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jedi

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I think as tempting as a IC-hybrid style power system seems, it does have a bundle of its own complexities and compromises. For starters you've just upped the complexity by at least a factor of two. You need to add significant cooling systems (and drag) into the equation (unless you go turbine, perhaps). More significantly you need to carry at least twice the weight in electrical machines than you do for a battery only solution and you need to deal with engine noise, vibration isolation and heat management, fuel systems and pumps. None of this is new news but it all adds to the plates you're already spinning to get a design together. Oh, and you'll need to carry some (high-power density = heavy and expensive) batteries anyway...

Generally not as cut-and-dried a decision as you might think.
Or you could use a 100 foot extension cord to get up and away to a reasonable altitude and airspeed and avoid the high power VTO battery drain. The VL can be much less power hungry and is not as severe operating condition. A good landing gear might absorb a landing thrust deficiency as well as a non vertical landing particularly in an engine out situtation.
 

addicted2climbing

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Hey at least this one has a fighting chance with an engine out and can glide to the crash site if needed. Better than most of the quad copter only options with or without a BRS.
 

Aesquire

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It has flown.
Not according to the web site, or any footage shown here.

It's hovered. Big step. Reasonably fast taxi/hover! Another big step. "Flown?" Not that I've seen.

no transitions, no forward flight. Haven't seen high hover out of ground effect....

The overall design, the dual tiltrotor on a sort of conventional airplane, is, as I said, a conservative approach, in some ways, but that approach let them fast taxi to a fast hover.... Is there a better phrase for rotor borne drone like flight? Than fast hover? It's a technical matter and the language must be precise or it's propaganda, not engineering.

Anyhoo.... Fast taxi to hover is far beyond a Moller aircar afaik. I'm impressed.

Let me know when they open the envelope to transitions or forward flight.
 

Aesquire

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I really wish they would quit with the tiltrotor nonsense and rotate the passenger compartment instead so you can land the thing on it's butt ........
Not a well proven system.

Ryan X-13, two test pilots.

SNECMA Coleoptere, crashed before transition.

Lockheed XFV-1, transitioned from horizontal to vertical, and back, hovered briefly at altitude, not VTOL landings.

Convair XFY Pogo. One pilot?

Any other successful tail sitting VTOL craft? I could have missed one.

3 pilots. Less than landed rocket ships on the Moon.

And they used the Grumman method of standing up for visibility and control ergonomics.... and the Grumman Lunar Lander was "takes an Astronaut" level in handling quality.


I do admire the Black Fly for bypassing the argument & just standing the passengers on their heads with an autoland button. And if you have autoland, then, sure, a tail sitter, with the aerodynamics wanting to flip you nose down, might work ok. As the 21st century has shown, enough power and fly by computerized control and stability makes silly things work.
 

Sockmonkey

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Not a well proven system.

Ryan X-13, two test pilots.

SNECMA Coleoptere, crashed before transition.

Lockheed XFV-1, transitioned from horizontal to vertical, and back, hovered briefly at altitude, not VTOL landings.

Convair XFY Pogo. One pilot?

Any other successful tail sitting VTOL craft? I could have missed one.

3 pilots. Less than landed rocket ships on the Moon.

And they used the Grumman method of standing up for visibility and control ergonomics.... and the Grumman Lunar Lander was "takes an Astronaut" level in handling quality.


I do admire the Black Fly for bypassing the argument & just standing the passengers on their heads with an autoland button. And if you have autoland, then, sure, a tail sitter, with the aerodynamics wanting to flip you nose down, might work ok. As the 21st century has shown, enough power and fly by computerized control and stability makes silly things work.
Blackfly doesn't land them on their heads, it lands them on their backs. Planes like the Pogo tilted the seat, but the pilot was still leaning back and had to land looking over their shoulder. This is why I say rotate the whole darn cockpit for tailsitting so you can see forwards and down past your feet.
 
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blane.c

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If it is to complicated to integrate batteries with a generator, get rid of the batteries and just go with the generator.
 

Aesquire

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Tail sitting isn't just the visibility and ergonomics. The Coleoptere had a rotating seat and the Grumman LM was a stand up. With great visibility for the size of the windows.

The problem is the flying backwards part while backing down.

There's a reason the Short SC.1 to Hawker Harrier lineage gave us the only really successful VTOL configuration, not counting helicopters..... Which also prefer not to land 90 degrees different than they fly.

I could be overly pessimistic on the configuration.
 

Himat

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I really wish they would quit with the tiltrotor nonsense and rotate the passenger compartment instead so you can land the thing on it's butt and not need a dozen motors and props just to make sure it can survive the loss of one.
Why?
And why is tilt/multirotor nonsense?
 

Sockmonkey

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Tail sitting isn't just the visibility and ergonomics. The Coleoptere had a rotating seat and the Grumman LM was a stand up. With great visibility for the size of the windows.

The problem is the flying backwards part while backing down.

There's a reason the Short SC.1 to Hawker Harrier lineage gave us the only really successful VTOL configuration, not counting helicopters..... Which also prefer not to land 90 degrees different than they fly.

I could be overly pessimistic on the configuration.
The backing down isn't much different from how helicopters land. If your tail-sitter is powered by an ICE, you need a helicopter-type collective on the rotor or you're going to have problems because your engine speed doesn't respond fast enough. With electric motors, throttle response is fast enough to use non-articulated rotors, which is what's usually done.
Why?
And why is tilt/multirotor nonsense?
The overall complexity like the number of rotors needed and the number of stressed swivel joints needed.
 

Victor Bravo

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You and VB should team up and pursue some grant money. My fee for suggesting this is quite low, BTW...
With his ability to do renderings, we could actually come up with something that appears every bit as legit as some of the nonsense being tossed around.

Too bad that neither Sockmonkey's renderings or my grant writing are quite good enough to escape the laws of physics or energy storage.

I do think that the new Blackfly has very cleverly managed to side-step the need for tilting anything. My hat's off to that inspired bit of industrial design, regardless of whether it is economically or operationally viable.
 

Sockmonkey

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With his ability to do renderings, we could actually come up with something that appears every bit as legit as some of the nonsense being tossed around.

Too bad that neither Sockmonkey's renderings or my grant writing are quite good enough to escape the laws of physics or energy storage.

I do think that the new Blackfly has very cleverly managed to side-step the need for tilting anything. My hat's off to that inspired bit of industrial design, regardless of whether it is economically or operationally viable.
Technically none of what I post is actually rendered as I just screencap my work while it's open in sketchup.
Running it through a rendering program would make it more photogenic but I'm usually just trying to illustrate concepts rather than make art.
 

Himat

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The overall complexity like the number of rotors needed and the number of stressed swivel joints needed.
Multirotors do have complex control algorithms, but the implementation is not. One basic propel, motor and speed control times the number of rotors. Ok, there have to be clockwise and counter clockwise props, but that is it. Batteries can be one for all motors or in different ways distributed. I do not consider the multirotor hardware being complex. Add one more rotor and more parts are added, but the overall complexity is not that different from a quadrocopter to a octocopter.

Tilt rotors, add complexity and weight, still even with two tilting booms like on the Beta Technologies Octocopter I will not consider it complex. Again, they have made one tilt mechanism and duplicated it.
 

Andy_RR

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One of the fundamental limitations of tilt-rotor/wing designs is the almost certain requirement for a variable pitch rotor hub and control system to make it sufficiently efficient in hover and high-speed flight. I guess this is why separate lift-thrust (SLT) designs are popular especially in the UAV world. As ever, there are no simple and obvious solutions to any of this stuff...
 

jedi

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One of the fundamental limitations of tilt-rotor/wing designs is the almost certain requirement for a variable pitch rotor hub and control system to make it sufficiently efficient in hover and high-speed flight. ........... As ever, there are no simple and obvious solutions to any of this stuff...
The "simple and obvious solution" would be to eliminate the "variable pitch rotor hub and control system". Gee, isn't that what all the current quad copter like drones and fancy autonomous vehicles do? Might there be an other way to eliminate the "variable pitch rotor hub and control system"? 99% + of all flying things have succeeded in doing just that.
 

BBerson

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Efficient and fast forward flight requires only a single typical 72-80" prop, for optimal blade area (drag).
Those huge rotors are optimal for hover only, and too much drag in fast flight even with variable pitch.
Bell proved that long ago.
 

Andy_RR

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The "simple and obvious solution" would be to eliminate the "variable pitch rotor hub and control system". Gee, isn't that what all the current quad copter like drones and fancy autonomous vehicles do? Might there be an other way to eliminate the "variable pitch rotor hub and control system"? 99% + of all flying things have succeeded in doing just that.
Do you misunderstand my point to be purposely obtuse or did I really not make it very clear? A prop tuned for hovering is going to run out of beans very quickly in forward flight. Sure a quadcopter-type device can generate some forward speed but the power levels go through the roof even at relatively modest speeds.
 

mcrae0104

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giraffe.JPG

Wait, wait--I've heard this one: a Lancair and a three-legged giraffe walk into a bar, and...

(or was it an Osprey and a Cirrus? I can't remember.)
 

jedi

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Do you misunderstand my point to be purposely obtuse or did I really not make it very clear? A prop tuned for hovering is going to run out of beans very quickly in forward flight. Sure a quadcopter-type device can generate some forward speed but the power levels go through the roof even at relatively modest speeds.
No, and I believe I understand your comments. I got it and agree!

Tilt rotors are to complex. Quad copters, while not mechanically complex, do not go fast and suck a lot of power making them inefficient. If they were to rotate for wing supported forward flight the prop pitch would be too flat contributing to poor efficiency. I think we agree on that. In other words neither system works very well for combining slow or hovering flight with fast and efficient forward flight! So what is the next step or alternative solution?

I expect what was not clear was my hint at finding an alternative to both. What system do 99% of all flying things use to overcome these issues? Hint, evolution is a powerful development tool.
 
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jedi

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View attachment 77657

Wait, wait--I've heard this one: a Lancair and a three-legged giraffe walk into a bar, and...

(or was it an Osprey and a Cirrus? I can't remember.)
Oh oh! Now you are going to make me look stupid!

A Lancair and a three-legged giraffe walk into a bar, and the Three-Legged Giraffe says to the Lancair, "How did you get in here? I know you can't walk and your legs are to stiff to roller skate?" The Lancair says, while rolling his eyes, oh I just rolled in behind that tumble weed over there.

Dah!

Bar talk can be so boring if you are not drinking.
 
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