# US 8,783,606 B2 · Method for improving the aerodynamic efficiency of the vertical tail of an aircraft

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- Number: US 8,783,606 B2
- Document ID: US8783606B2
- Status: Granted
- Kind: B2
- Application number: 13/439,341
- Filed: 2012-04-04
- Published: 2012-10-11
- Granted: 2014-07-22
- Earliest claimed: 2011-04-06
- Assignees: Airbus Operations GmbH
- Applicants: Alain Tanguy
- Inventors: Alain Tanguy
- Web page: https://patentgrep.com/patent/US8783606B2

## CPC

- B64C 5/06: Fins (B64C5/08 takes precedence)
- B64C 9/00: Adjustable control surfaces or members, e.g. rudders (trimming stabilising surfaces B64C5/10)
- B64C 2003/147: {comprising trailing edges of particular shape}
- Y02T 50/10: Drag reduction
- B64C: AEROPLANES; HELICOPTERS
- Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION

## Abstract

A method for improving the aerodynamic efficiency of the vertical tail of an aircraft includes varying the thickness of the trailing edge of the rudder as a function of the span of the vertical tail. This variation is intended to adapt the local value of the coefficient of lateral lift applied to the vertical tail closer to a maximum allowable value. The maximum allowable value is specifically the value at which a separation of the aerodynamic flow is observed on the surface of the vertical tail.

## Claims

### Claim 1

A method for improving the aerodynamic efficiency of an aircraft vertical tail, comprising a drift and a rudder able to pivot with respect to the drift, the method comprising:
varying a thickness of a trailing edge of the rudder as a function of a span of the vertical tail, to bring a local value of a coefficient of lateral lift applied to the vertical tail closer to a maximum allowable value, wherein the maximum allowable value of the coefficient of lateral lift is the value beyond which, for a given angle between the rudder and the drift, a separation of the aerodynamic flow is observed on the surface of the vertical tail.

### Claim 2 (depends on 1)

The method according to claim 1, wherein the variable thickness of the trailing edge of the rudder is determined, as a function of the local value of the coefficient of lateral lift calculated with an angle of the rudder with respect to the drift, for which a separation of the aerodynamic flow is observed on the surface of the vertical tail.

### Claim 3 (depends on 1)

The method according to claim 1, wherein the thickness of the trailing edge of the rudder is varied as a function of the span of the vertical tail, according to a thickness variation linear law (EP1), with a thickness decreasing from an internal end to an external end of the vertical tail.

### Claim 4 (depends on 1)

The method according to claim 1, wherein the thickness of the trailing edge of the rudder is varied as a function of the span of the vertical tail, with a thickness decreasing from an internal end to an external end of the vertical tail, according to an optimized thickness variation law (EP2) enabling to match the local value of the coefficient of lateral lift and the maximum allowable value.

### Claim 5

An aircraft vertical tail, comprising:
a drift and a rudder able to pivot with respect to said drift,
wherein said rudder has a variable thickness from a trailing edge thereof following a span of the vertical tail, enabling to bring a local value of a coefficient of lateral lift applied to the vertical tail closer to a maximum allowable value, and
wherein the maximum allowable value of the coefficient of lateral lift is the value beyond which, for a given angle between the rudder and the drift, a separation of the aerodynamic flow is observed on the surface of the vertical tail.

### Claim 6 (depends on 5)

The vertical tail according to claim 5, wherein the thickness of the trailing edge of the rudder is varied as a function of the span of the vertical tail, according to a thickness variation linear law (EP1), with a thickness decreasing from an internal end to an external end of the vertical tail.

### Claim 7 (depends on 5)

The vertical tail according to claim 5, wherein the thickness of the trailing edge of the rudder is varied as a function of the span of the vertical tail, with a thickness decreasing from an internal end to an external end of the vertical tail, according to an optimized thickness variation law (EP2), enabling to match said local value of the coefficient of lateral lift and said maximum allowable value.

### Claim 8 (depends on 5)

An aircraft, comprising:
a fuselage; and
a vertical tail such as specified in claim 5.