Malloy´s HoverBike

[AngelLestat]

Forget about lift one min so we dont make this more harder to explain.

In the picture that I gave you is easy to see it.

Is all about pitch angle and direction of rotation, you can not keep the same pitch (or low angle pitch) once your engine stop, because you will fully stop the rotation and it will start to rotate in reverse (because the air flow change, now the wind comes from below.)

But you dont want to fully stop the rotation and wait until start to rotate in the other direction, so you change the pitch to negative, this way you keep the direction and energy in the blades after you are close to ground, at that moment you change the pitch again to get lift.

"Autorotation is permitted mechanically because of both a freewheeling unit, which allows the main rotor to continue turning even if the engine is not running, as well as curved main rotor blades such that when the collective pitch is fully down the inner part of the blade has negative pitch relative to the horizontal plane and can be spun up by the relative wind. It is the means by which a helicopter can land safely in the event of complete engine failure. Consequently, all single-engine helicopters must demonstrate this capability to obtain a type certificate.[5]"

https://en.wikipedia.org/wiki/Autorotation

http://www.rcgroups.com/forums/showthread.php?t=491271

In other words, the only way to accelerate the rotor without stop it, is to change the pitch, why? because the air flow is inverted, now it comes from below.

[K^2]

Forget about lift one min so we dont make this more harder to explain.

It's all about the lift.

In the picture that I gave you is easy to see it.

Is all about pitch angle and direction of rotation, you can not keep the same pitch (or low angle pitch) once your engine stop, because you will fully stop the rotation and it will start to rotate in reverse (because the air flow change, now the wind comes from below.)

And the picture I gave you shows why this doesn't happen. Note that on all 3 sections relative wind points up. The flow is same as on your picture. Note that on middle section the net aerodynamic force points FORWARD, which keeps the blade turning. It does not stall, despite all three section having positive pitch and wind going up. That's the most fundamental thing they teach about auto-rotation.

Know what? Lets go for some hard quotes. Here is my copy of Rotorcraft Flying Handbook, published by U.S. Department of Transportation for Federal Aviation Administration, publication number FAA-H-8083-21. Chapter 3 - Aerodynamics of Flight. (This is actually where images on Wiki were taken from.)

During vertical autorotation, the rotor disc is divided into three regions as illustrated in figure 3-21 - the driven region, the driving region, and the stall region. [...] Force vectors are different in each region because rotational relative wind is slower near the blade root, and increases continually toward the blade tip. Also, blade twist gives a more positive angle of attack in the driving region than in the driven region.

I added the emphasis on the critical part of this statement. Pitch is more positive near the center, in the driving region. It is NEVER negative.

(Edit: As with most FAA publications, this one is available on-line as well. Here is a link: Rotorcraft Flying Handbook. Please, take a look at section 3-10, and in particular, figure 3-22.)

"Autorotation is permitted mechanically because of both a freewheeling unit, which allows the main rotor to continue turning even if the engine is not running, as well as curved main rotor blades such that when the collective pitch is fully down the inner part of the blade has negative pitch relative to the horizontal plane and can be spun up by the relative wind. It is the means by which a helicopter can land safely in the event of complete engine failure. Consequently, all single-engine helicopters must demonstrate this capability to obtain a type certificate.[5]"

https://en.wikipedia.org/wiki/Autorotation

That section was written by a complete idiot. I will fix it with a reference to the flight manual. Thank you for bringing it o my attention.

(Edit: The article has now been corrected. The actual aerodynamics of auto-rotation is better explained in the external link at the bottom of the page. Aerodynamics of Autorotation)

http://www.rcgroups.com/forums/showthread.php?t=491271

They are discussing body pitch. You do point the helicopter down, towards the ground. But this is also the case in forward flight, see your own image. If anything, body pitch is less negative in auto-rotation. Again, see your own image.

What we are talking about is blade pitch. Also known as collective. That always remains positive. There are VERY few aircraft that are even capable of generating negative pitch on collective. These are usually military and high performance stunt choppers that are designed to be capable of brief inverted flight. They can actually benefit from negative pitch. In virtually all commercial aircraft, pitch remains positive. In many autogyros, not only is the pitch positive, but it's fixed and cannot be changed.

If you are still confused about how the blade can keep turning forward despite positive pitch, I can try and help with that. But we first need to establish that this is the case. If you need to go out and see a real helicopter, and convince yourself that inner part of the blade has higher pitch, then do so.

Edited September 8, 2015 by K^2

[KerikBalm]

And I have no idea what you mean about speed limits. The 55 knots is more than generous enough. I doubt that Malloy's could top that.

From their website, they claim:

"the basic design is such that we expect it should reach around 150knts given necessary adjustment for in-flight stability."

Ground-effect aircraft will "auto-rotate" on inertia of the blades alone long enough to settle down, even without variable collective pitch.

...

The bottom line, from perspective of FAA, is whether the aircraft can be landed safely in case of engine failure.

This seems to be a misconception that persists in this thread, they are not intending this to be a ground effect only craft:

"Given the thrust to weight ratio (remember its all about the thrust to weight with VTOL craft), the hover ceiling is greater than 10,000ft. In theory you could go higher, but you need oxygen to do so – also there is not much point, as the hoverbike is designed for safe low level aerial work."

Just because they can auto-rotate, doesn't mean they'll do that without pilot's help.

I was under the impression that this was flown by a computer that attempts to execute the controller's directions, like the popular RC "drones" today.

In my mind, the chief distinction between the old RCs, and the new drones, is the skill needed to fly them.

The old RCs, every control surface/mechanism is directly controlled by the pilot. I would tell the servo to pull the elevator up or down... these new drones will hold a hover if you tell them to hold a hover, automatically controlling their 4/6/8/whatever rotors... etc. They take about as much skill to fly as that craft in the old game descent.

They say: "The Hoverbike has a fly-by-wire system, so can be flown without need of pilot input" that sounds like more than just fly by wire to me... its a big drone that doesn't need remote control.

But if they are smart enoght, I guess is possible to find a good solutions to the safety, range and energy source.

They can't outsmart physics, to get more out of 5 gallons of fuel, they need to move more air at a low speed, rather than less air at a higher speed - this means bigger rotors. This means helicopter sized rotors (or ultralight sized wings), which is not in their design goal, so it will neccesarily be less efficient.

This thing has 4 engines, and I guess it would be able to flight (or descend slowly) with just 3.

I doubt it, the lift/thrust and CoM would be unbalanced, unless it shut down the 3rd engine, and just used a pair of two - but then you'd have insufficient control authority, unless you could run the 3rd in reverse.

I doubt it has 4 engines. My guess is it has 1 gasoline engine driving an alternator, and 4 electric motors like a normal quadcopter.

There are clearly no gasoline engines in the 4 rotors, and I don't think direct mechanical linkages (like a chain or belt drive) would be a good idea.

Assuming they are brushless motors... the motors themselves should be very very reliable, so its just the case of the single motor.

If that fails, its complete power failure.

They themselves say that it can't autorotate.

" With the hoverbike you have the choice to wear an emergency parachute and have two explosive parachutes attached to the airframe, with a helicopter you have no such choice. The hoverbike cannot autorotate – but this should not be viewed as a discredit to the design. After engine failure in a helicopter or plane, autorotation or gliding is by no means a guarantee you that you will survive, as air crash statistics show."

Nor is a parachute a guarantee that you will survive, as air crash statistics show veyr well.

Moreover, a parachute is prettymuch useless below about 150 meters, which seems to be what this thing is meant to be used for ("low level aerial work") and the regime in which most recreactional ultralights are flown.

If you have a power failure at 100 meters, you are SOL (S.... Out of Luck).

A computer controlled autorotation system could probably increase the success rate of autorotation, but most ultralights are meant to be simple and computer control seems a bit out of place.

As far as the autorotation, basically, the blades are "gliding"

A sailplane or hangglider will keep gliding forward, even with a positive pitch.

The pitch will always be positive relative to the airflow, or it won't generate any lift at all.

If something has a good L/D, the pitch may be positive relative to the horizon.

If something has a glide slope of 1:1, its pitch is probably going to be negative relative to the horizon, but it will still have a positive AoA.

Now when you turn off the engine on a powered glider, you will reduce your pitch to maintain airspeed and prevent a stall.

A helicopter blade is a wing too (hence the term rotary wing), and it too must reduce its pitch to maintain speed/lift, and prevent a stall.

Depending on the specifics of the blade and loading, this may or may not result in a negative pitch relative to the horizon, but I guess the parameters of current designs means that this is pretty much always positive.

I dint notice that in the video he take off with high wind in front. So it only use the back propeller to takeoff and the top blades work as a wing.

I'm not sure he did... if he did, then I should find a better video.

As was said, the rotor on an autogyro is unpowered... but that is not strictly true. Some have what is called a "pre-rotator" that allows you to use power to spin up the blades on the ground. This doesn't work in the air because there is no tailrotor to counteract the torque, and the pre-rotators are also too weak to sustain flight.

This can simply be used to reduce the space needed for takeoff - without one, the main rotor starts completely stationary, and the autogyro has to move forward fast enough to get the rotor to start spinning.

It can also be used for a "jump jakeoff" if the blade's pitch can be varied.

This means that the pitch is neutral when the pre-rotator is engaged, and the blades spin up fast, faster than they spin in normal flight.

Then the pitch on the blades is increased, and the craft "jumps" into the air. At this point the blades will lose energy, and the thing will settle back down after a short time.

However, during the jump, if you throttle up the engine and start moving forward, then it will enter horizontal flight.

If I recall from the video, the rotor was actually pointing a bit backwards when on the ground, so the jump would actually take it slightly bakcwards, and the pilot balances this with thrust from the propellor.

You can find wany jump takeoff videos on youtube.

Jump takeoffs can be done in no wind.

[K^2]

A fly-by-wire hybrid drive quadcopter is a bit different than the way they originally presented the concept. But I suppose, there's nothing wrong with ideas evolving. This is all quite sensible.

In this case, they'll probably have to put a governor to limit air speed to 55 KIAS for the ultralight package, and they can have a pro version with no such restriction, which actually requires a rotor PPL. That version can come with a larger gas tank as well. Perhaps even additional instrumentation for IFR flight, etc. A rider seat? So many possibilities!

Speaking of possibilities, if they go with hybrid drive, they can absolutely add a battery to cover main engine failure, and even deduct it from total weight limit, since it'd count as safety equipment.

As for landing on motor failure, that's trickier. But yeah, going to two motors, using third for steering actually sounds reasonable. I don't see why it couldn't run an electric motor in reverse to help balance the thing.

Actual auto-rotation is out of the question, though. There is absolutely no reason to make props variable pitch, and something that's built to work as an efficient ducted fan simply cannot auto-rotate. I guess they'll have to go with parachutes, same as Martin's, to cover these requirements. And have hover-to-land as a low altitude failure mode.

As was said, the rotor on an autogyro is unpowered... but that is not strictly true. Some have what is called a "pre-rotator" that allows you to use power to spin up the blades on the ground. This doesn't work in the air because there is no tailrotor to counteract the torque, and the pre-rotators are also too weak to sustain flight.

Yeah, it's an optional piece of equipment that makes takeoff way easier. Before these became standard, you had to have people on the ground actually spin the rotor manually to get it going. PitA that is. So modern autogyros do tend to have a drive from the main engine that lets you pre-spin the rotor during takeoff. As you've said, though, it doesn't have nearly enough power for actual flight.

Edited September 8, 2015 by K^2

[KerikBalm]

Speaking of possibilities, if they go with hybrid drive, they can absolutely add a battery to cover main engine failure, and even deduct it from total weight limit, since it'd count as safety equipment.

I doubt it would, any more than an auxiliary fuel tank should count as safety equipment in the event that you run out of fuel for the main tank.

It seems somewhat related, but there is a small electric ultralight community, and they'd like the batteries to be considered fuel and not count towards the dry weight. The FAA doesn't agree.

Also, the FAA doesn't actually bother to weigh the safety equipment, and as such in practice just sets a higher weight limit if it has floats for water landings.

The enclosed Mosquito ultralight takes advantage of this (exploits it), by putting floats on it they are allowed a weight of up to 312 lbs. I don't think this craft could get away with something similar

As for landing on motor failure, that's trickier. But yeah, going to two motors, using third for steering actually sounds reasonable. I don't see why it couldn't run an electric motor in reverse to help balance the thing.

It should be able to if it has battery storage.

Actual auto-rotation is out of the question, though. There is absolutely no reason to make props variable pitch, and something that's built to work as an efficient ducted fan simply cannot auto-rotate. I guess they'll have to go with parachutes, same as Martin's, to cover these requirements. And have hover-to-land as a low altitude failure mode.

Well, in theory, it is sort of still possible.... but you would need a lot more altitude. If you had a lot of altitude, and some sort of stability system (maybe a streamer could work?), the blades would stall, stop, and then reverse direction (as the direction of the airflow reverses direction). If you fall fast enough, even rotating backwards, they'd have positive pitch relative to the airflow.

The faster they spin, the lower their effective AoA. In this case, all you'd need to do is have some braking force on the rotors

Any electric motor can run in reverse as a generator, which should supply a braking force as well.

This should result in a stable descent rate (although the descent rate would be far too high) that would charge the battery.

The regenerated battery power could (in theory) be used to soften the landing, just as you can soften the landing on an autorotation by using up the stored energy of the rotating rotor.

This sort of system might work if you run out of charge and gas at 10,000' but it certainly won't work at 500'

A parachute would be better.

Still, a power failure at 300' (100 meters) would be fatal.

That is too low for a parachute to work in time, an autorotation system as on a helicopter could save it, but the ridiculous "electric motors running as generators in reverse to generate electricity" system I described above would be completely impractical under any scenario.

Without variable pitch, a parachute system is the best they can do.

And if that is the case, if I was flying it, I would want to always stay above 500' (obviously except for takeoff and landing), which seems to contradict their "low level" focus (although low level is relative, I will again point out that currently, most powered ultralight spend a lot of time at these altitudes.

[magnemoe]

A fly-by-wire hybrid drive quadcopter is a bit different than the way they originally presented the concept. But I suppose, there's nothing wrong with ideas evolving. This is all quite sensible.

In this case, they'll probably have to put a governor to limit air speed to 55 KIAS for the ultralight package, and they can have a pro version with no such restriction, which actually requires a rotor PPL. That version can come with a larger gas tank as well. Perhaps even additional instrumentation for IFR flight, etc. A rider seat? So many possibilities!

Speaking of possibilities, if they go with hybrid drive, they can absolutely add a battery to cover main engine failure, and even deduct it from total weight limit, since it'd count as safety equipment.

As for landing on motor failure, that's trickier. But yeah, going to two motors, using third for steering actually sounds reasonable. I don't see why it couldn't run an electric motor in reverse to help balance the thing.

Battery also have the benefit of handling trust peaks, and yes main engine out is an problem, a battery to let you land should let you get you out of this. For extra parachute why don't put it on the harness/ seat? One rotor out and you will pop parachute to reduce speed and increase stability then do an emergency landing total failure and you detach the bike from seat.

Else I liked the two mode idea

[sgt_flyer]

if you use a battery backup to your engine, if you want to do emergency landings from low altitudes, you'll need a system that can last at least 1mn on battery power alone (starting from generator failure) - that's going to be heavy

[K^2]

Limiting factor is likely to be power, not capacity. Cellphone battery would give you about 1HP if it gave up all of its charge in 1 minute. I don't think any cellphone battery could survive that.

[KerikBalm]

Even if they could give you 1 HP, you'd need about 110.

Meanwhile powered hanggliders mostly use 15 HP motors, but you can get by with as little as 10 HP (well 7-8 HP for level flight, but you don't want to do a foot launch with such a low power margin)

The motor+glider combo also comes in at far less than 105 kg, and with 5 gallons of fuel, you'll have a lot more range than that thing

[AngelLestat]

Ok, first I want to finish with this autorotation discussion.

You are right about that mostly all real helicopters does not have negative collective pitch and is not needed to have autorotation. Also many autogyro, or stunt helicopters or almost all RC helicopters has negative collective pitch as we see in this picture:

And is used to improve the autorotation, as we can see in all these links:

http://www.com-pany.com/MasTechAutos.pdf

"While there are many variables that produce optimum results during an auto, such as the amount of negative pitch. I recommend that you initially set your pitch at 2-3 degrees negative at full low stick. As you enter the descent, hold the throttle at full low position all the way down, right through the flare.

Ideally at a later time you will increase the negative thereby offering you greater flexibility during the descent."

"Immediately after the flare, the landing is performed by moving the pitch from negative to positive pitch. At this time whatever forward speed that remains afte the flare, must be halted prior to the actual touch down. Keep in mind that if you executed the entry, descent and flare correctly you should have plenty of rotor speed for the collective to stop the machine and perform the landing."

http://www.helibuf.com/autorotation.htm

"The helicopter for are example will have the normal pitch settings at a -2 degrees to a +8 degrees and will hover at + 5 degrees of pitch. For the most part the helicopter will do autorotation's at a -4 degrees to a +8 degrees. You need the extra negative pitch so that on a decent you can keep the blades spinning. This -4 degrees is just an initial starting point, we will adjust the pitch later, but this will keep you out of trouble at first."

But as this rudimentery video test show, we can have autorotation with 0 pitch or a bit positive as you show, but it higly depends on the RPM, if your rotor is not spining faster or you delay a bit to lower the pitch (in a engine failure), then is possible that you would not be able to start autorotation without negative collective pitch.

That is why (I guess) in the wikipedia was mention (now is gone XD) that new helicopters should have as safety measure able to do negative pitch. (I dont remember the exact words"

The flow is same as on your picture. Note that on middle section the net aerodynamic force points FORWARD, which keeps the blade turning. It does not stall, despite all three section having positive pitch and wind going up. That's the most fundamental thing they teach about auto-rotation.

Yeah I see it.

I added the emphasis on the critical part of this statement. Pitch is more positive near the center, in the driving region. It is NEVER negative.

But the most important is the outer area of the blades (higher distance to the rotor), because that part is the one that produce almost all the lift and drag. So even a bit negative angle in that position, may have a great influence.

(Edit: As with most FAA publications, this one is available on-line as well. Here is a link: Rotorcraft Flying Handbook. Please, take a look at section 3-10, and in particular, figure 3-22.)

It said page not found.

That section was written by a complete idiot. I will fix it with a reference to the flight manual. Thank you for bringing it o my attention.

heh, lets see if it last. You checked the source [5] before change it? Maybe he had proves about that, but yeah, is not the general case.

If anything, body pitch is less negative in auto-rotation. Again, see your own image.

Yeah but I was not talking about body pitch, neither my links.

If you are still confused about how the blade can keep turning forward despite positive pitch, I can try and help with that. But we first need to establish that this is the case.

No, I saw the manuals and pictures you show about aerodynamics.

The resultant force seems to have a tiny tiny component forward which may keep the blades rotating, now not sure if this can be achieve it at any body pitch (angle of descent).

[AngelLestat]

.

They can't outsmart physics, to get more out of 5 gallons of fuel, they need to move more air at a low speed, rather than less air at a higher speed - this means bigger rotors. This means helicopter sized rotors (or ultralight sized wings), which is not in their design goal, so it will neccesarily be less efficient.

Not sure in the case of ducted fans, they tend to be very efficient.

I doubt it has 4 engines. My guess is it has 1 gasoline engine driving an alternator, and 4 electric motors like a normal quadcopter.

There are clearly no gasoline engines in the 4 rotors, and I don't think direct mechanical linkages (like a chain or belt drive) would be a good idea.

Yeah that is what I wanted to said when I mention hybrid.

But something hard to imagine would be 4 gasoline motors. If later the the fuel cell tech highly improve in density and cost, it will be perfect for this.

Moreover, a parachute is prettymuch useless below about 150 meters, which seems to be what this thing is meant to be used for ("low level aerial work") and the regime in which most recreactional ultralights are flown.

Parachutes are useless under 50 mts. First these are explosive parachutes, there are parachutes that are especially designed to fast opening. But as K2 said, you may have other methods to land if the computer detect that you are at low altitude.

A parachute at low altitude may not save you, but it may reduce your speed to half, enoght to surive.

The pitch will always be positive relative to the airflow, or it won't generate any lift at all.

It would not generate lift by drag.. but it will generate lift by the aerodynamic blade shape.

As was said, the rotor on an autogyro is unpowered... but that is not strictly true.

Maybe the tail rotor as it spins very close to the lift blades, it may produce at air current which makes the main blades to spin.

In this case, they'll probably have to put a governor to limit air speed to 55 KIAS for the ultralight package, and they can have a pro version with no such restriction, which actually requires a rotor PPL. That version can come with a larger gas tank as well. Perhaps even additional instrumentation for IFR flight, etc. A rider seat? So many possibilities!

You should not forget that laws also involve, if this thing show to be safe enoght, it can have a certificate as exception.

Some time back, I was discussing in this forum about combine airships with quadcopters to manage all mail in the cities, but people told me that it was impossible, that the FAA rules will never alow it, I said that rules will follow the needs always that it will be prove it safe enoght.

Only 3 months later, the FAA change their rules to alow and give certifacates to commercial use of auto piloted drones in cities.

Speaking of possibilities, if they go with hybrid drive, they can absolutely add a battery to cover main engine failure, and even deduct it from total weight limit, since it'd count as safety equipment.

Yeah the battery does not need to be big, just enoght to support 2 minutes of flight.

As for landing on motor failure, that's trickier. But yeah, going to two motors, using third for steering actually sounds reasonable. I don't see why it couldn't run an electric motor in reverse to help balance the thing.

You also have your same weight as a way to balance. So 3 rotors can work.

[K^2]

And is used to improve the autorotation

Sure. Slightly negative pitch can reduce the stall section during vertical auto-rotation. But you need to understand that a) it's not critical, and the angle of attack remains positive.

But the most important is the outer area of the blades (higher distance to the rotor), because that part is the one that produce almost all the lift and drag. So even a bit negative angle in that position, may have a great influence.

Outer section is the one that generates all the lift for you during auto-rotation. Sure, you can reduce pitch there to cut the drag. It will also reduce lift, and you'll be coming down like a rock. That does not seem like a sound plan.

The reason heli blades have higher pitch near the hub is because it makes sense during powered flight. The relative wind points down, so as the horizontal speed of the blade is lower near the hub, the pitch needs to be higher to get good angle of attack. Unfortunately, that leads to significant stall section on a prop during auto-rotation.

Autogyro blades tend not to have that twist, because for them, the airstream is always from bellow. That allows autogyro rotor to operate with no stall section. It goes from driving to driven. Still, I can't say I've ever seen an autogyro with an opposite twist on the blade, to have a slightly negative pitch near the hub. They might exist, though. It would make perfect sense for an autogyro.

But again, the critical part here is that you don't have to have that negative pitch near the hub or anywhere else on the prop. Auto-rotation relies on blades "gliding" down to generate rotation, not on turbine effect. The reason is that with auto-rotation you want to generate as much lift as possible, while with a turbine, you want to generate as much torque as possible. Hence one has positive angle of attack, the other negative.

It said page not found.

Hm. Maybe they filter by IP. I'm going to change it to http from https. Maybe it will help. Try again.

heh, lets see if it last. You checked the source [5] before change it? Maybe he had proves about that, but yeah, is not the general case.

Yeah, source is about FAA regs on the matter, not on aerodynamics of it. I've intentionally avoided making any specific claims in that sentence. Just took away the part about negative pitch, which was absolutely not true for helicopters (even if they are neg-pitch capable, pitch is higher near the hub), and might only be true for some autogyros.

I doubt this will cause a discussion, but if it is, it'll get resolved in a talk page.

The resultant force seems to have a tiny tiny component forward which may keep the blades rotating, now not sure if this can be achieve it at any body pitch (angle of descent).

Yes, both vertical and horizontal auto-rotation work the same way. Although, your typical general aviation helicopters tend to settle much faster in vertical auto-rotation, so coming in at an angle is highly recommended when possible. The reason is the aforementioned stall region on a general aviation heli. It's still there even if you come down at an angle, but you get more lift from the driven section, so you are still better off.

Autogyros tend to be designed for horizontal flight, so it's very difficult to get them to settle vertically. But some lighter ones are capable of almost vertical, zero-roll landings.

[KerikBalm]

Not sure in the case of ducted fans, they tend to be very efficient.

It absolutely is the case.

It takes more energy to move less mass at higher velocity, than more mass at lower velocity.

KE = 1/2 mv^2 does not depend on the rotor type.

By opting for small rotors for a more compact package, this thing's efficiency sufferes severely severely

Parachutes are useless under 50 mts. First these are explosive parachutes, there are parachutes that are especially designed to fast opening. But as K2 said, you may have other methods to land if the computer detect that you are at low altitude.

I know quite a bit about emergency parachute systems. I fly an unpowered ultralight. My Dad flies one, my brother flies one.

My brother had to use his parachute once.

While there are cases of deployments under 500' /150m being successful, the odds are very much not in your favor.

That low, you have very very very little time to react.

Even the ballistic deployment still will require time to have the parachute fully deploy.

Of course, there are many variables, it will deploy faster if you have significant airspeed, it will deploy much slower if you lost power while hovering.

Also, you can pretty much count on the system only firing in one direction, and with a sudden loss of power to a rotor, if this thing starts to tumble, it could very well fire the parachute down.

There is so much that could go wrong, that flying around with only 50m as a safety margin will very likely result in a fatality if there is a power loss

It would not generate lift by drag.. but it will generate lift by the aerodynamic blade shape.

huh? who said anything about generating lift by drag? I said the blade needs a positive AoA.

Maybe the tail rotor as it spins very close to the lift blades, it may produce at air current which makes the main blades to spin.

Huh?

An autogyro has no tailrotor. Do you mean the "pusher" propellor?

You should not forget that laws also involve, if this thing show to be safe enoght, it can have a certificate as exception.

Sure laws can be changed, but I don't think it will ever be safe enough to have a >100 kg thing flying around over a city with minimal regulation.

For what its worth, I think this shrouds that they put over the rotors aren't worth much and are more for PR.

*edit*

For what its worth, the Hoverbike page is also making a false comparison.

They do have parachute recovery systems for autogyros and helicopters

http://www.galaxysky.cz/gyro-amp-helicopters-s65-en

I'm a bit skeptical that it works under all conditions, but so far it works in their test videos.

Also worth noting what they themselves say:

"New patented system from Galaxy GRS s.r.o. enables a parachute rescue of gyrocopters and light helicopters from 60m above ground at the forward speed of 60 km/h and higher and in hover at very low forward speeds already from 110 m above ground. "

So... 60 meters with significant forward speed, but at slow speed, you need 110 meters.

And of course, that is ideal conditions... when something goes wrong, some time will pass as you realize what has gone wrong, as you realize you need to deploy your parachute, and when you actually start the deployment.

I stand by the 150m minimum safety margin.

Flying this thing under 150 meters will be very dangerous if losing power (or worse... control)

Edited September 9, 2015 by KerikBalm

[AngelLestat]

It absolutely is the case.

It takes more energy to move less mass at higher velocity, than more mass at lower velocity.

KE = 1/2 mv^2 does not depend on the rotor type.

By opting for small rotors for a more compact package, this thing's efficiency sufferes severely severely

Ok you are right, ducted fans are more efficiency than not ducted fans for the same blade size.. I remember this fact just now.

I know quite a bit about emergency parachute systems. I fly an unpowered ultralight. My Dad flies one, my brother flies one.

My brother had to use his parachute once.

While there are cases of deployments under 500' /150m being successful, the odds are very much not in your favor.

That low, you have very very very little time to react.

Even the ballistic deployment still will require time to have the parachute fully deploy.

Of course, there are many variables, it will deploy faster if you have significant airspeed, it will deploy much slower if you lost power while hovering.

Also, you can pretty much count on the system only firing in one direction, and with a sudden loss of power to a rotor, if this thing starts to tumble, it could very well fire the parachute down.

There is so much that could go wrong, that flying around with only 50m as a safety margin will very likely result in a fatality if there is a power loss

my dad also practiced skydiving and I did a bit of paragliding.

Of course this means nothing. We need to use physsics and calculations about the minimun height that a parachute can slow you enoght to survive, special parachutes designed for base jumping can slow you down in 30m, of course this may not be the case depending the wind, the deployment conditions, etc.

There was people who jump from that high without damage. But this is not about to have an equipment that guarantee you safety falling from those heights, this is not a recreational thing to do.

This may be an extra measure to save your life when you dont have any other option. So is that or nothing. You choose.

The bike can be software prepare to fly at very low altitude or high altitude, reducing to the minimun the amount of time you spend between, then it can choose depending the failure, the most correct way to save you, using engines or parachute.

huh? who said anything about generating lift by drag? I said the blade needs a positive AoA.

RC helicopters use negative collective pith to glide towards ground increasing the rotor speed, which is extra energy that can be used to slow the descent before touch ground.

Huh?

An autogyro has no tailrotor. Do you mean the "pusher" propellor?

Yeah I mean that.

Sure laws can be changed, but I don't think it will ever be safe enough to have a >100 kg thing flying around over a city with minimal regulation.

For what its worth, I think this shrouds that they put over the rotors aren't worth much and are more for PR.

It would not fly over the city without improvements and a lot of testing, proving if these thing can be safe enoght as an helicopter (which they can fly over cities), it needs also become a lot more popular.

What is PR?

http://www.galaxysky.cz/gyro-amp-helicopters-s65-en

I'm a bit skeptical that it works under all conditions, but so far it works in their test videos.

It looks like a good idea.

I stand by the 150m minimum safety margin.

Flying this thing under 150 meters will be very dangerous if losing power (or worse... control)

Why you focus in that? if you are faling and the main rotor can not help you, you will use everything you can.

This is not something you will do for fun. The same that nobody crash with their cars on purpose to see if the airbag is enoght to save them.

[KerikBalm]

my dad also practiced skydiving and I did a bit of paragliding.

Skydiving isn't very relevant, because those chutes are not designed at all to open fast and in a short time.

"did a bit of paragliding" also doesn't seem very relevant to me (what does this mean, you took a few lessons and didn't continue?)

We need to use physsics and calculations about the minimun height that a parachute can slow you enoght to survive,

The site I linked has such calculations, they are the same site claiming 110 meters from slow flight with the ballistic parachute system

special parachutes designed for base jumping can slow you down in 30m

Citation?

There are cases like d-bagging a paraglider:

http://www.liveleak.com/view?i=7ba_1247879006

But that wouldn't apply here (its a bit like a static line deployment)

https://en.wikipedia.org/wiki/Static_line

This may be an extra measure to save your life when you dont have any other option. So is that or nothing. You choose.

Of course, One should take a 10% chance over a 0% chance...

But to be safe, one should fly above 150m whenever possible.

This thing will have no reasonably safe option if power goes out below 150m. Therefore, its flight operations should be >150m at all times except when taking off or landing.

The bike can be software prepare to fly at very low altitude or high altitude, reducing to the minimun the amount of time you spend between, then it can choose depending the failure, the most correct way to save you, using engines or parachute.

The software won'y help, low altitude power loss will *probably* = death, fly above 150. Don't take the 50% chance of survival at 100m, or the 10% chance of survival at 50...

stay above 150m.

Also, unless this thing has a 2:1 TWR, 2 motors lifting with a 3rd operating for control won't be enough, and you'll still accelerate downward, just a bit slower and to a lower terminal velocity.

And, that assumes you even have power. If there is something like an electrical short in the battery/a battery fire (which happens a bit too often when people try to use the most lightweight high capacity battery they can make), you won't have power.

And I'm not sure I'd want to automate parachute deployment, that could lead to other issues.

I suppose it could be acceptable if there is an "arm" switch/button for an automated parachute deployment in the case of power loss, and a manual deployment button.

You'd arm the automated deployment at low altitude, and disarm it and have manual deployment at high altitude.

RC helicopters use negative collective pith to glide towards ground increasing the rotor speed, which is extra energy that can be used to slow the descent before touch ground.

What does that have to do with what you said earlier about lift from drag, and what did that have to do with having a positive AoA (AoA is measured relative to the incoming airstream, you can have negative pitch relative to the horion, and positive AoA)

It would not fly over the city without improvements and a lot of testing, proving if these thing can be safe enoght as an helicopter (which they can fly over cities), it needs also become a lot more popular.

Helicopters are generally not permitted to fly *low* over cities, just like other aircraft are not

What is PR?

"Public Relations" basically, propaganda. I mean that they do it because it looks nice to the public. I wouldn't trust that shround to actually stop something from contacting the blades.

It does make it a bit safer, but there are still huge gaps. It gives less protection than the shroud around an indoor circular fan - which won't even take off a finger (though it can hurt a lot)

Why you focus in that? if you are faling and the main rotor can not help you, you will use everything you can.

This is not something you will do for fun. The same that nobody crash with their cars on purpose to see if the airbag is enoght to save them.

Of course, you will try to use the chute if there is no other option.

But you should avoid the situation to begin with, and avoid flying that thing below 150m whenever possible.

Edited September 9, 2015 by KerikBalm

[AngelLestat]

Skydiving isn't very relevant, because those chutes are not designed at all to open fast and in a short time.

"did a bit of paragliding" also doesn't seem very relevant to me (what does this mean, you took a few lessons and didn't continue?)

We are having a racional discussion or your are in fully negative mode? Because you are not even taking the time to read.

I said: Of course this means nothing. We need to use physsics and calculations about the minimun height that a parachute can slow you enoght to survive

It does not matter how much experience we have, if you said that you need 200 mts to survive and we can see a lot of cases of people surviving at 50 mts then where is the point?

My dad really did skydiving with figures in the sky with the old parachutes, and I just use a paragliding with my uncle.

Of course, you will try to use the chute if there is no other option.

But you should avoid the situation to begin with, and avoid flying that thing below 150m whenever possible.

Again, that is the exact thing I am saying here:

The bike can be software prepare to fly at very low altitude or high altitude, reducing to the minimun the amount of time you spend between, then it can choose depending the failure, the most correct way to save you, using engines or parachute.

at what you answer was:

The software won'y help, low altitude power loss will *probably* = death, fly above 150. Don't take the 50% chance of survival at 100m, or the 10% chance of survival at 50...

stay above 150m.

Meaning that you dond read.

The site I linked has such calculations, they are the same site claiming 110 meters from slow flight with the ballistic parachute system

Nobody is so fool to claim that you will be save at low altitude deployment, because if someone dies they can denounce the company who made the parachute.

And not real site or important source will mention the possibility either. Because someone can try it and if goes wrong they will said, ohh I read it here..

Citation?

There are cases like d-bagging a paraglider:

http://www.liveleak.com/view?i=7ba_1247879006

But that wouldn't apply here (its a bit like a static line deployment)

https://en.wikipedia.org/wiki/Static_line

This is not a good source, but well:

http://askville.amazon.com/minimum-height-parachute-open-properly-land-safely-floor-building/AnswerViewer.do?requestId=259642

Some records:

http://hypertextbook.com/facts/2005/KristinaArthurs.shtml

This parachute is very small, so it needs lower deployment time, but what if we can reduce the deployment (inflation) time?

http://www.altusuas.com/#!parachute/c1kfn

So the answer for a emergency parachute is how to eject/launch the parachute and how to inflate the canopy once is ejected fast enoght?

There are many ballistic parachutes who solve the first issue. But I guess I need to help to solve the second.

If we have a cilinder with compress air below, is enoght to shoot the parachute out and fast, then at the moment it start to go out, a second small pressure vessel in the top of the parachute inflate blooms that go out from the canopy center to the edges (cords support), this force the parachute to instant deploy instead wait that the wind do the job.

This also prevents air currents folding the parachute when is not fully inflated.

With this system it will be almost possible to have the same deploy time watched in the video for the small scale parachute.

And I'm not sure I'd want to automate parachute deployment, that could lead to other issues.

depending how well designed it is.

Fully Mechanical activation (or user activation) is not a good idea either.

What does that have to do with what you said earlier about lift from drag, and what did that have to do with having a positive AoA (AoA is measured relative to the incoming airstream, you can have negative pitch relative to the horion, and positive AoA)

I said that for the aerodynamic shape of the blade, even if you have negative AoA, you produce lift by the aerodynamic shape... not due drag.

And all this is the same thing I said with the first commnet, if you understand a different thing not sure why we need to continue with this discussion, helicopters with negative pitch can also glide.. that is the main point.

Helicopters are generally not permitted to fly *low* over cities, just like other aircraft are not

Ok, then this thing after some years proving if is safe enoght, will be able to fly over cities high enoght..

Also how many helicopters we see landing in the middle of cities or in top of buildings?

[KerikBalm]

If you said that you need 200 mts to survive and we can see a lot of cases of people surviving at 50 mts then where is the point?

#1) I said 150

#2) I did not say it was impossible below 150, I just said that the success rate will decrease to unacceptable levels.

Keep in mind that there are many many factors, so one example of 50m does not mean that it would work in other situations at 50m.

The success rate of a parachute will start to be much worse as you get below150m

Again, that is the exact thing I am saying here:

The bike can be software prepare to fly at very low altitude or high altitude, reducing to the minimun the amount of time you spend between, then it can choose depending the failure, the most correct way to save you, using engines or parachute.

at what you answer was:

Meaning that you dond read.

Chill out man...

I did read.

If there is no safe option at 75m, what is the software supposed to do?

At 500m, you don't need software to fire a parachute.

If you lose one rotor, the softwar should always try and stabilize it with thrust from 2, and the 3rd for control, and that won't matter if it is high or low altitude.

Nobody is so fool to claim that you will be save at low altitude deployment, because if someone dies they can denounce the company who made the parachute.

Nobody will say you will be safe from a 500m deployment. But statistics show that you will be a lot safer from a 500m deployment than a 50m deployment.

The success rate of low altitude deployments is unacceptably high (at least to me), and this thing will have no other option than a parachute deployment in the event of power loss.

Therefore to me, the only safe way to fly this, is at higher altitudes.

This is not a good source, but well:

http://askville.amazon.com/minimum-height-parachute-open-properly-land-safely-floor-building/AnswerViewer.do?requestId=259642

Static line deloyments are not relevant here.... because you can't do that from a falling vehicle.

There are many ballistic parachutes who solve the first issue. But I guess I need to help to solve the second.

Still won't be solved if the craft has tumbled 180 degrees, and the parachute is shot down, not up.

Then the parachute will deflate, and you will fall 2x the bridal length+ the time needed to reinflate.

I said that for the aerodynamic shape of the blade, even if you have negative AoA, you produce lift by the aerodynamic shape... not due drag.

http://avstop.com/ac/flighttrainghandbook/imageurj.jpg

That doesn't show a negative AoA generating lift, and I still don't understand why you keep talking about drag.

helicopters with negative pitch can also glide.. that is the main point.

How is this anywhere close to the main point?

Also how many helicopters we see landing in the middle of cities or in top of buildings?

Very very few.....

[AngelLestat]

The success rate of a parachute will start to be much worse as you get below150m

I know, but not 10% of survival for 50 mts as you said.. maybe that value is for normal parachutes that are not designed for that work.

If there is no safe option at 75m, what is the software supposed to do?

At 500m, you don't need software to fire a parachute.

If you lose one rotor, the softwar should always try and stabilize it with thrust from 2, and the 3rd for control, and that won't matter if it is high or low altitude.

Lets imagine that we are at 75 mts

a) 1 electric engine failure: it keeps flying with 3 engines, your body helps to balance until reach the ground.

2 electric mirror engines failure: It keeps flying with 2 engines, activate the 2 parachutes which give you more time to the deployment, it goes down with the 2 engines and 2 parachutes.

c) generator engine failure: it goes down with the 2 min battery

d) out of control (turn over): activate each parachute depending the tilt angle at each precise time, the parachute in your back can be frequency signal activated.

Static line deloyments are not relevant here.... because you can't do that from a falling vehicle.

Static line deployment is not so fast either, there are parachutes which open faster without that.

Still won't be solved if the craft has tumbled 180 degrees, and the parachute is shot down, not up.

Then the parachute will deflate, and you will fall 2x the bridal length+ the time needed to reinflate.

There are some options, a) the engines turn them straight again, if that is not working the vehicle parachutes activate first, then short moments after your parachute activates, the first parachutes will give you enoght separation for your main parachute.

By the way.. why it will deflate?

That doesn't show a negative AoA generating lift, and I still don't understand why you keep talking about drag.

How is this anywhere close to the main point?

Ok, sorry, I dint read "positive relative to the airflow" in the first question.

[KerikBalm]

I know, but not 10% of survival for 50 mts as you said.. maybe that value is for normal parachutes that are not designed for that work.

I don't have exact statistics (I doubt anyone does because these sort of situations aren't exactly common and taking data when they happen is a very low priority).

My point is simply that the success rate is too low to be considered reliable.

Lets imagine that we are at 75 mts

a) 1 electric engine failure: it keeps flying with 3 engines, your body helps to balance until reach the ground.

2 electric mirror engines failure: It keeps flying with 2 engines, activate the 2 parachutes which give you more time to the deployment, it goes down with the 2 engines and 2 parachutes.

c) generator engine failure: it goes down with the 2 min battery

d) out of control (turn over): activate each parachute depending the tilt angle at each precise time, the parachute in your back can be frequency signal activated.

a) We don't know that it can keep flying with 3. 2 lifting and a 3rd for control may not be enough. It should be enough to keep it pointing up and get you a little more time though.

It would be completely unstable with 2 engines, it would rapidly start tumbling. Now you have issued of falling back into the parachutes, wrapping up the cord, etc etc.

c) You are assuming it has a 2 minute battery. Pure speculation.

c_2) Electrical system failure, complete power loss, no battery, no chance.

d) And if it never reaches the tilt angle it requires to fire the parachutes? Imagine it pitches over and then starts to fall upside down in a stable configuration (or fall vertically... or precess around, but always pointing down) - does your automatic system never fire? how does it know how long to wait? after you going to give this thing a radar altimeter now?

e) The rotors overlap, if you have an object pass through the overlapping area, you could lose both rotors simultaneously, which would result in a massive thrust imbalance between the front and the back, and a rapid tumble. There would be no way to stabilize that.

My point is simply that without the ablity to autorotate, its *only* option in the event of power loss is a parachute deployment.

Parachute deployments are very risky at low altitudes, and they want to design something to operate at low altitude.

All the conceivable systems to try and make this safer add more and more complexity. They were trying to sell this thing on its simplicity relative to a helicopter.

Personally, I would just take an autogyro... simpler and safer.

Static line deployment is not so fast either, there are parachutes which open faster without that.

I'm pretty sure the low altitude opening records were all done by static line

There are some options, a) the engines turn them straight again, if that is not working the vehicle parachutes activate first, then short moments after your parachute activates, the first parachutes will give you enoght separation for your main parachute.

By the way.. why it will deflate?

a) may not be possible depending on what goes wrong

I've never heard of or seen a personal ballistic parachute system. Please show an example of a personal parachute system working below these altitudes that is not either static line or starts in a pre-deployed state.

It will deflate because there would be no tension on the lines as you fall from above it to below it.

*edit*

I wonder how safe this is.... a similar concept of applying the drone technology on a larger scale:

http://www.iflscience.com/technology/man-straps-drones-together-and-creates-working-hovercraft

I'll give it points for having massive redundancy

Edited September 10, 2015 by KerikBalm

[Endersmens]

d) And if it never reaches the tilt angle it requires to fire the parachutes? Imagine it pitches over and then starts to fall upside down in a stable configuration (or fall vertically... or precess around, but always pointing down) - does your automatic system never fire? how does it know how long to wait? after you going to give this thing a radar altimeter now?

e) The rotors overlap, if you have an object pass through the overlapping area, you could lose both rotors simultaneously, which would result in a massive thrust imbalance between the front and the back, and a rapid tumble. There would be no way to stabilize that.

Possible solution for those problems. If both front/back rotors stop functioning, it activates a brake on the other side's rotors. This would prevent tumbling, allowing a parachute system to fire towards the sky instead of towards the ground.

I know if I was designing this thing, I would make very well sure that it can fly on two rotors, both diagonally and on one side. I don't see an excuse to not make it this way. If both right rotors go out, you would naturally lean left to compensate. It probably wouldn't be enough though, so there would have to be some system in place to help balance on those two rotors.

As of now, I don't see it becoming a thing. However, if they can prove that it can handle a single or double rotor failure (excluding both front of both back) and emergency land, and they have a proven method of recovering from double front or double back rotor loss, and prove some other things, I think it could be a possibility for 5 years down the road.

[AngelLestat]

a) We don't know that it can keep flying with 3. 2 lifting and a 3rd for control may not be enough. It should be enough to keep it pointing up and get you a little more time though.

This thing can do it, not sure how less would be the rotation by scaling up, to avoid high G on the pilot.

But remember that you also have your body weight to help in the balance, we could not handle a real bike if we were a fixed weight.

So always keep that in mind, in this case, this vehicle has a dynamic weight controled by our brain to help in the balance.

It would be completely unstable with 2 engines, it would rapidly start tumbling. Now you have issued of falling back into the parachutes, wrapping up the cord, etc etc.

Not with the 2 in board parachutes deploy, in the video they also show how to keep it straight with 2 engines, and the extra parachutes can help in that matter.

But even if you have low chances.. what are the odds to have 2 engines failure?

c) You are assuming it has a 2 minute battery. Pure speculation.

We are also assuming that is hybrid and a lot of other things. A normal full tank of gasoline will give us 30 or 40 min of fly (depending the passagers weight), if we get ride of the ICE engine and we use pure battery, our range decrease to 10 or 15 min.

But the ICE engine setup also needs a battery, so provide only 2 min of range with battery it does not change much the weight ratio.

c_2) Electrical system failure, complete power loss, no battery, no chance.

If that happens is because the system is not well designed. A 747 may have several circuits and CPUs failures and it will keep working fine.

But if you want to find the exact parameters to something crash, you will find it in any vehicle as your autogyro.

d) And if it never reaches the tilt angle it requires to fire the parachutes? Imagine it pitches over and then starts to fall upside down in a stable configuration (or fall vertically... or precess around, but always pointing down) - does your automatic system never fire? how does it know how long to wait? after you going to give this thing a radar altimeter now?

We are in the self machine learning age, you make a software simulation, and you train your algoritm there, then you do it with the right scale prototype in a safe place with nets to avoid damage, after a year of test, it will learn the best way to solve all kind of failures.

It does not have more inputs and outputs than this:

They also sell this new neural networks chips that consume miliwatts, and they can recoignize places or help with the quadcopter handle.

http://www.extremetech.com/extreme/193532-darpas-new-autonomous-quadcopter-is-powered-by-a-brain-like-neuromorphic-chip

e) The rotors overlap, if you have an object pass through the overlapping area, you could lose both rotors simultaneously, which would result in a massive thrust imbalance between the front and the back, and a rapid tumble. There would be no way to stabilize that.

With that mentality dont go out from your house, you can trip over and hit your head with something hard and die.

The thing you said can only happen flying in a forest, in that case you are flying low enoght to survive.

The rotors has security nets to avoid big objects to fall into.

My point is simply that without the ablity to autorotate, its *only* option in the event of power loss is a parachute deployment.

Parachute deployments are very risky at low altitudes, and they want to design something to operate at low altitude.

All the conceivable systems to try and make this safer add more and more complexity. They were trying to sell this thing on its simplicity relative to a helicopter.

Personally, I would just take an autogyro... simpler and safer.

Helicopters, airplanes, autogyros.. None of them are very good flying in adverse wind conditions or with stalls.

This is not the case for quadcopters. So yeah, they all have pros and cons. But I guess we said enoght to allow this technology a chance dont you think?

Regulations will handle that this thing do not go out until all safety concern are prove it.

I'm pretty sure the low altitude opening records were all done by static line

The problem with the static line, that your parachute go out from your backpack in a forced thin line until reach the cord range, and then the wind needs to inflate the parachute using a very small area from that thin line.

This is used to jump from airplanes, because if your parachute inflate too fast (at airplane speed) it may tear apart or produce high G forces on you.

There are other methods to push the parachute from your backpack without reducing the area that helps in the inflation.

But as I said, my idea of inflated blooms can solve that.

*edit*

I wonder how safe this is.... a similar concept of applying the drone technology on a larger scale:

http://www.iflscience.com/technology/man-straps-drones-together-and-creates-working-hovercraft

I'll give it points for having massive redundancy

But according to you that is a lot more ineficient from the energy perspective.

But looks cool.