I thought I would have found at least a few discussions on this subject, but haven't dug up much. I'm curious to the efficiency comparisons of the various popular VTOL types. For example, I usually see a tilt rotor and think of a compromised forward flight propulsion system, since it of course has to be optimized for such a small portion of the flight. In reality, I wonder if the lower motor count/weight makes up for this. Would a variable pitch tilt rotor be the best solution?

This is just one example. I'm interested in people's thoughts and experiences with various configurations.

Would a variable pitch tilt rotor be the best solution?

Yes but also twisted so it acts like a prop when it's at it's max pitch.

Tons of information here:

Google search here < vtol configuration efficency site:rcgroups.com >

Yeah, I looked through and picked some great info out. Just thought it would be cool to have a thread dedicated to comparisons.

I like the idea of a dedicated thread as well. From my perspective with fixed pitch props:

Bicopter Tail Sitter:
extremely simple and light
lower efficiency in hover if you want to have good control authority
good forward flight efficiency because it's just a wing and two motors
bad wind resistance

Bicopter tilt rotor:
can have good efficiency in hover or forward flight, but not as easy to have both
minimal tilt mechanisms
Dead weight is only the tilt mechanism

Tricopter tilt rotor:
Same efficiency issues with hover vs forward flight trade off as bicopter
either requires an additional tilt mechanism for the third motor, or has a third motor as dead weight

Quadcopter tilt rotor:
as more rotors are added for tilt rotors things get more complicated and less efficient in forward flight

Quadplane:
Has good hover and forward flight prop efficiency
has 4 motors of dead weight to drag around

Pentacopter plane:
Has good hover and forward flight prop efficiency
Has 3 motors of dead weight to drag around

Don't forget the single motor tail-sitters like the Pogo. Also, I suspect attempting to compare efficiency between various mission objectives could become a real "sticky wicket".

How about this single motor for efficiency --

RA-Letters / ICRA 2017 - SUWAVE Aquatic Drone (2 min 32 sec)

and an article on it --

https://www.suasnews.com/2017/06/spl...eid=13417932f1


But then, it could all depend on how you define 'efficiency'.

Originally Posted by eflightray

.........................................


But then, it could all depend on how you define 'efficiency'.

If it needs to hover, is a helicopter more efficient ?

'Efficiency', a word with many ,meanings.

Originally Posted by eflightray

If it needs to hover, is a helicopter more efficient ?

'Efficiency', a word with many ,meanings.

Yes, a helicopter is probably more efficient for hovering.

As stated, the question is too vague to be answerable.

For hovering alone, the power required is directly, mathematically, related to disk loading (Weight/Disk Area), the lower the better. For forward flight, the common measure of goodness is L/D (Lift over Drag). Neither of these is technically efficiency. Any reasonable design choice also contains elements of cost, simplicity, durability, reliability, etc.

If you want an answer, define a specific mission, and be prepared to do a lot of math. That is what the professionals do.

I think the machine concept sown below has good potential for high hover efficiency and very good forward flight efficiency. In hover this type of design can easily have a low disk loading. In forward flight it is like a powered glider. This may not be a good configuration for all missions, but it has good potential as a duration copter and duration plane .

DZYNE Creates A New Approach to Vertical Takeoff and Landing (VTOL): Rotate the Wings (4 min 12 sec)

NASA Tanzenflugel VTOL UAV Concept (2 min 20 sec)

smaller lower aspect ratio wing version of same concept:

SUTD Transformable HOvering Rotorcraft (THOR) (0 min 52 sec)

That's cool! Like a tipjet stoprotor kinda. Also similar to Ran D's circle plane. Transition seems difficult though

I and another guy had talked much about this same idea ,,, only using some kind of compressed air tip jets ,,, but it never looked like it would be easy so we never did anything on it .... but this is so easy ,,,, well the physical build .. I am sure the software is a night mare .

Very interesting thread ,,, thanks for starting it Flywall

No worries, I love this stuff! I think it's interesting that fixed wing VTOL was the red headed step child for so long, with the wheel of failure, or circle of atrocities, or whatever you call it.

Lately, all I seem to hear about is VTOL everything. I enjoy seeing the crazy, out of the norm type designs that really seem to have a legitimate use case (as opposed to the obvious non engineered scams designed to suck investment money out of the market). With so many designs, I thought it would be cool to have a thread dedicated to comparing them, pondering best uses for different designs, etc.

Not a terribly new idea:
https://en.wikipedia.org/wiki/Focke-...iebfl%C3%BCgel
https://en.wikipedia.org/wiki/Rotary_Rocket

The difference is that these stop the rotation for forward flight. So it's a combination of two older ideas (Stop rotor and tip rotor driven heli), but the combination does seem to be relatively new