A155

OTHER: AeroVantage ~ Concerns & Tasks

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Overview:

A listing of Potential Concerns, Tasks and Thoughts, regarding the AeroVantage PropRotor [1x2] & [2x4].

Concerns and Potential Solutions:

Primary Concern:

The application of this craft is medium-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?

Weight, Strength and Drag of the Transition Mechanisms:

1x2 & 2x4: The strength (also consider the opposing gyroscopic forces between the fore and aft proprotors - [they must be 'locked' in position during cruise]); and the subsequent weight and drag of a selected transition mechanism.

Alignment of Fore and Aft Streamtubes:

DESIGN: AeroVantage ~ PropRotor - Disk - Effective Aerodynamic Disk Area ~ Concern

Remotely Piloted Testing:

When doing remotely piloted testing and a problem arises, consider the plausibility of;

Braking the rotation of the rotors by regeneration to a capacitor, plus
The discharge of a parachute from the center of gravity, which is located in the clear area between the two rotors.

Trim, Stability & Control:

Particularly lateral stability during rapid descent and when in ground effect. ~(roll control). Consider reducing the area of the wings (since they are only needed for cruise not slow-speed landing ~ flaps could be considered for this). Consider the pros and cone of reducing the lateral rotational inertia of the craft.

Vortex Ring State:

See; AeroVantage ~ Trim, Stability & Control - Stability

Noise:

See; DESIGN: AeroVantage ~ PropRotor - Outside Information - Contra-Rotating Props and Related Material ~ Noise

Weight:

The ratio of Payload to Empty weight.

1x2 Related:

Motor Failure (particularly on a manned craft):

This may not present a meaningful problem; since;

During cruise; either engine should be able to maintain flight and on short final for landing the PropRotors can be tilted up 30º to 45º for a run-on landing.
During hover; power to the operational motor must be immediately and automatically stopped. The craft should then enter autorotation, with the wings providing some of the lift.
The motors should have 2 (or 3) interspaced windings so that the loss of 1 power circuit will not totally disable that motor.
A crazy idea is that of having a hydraulic pump/motor in both of the drive trains, preferable outboard of the motor and transmission. The dumping of the oil would be automatically stopped if one PropRotors were to fail. An even crazier alternative is to utilize pneumatic instead of hydraulic.

Control Failure (particularly on a manned craft):

This may not present a meaningful problem; since;

The electrical control circuits should have double or triple redundancy; for a sensor, controller, wiring and activator perspective.

Power Failure (particularly on a manned craft):

This may not present a meaningful problem; since;

Each of the 2 (or 3) power circuits must have totally independent power source and power wiring.

Lateral Stability:

May be big concern. See; AeroVantage ~ Trim, Stability & Control - Stability ~ Lateral

Restricted pilot's View:

The wings will restrict the downward view of the pilot during hovering activities. Perhaps a larger sweep of the wings will provide a better view, in addition to raising the elevation of the front proprotor during hover.

Lift/drag Ratio:

The vertical depth of the cockpit in a smaller craft will be detrimental to the lift/drag ratio or the craft. I.e. it will detract from the 'lifting body' aspect of a flying wing.

2x4 Related:

To be located to appropriate A-group sections where possible, and linked to from this page..
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:

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. The aft props should also have one or mor blades than the front; to reduce vibration. ~ I think

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.

This may not be so much of a problem now that all PropRotors are now higher in hover.

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.

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.

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

Which craft to go with, Which configuration 1x2 or 2x4? Which scale?

1x2: Raise the elevation of the hovering rotors by a few inches.

1x2: Reduce the wing area slightly.

1x2: Increase the rear longitudinal moment and decrease the front longitudinal moment of the rotors. 1610.html

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

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Last Revised: September 10, 2009