Jump take-offs

[Vance]

I was looking at pictures of wrecked gyroplanes that were learning to jump take off and watching the video of the pa 36 jump take off and I began to wonder why they didn't use the colective pitch to shorten the take off roll, instead of the jump take off.

I would think that it would be hard to control the aircraft with it nearly stoped adn the engine at full throttle. It seems to me that the control surfaces wouldn't work well at such low air speeds.

I also wondered what would happen if the engine stoped at the top of the jump.

When I would start my take-off roll with the rotor full back it always felt like the brakes were on and that I was reducing the braking as I moved the stick foward. The acceleration seemed a little week. The gyroplane sort of took off when it felt like it, it was not a comanded event for me.

I would think that if you could flat pitch the blades and begin the take off roll with the disk foward pre- rotated to flight rpm that flight speed would occur much sooner and lift off could be comanded by pitching the blades. It would seem to me that this would require less skill, and a less powerfull pre-rotor than one that can overspeed the blades by 50%. It would seem to me that this would be less risky than a true jump take-off.

I understand that the J-2 has a little trouble jumping because of the high disk loading and I was wondering if the aboove method wouldn't shorten their take off roll.

Is there a name for what I am describing?

I would be gratefull for help in understanding any part of this a little better.

Understanding the history time line, where things came from and why they didn't survive hase value for me. I would expect that others had wondered about this as well.

I realize that these are not practical questions and I am a little nervous to ask after the reaction to Michael's question, but everyone of the forum has been very patient with my ignorance and curiosity. I am gratefull for that.

I was also wondering if they used the colective pitch when they would do those wonderfull zero roll landings.

Thank you, Vance

[KenSandyEggo]

Hoping I'm understanding what you're asking. The J-2 blades are flat-pitched during spin-up. Once you reach +400 rrpm, you pitch the blades and add full throttle simultaneously. Are asking what would happen if you left the blades at flat pitch, but prerotated during the take-off roll and pitched them after attaining some ground speed? Dunno. You'd probably over-rev the prerotator system and get belt slipping and burn-up, is my guess.

I should be up and flying soon. Radio, tx, encoder, intercom are installed. The old radio fed into an "intercom, power pack switch-box," and radio-man can't find it in order to unscramble the phone-jacks and PTT buttons on the stick. I sent him some schematics from one of the manuals, and hopefully he can unscramble it. If push comes to shove, I told him to just put 2 new jacks under the panel (old ones are on the back wall), rewire the PTT buttons in the sticks and get it working. The original intercom worked only by throwing a switch to switch from radio to intercom, and you had to use the PTT buttons.

[PW_Plack]

Vance,

I've wondered about the same thing. When I started training, full-time awareness of the height/velocity curve was drilled into me. When you get below about 400 feet, make sure you're maintaining enough airspeed to flare when the time comes, that sort of thing.

Jump takeoffs would seem to tempt the height/velocity curve on a regular basis. It might be one thing in the GBA Hawk-IV, powered by an ultra-reliable turbine, but a very different proposition in a lesser machine.

[karlbamforth]

Vance,

I think with jump take off ppl are looking at the age old dream of flying from your back garden. I can understand why they would want it, no requirement to drive to the airfield. But you are right, it adds an amount of danger from failure of components at low flying speed.
I also think you are probably right in your ideas that pitching the blades would produce a short take off, but most gyro's already have a fairly short take off capability, is the expense and complexity of a pitching system really worth the effort to shorten it even more.

What pics were you looking at ? I would be interested to see them.

[C. Beaty]

During the initial test flying of any jump capable machine, rolling jumps are always explored before stationary jumps are attempted.

[Victor Duarte]

Chuck, Vance,
sorry to hijack the thread...
Chuck : i can't email you or send you a PM, so i don't know how to tell you Thankyou Very much for your CDROM, a real delight. Thanks again.

Vance :
i really wonder about the utility of a Jump TO...given the complication and the level of attention and skills required to perform it...
Instead, i tend to think that a GOOD prerotator on a ligh machine will do the job...
here's a vid of My instructor Xavier AVERSO, we performed the same take off on rough grass when i was training with him.
http://www.averso.info/temp/videos/video-decollage.htm
on my opinion, the ideal gyro has tip jets and allows a real hover take off...call it the rotodyne.
cheers

[pwendell]

Vance,

I've always felt the same way about jump-takeoff. In many ways it seems like the worst case of taking off behind the power-curve. From what I've been told, it can be real attention getter when an x-wind gust hits during the jump. A pre-rotator capable of spinning the blades to flight rpm combined with a simple, two-position collectiveseems to me like an ideal configuration for arecreational gyro. The collective pitch would only have to be adjustable in one direction from the cockpit. This would allow for very short takeoffs with enough airspeed to provide some options if things don't go as planned.

[C. Beaty]

Victor, I’d previously sent CDs via US domestic mail by simply gluing a label to the plastic case but didn’t know if the plastic case would survive international mail. Evidently it did survive international airmail but a transatlantic crossing on a boat might be a different story.

When I first mailed a CD that way, I asked the lady at the post office if it would be OK; she replied someone had once mailed a pumpkin by gluing on a label.

[Doug Riley]

Vance, your thinking seems right on target to me. A couple of random additions:

I have heard that the collective system on the J-2 can be "hacked" to create a true jump takeoff. Presumably this would be done by increasing the range of travel at one end or the other. Without a STC, this would violate the aircraft's type certificate, though.

It's seldom mentioned that the fore-aft cyclic in a gyro is in fact a sort of poor man's collective. Tipping the disk back with cyclic increases the angle of attack of all the blades in all azimuth positions (advancing, retreating and everything in between) -- as long as the aircraft has forward airspeed. This is easy to picture in the case of the advancing blade but maybe a little trickier for the retreating blade. Both blades, however, see the air coming at them more from beneath as you tilt the rotor back. This increases their AOA and produces a pseudo-cyclic effect. Obviously, though, it doesn't work at zero airspeed, as real collective does.

Once you get a gyro's rotor up to speed on a takeoff run, you neutralize the stick to prevent a premature takeoff. The classic technique is then to let the gyro levitate with the controls neutral. Levitation, as you say, happens when the gyro is good and ready, not exactly the moment you order it.

If instead of neutralizing the stick, you move it a bit forward of neutral and pick up some extra airspeed, you can "pop" it off at the exactly the moment YOU choose, with a firm nudge of back stick. I think most gyro pilots do a little of this, rather than using the pure fly-it-off technique. It's best to start out pure, though, and let this corruption creep in over time.

Once you add collective pitch, the deadman's curve gets more complicated. Depending on the energy-storing ability of the rotor, you may be able to nurse a collective-equipped gyro back down from a low altitude in a non-destructive way, even at very slow airspeed. IOW, you may be able to save it even if your engine quits at the top of a jump. This would be more likely to be possible with a massive rotor having some spare overspeed capacity -- one that doesn't use up every bit of energy it has just executing a basic jump.

I don't have any sense of how completely "spent" the rotor of the Gyrrhino or Air and Space is at the top of a jump. Maybe those who've flown them can comment.

[PW_Plack]

Jay Carter was quoted as saying the rotor on the Carter Copter had enough inertia to let a pilot jump, kill the engine, land gently then jump and land a second time without restarting the engine.

Most homebuilders, however, will not have blades tip-weighted with depleted uranium.

[Vance]

Thank you all, I feel less alone in my confusion.

Thank you Ken, I was not familiar with you take-offf protocal. What is the angle of the disk when you give it full power?

Thank you Paul, I started in helicopters and the height velocity curve is something I see ignored all the time in the NTSB reports. One of my favorite things about autogyros is the ease of an engine out landing. Perhaps at some point I would have become comfortable with engine out autorotations. When my instructor wold kill the power, usually down wind and I had to manage rotor pitch, rotor rpm, rapid decent, a place to land, the radio comunications and worse for me the flair. We were coming down so fast, I always felt that I would miss by 10 feet and dig a trench with he tail rotor. My first simulated engine out landing form 500 feet, 70 miles per hour, a quarter mile out on the down wind leg was such a non event, I fell in love.

Thank you, Vance

[Vance]

Thank you Karl, That was nicely put. I love dreams and I think you have it exactly right.

I have two books that I was looking at the picture in last night.

The Ciervia Autogiro

The Windmill Plane

If you want, I will get the proper names and authors. I am at work now and I don't have internet at home. I also have very poor short term memory because I have landed on my head too many times so I don't remember the aurthor"s names.

Thank you, Vance

[Vance]

Thank you Mr Beaty, I am always honored to here from you. Is there a name for an almost jump take off?

Thank you, Vance

[Vance]

Thank you Doug, I am there with you when you describe the take-off. You write so well. I expermented with just what you are describing and was properly admonished for it. I guess I have control issues. When I would let her have her own way it was very nice.

Thank you, Vance

[Vance]

Thank you Paul,

It is interesting you should describe it that way. Stanley Hiller describe it in the same way about his jet tip helicopter. It would decend very rapidly and you would begin the flare quite high, but there was enough inertia left to take off and land again.

Mr Hiller is part of my reason for the curiorsity about collective. He has said many times that anything without collective is dangerous. He is leaving us my degrees, so I have not been able to get him to expand on this.

Thank you, Vance

[Vance]

Victor, it is always a treat to hear from you. You always bring such a fresh perspective.

I was building a jet tip helicopter when I left her for my afair with Autogyros. This was the cause of my meeting Mr. Hiller. He had already solved many of the challenges I was encountering and had addresed them in many creative and entertaining ways.

I still love jet tip helicopters, but they are not the same as an Autogyro and I love Autogyros more.

I believe that trouble comes from having too many mistresses, so I will stick with the Autogyro.

Thank you, Vance

[C. Beaty]

I believe Raoul Hafner called a near jump a “towering takeoff.”

[Vance]

I like the sound of that Chuck. Thank you, Vance

[mrford61]

I believe that trouble comes from having too many mistresses, so I will stick with the Autogyro.

Thank you, Vance

I think that is an inkling of humour lurking there Vance. :D

[The Last Church]

My first simulated engine out landing form 500 feet, 70 miles per hour, a quarter mile out on the down wind leg was such a non event, I fell in love.
Thank you, Vance
What is the presager for engine out landing.?

[Cobra Doc]

It's usually presaged by a sudden unexpected sound of silence from the part of the aircraft that really should be making a lot of noise and a sudden stoppage of the big fan that keeps the pilot cool.

[Timchick]

Victor,
What type of prerotator does that gyro use? How many rrpm's do you get at the end of prorotation?

[The Last Church]

It's usually presaged by a sudden unexpected sound of silence from the part of the aircraft that really should be making a lot of noise and a sudden stoppage of the big fan that keeps the pilot cool.

I think one would just choose a glide path to the nearest flat surface keeping enough speed to keep the rotors loaded until touch down.

[Vance]

Michael, the answer to your first question is practice. I practice engine outs so that when it happens I will know what to do and when to do it. In helicopter training I would practice autorotation almost every time we flew. The height velocity curve that Paul spoke of has to do with when you can sucessfully complete an autorotation. You must have enough energy at the end to cushion the landing. You can change altitude into foward speed and then use the foward speed to flair and put energy into the rotor to cushion the landing. If you don't have height or velocity, the aircraft will probably sustain damage because you have no way to cushion the decent at the bottom.

There is a lot to manage in a helicopter and it must be managed at the proper time. I like to fly low and slow. If I remember corectly in the helicopter I was flying needed around 70 miles per hour and 500 feet although it is actualy a little more complicated than that. The glide slope is very steep, so you don't have a very big circle that you can land in. You must began very quickly, manage the rotor speed, manage your foward speed, select your landing spot, flair at 40 feet, level the helicopter and land.

In an autogyro when the engine stops, you began to decend, manage your foward speed, find a place to land, flair at 5 feet and land. The rotors will take care of themselves.

The idea of wadding up a $300,000 helicopter because I didn't do something correctly at the proper time detracted from the joy of flight for me. I was still in love, but it was a dificult relationship. An autogiro is challenging, but not problematic.

Mark, I didn't mean to be funny, that is just how I think. It is important to manage my limited resources in a joyus and productive way. Unbridled passion has often caused me to over extend my resorces.

Thank you, Vance

[Udi]

...The idea of wadding up a $300,000 helicopter because I didn't do something correctly at the proper time detracted from the joy of flight for me. I was still in love, but it was a dificult relationship. An autogiro is challenging, but not problematic.

Mark, I didn't mean to be funny, that is just how I think... It is important to manage my limited resources in a joyus and productive way. Unbridled passion has often caused me to over extend my resorces.

Thank you, Vance
Vance - you may not have meant to be funny, but you made me lough :) Thanks. I am getting a lot of pleasure reading your posts. Are you coming to Bensen Days? I'de like to meet you in person.

Udi

[The Last Church]

Michael, the answer to your first question is practice. You must have enough energy at the end to cushion the landing. .


I have another Question. What cause's PIO and what to do for recovery?

[Victor Duarte]

Tim,
it uses a simple rigid shaft with an angle coupling and a cardan on the head.
it currently prerotates at 250-300 rpm but i guess he may have reached higher rpm for the vid. It is a simple machine, a simple (but efficient) rotor.
the engine is a 912.
cheers

[Timchick]

Victor, Could you post some photos of the prerotator setup?

[Victor Duarte]

here it is Tim,
sorry, i don't have closer details.
I am currently updating his website, wait till the end of the week for more details about the rotor.
cheers

[Heron]

Hello Church
Pilot
Induced
Oscilation
Caused by the pilot
Remedy: let go on it . . . :D
Heron (master of AOTPPIO)
All over the place pilot induced oscilation :)

[Victor Duarte]

Heron,
i thought you were the well-known expert of WIHO

(women induced head oscillation) ;)

[Vance]

Hello Udi, I didn't know you were coming. I would be very pleased to meet you also. I hope to be there, there are still a couple of things that could stop me, but the chalenges are being overcome day by day. Last year was my last trip before my financial world exploded and I have been working hard since. I need a break. Thank you, Vance

[Vance]

Exactly Guy.

My instructor would not warn me and cut the engine on a down wind leg, I would drop the colective and began managing my rotor speed, keep my airspeed at seventy, check the wind direction, make a 180 degree turn,aim for a landing spot, call on the radio who I was, where I was and what I was doing. I would continue to aim for the spot, managing rotor speed and air speed, flair at 40 feet agl, level the ship and land. This is a lot of very important stuff that must be done at the correct time under difficult conditions. I don't multi task well and because I am blind in one eye, my depth perception is not what it could be at less than 50 feet.

In an autogyro, I would check the wind, find a place to land, call it on the radio, and land with a slightly steeper decent than a typical landing. My rotor speed takes care of itself and if I don't manage the flair to where I am stopped when I touch down it doesn't matter because I have wheels on an autogyro as opposed to skids on all the helicopters I have flown.

A run on landing in a helicopter frightens me as the helicopter tries to end up on its nose and makes terrible grinding noises.

Either way, when the engine stops, you are comming down and the object is to not damage the aircraft or the airmen and this takes practice, practice and more practice. It must be done correctly the first time.

This is part of why I like Autogyros best.

Thank you, Vance

[Doug Riley]

I built a VW-powered Bensen while I was in high school in the early 70's. I had only lawn-mowing money to spend, so of course my engine was -- literally -- a $15 piece of junk. My state of engine knowledge was, too.

After a summer of crow-hopping and runway flights (following the previous year of gyrogliding on a rope), winter arrived and I screwed up my courage for pattern flying. I did a few patterns one day without catastrophe.

The next time out I decided to tour the neighborhood a bit.

Naturally, once I got out of gliding range of the airport that junk VW decided to quit. I glided down to a farm field and did a pleasant deadstick landing into about 6" of wet snow. It was amusing to see the machine sitting in the field, with 20 feet of tracks in the snow behind it, beginning at nothing.

As green as I was, my first engine-out was uneventful. A gyro is pretty easy to land deadstick if you stay alert but don't panic.

That VW continued to help me in perfecting engine-outs into odd places. Green Haven State Prison was one of the more colorful unplanned destinations.

[Harry_S.]

At the present time, we can look back on those happenings in a relaxed and maybe, as a humorous frame of events.:cool:

I remember one particular MAC attack, where I thought my arrival would be in the middle of the Mississippi River. With luck, a brisk tailwind and *superb airmanship* I barely made it to dry land on the Illinois side. No damage at all except a seized piston.


Cheers :)