METHOD OF OPTIMIZING SECTIONS OF A TAIL BOOM FOR A ROTARY WING AIRCRAFT

• US 20180029702A1
• Filed: 07/28/2017
• Published: 02/01/2018
• Est. Priority Date: 07/28/2016
• Status: Active Grant

• Current Assignee: Airbus Helicopters
• Original Assignee: Airbus Helicopters
• Inventors: ALFANO, David, LEGRAS, Guillaume, LEUSINK, Debbie
• Granted Patent: US 10,640,206 B2
• Time in Patent Office: Days
• CPC Class Codes: B64C 1/0009 Aerodynamic aspects
• CPC Class Codes: B64C 27/06 with single rotor
• CPC Class Codes: B64C 27/82 characterised by the provision of an auxiliary rotor or fluid-jet device for counter-balancing lifting rotor torque or changing direction of rotorcraft
• CPC Class Codes: B64F 5/00 Designing, manufacturing, assembling, cleaning, maintaining or repairing aircraft, not otherwise provided for; Handling, transporting, testing or inspecting aircraft components, not otherwise provided for
• CPC Class Codes: G06F 2113/28 Fuselage, exterior or interior
• CPC Class Codes: G06F 30/20 Design optimisation, verification or simulation optimisation, verification or simulation of circuit designs G06F30/30
• CPC Class Codes: Y02T 50/10 Drag reduction
• CPC Class Codes: Y02T 90/00 Enabling technologies or technologies with a potential or indirect contribution to GHG emissions mitigation

Abstract

A method of optimizing sections of a tail boom for a rotary wing aircraft, and also to a tail boom including such sections. The method comprises the step of creating a database characterizing standard sections for a tail boom that give precedence to minimizing a negative lift and/or to increasing a lateral force generated by the air stream from the main rotor of the aircraft flowing over the tail boom, a step of establishing looked-for aerodynamic and structural characteristics for said tail boom, and a step of defining the sections of the tail boom as a function of the standard sections and of the looked-for aerodynamic and structural characteristics. The tail boom as defined in this way optimizes the reduction in the negative lift and/or the increase in the lateral force generated by the air stream from the main rotor.

Claims

1. A method of optimizing sections of a tail boom for a rotary wing aircraft having at least one main rotor, the tail boom extending in a longitudinal direction, each section being defined in a plane perpendicular to the longitudinal direction by a chord between a leading edge and a trailing edge of the section, and by a maximum thickness measured perpendicularly to the chord, wherein the method comprises the following steps:

a step of performing studies, digital simulations, and/or tests on section profiles for a tail boom;

a step of creating a database characterizing standard sections for a tail boom, the database having four types of standard sections for the tail boom, a first type of standard sections being symmetric and maximizing the lateral force of the tail boom, a second type of standard sections being asymmetric and maximizing the lateral force, a third type of standard sections being symmetric and minimizing the negative lift of the tail boom, and a fourth type of standard sections being asymmetric and minimizing the negative lift;

each standard section being defined by extreme characteristic points A0, A1, A2, A3 and by intermediate characteristic points A01, A02, A11, A12, A21, A22, A31, A32, the characteristic points being defined in a secondary reference frame attached to each standard section and defined by the directions of the chord and of the maximum thickness, one unit along the abscissa axis or along the ordinate axis being equal to the chord, the extreme characteristic points A0, A1, A2, A3 belonging to an outline of the standard section, A0 being situated at the trailing edge and having coordinates (1,0), A2 being situated at the leading edge and having coordinates (0,0), the extreme characteristic points A1 and A3 forming the maximum thickness and having respective coordinates −

t/(2.c) and t/(2.c), the intermediate characteristic points A01, A02, A11, A12, A21, A22, A31, A32 being construction points for constructing the outline of the standard section serving to define a direction of the outline of the section at each extreme characteristic point A0, A1, A2, A3;

a step of establishing looked-for aerodynamic and structural characteristics of the tail boom in terms of lateral force and negative lift generated by the air stream from the main rotor flowing over the tail boom; and

a step of defining the sections of the tail boom as a function of the standard sections and of the looked-for aerodynamic and structural characteristics for the tail boom in order to give precedence to minimizing the negative lift and/or to maximizing the lateral force of the tail boom.

2. A method according to claim 1, wherein the standard sections are defined as a function of the ratio of the maximum thickness of each standard section divided by the chord of the standard section.

3. A method according to claim 2, wherein for standard sections of the first type that are symmetric and maximize the lateral force, the maximum thickness of a standard section is arranged downstream from the middle of the chord of the standard section in the flow direction of the air stream from the main rotor, for standard sections of the second type that are asymmetric and maximize the lateral force, the maximum thickness is arranged downstream from the middle of the chord and in the proximity of the middle of the chord, and for standard sections of the third type that are symmetric and for standard sections of the fourth type that are asymmetric, and minimize the negative lift, the maximum thickness is arranged upstream from the middle of the chord.

4. A method according to claim 1, wherein the database comprises the following first table defining ranges for the characteristic points for the symmetric standard sections of the first type:

5. A method according to claim 4, wherein the ordinate coordinates of the intermediate characteristic points A02, A11 are equal to the ordinate coordinate of the extreme characteristic point A1, the ordinate coordinates of the intermediate characteristic points A22, A31 are equal to the ordinate coordinate of the extreme characteristic point A3, the abscissa coordinates of the intermediate characteristic points A01, A32 are equal to the abscissa coordinate of the extreme characteristic point A0 and the abscissa coordinates of the intermediate characteristic points A12, A21 are equal to the abscissa coordinate of the extreme characteristic point A2.

6. A method according to claim 1, wherein each section of the tail boom is formed by 4^th-order Bezier curves connecting the extreme characteristic points A0, A1, A2, A3, A0 together in pairs and constructed using the intermediate characteristic points A01, A02, A11, A12, A21, A22, A31, A32.

7. A tail boom for a rotary wing aircraft having at least one main rotor, the tail boom extending in a longitudinal direction, the tail boom being constituted by successive sections defined in planes perpendicular to the longitudinal direction by a chord between a leading edge and a trailing edge of the section and by a maximum thickness measured perpendicularly to the chord, wherein the sections of the tail boom are defined using the method according to claim 1 for optimizing sections of a tail boom, the sections of the tail boom being defined using a predefined database and as a function of looked-for aerodynamic and structural characteristics of the tail boom, the database characterizing standard sections of the tail boom and the looked-for aerodynamic and structural characteristics of the tail boom quantifying a lateral force and a negative lift generated by the air stream from the main rotor flowing over the tail boom.

8. A rotary wing aircraft including a fuselage and at least one main rotor having a plurality of blades, the fuselage being extended by a tail boom extending in a longitudinal direction, wherein the tail boom is a tail boom according to claim 7.