@Graviman
I became aware of the MTR on reading a paper by Leishman.
Yes, Dr. Leishman lead the initial study in 2004 that concluded the MTR, if ultimately found to be technically feasible, would be half the size, 1/3 the weight, and 1/3 the fuel burn compared to convention helicopters for long range (750nm to 1000nm) missions. In 2005-2006, he performed the fundamental aerodynamic analysis and efficient performance design of the coaxial proprotor blade planform.
It is an interesting concept because it overcomes the disk loading limitations of a conventional tilt-rotor for a given landing area.
Yes, the single MTR rotor design has twice the disk area compared to a conventional wingtip mounted dual tiltrotor for the same tip-to-tip clearance when viewed from above in hover. Dr. Leichman concluded the effective disk area benefit is even greater, because the coaxial is best analyzed as two interfering rotors which results in an effective disk area closer to the sum of the two independent rotors.
The swing wing could add a lot of complication (read weight) when it is notable that "fixed" wing have moved away from swing wings.
No, its not a swing wing. A swing wing rotates about its yaw axis, pivots on a short titanium pin, and has a powerful actuator to overcome aerodynamic and mechanical forces.
The MTR's hinged wing has relatively insignificant additional weight when compared to a conventional wing. The hinge extends from leading edge to trailing edge; the wing's inboard spar extends outboard of the hinge to serve as a "doorstop" and to connect with the outboard spar after the wing fully deploys. Wing deployment is effected by aerodynamic forces and so adds no weight. Engineering analysis of our full scale design reveals additional weight only for the hinge along one wing rib and for a zero insertion force latching mechanism to connect the inner and outer spars. For our flight demonstrator, we built both conventional and hinged wings, and the weight difference is insignificant.
There are still the concerns over autorotation during transition, when the rotor is inclined forwards but the wings are not flying.
This aircraft design is most stable at a 45 degree conversion angle. This statement does not directly answer your concern, but it does indicate an interesting feature of the flight envelope that can be explored for powered off behavior. The MTR design places the CG forward of the wing leading edge in helicopter mode, and underneath the wing quarter-chord in airplane mode. At 45 degrees, half the GW is carried by the rotor and half by the wing which acts as a large horizontal stabilizer just aft of the aircraft CG. The rotor at this 45 degree tilt condition is essentially neutrally stable in pitch and so in combination the stabilizing wing results in a stable aircraft configuration. Yes, we have some work to do to develop a complete answer regarding autorotation, which is planned for both our functional demonstrator and in computer simulation.
At least there is only one rotor system which could be subject to VRS.
True, the value of which should not be underestimated.
What type of role is envisaged for the machine other than cargo?
I ask because cargo seems to be less restrictive on aircraft planform size.
I think it reasonable to envision all roles performed by vertical lift aircraft at all scales, manned or unmanned. I personally have focused on pure technical efficacy, and have so far been influenced by my customers to primarily tailor the design for cargo. The video at Post#1 indicates a JMR attack role.
Doug