A155

OTHER: AeroVantage ~ Concerns & Tasks

Overview:

A listing of Tasks, Potential Concerns and Thoughts, regarding the AeroVantage PropRotor 2x4.

Concerns and Potential Solutions:

Primary Concern:

The application of this craft is long range, high-speed flight, with vertical takeoff and landing. Today's electric storage technology is far from satisfying this requirement. Will research and development be able to provide the required power storage in the relatively near future? Can a turbine-generator converter provide a satisfactory interim solution?

Serious Concerns; at Present:

2x4 only: The strength; and the subsequent weight and drag of a selected transition mechanism.

1x2 & 2x4: Motor failure during hover. See below

To be located to A-group sections where possible.
The Following is Primarily Related to the 2x4:

Prototype:

Would 2-seats or 1-seat be more appropriate for a high-speed aircraft with VTOL capability (i.e. this craft). Being that this craft has high forward speed, it would imply that transportation over a reasonably long distance in a reasonably short time is its strength. This implies more than one seat so that the prototype could be modified into a production craft.

Principal:

Motor failure:

During Cruise: the same motor on the opposite side can be shut down. Actually, during cruise it may not be necessary to shut down a second engine since the rudder can be used.

During Hover: the cruise solution will not work since it would result in a large fore or aft moment about the normal center of lift. Shutting down the diagonally opposed motor will result in the yawing of the craft. There must be double or triple redundancy in the winding of the motors plus the power sources and control circuitry. In addition, the motor's bearings and frame etc. must be oversized. A motor must never totally fail. It may be possible to transition into cruise. Autorotation may be the only solution.

During Transition: Think about this.

The aerodynamics and optimization of the counterrotating coaxial rotors in forward flight, while at the same time optimizing the rotors for independent hovering flight. See; PropRotor

A simple, efficient, reliable and economical Transition Mechanism. See; Transition Mechanism

Will the additional weight, complexity and cost of the two transition mechanisms negate any perceived advantages derived from this concept?

2x4 mainly: Transition Mechanism:

The single worm and wormgear, plus the crown and spider gears at both transition drives, must be strong enough.
Flexing of the wires from the Electronic Speed Controller to the Motors.

PropRotor:

The aft proprotor is TOO low.

Will the rear PropRotors remove the lift from under a segment of the main wings during transitional rotation? Can flaps eliminate this?

Vibration caused by the rear proprotor operating in the streamtube of the front proprotor, particularly when the tilt is not full completed to cruise. Mentioned by Christian [Helidev II]

Make the smaller rear proprotor stronger.

Put more blades on the front and the aft proprotors.

Did Hans test the interaction of two RC propellers at various angles that duplicate transition and cruise?

See; AeroVantage - Vibration

The forward proprotor is putting a downwash on part of the wing when tilt (transitioning and the rear proprotor is removing lift from under a portion of the wing during transition.

Consider reducing the chord of the wing at this location.
The front proprotor may no longer be so much of a problem.
For the aft proprotor consider flaps in the skin of the wing ant the span of the proprotor and have the proprotor draw some free air through the wing.

Stones and debris striking the rear rotor when hovering near the ground. Do not just pivot the rear proprotor a bout a fixed axis . Have it elevate as it assumes the hover position. This should also decrease the removal of lift from under the wing during transition.

Will gyroscopic precession in the motor-rotors generate excessively large moments and forces?

It will be advantageous to reduce the disk loading (larger diameter PropRotors); as long as the ground clearance on the front PropRotor in cruise configuration is great enough.

Trim, Stability & Control:

Vortex Ring State: See; AeroVantage ~ Trim, Stability & Control - Stability

Noise:

There appears to be a number of NASA articles on the subject of noise and counter-rotating propellers See; High Speed Turboprop Aeroacoustic Study (counterrotation). Perhaps noise may not be a concern with the large, lower angle of attack, slower turning PropRotors.

Tasks (to do):

A Transition Mechanism that is; Lightweight, Reliable, Aerodynamic, Simple. An efficient delivery of thrust in both configurations and all conditions. Adjustable Pitch (re: Power, RPM, Torque: Pitch, Drag; Induced, Profile, Parasitic)

Review and elaborate on the flight attitudes and controls. 1636.html

Same Page - Different Craft: ~ Electrotor-Plus ~ UniCopter-UAV ~ Electrotor-Simplex ~ Electrotor-SloMo ~ SynchroLite ~ UniCopter ~ Nemesis

Last Revised: November 22, 2008