EP0037633A1
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Helicopter rotor blade
Assignee: Westland Group PLC
•
Filing: 1981-02-27
•
Granted: —
•
Expires: 2001-02-27
Abstract
Abstract A helicopter rotor blade includes inboard and outboard regions (17,18), the outboard region (18) having a basic pitching moment coefficient chosen to improve overall blade performance and the inboard region (17) having a basic pitching moment coefficient chosen to counteract undesirable effects of the high performance outboard region. More particulary, the outboard region (18) has a negative basic pitching moment coefficient greater in absolute value than that of the inboard region (17) and, in one embodiment has a negative basic pitching moment coefficient greater in absolute value than 0.02. A method of selecting and achieving the characteristics of the respective regions is disclosed.
Inventors
- 👤 Frederick John Perry
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-08 05:24
CPC Classifications
B; B64; B64C; B64C27/00; B64C27/32; B64C27/46; B64C27/463
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
78 words
A helicopter. rotor blade having a root end (14) for attachment to a rotor head, a tip end (15) defining the end of the blade farthest from the root end, and a central portion (16) of aerofoil section extending between and attached to the root end and the tip end, characterised in that an outboard region (18) of the central portion has a negative basic pitching moment coefficient greater in absolute-value than that of an inboard region (17)thereof.
Claim 2
Dependent Claim
78 words
A helicopter. rotor blade having a root end (14) for attachment to a rotor head, a tip end (15) defining the end of the blade farthest from the root end, and a central portion (16) of aerofoil section extending between and attached to the root end and the tip end, characterised in that an outboard region (18) of the central portion has a negative basic pitching moment coefficient greater in absolute-value than that of an inboard region (17)thereof.
Claim 3
Dependent Claim
26 words
A rotor blade as claimed in Claim 1, characterised in that said outboard region comprises a region outboard of a seventy per cent rotor radius station.
Claim 4
Dependent Claim
29 words
A rotor blade as claimed in Claim 2, characterised in that said outboard region extends between said seventy per cent station and an eighty per cent rotor radius station.
Claim 5
Dependent Claim
27 words
A rotor blade as claimed in any preceding Claim, characterised in that said inboard and outboard regions and said outboard and tip regions are blended smoothly together.
Claim 6
Dependent Claim
28 words
A rotor blade as claimed in any preceding Claim, characterised in that said outboard region has a negative basic pitching moment coefficient greater in absolute value than 0.02.
Claim 7
Dependent Claim
36 words
A rotor blade as claimed in any preceding Claim, characterised in that the respective pitching moment characteristics of the inboard and outboard regions of said central portion are obtained by camber distribution in the respective regions.
Claim 8
Dependent Claim
25 words
A rotor blade as claimed in Claim 6, characterised in that the camber of the aerofoil section of said inboard region comprises a reflex camber.
Claim 9
Dependent Claim
24 words
A rotor blade as claimed in any preceding Claim, characterised in that said tip end is swept rearwardly with respect to said central portion.
Claim 10
Dependent Claim
29 words
A rotor blade as claimed in any preceding Claim, characterised in that a thickness to chord ratio of said tip end is less than that of said central portion.
Claim 11
Dependent Claim
91 words
A helicopter rotor blade having a root end (14) for attachment to a rotor head, a tip end (15) defining the end of the blade farthest from the root end, and a central portion (16) of aerofoil section extending between and attached to the root end and the tip end and co-operating therewith to define a rotor radius, characterised in that an outboard region (18) of said central portion has a negative basic pitching moment coefficient and inboard region (17) of said. central portion has a positive basic pitching moment coefficient.
Claim 12
Dependent Claim
91 words
A helicopter rotor blade having a root end (14) for attachment to a rotor head, a tip end (15) defining the end of the blade farthest from the root end, and a central portion (16) of aerofoil section extending between and attached to the root end and the tip end and co-operating therewith to define a rotor radius, characterised in that an outboard region (18) of said central portion has a negative basic pitching moment coefficient and inboard region (17) of said. central portion has a positive basic pitching moment coefficient.
Claim 13
Dependent Claim
27 words
A helicopter rotor blade as claimed in Claim 10, characterised in that said negative and positive basic pitching moment coefficients have an absolute value greater than 0.02.
Claim 14
Dependent Claim
39 words
A helicopter rotor blade as claimed in Claim 11, characterised in that the basic pitching moment coefficient of said outboard region is between minus 0.02 and minus 0.04 and that of said inboard region is between 0.02 and 0.04.
Claim 15
Dependent Claim
39 words
A helicopter having a main sustaining rotor system comprising a plurality of rotor blades arranged for rotation about a generally vertical axis, characterised in that the rotor blades are constructed in accordance with any one of the preceding Claims.
References Cited (Backward Citations)
US3721507A
Cited
US3728045A
Cited
US3822105A
Cited
GB1450965A
Cited
US4077741A
Cited
US4142837A
Cited
USPTO Annuity & Maintenance Windows
Maintenance schedule is calculated for granted US utility patents.