Blade for a helicopter anti-torque device

Patent metadata

Field	Value
Publication number	US-9162749-B2
Application number	US-201414528507-A
Country	US
Kind code	B2
Filing date	Oct 30, 2014
Priority date	Dec 15, 2010
Publication date	Oct 20, 2015
Grant date	Oct 20, 2015

Abstract

A blade ( 1 ) for a tail anti-torque device of a helicopter, said device comprising a ducted rotor ( 13 ). The blade ( 1 ) has an assembly of sections, a leading edge ( 2 ) and a trailing edge ( 3 ); a stacking line ( 4 ) of the profiles extending at a distance lying in the range 25% to 50% of the chord (C). The stacking line ( 4 ) presents a shape that is curved having successively from the root ( 5 ) to the end ( 6 ) of the blade a back sweep, a forward sweep, and a last back sweep; and a chord (C) that becomes larger going towards the end ( 6 ) of the blade ( 1 ) over at least the end profile ( 1 a ).

First claim

The invention claimed is:

1. A blade for a tail anti-torque device of a rotorcraft, the device comprising a ducted rotor, the blade having a three-dimensional geometrical shape defined by different airfoil profile sections extending between a leading edge and a trailing edge of the blade and defined radially by a root section and by an end section of the blade; at least two of the airfoil profile sections having different chord values along a stacking line extending from the root section to the end section, the blade being twisted, the stacking line, prior to twisting, defining a plane extension surface defined radially from the root section to the end section, and a twisting line of the plane extension surface that is defined by a predetermined twisting relationship, the stacking line extending at a distance lying in a range 25% to 50% of a respective chord (C) for each of the airfoil profile sections from the leading edge and presenting a curve on the plane extension surface comprising in succession from the root section: a first back sweep; a forward sweep; and finally a last back sweep going to the end section; the end section having an end chord (c max ) and the root section having a root chord (C ref ) less than the end chord (c max ), the end chord (c max ) being the largest of the respective chords, and the end chord (C max ) being equal to or less than 1.6 times the root chord (C ref ) of the root section, wherein the stacking line is a curve traced relative to a radial direction of the tail anti-torque device and given by a polynomial such that:
Y AC /C ref =a e ×Q 3 +b e ×Q 2 +c e ×Q with 0 ≦Q≦ 1

where:

Q
=

r
-
k

R
max

-
k

is a non-dimensional number;
Y AC is a position of the stacking line of the respective airfoil profile sections for a radius r; k is a radius of the root section, R max designates a maximum radius of the end section, and a e , b e and c e are first, second, and third predetermined values,
wherein the respective chords (C) are defined by a variable relationship such that a chord value C(r) for a radius r of a respective section of the airfoil profile sections, is given by:

⁢

C
⁡

(
r
)

=

C
ref

,

if
⁢

⁢
k

≤
r
≤

b
c

×

R
max

⁢
and

C
⁡

(
r
)

=

C
ref

+

[

C
max

-

C
ref

]

×

[

r
-

(

b
c

×

R
max

)

]

n

{

R
max

-

(

b
c

×

R
max

)

]

n

⁢

⁢
if
⁢

⁢
r

≥

b
c

×

R
max

where k is the radius of the root section, R max designates the maximum radius of the end section, C max designates the chord of the end section and is equal to a c ×C ref , where a c is a factor, x designates the multiplication sign and b c and n designate first and second predetermined constants, and
wherein the first predetermined constant b c lies in a range 0 to 1.

2. The blade according to claim 1 , wherein the respective airfoil profile sections present relative thickness that decreases progressively in a radial direction from the root section towards the end section to present a relative thickness at the end section that lies in a range 9% to 6%.

3. The blade according to claim 1 , wherein the root section presents a relative thickness that lies in a rang

Assignees

• Airbus Helicopters

Inventors

• Gervais Marc
• Gresle Benoit
• Finck Sebastein
• Sudre Laurent

Classifications

• Y10S416/05

  Variable camber or chord length · CPC title

• Y10S416/02

  Formulas of curves · CPC title

• B64C27/82

  characterised by the provision of an auxiliary rotor or fluid-jet device for counter-balancing lifting rotor torque or changing direction of rotorcraft · CPC title

• B64C2027/8254

  Shrouded tail rotors, e.g. "Fenestron" fans · CPC title

• B64C11/18 Primary

  Aerodynamic features · CPC title