US 5,735,670 AGranted

Rotor system having alternating length rotor blades and positioning means therefor for reducing blade-vortex interaction (BVI) noise

AssigneeSikorsky Aircraft Corporation

InventorsRobert C. Moffitt, David G. Matuska, Evan A. Fradenburgh

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Abstract

A Variable Diameter Rotor (VDR) system (4) having telescoping odd and even blade assemblies (O.sub.b, E.sub.b) wherein the odd blade assemblies define a radial length R.sub.O and the even blade assemblies define a radial length R.sub.E. Each blade assembly (O.sub.b, E.sub.b) defines an internal chamber (64) for accepting a positioning means (70) operative to effect telescopic translation of the blade assemblies (O.sub.b, E.sub.b) such that the radial length R.sub.E of the even blade assemblies (E.sub.b) is equal to the radial length R.sub.O of the odd blade assemblies (O.sub.b) in a first operating mode, and such that the radial length R.sub.E is between about 70% to about 95% of the length R.sub.O in a second operating mode. The positioning means (70) includes a centrifugal restraint assembly (80) disposed within each internal chamber (64) of the rotor blade assemblies (O.sub.b, E.sub.b), a stop surface (64s) formed internally of each internal chamber (64), and an actuation means (90) operative for transpositioning the centrifugal restraint assemblies (80) within the internal chambers (64) such that, in one operating mode, the centrifugal restraint assemblies (80) are disposed in abutting engagement with the stop surfaces (64s) and, in another operating mode, the actuation means (90) is disposed in abutting engagement with the centrifugal restraint assemblies (80) of at least one of the blade assemblies (O.sub.b, E.sub.b).

Claims23

Dependent claims

A Variable Diameter Rotor system (4) for rotorcraft and operative to reduce Blade-Vortex Interaction (BVI) noise, said rotorcraft operating in first and second operating modes, comprising:

a rotor hub assembly (6) defining an axis of rotation (8) about which said rotor hub assembIy (6) rotates;
odd and even blade assemblies (O.sub.b, E.sub.b) mounting to and rotating with said rotor hub assembly (6), each of said rotor blade assemblies (O.sub.b, E.sub.b) having inboard and outboard blade sections (10, 12) defining an internal chamber (64), said outboard blade section (12) telescopically mounted to said inboard blade section (10) and being biased outwardly of said rotational axis (8) by centrifugal forces C.sub.f acting thereupon;
said odd and even rotor blade assemblies (O.sub.b, E.sub.b) each defining a radial length R.sub.O and R.sub.E, respectively;
means (70) for positioning said outboard blade sections (12) with respect to said inboard blade sections (10) such that, in the first operating mode, said radial length R.sub.E of said even blade assemblies (E.sub.b) is equal to said radial length R.sub.O of said odd blade assemblies (O.sub.b), and, in the second operating mode, said radial length R.sub.E is between about 70% to about 95% of said radial length R.sub.O, said positioning means (70) including:
a centrifugal restraint assembly (80) disposed in each said internal chamber (64) and disposed in combination with said outboard blade section (12), said centrifugal restraint assembly (80) being biased outwardly of said rotational axis (8) by said centrifugal forces C.sub.f acting on said outboard blade section (12);
a stop surface (64s) formed internally of each said internal chamber (64):
and
actuation means (90), in combination with said centrifugal forces operative for transpositioning said centrifugal restraint assemblies (80) within said internal chambers (64) such that, in the first operating mode, said centrifugal restraint assemblies (80) of said even blade assemblies (E.sub.b) are disposed in abutting engagement with said stop surfaces (64s.sub.E) thereof and said centrifugal restraint assemblies (80) of said odd blade assemblies (O.sub.b) are disposed in abutting engagement with said actuation means (90) and, in the second mode, said centrifugal restraint assemblies (80) are disposed in abutting engagement with said stop surfaces (64s).

5 more elements

A Variable Diameter Rotor system (4) for rotorcraft and operative to reduce Blade-Vortex Interaction (BVI) noise, said rotorcraft operating in first and second operating modes, comprising:

a rotor hub assembly (6) defining an axis of rotation (8) about which said rotor hub assembly (6) rotates;
odd and even blade assemblies (O.sub.b, E.sub.b) mounting to and rotating with said rotor hub assembly (6), each of said rotor blade assemblies (O.sub.b, E.sub.b) having inboard and outboard blade sections (10, 12) defining am internal chamber (64), said outward blade section (12) telescopically mounted to said inboard blade section (10) and being biased outwardly of said rotational axis (8) by centrifugal forces C.sub.f acting thereupon;
said odd and even rotor blade assemblies (O.sub.b, E.sub.b) each defining a radial length R.sub.O and R.sub.E, respectively;
means (70) for positioning said outboard blade sections (12) with respect to said inboard blade sections (10) such that, in the first operating mode, said radial length R.sub.E of said even blade assemblies (E.sub.b) is equal to said radial length R.sub.O of said odd blade assemblies (O.sub.b), and, in the second operating mode, said radial length R.sub.E is between about 70% to about 95% of said radial length R.sub.O, said positioning means (70) including:
a centrifugal restraint assembly (80) disposed in each said internal chamber (64) and disposed in combination with said outboard blade section (12), said centrifugal restraint assembly (80) being biased outwardly of said rotational axis (8) by said centrifugal forces C.sub.f acting on said outboard blade section (12);
a stop surface (64s) formed internally of each said internal chamber (64);
and
actuation means (90), in combination with said centrifugal forces C.sub.f, operative for transpositioning said centrifugal restraint assemblies (80) within said internal chambers (64) such that, in the first operating mode, said centrifugal restraint assemblies (80) are disposed in abutting engagement with said stop surfaces (64s) and, in the second operating mode, said centrifugal restraint assemblies (80) of said even blade assemblies (E.sub.b) are disposed in abutting engagement with said actuation means (90).

5 more elements

A Variable Diameter Rotor system (4) for rotorcraft and operative to reduce Blade-Vortex Interaction (BVI) noise, said rotorcraft operating in first, second and third operating modes, comprising:

a rotor hub assembly (6) defining an axis of rotation (8) about which said rotor hub assembly (6) rotates;
odd and even blade assemblies (O.sub.b, E.sub.b) mounting to and rotating with said rotor hub assembly (6), each of said rotor blade assemblies (O.sub.b, E.sub.b) having inboard and outboard blade sections (10, 12) defining an internal chamber (64), said outboard blade section (12) telescopically mounted to said inboard blade section (10) and being biased outwardly of said rotational axis (8) by centrifugal loads C.sub.f acting thereupon;
said odd and even rotor blade assemblies (O.sub.b, E.sub.b) each defining a radial length R.sub.O and R.sub.E respectively;
means (70) for positioning said outboard blade sections (12) with respect to said inboard blade sections (10), said positioning means (70) further including:
a centrifugal restraint assembly (80) disposed in each said internal chamber (64), each said centrifugal restraint assembly (80) including:
a retention block (82) disposed in combination with said outboard blade section (12);
a cradle member (84) disposed in sliding combination with an internal wall (64w) of said internal chamber (64);
and
a connecting means (86) disposed between and mechanically coupling said retention block (82) to said cradle member (84);
said cradle members (84) being biased outwardly of said rotational axis (8) by said centrifugal forces C.sub.f acting on said outboard blade section (12);
said cradle members (84) and the tip end of said outboard blade sections (12) defining a length dimension L therebetween;
a stop surface (64s) formed internally of each said internal chamber (64), said stop surfaces (64s.sub.O) of said odd blade assemblies (O.sub.b), defining a radial distance Rs.sub.O from said rotational axis (8) and said stop surfaces 64s.sub.E of said even blade assemblies (E.sub.b) defining a radial distance Rs.sub.E from said rotational axis (8), said radial distance Rs.sub.E of said stop surface (64s.sub.E) being between about 0.7Rs.sub.O -0.3L to about 0.95Rs.sub.O -0.05L;
and
actuation means (90), in combination with said centrifugal forces C.sub.f acting on said outboard blade section (12), operative for transpositioning said cradle members (84) within said internal chambers (64) such that said cradle members (84) are disposed in abutting engagement with said stop surfaces (64s) in one of the operating modes and in abutting engagement with said actuation means (90) in another of said operating modes;
whereby, in the first operating mode, said actuation means (90) is disengaged from said cradle members (84.sub.E) of said even blade assemblies (E.sub.b) such that said cradle members (84.sub.E) thereof are positioned in abutting engagement with said stop surfaces (64s.sub.E) of said even blade assemblies (E.sub.b), and said actuation means (90) is disposed in abutting engagement with said cradle members (84.sub.O) of said odd blade assemblies (O.sub.b) such that said odd and even blade assemblies (O.sub.b, E.sub.b) are fully-extended, and said radial length R.sub.E of said even blade assemblies (E.sub.b) is equal to said radial length R.sub.O of said odd blade assemblies (O.sub.b);
whereby, in the second operating mode, said actuation means (90) transpositions said cradle members (84.sub.O) of said odd blade assemblies (O.sub.b) such that said cradle members (84.sub.O) thereof are disposed in abutting engagement with said stop surfaces (64s.sub.O), said odd and even blade assemblies (O.sub.b, E.sub.b) alternately vary in length, and said radial length R.sub.E is between about 70% to about 95% of said radial length R.sub.O ;
and
whereby, in the third operating mode, said actuation means (90) engages said cradle members (84) of said odd and even blade assemblies (O.sub.b, E.sub.b) for transpositioning said cradle members (84) thereof such that said odd and even blade assemblies (O.sub.b, E.sub.b) are fully-retracted and said radial length R.sub.E of said even blade assemblies (E.sub.b) is equal to said radial length R.sub.O of said odd blade assemblies (O.sub.b).

15 more elements

A Variable Diameter Rotor system (4) for rotorcraft and operative to reduce Blade-Vortex Interaction (BVI) noise, said rotorcraft operating in first, second and third operating modes, comprising:

a rotor hub assembly (6) defining an axis of rotation (8) about which said rotor hub assembly (6) rotates;
odd and even blade assemblies (O.sub.b, E.sub.b) mounting to and rotating with said rotor hub assembly (6), each of said rotor blade assemblies (O.sub.b, E.sub.b) having inboard and outboard blade sections (10, 12) defining an internal chamber (64), said outboard blade section (12) telescopically mounted to said inboard blade section (10) and being biased outwardly of said rotational axis (8) by centrifugal forces C.sub.f acting thereupon;
said odd and even rotor blade assemblies (O.sub.b, E.sub.b) each defining a radial length R.sub.O and R.sub.E, respectively;
means (70) for positioning said outboard blade sections (12) with respect to said inboard blade sections (10), said positioning means (70) further including:
a centrifugal restraint assembly (80) disposed in each said internal chamber (64), each said centrifugal restraint assembly (80) including:
a retention block (82) disposed in combination with said outboard blade section (12);
a cradle member (84) disposed in sliding combination with an internal wall (64w) of said internal chamber (64);
and
a connecting means (86) disposed between and mechanically coupling said retention block (82) to said cradle member (84);
said cradle members (84) being biased outwardly of said rotational axis (8) by said centrifugal forces C.sub.f acting on said outboard blade section (12);
a stop surface (64s) formed internally of each said internal chamber (64), said stop surfaces (64s.sub.O) of said odd blade assemblies (O.sub.b) defining a radial distance Rs.sub.O from said rotational axis (8), and said stop surfaces (64s.sub.E) of said even blade assemblies (E.sub.b) defining a radial distance Rs.sub.E from said rotational axis (8), said radial distance Rs.sub.O being equal to said radial distance Rs.sub.E ;
and
actuation means (90), in combination with said centrifugal forces C.sub.f acting on said outboard blade section (12), operative for transpositioning said cradle members (84) within said internal chambers (64) such that, in one of the operating modes, said cradle members (84) are disposed in abutting engagement with said stop surfaces (64s) and, in a second operating mode, said cradle members are in abutting engagement with said actuation means (90);
whereby, in the first operating mode, said actuation means (90) is disengaged from said cradle members (84) such that said cradle members (84) are disposed in abutting engagement with said stop surfaces (64s), said odd and even blade assemblies (O.sub.b, E.sub.b) are fully-extended, and said radial length R.sub.E of said even blade assemblies (E.sub.b) is equal to said radial length R.sub.O of said odd blade assemblies (O.sub.b);
whereby, in the second operating mode, said actuation means (90) engages said cradle members (84.sub.E) of said even blade assemblies (E.sub.b) for transpositioning said cradle members (84.sub.E) thereof such that said odd and even blade assemblies (O.sub.b, E.sub.b) alternately vary in length and said radial length R.sub.E is between about 70% to about 95% of said radial length R.sub.O ;
and
whereby, in the third operating mode, said actuation means (90) engages said cradle members (84) of said odd and even blade assemblies (O.sub.b, E.sub.b) for transpositioning said cradle members (84) thereof such that said odd and even blade assemblies (O.sub.b, E.sub.b) are fully-retracted and said radial length R.sub.E of said even blade assemblies (E.sub.b) is equal to said radial length R.sub.O of said odd blade assemblies (O.sub.b).

14 more elements

Dependencies are inferred from the claim text.