Patent US4416434A successfully refreshed from Google Patents.
US4416434A
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Blade section for rotating wings of an aircraft
Assignee: Office National d'Études et de Recherches Aérospatiales
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Filing: 1981-08-17
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Granted: 1983-11-22
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Expires: 2001-08-17
Abstract
Abstract The present invention relates to a blade section for rotating wings of an aircraft comprising, between the leading edge and the trailing edge, a convex lower surface and an upper surface which is convex over the greater part of its length, but concave near the trailing edge. According to the invention, the upper surface of the section comprises a region of small extent, close to the leading edge but not contiguous thereto, in which the curvature is substantially constant. The invention is applicable to the improvement of the performances in maneuvering flight, while hovering and in advance flight of the aircraft.
Inventors
- 👤 Jean-Jacques Thibert
- 👤 Anne-Marie Rodde
- 👤 Jean-Marc E. Pouradier
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 05:20
CPC Classifications
B; B64; B64C; B64C27/00; B64C27/32; B64C27/46; B64C27/467
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
179 words
A blade section for a helicopter rotor blade comprising, between the leading edge and the trailing edge, a convex lower surface and an upper surface which is convex over the greater part of its length, but concave near the trailing edge, the upper surface comprising: a first zone extending from the leading edge to not more than 30% of the length of the chord in the direction of the trailing edge, said first zone comprising: a first region in which the curvature of the surface has a maximum value at the leading edge and decreases rapidly toward the trailing edge; a second region adjacent said first region in which the curvature is substantially constant, and a third region adjacent said second region and extending to not more than 30% of the chord from the leading edge in which the radius of curvature decreases rapidly; and a second zone adjacent said first zone and extending to at least 60% of the length of the chord from the leading edge in which the curvature of the upper surface is substantially constant.
Claim 2
Dependent Claim
179 words
A blade section for a helicopter rotor blade comprising, between the leading edge and the trailing edge, a convex lower surface and an upper surface which is convex over the greater part of its length, but concave near the trailing edge, the upper surface comprising: a first zone extending from the leading edge to not more than 30% of the length of the chord in the direction of the trailing edge, said first zone comprising: a first region in which the curvature of the surface has a maximum value at the leading edge and decreases rapidly toward the trailing edge; a second region adjacent said first region in which the curvature is substantially constant, and a third region adjacent said second region and extending to not more than 30% of the chord from the leading edge in which the radius of curvature decreases rapidly; and a second zone adjacent said first zone and extending to at least 60% of the length of the chord from the leading edge in which the curvature of the upper surface is substantially constant.
Claim 3
Dependent Claim
41 words
The section of claim 1, wherein said second region encompasses the point on the upper surface whose projection on the chord of the section is at a distance from the leading edge equal to 1% of the length of the chord.
Claim 4
Dependent Claim
32 words
The section of claim 1, wherein said second region extends, in projection on the chord of the section, over a length at least equal to 1% of the length of said chord.
Claim 5
Dependent Claim
41 words
The section of claim 1, wherein said second region is centred at a point whose projection on the chord of the section is at a distance from the leading edge at least equal to 0.5% of the length of said chord.
Claim 6
Dependent Claim
20 words
The section of claim 1, wherein, in said second region, the curvature is about one-fifth that at the leading edge.
Claim 7
Dependent Claim
145 words
The section of claim 1, having a maximum relative thickness between about 11 and 15%, wherein said first zone extends from the lading edge to about 20% of the length of the chord in the direction of the trailing edge, said first region extends from the leading edge, where the curvature is maximum and chosen as base equal to 100, to less than 1% of the length of the chord, said second region is disposed on either side of a point of the chord located at 1% of the length of the chord from the leading edge and has a constant curvature of about 20, said third region has a curvature which decreases from about 20 to about 1, and said second zone extends to about 70% of the length of the chord from the leading edge and has a curvature substantially equal to 1.
Claim 8
Dependent Claim
81 words
The section of claim 6, wherein said second zone is followed by a third zone comprising a first region extending to about 80% of the length of the chord in which the curvature decreases from about 1 to 0, a second region extending to about 97% of the length of the chord in which the curvature decreases from 0 to about -5, and a third region extending to the trailing edge in which the curvature increases from about -5 to 0.
Claim 9
Dependent Claim
83 words
The section of claim 6, wherein said convex lower surface comprises a first zone extending from the leading edge a distance along the chord equal to 1.5% of the length of the chord, in which the curvature decreases continuously from a maximum value chosen as base equal to 100 at the leading edge to about 10, and a second zone adjacent said first zone and extending to about 10% of the chord in which the curvature decreases from about 10 to about 1.
Claim 10
Dependent Claim
41 words
The section of claim 8, wherein said second zone of curvature of the lower surface is followed by a third zone extending to about 95% of the length of the chord, in which the curvature is substantially constant and very small.
Claim 11
Dependent Claim
43 words
The section of claim 9, wherein said third zone of the lower surface is followed by a fourth zone extending substantially to the trailing edge, in which the lower surface is rectilinear and substantially parallel to the corresponding part of the upper surface.
Claim 12
Dependent Claim
23 words
The section of claim 10, wherein, near the trailing edge, the section has a constant thickness substantially equal to 0.4% of the chord.
Claim 13
Dependent Claim
88 words
The section of claim 6, referenced to a system of orthogonal axes OX, OY of which the origin 0 is merged with the leading edge, of which the axis OX is merged with the chord and oriented positively from the leading edge towards the trailing edge and of which the axis OY is oriented positively from the lower surface towards the upper surface, wherein its upper surface is defined by the following relationships, in which C is the length of the chord and x the ratio X/C: ##EQU3##
Claim 14
Dependent Claim
96 words
The section of claim 6, presenting a maximum relative thickness of 13% and referenced to a system of orthogonal axes OX, OY of which the origin 0 is merged with the leading edge, of which the axis OX is merged with the chord and oriented positively from the leading edge towards the trailing edge and of which the axis OY is oriented positively from the lower surface towards the upper surface, wherein its lower surface is defined by the following relationships in which C is the length of the chord and x the ratio X/C: ##EQU4##
Claim 15
Dependent Claim
40 words
A helicopter rotor blade, wherein at least 75% of the length of the blade from its root has a section as specified in any one of claims 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 or 13.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1986-11-21 | 1987-05-23 | 1987-11-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1990-11-21 | 1991-05-23 | 1991-11-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1994-11-21 | 1995-05-23 | 1995-11-22 | $7700.00 | Window Closed / Lapsed |