Separate lift/thrust systems are growing fast in popularity, to the point that there are already a variety of commercially available systems.  They seem to be the future and continually get better.  Thanks to our developers, Ardupilot has some great features like holding position with forward thrust and is becoming very good at leveraging the benefits of an SLT system.  These systems have the potential to perform very well in windy conditions, since airplanes rely on wind to fly.  It is only a matter of time before the developers have it perfected.  The main argument against SLT systems, is the dead weight they carry around.  The large majority of propulsion weight, is dead weight 95% of the time.

This concept, the tilt rotor/SLT hybrid is an attempt to reduce this dead weight by using horizontal propulsion during both VTOL and cruise.  Compared to typical SLT systems, this would allow lift motor weight to be much lighter.  Unlike typical tilt rotors, nacelle propulsion could be highly optimized for forward flight while the usual structural requirements on the wing would be reduced with the wing being supported at multiple points along the span.

Nacelles could be controlled by differential thrust, containing an IMU and stabilized independently from the main body, eliminating the need for actuators or mechanics of any kind.  The nacelles would be able to tilt forward during VTOL to help with position holding as well as provide very powerful yaw control which is typically a problem for SLT systems.

Feel free to comment.  I would love to get some feedback, good or bad.

I have more info, images and videos about this concept here:

electronflight.com

Views: 1318

Comment by Rainer K. on February 22, 2017 at 5:40am

Your ideas are getting better and better

Comment by Joe Renteria on February 22, 2017 at 8:42am
Thank you Rainer. I appreciate that...
Comment by Martin on February 23, 2017 at 3:35am

Unfortunately the requirements for for forward flight and hovering a very different. For forward flight the thrust needed equals to the the drag of the airframe, which is a lot less then the thrust needed for hovering. It is very inefficient to use the same propeller for hovering and forward flight. The only way to do it efficiently is to use variable pitch propellers. The propulsion system needed for ONLY forward flight is on the order of magnitude lighter than your tilting propeller system.

Comment by Joe Renteria on February 23, 2017 at 9:47am

Hi Martin.  This concept uses two separate propulsion systems.  One is optimized for forward flight, the other for hovering.  The nacelle propulsion only supplements the VTOL propulsion, allowing the VTOL propulsion to be lighter in mass and drag and less of a penalty during cruise.

As a side benefit, the nacelles offer increased redundancy as well as increased maneuverability during both hover and cruise. 

Comment by Mateusz Sadowski on February 23, 2017 at 10:44pm
Hi Joe,
Good idea with the concept. It's a bit difficult to give constructive feedback without knowing the size of the UAV. Some of my thoughts are:
* The motors and propellers seem disproportionally small
* The wing is going to add lots of drag when you do vertical takeoff
* What kind of mechanism are you going to use to tilt the 'wingtips'? Since it's basically a single point connection I'm expecting you to have lots of stresses put on this joint (again it depends on scale and on your thrust)

Keep on the good work!
Comment by Joe Renteria on February 24, 2017 at 2:49pm

Hey Mateusz.  I am looking at all sizes, from small UAV to small manned aircraft.  Sizing was made roughly in comparison with the ehang184.

The wingtips are tilted through differential thrust by the thrusters themselves.  The nacelles contain their own IMU and are self stabilized.  This set up makes more sense for larger aircraft, where sizing motors and props up becomes a problem so instead you would want multiple, smaller rotors.

Thanks!

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