AUTOGYRO Ela jump takeoff

[kolibri282]

Igor Bensen wrote a paper titled "A Study of Design and Economics of Rotary Wing Gliders" for the seventh annual forum of the American Helicopter Society, 8th April 1951 (see entry 2691 here: 7th Annual Forum AHS), where he proposed to control the rotor pitch for a large gyro assault glider by trailing edge tabs, similar to those used by Kaman for his helicopters. Bensen reports, that the method was tested on a 24 foot rotor. This design would do away with most of the moving parts of the pitch control of a conventional helicopter. The tab control is mechanically fairly easy and the parts are not subject to any excessive loads. This would be, in my opinion, the best design for a jump takeoff gyro. It requires, of course, the design of blades which have just the right amount of torsional flexibility but once you have those no design with a conventional rotor head could compete in terms of cost, including maintenance, and service life.

 

[Abid]

Isn't Nachobe a kind of cheese dip? Or I might be mistaken...

Abid, I guess a half a helicopter is like a half-full glass of water... or half-empty. Fact is, by the time you add collective pitch, probably a controllable-pitch prop, a swashplate cyclic and a robust drive mechanism that allow for jumps, you've built more than half a helicopter -- even if you don't include Dick's in-flight rotor drive.

I imagine this is the unfortunate truth that sank the gorgeous (but unmarketable) Groen Bros Hawk IV. Just add a tail rotor and you get a fully hover-capable helo for about the same money.

Exactly Doug. I would just switch over to a helicopter if I had to design all that. Not a big difference in effort in design from that point. And then I can hover.

 

[Smack]

Igor Bensen wrote a paper titled "A Study of Design and Economics of Rotary Wing Gliders" for the seventh annual forum of the American Helicopter Society, 8th April 1951 (see entry 2691 here: 7th Annual Forum AHS), where he proposed to control the rotor pitch for a large gyro assault glider by trailing edge tabs, similar to those used by Kaman for his helicopters. Bensen reports, that the method was tested on a 24 foot rotor. This design would do away with most of the moving parts of the pitch control of a conventional helicopter. The tab control is mechanically fairly easy and the parts are not subject to any excessive loads. This would be, in my opinion, the best design for a jump takeoff gyro. It requires, of course, the design of blades which have just the right amount of torsional flexibility but once you have those no design with a conventional rotor head could compete in terms of cost, including maintenance, and service life.

Thanks for the reference, Juergen.

So much more useful than the swearing, spelling error, and redundant nonsense.

 

[Aerofoam]

Igor Bensen wrote a paper titled "A Study of Design and Economics of Rotary Wing Gliders" for the seventh annual forum of the American Helicopter Society, 8th April 1951 (see entry 2691 here: 7th Annual Forum AHS), where he proposed to control the rotor pitch for a large gyro assault glider by trailing edge tabs, similar to those used by Kaman for his helicopters. Bensen reports, that the method was tested on a 24 foot rotor. This design would do away with most of the moving parts of the pitch control of a conventional helicopter. The tab control is mechanically fairly easy and the parts are not subject to any excessive loads. This would be, in my opinion, the best design for a jump takeoff gyro. It requires, of course, the design of blades which have just the right amount of torsional flexibility but once you have those no design with a conventional rotor head could compete in terms of cost, including maintenance, and service life.

This is exactly what I plan on testing, I was wondering if anyone tried it before, it seems rather obvious.
The mechanism could even be linked to fly weights so the de-pitching automatically happened at higher than flight RPMs.

 

[Aerofoam]

Additionally, I was not thinking of it as a jump, but as a very short take off because with the de-pitching, if the forward roll is initiated, the transition
of the rotor from "Fan" to flowing through "Autorotation" should happen almost immediately, so the take off would not have to suffer through the "Translation" phase. (not sure if that term is correct...)

 

[kolibri282]

My idea is, that jump takeoff only makes sense with zero forward roll and as much height as you can muster. I read a story about two pilots who landed their gyros up in the mountains. The aircraft got stuck in the snow and had to be retrieved by helicopter. Had they been able to do what the ELA does, just get the landing gear clear of the snow and then accelerate forward, they would have been able to get out of that mess on their own.

 

[Aerofoam]

My idea is, that jump takeoff only makes sense with zero forward roll and as much height as you can muster. I read a story about two pilots who landed their gyros up in the mountains. The aircraft got stuck in the snow and had to be retrieved by helicopter. Had they been able to do what the ELA does, just get the landing gear clear of the snow and then accelerate forward, they would have been able to get out of that mess on their own.

I can see the benefit of that, but with the expectation of keeping it light and simple, I was thinking that a 10 ft. roll would be a reasonable expectation and reduce the height needed at the jump to transition. Maybe the vertical jump is possible, but it seems a lot more likely to be effective without having to reverse the flow through the rotor and having forward motion should accomplish that.

 

[WaspAir]

Is the short roll you envision to be done while driving a depitched rotor? If you try that in an A&S18A, the applied torque will drive you off the runway sharply to the right. In the McCulloch J-2, which was made for 125% depitched pre-spin but not to jump routinely, you de-clutch before the ground roll begins to avoid that.

Jumping should never be vertical. You want full thrust from the prop as you rise, so by the time you have peaked in height and dropped to flight rpm, you have gained significant airspeed to maintain autorotative flight. In the 18A, that's about 30 knots at 100% and 4°, down from 150% and 8° at the initial hop. You jump up and forward.

 

[Aerofoam]

I would

Is the short roll you envision to be done while driving a depitched rotor? If you try that in an A&S18A, the applied torque will drive you off the runway sharply to the right. In the J-2, which was made for 125% depitched pre-spin but not to jump routinely, you de-clutch before the ground roll begins to avoid that.

Jumping should never be vertical. You want full thrust from the prop as you rise, so by the time you have peaked in height and dropped to flight rpm, you have gained significant airspeed to maintain autorotative flight. In the 18A, that's about 30 knotsat 100% and 4°, down from 150% and 8° at the initial hop. You jump up and forward.

I don't think a vertical jump is even possible unless you could decouple the prop, which would not be desirable....
The Gyrhino's jumped with prerotation engaged and they noticeably torque turned a bit in the air, but the tall tail was enough to immediately straighten them out.
I would think with less torque on a lighter teetering rotor, the roll while engaged would be possible,
The first part of the test will be using a rotor on a trailer that will never fly, but the torque will be measurable...

 

[WaspAir]

I'm talking about the torque applied to the rotor through the rotor drive system, not the torque through the prop, and the tail configuration is irrelevant for that purpose.

The lower the rotor torque and lighter the system, the less excess energy you store in the rotor, and the more anemic any "jump" would be.

 

[Aerofoam]

I would

I don't think a vertical jump is even possible unless you could decouple the prop, which would not be desirable....
The Gyrhino's jumped with prerotation engaged and they noticeably torque turned a bit in the air, but the tall tail was enough to immediately straighten them out.
I would think with less torque on a lighter teetering rotor, the roll while engaged would be possible,
The first part of the test will be using a rotor on a trailer that will never fly, but the torque will be measurable...

That's stating the obvious, of course it's the torque from the prerotater which the Gyrhino proves is manageable with only rudder compensation
and that was with a very powerful prerotator once the aircraft was in the air. Would it have uncontrollably turned the aircraft if a roll was attempted?
I wish I would have asked Dick about that at Bensen days.......

 

[WaspAir]

I have never examined a Gyrhino and don't know the structure or the operation.

But we all know that no single rotor helicopter has ever successfully used a rudder in place of a tail rotor. If your rotor is torque driven, it needs torque compensation.

Wimpy prerotators on light systems need little compensation (and aren't new), but they also don't jump.

 

[Aerofoam]

I have never examined a Gyrhino and don't know the structure or the operation.

But we all know that no single rotor helicopter has ever successfully used a rudder in place of a tail rotor. If your rotor is torque driven, it needs torque compensation.

I think powering a depitched rotor doesn't provide enough torque to be an issue, I believe the rotor is being driven by less than 25% of what would be needed if it were a helicopter, but I am not sure of that number.
I noticed the torque turn happens immediately after lift off, but have seen a couple videos where there wasn't much of a turn.
There would probably be an issue if the time on the ground was too long and the front wheel came up.
Maybe enough of an issue to rule out a ground roll.

 

[Jason312]

As density altitude affects everything.... I wonder if this will still perform a jump takeoff at 8k-9k density altitude as we commonly see in Utah whether your at 4,500ft in July-Aug or up in the mountains.

 

[WaspAir]

Good point. The 18A won't jump much above 4,000 feet unless the load is very light.

 

[kolibri282]

To give an idea about the influence of height on jump performance I calculated the curves below for certain aircraft parameters at 0 and 5000 ft. It would be interesting to compare the calculation to test data, but I have not found any so far. I think that Wasp is right, you want to jump with full throttle. I don't think a short ground roll of e.g. ten feet would be beneficial, as the difference in rotor inflow, that would make, is close to zero. The curves below are height vs. time.
(the negative coordinates below would usually not make sense, unless you jump off the Corcovado and have some height to drop below your take off height)

throttel

 

[Strike]

ILI think Ela is the first modern builder! For having included the Jump Take-off in modern gyros. Now you can write about anything!! What's the use! May it be useless! That's too expensive! Let it be complicated! That maintenance will be difficult and expensive Even more so! Bla Bla Bla, meanwhile they did it! They believed in it, and they are marketing it. Maybe who will buy a model like this his whole life he will use it perhaps only once! However.....

 

[wolfy]

Lets not forget the amazing work the frenchman Michel has done with his simple and automatic pitch jump gyro.

wolfy

 

[wolfy]

I think powering a depitched rotor doesn't provide enough torque to be an issue, I believe the rotor is being driven by less than 25% of what would be needed if it were a helicopter, but I am not sure of that number.
I noticed the torque turn happens immediately after lift off, but have seen a couple videos where there wasn't much of a turn.
There would probably be an issue if the time on the ground was too long and the front wheel came up.
Maybe enough of an issue to rule out a ground roll.

Thats not how Dicks machine works.
He could probably sit on the ground all day with RRPM above flight rpm.
He is very clever in that he splits the torque between prop and rotor via a differential, so that like a diff the torque will drive the easiest.
So on the ground at flat pitch it is easier to drive the rotor than prop, but once he pulls pitch its easier to drive the prop so torque is now acting on prop so will not try to spin fuselage. After the jump pitch is reduced to flight pitch and then the torque is split at about 10% to rotor and 90% to prop.

wolfy

 

[Strike]

Non dimentichiamo lo straordinario lavoro svolto dal francese Michel con il suo giroscopio semplice e automatico per il salto del passo.

luposo

AAbsolutely yes Michel did a great job, the fact that the rotor speeds remain constant in all flight conditions is very ingenious, of course his model is truly minimal but very good