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Sep 03, 2017, 01:29 AM
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Flywall's Avatar

VTOL type efficiencies

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.
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Sep 03, 2017, 04:48 AM
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rchopper56's Avatar
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.
Sep 03, 2017, 11:11 AM
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Tons of information here:

Google search here < vtol configuration efficency >
Sep 03, 2017, 02:24 PM
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Flywall's Avatar
Yeah, I looked through and picked some great info out. Just thought it would be cool to have a thread dedicated to comparisons.
Sep 03, 2017, 04:32 PM
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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

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
Sep 03, 2017, 06:31 PM
Registered User
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".
Sep 07, 2017, 01:02 PM
An itch?. Scratch build.
eflightray's Avatar
How about this single motor for efficiency --

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

and an article on it --

But then, it could all depend on how you define 'efficiency'.
Sep 07, 2017, 01:07 PM
An itch?. Scratch build.
eflightray's Avatar
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.
Sep 07, 2017, 03:33 PM
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Ran D. St. Clair's Avatar
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.
Sep 07, 2017, 07:49 PM
Winging it Ō>
leadfeather's Avatar
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)
Last edited by leadfeather; Sep 07, 2017 at 08:12 PM.
Sep 08, 2017, 09:31 AM
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That's cool! Like a tipjet stoprotor kinda. Also similar to Ran D's circle plane. Transition seems difficult though
Sep 08, 2017, 11:49 AM
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v22chap's Avatar
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
Sep 13, 2017, 01:08 AM
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Flywall's Avatar
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.
Sep 19, 2017, 08:56 AM
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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

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