1471

Item 1471

OTHER: Aircraft - PropRotor - AeroVantage - 2x4 Overview

Drawing:

This transition method IS NOT the currently preferred one.

For the currently preferred Transition Mechanisms see; 2x4 - Underslung Arms and Pivots & 2x4 - Extendable Tubes

For all considered mechanisms see AeroVantage ~ Transition Mechanism - Proposed Methods

Perceived Advantages:

Hover:

The 10% loss of thrust due to the downloading on the wings of the V-22 (Leishman) will not exist on this craft.
The disk loading of this configuration will be significantly less than that of the comperable V-22 configuration.

Cruise:

The coaxial counterrotating PropRotors reduces the swirl loss.
The smaller effective disk area and coaxial arrangement allows for higher induced velocities and therefore faster forward velocities.

All:

Capitalizes on the aerodynamic concept known as span-loading. Span-loading refers to the condition where the weight of the aircraft is distributed along the wing in exact proportion to the lift produced thereby eliminating "the need for a heavy wing structure to carry the weight of the fuselage to the opposing lift force exerted by the wing".

Opposing gyroscopic forces from the forward proprotor and the aft proprotor are self cancelled within the two-proprotor and transition mechanism.

Fore and aft wing mounting of PropRotors results in a fairly small gap between the CW and CCW 'props'.

Miscellaneous:

So far, it appears that there is sufficient proprotor to ground clearance to takeoff and land in both helicopter and airplane modes.

Basic Concept of this Proposal:

To be an improvement over the current V-22, Bell-Agusta BA609 and the proposed Sikorsky VRD; by providing;

A large disk area and a lower induced velocity during hover; due to four physically isolated rotor disks, plus no download on the wings.⁽¹⁾
A small 'effective' disk area ⁽²⁾ and a higher induced velocity during cruise; due to the coaxial combining of the fore and the aft disks in the same streamtube.

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Download: The total download for a tilt rotor is typically around 10% of the total rotor thrust in hover OGE. For a QTR, this can lead to a loss of payload carrying capacity of about 30% in VTOL operation, From; .An Experimental Invertigation of Ground Effect on a Quad Tilt Rotor in Hover and Low Speed Forward Flight, Section 1.2.1.

Effective Disk Area: The average of the combined forward and the aft disk areas. Functionally, the forward and the aft rotor disk are located in the same streamtube with the aft disk having a smaller diameter to match the diameter of the front disk's streamtube at the location of the aft disk. See Effective Aerodynamic Disk Area

Elaboration on the Concept:

The concept is to have four independent PropRotor and Motor Assemblies (PRAMA) Later add sketch and put on separate page.

Clean up the following.

Hover:

All four PropRotors face upward. The total disk area is the sum of the area of the four individual disks. The disk loading is to be lower than that of the TiltWing and that of the TiltRotor. The pitch of the blades will be relatively low and the induced velocity will be relatively low.

These four assemblies can be tilted upward so that they act as helicopter rotors. They will have a greater disk loading than the helicopter has, however, they will have a lower disk loading then the existing and proposed tilt-rotors have. In addition, there will be no downloads on the wings.

Cruise:

All four PropRotors face forward. For the total 'effective' disk area see Effective Aerodynamic Disk Area. The pitch of the blades will be relatively high and the induced velocity will be relatively high.

The front PropRotors act as tractor propellers and the rear PropRotors act as pusher propellers.

It also appears that the flight-control (pitch, roll, yaw) in both modes of flight, can be done by independent assembly collective (variable pitch propellers) and independent tilting of the assemblies.

This could probably be initially modeled quite easily in an RC aircraft. Four hollow-shaft motors w/ in-flight variable pitch propellers (I.e. collective, not cyclic)' and four servos w/ independent tilt of each PropRotor.

PropRotor Pros & Cons VS. Coaxial ABC Helicopter and TiltRotor: & OTHER: Aircraft - PropRotor - Pros & Cons vs. TiltRotor This may be duplication.

Center of Thrust and Thrust Vector:

The PropRotors are located below or inline with their respective wings and horizontal stabilizers during cruise. When transitioning to hover, all four PropRotors are to transition in unision. The forward PropRotors may be larger than the aft ones. This is done so that during hover all of the four moments between the PropRotors and the craft's center of gravity are relatively equal.

Miscellaneous:

Disk Loading:

At a gross weight of 750 lbs 2 only 7 ft dia. and 2 only 5.6 ft dia. PropRotors will give a hovering disk area of 126 ft-sq for a disk loading of 6 lb/ft-sq.

At a gross weight of 1,320 lbs 2 only 8 ft dia. and 2 only 7 ft dia. PropRotors will give a hovering disk area of 177.8 ft-sq for a disk loading of 7.45 lb/ft-sq.
Ref. The Osprey V-22 disk loading is 20 lb per ft-sq.
Ref. The TR916 Eagle Eye has 2 only 3-blade rotors with a 10-ft diameter for a total disk area of 157 ft-sq. The maximum gross weight is 3,000 lb giving a disk loading of 19 lb per sq-ft. The maximum speed is 210 kts.

Rotor Stagger:

The streamtubes of the forward rotors may move toward each other during cruise. This means that the lateral ctr-ctr distance of the two aft rotors might be able to be reduced slightly.

Existing Bell Tiltrotors, Sikorsky Patents etc. and Work by Others:

See; AeroVantage ~ PropRotor - Outside Information

This Proposal; 2x4 PropRotor:

The implementation of four isolated PropRotors (quad rotor) for hovering, that when rotated 90º they align as two pair of counterrotating coaxial PropRotors for cruise.
See the following drawing.

Other Information:

OTHER: Aircraft - PropRotor - Pros & Cons vs. TiltRotor

Outside Threads with Request for Input on this Subject:

Associated Ideas on this Site:

OTHER: Aircraft - VTOL - AeroVantage - 1x2 Overview

Initially displayed: January 30, 2008 ~ Posted on PPRuNe; January 31, 2008 ~ Posted on Rotary Wing: January 31, 2008 ~ Posted on Eng-Tips: February 1, 2008 ~ Latest revision; September 2, 2009

The above utility invention is openly and publicly disclosed on the Internet to negate an entity from patenting it, to the exclusion of all others whom may wish to use it. ~ Reference patent law 35 U.S.C. 102 A person shall be entitled to a patent unless - (a) the invention was known ... by others in this country, ..., before the invention thereof by the applicant for patent.