Another attempt,back-pack helicopter

Kamov KA 56

Kamov KA 56

Now i like show the Kamov foldable helicopter.The helicopter looks like a mockup.
I believe this helicopter was never flown.The concept of the helicopter its a good idee,small ,foldable,not heavy.

I am interesst to get mor information over this great helicopter concept.


thanks
Jetman

Rotor Rooter said:

If not, then is the specific danger the combination of powered rotating rotors and the proximity of the ground?

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The danger is powered rotors contacting the ground (or the operator). If the machine tips over parts go flying, and a few of us here feel that's much more likely to happen using your legs instead of proper landing gear.

Highly responsive controls won't help once you exceed the critical angle & start a dynamic rollover, it'll just happen faster if the pilot reacts incorrectly & doesn't immediately reduce collective before getting to that point.

Using less than 1" of control when hovering a helicopter is perfectly normal btw.

Electric Heli

Electric Heli

Hello Dave i like get more information over the heli from Pascal please.Will be posible to get me in touch with Pascal ?


thanks
Jetman

Brett,

Thanks for bringing up the concern.

The following is the objective that I am "trying' to achieve; initially under the condition of fully powered rotors. It is based on the premise that a person has more stability standing, when he is also holding on to a railing.

It involves having extremely fast responses from the rotors to the pilot's arm and hand inputs.

• One is the collective. Pascal just mentioned that his electric helicopter takes about 4 seconds between the demand for thrust and the initial increase of thrust. The reasons are that the motors are working near their maximum and there is time required to increase the rpm of the rotors. The solution of more power is an obvious one. Also he is very interest in pursuing the Torque-Pitch coupling c/w extremely rigid, low-inertia blades. So am I, for the Electrotor-SloMo. This T-P coupling is intended to use the instant increase of the torque to give an instant increase in the pitch, and then let the rotor speed partially catch up. It is intended that, if need be, a fast reaction will 'lift' the pilot out of the problem.
• An efficient throttle will allow the pilot to play with the weight on his feet.
• Another is the rate of cyclic response. This is to be tackled by having the moments of the 2-rotors, 2 motors and connecting frame assembly concentric with the gimbal. In addition the low mass of this assembly and the very rigid blades will, hopefully provide very fast pitch and roll responses.
• There are also a number of ideas for yaw control.
• Another consideration is for slow rotors and/or a very fast rotor brake. Theoretically, instantaneous stopping of the rotors on a Coaxial configuration and an Interleaving configuration should have no effect at and beyond the gimbal, assuming that the rotors plus connecting frame can handle the heavy shock load.

There is much theoretical and hypothetical assumption, but that is the challenge and the fun.
Hell, there is no rush since the development of good batteries might take a week or two.


Jetman,

I am trying to talk Pascal into joining the forum. If you send me your e-mail by private message, I will pass it on to him.

Dave

But here you're not holding onto a fixed railing - the machine moves.

brett s said:

But here you're not holding onto a fixed railing - the machine moves.

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perhaps Dave meant that the powered rotor provided the "fixed railing"

But it doesn't, that's my point.

"Lean" against a hovering helicopter & it just moves.

Right,but I think he means when your landing gear is in contact with the ground.
If the machine is in the air and you lean on it it certainly will move but than there's no chance to trip or falling.

As soon as your feet touch the ground the rotor "should" provide the fixing railing,at least that's my understanding of what Dave's trying to tell.

Brett,

Thanks for the specific concern.

My objective is to have a very close pilot/craft relationship. A relationship where he instinctively works with his arms and legs to maintain full control.

"Lean" against a hovering helicopter & it just moves.

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A person who wants to back away from a railing can push on it, as he backs up with his feet. The objective is that the same action will apply to a backpack helicopter with a fast response time.

A pilot who wants to back up can push on the overhead control arms (short forward tripod legs) and the resulting rearward thrust of the rotors will pull him back, as he backs up with his feet.


Cita,

You have got it, but, the landing gear is not in touch with the ground until he squats.


Dave

"Leaning" against the helicopter attached to you can't keep you from falling over.

Cyclic input can't save you either if contacting the ground & you exceed the critical angle. The classic dynamic rollover scenario is from doing exactly that.

brett s said:

"Leaning" against the helicopter attached to you can't keep you from falling over.

Cyclic input can't save you either if contacting the ground & you exceed the critical angle. The classic dynamic rollover scenario is from doing exactly that.

Click to expand...

The situation is like the right hand sketch.
This craft is not going to have large diameter rotors, flexible hinges or flexible blades. It will be quite similar to Schoefmann's.

There is no intention to lean against the helicopter. The intention is for the pilot, who is attached to gimbaled the back post, to instinctively push the front posts [railing] forward while increasing the throttle. The assumption is that the rotors are capable of a fast power increase [torque-pitch coupling] that will pull the pilot, batteries and back post backward, and with enough power upward, if necessary.


Dave

Rotor rooter
What rpm and pitch does this fantastic electric heli have?

Im about seting up my machine any day now so I need some last input to my calculations...

It must be fenomenal to have electric motors -no vibrations or sound!

Zigge,

Please wait a day or two.
See posting #820 above.


Thanks.

Dave

"Rigid" rotors and small diameter may make a big difference in chances having a rotor strike in a roll over situation.

I made a very rough sketch to see what the difference is between a BPH rotor and a small homebuilt helicopter rotor balancing at the "tip over point" in reference to the ground.

In the sketch there isn't any "correction" made for teetering of the rotor so the rotor tip might hit the surface much earlier than in the "drawing".

Anyhow,the information from Pascal about delay in response (due to to "weak power" arrangement ?) between power input and rotor rpm increase must be considered.
Four seconds seems to be so unreal and makes one wonder how he can control altitude.
Sufficient power seems to be the answer if we want to keep things simple but question is how much power is needed "on surplus" to "replace" collective with rotor rpm control.
Perhaps little less power and collective might be lighter in the end but certainly not simpler.

Cita

What would be the main cause of dynamic roll over situation in small helicopters ?

The only few video's I saw on youtube which had a "near roll over" situation had this caused by ground resonance.

What are the chances to have ground resonance with the human legs as main landing gear ? None I would guess because I assume that the human legs have no critical frequency.

I'm obviously just guessing here so maybe someone with a better understanding of these things can shed some light on it ?

Cita

Schöffman "leaning" in his little chopper.
At take-off (20sec.) you see Franz "leaning" backwards and keeping full control.

The World's Smallest Personal Helicopter - YouTube

Cita

Cita- Any helicopter, large or small can have a dynamic roll over. You can be lifting off and have a stuck skid, and the helicopter will pivot around that stuck skid. A skid can dig in by drifting sideways and the skid touches down and the drifting of the hellicopter will start pivoting around the dug in skid. In error, some will try to power out by pulling collective. What is happening is that the thrustline is many times not able to have enough opposite cyclic to move the thrustline to the outside of the stuck skid. If the thrustline is inside the stuck skid, opposite cyclic, even to the stops, any thrust from the rotor still tends to pull the helicopter on over , the critical angle is passed, and the dynamic rollover happens. Initially, first signs of a stuck skid should be to lower the collective, but not so much that you rock the helicopter over the other way. Smooth but decisive lowering of the collective is the best. Stan

Hello Stan,

yes I know that any helicopter can have dynamic roll over but I thought there would be something like a "top ten" in causes, 1)skid struck 2)ground resonance 3) gusting etc...etc....

It's obvious that once past the "push over point" any more input on the cyclic will only add to the situation.
It looks also obvious to me that the natural reaction would be to use the cyclic to "counter-act" that movement,making it worse than solving !!

Funny that you mention two situations Stan,lifting off with a stuck skid,a skid can dug in while drifting sideways, that would be hard to encounter with the human landing gear :tape:

Cita

Stan,

You raise a good point. if one of the tripod legs got stuck the chances of dynamic rollover certainly exist. The 'stuck' leg will also take over the flight control because the legs are a part of the weight-shift /gimbal flight control mechanism. The pilot must quickly realize that one or more of the legs is stuck as he his trying to move from squatting to standing up.

If his feet get stuck, then that's another problem.


While doing the above drawing another advantage of the weight-shift control appeared. It appears that the control, as drawn, has a larger range of pitch and roll than any commercial helicopter has.


Dave

Dave and others interested- I made a quick sketch showing a dynamic rollover. Picture this helicopter as being viewed from the rear.

The helicopter has a stuck right skid....either its stick in mud...or dug in with a right side drfit.

The pilot applies left cyclic, but has reached has reached full left cyclic.

The helicopter has exceeded its critical angle where the red thrustline can not go outside the stuck right skid to help pull the helicopter back over.

Any thrust only assists the tipping of the helicopter to the right because the thrustline being on the inside of the stuck skid is pulling the helicopter over.

Had he not reached the critical angle...full left cyclic would have the thrustline outside the stuck right skid and it would then assist in pulling the helicopter back level.

This is why collective must be dropped before the CG of the helicopter goes outside the stuck right skid....

Stan