabin but the poor pilots sat in open cockpits.

I felt the same way the only time I’ve ever flown an enclosed cabin gyro; Karol DeGraw’s partially powered rotor gyro.

I've been out of town, not online, and didn't see this thread until today.
I do jump take offs all the time in the A&S 18A, and it doesn't take a daredevil or Chuck Yeager to do it routinely and safely.

If you hop up only ten or fifteen feet you are NOT automatically in unsurvivable height-velocity curve peril. The aircraft jumps up and forward, not vertically, because of full power applied to the prop. In training, power failures at awkward times (such as during a jump) are simulated, and it's not hard to bring it back down to earth undamaged.

The risk of ground resonance after an unsatisfactory jump is no worse than for any other landing. If you have the lead-lag dampers set equally and appropriately (I check mine daily), the proper pressures in your tires, and proper servicing of the landing gear, there is very little risk.
[In general, I am quite content to trade the slight risk of resonance in a fully articulated system on a helicopter or gyroplane for the risks of mast bumping, "flap", endless hours of crow hops to learn "rotor management", and all the other things that come along with a teetering rotor. In my view, the primary advantage of the two-blade system on my Bell 47 is that it lines up nicely for a narrow hangar space footprint.]

Gyro's have been jumping for many years, there is no real reason that with modern design and technology that we cannot make this routine.

There is always the argument that good prespin and short take off is better but as in all things aviation compromise is what happens.

G force style landing gear to offset the risk of engine failure during the jump and adequate training will go a long way to make vertical TO and landing viable.