Method and apparatus for minimizing the noise emitted by a rotorcraft during take-off and landing
View Patent ↗The method includes a preliminary period in which a reference rotorcraft is used that corresponds to a rotorcraft of a particular type, with a series of noise measurements being performed on said rotorcraft ( 1 ) in flight using noise sensors (C) disposed on said reference rotorcraft, and with operating domains being determined for the reference rotorcraft in which noise is less than a maximum noise level. Thereafter, the operating point without wind and operating domains with wind are subsequently determined for a rotorcraft of the particular type on the basis of operating domains for the reference rotorcraft.
1. A method of minimizing the noise emitted during take-off and landing of a rotorcraft ( 1 ) of a particular type of rotorcraft, the method being characterized in that in a preliminary flight period, in which a reference rotorcraft corresponding to a rotorcraft ( 1 ) of said particular type is used, the following steps are performed:
a) taking a series of measurements on the reference rotorcraft, to obtain during preliminary flights, values for a plurality of noise levels detected by a plurality p of sensors C secured to the reference rotorcraft and representative of noise emission for n configurations of the reference rotorcraft, determined by:
m masses M of said reference rotorcraft;
q speeds of rotation R 1 for the main rotor ( 3 ); and
r speeds of rotation R 2 for the tail rotor ( 4 );
b) from said series of measurements, establishing a first series of n×p diagrams D 1 representing a series of equal noise levels L 1 in a system of coordinates (TA, VZA), where TA is the flight path air-speed and VZA is the vertical air-speed of said reference rotorcraft;
c) transforming said first series of diagrams D 1 into a second series of n×p diagrams D 2 representing a series of equal noise levels L 2 in the system of coordinates (TA, VZA) by:
firstly making a noise correction CV representative of noise nuisance depending on the duration of noise application; and
secondly making a correction CMA to correcting each mass M into an apparent weight MA of the reference rotorcraft as a result of atmospheric conditions at flying altitude;
d) selecting in each diagram D 2 the curve of equal noise levels L 2 P corresponding to a maximum acceptable noise BMA;
e) for each apparent weight MA, establishing the envelope of the curves L 2 P in the system of coordinates (TA, VZA) so as to determine m flight domains DV for which noise is less than said maximum acceptable noise BMA; and
f) selecting in each flight domain DV, an operating domain DF which determines a set of m operating domains of the reference rotorcraft.
2. A method according to claim 1 , characterized in that the correction CMA consists in calculating an apparent weight MA equal to M/(ρ/ρ 0 ) where ρ/ρ 0 expresses the mass per unit volume relative to air at the altitude of flight.
3. A method according to claim 1 , characterized in that the speed correction CV corresponds to a noise penalty in the form 10 log(V/TA), where V designates a reference speed of said rotorcraft ( 1 ).
4. A method according to claim 3 , characterized in that said reference speed V is the least-noise level overflight speed VS of the rotorcraft ( 1 ).
5. A method according to claim 3 , characterized in that said reference speed V is the maximum climb speed VY of the rotorcraft ( 1 ).
6. A method according to claim 1 , characterized in that for each subsequent period relating to take-off and landing of a rotorcraft ( 1 ) of a particular type of rotorcraft, the following steps are performed:
a) calculating the instantaneous equivalent mass ME of the rotorcraft ( 1 ); and
b) determining the operating point F without wind and the instantaneous operating domain with wind DF 1 of the rotorcraft ( 1 ) for said instantaneous equivalent mass ME on the basis of the set of m operating domains of the reference rotorcraft.
7. A method according to claim 6 , characterized in that said operating are determined domains DF and DF 1 occupy two angular sectors (S 3 , S 4 ), each of these angular sectors having the operating point F without wind as its vertex and presenting a safety margin MS respectively relative to two angular sectors (S 1 , S 2 ) coming from the operating point F without wind.
8. A method according to claim 7 , characterized in that the operating point F without wind is independent of the equivalent mass ME of the rotorcraft ( 1 ) of the particular type of rotorcraft.
9. A method according to claim 7 , characterized in that the effective operating points with wind FEF are situated on two straight half-lines Fu, Ff and Ft, Ff″, each of the straight half-lines passing via the operating point F without wind and being contained in a respective one of the angular sectors S 3 and S 4 , thereby determining a control law uFt, fFf′ with wind.
10. A method according to claim 7 , characterized in that the effective operating points with wind FEF are situated on a curve vFw passing through the operating point F without wind, the curve portions vF and wF being contained respectively in the sectors S 3 and S 4 , thereby determining a control law vFw with wind.
11. A method according to claim 9 , characterized in that the control law uFt, fFf′ is independent of the equivalent mass ME of a rotorcraft ( 1 ) of the particular type of rotorcraft.
12. A method according to claim 10 , characterized in that the control law vFw is independent of the equivalent mass ME of a rotorcraft ( 1 ) of the particular type of rotorcraft.
13. A method according to claim 6 , characterized in that the effective operating points with wind FEF are situated on a control curve vFw with wind passing through the operating point F without wind, said curve vFw being equidistant from the domains in which noise is greater than the maximum acceptable noise BMA.
14. A method according to claim 13 , characterized in that the control law vFw is independent of the equivalent mass ME of a rotorcraft ( 1 ) of the particular type of rotorcraft.
15. A method according to claim 9 , characterized in that an operating constraint is determined corresponding to a flight path of constant slope θ SH for a rotorcraft ( 1 ) of the particular type of rotorcraft.
16. A method according to claim 9 , characterized in that an operating constraint is determined corresponding to the maximum climb performance function.
17. A method according to claim 9 , characterized in that an operating constraint is determined corresponding to a relationship representing the flight path air-speed TA as a function of time.
18. A method according to claim 1 , characterized in that said plurality of noise levels includes at least the following noise levels whose values are measured by sensors (C) disposed:
a) on the side of the fuselage ( 2 ) of the reference rotorcraft corresponding to the blade advance side:
in a first zone N 1 at the front of the fuselage ( 2 );
in a second zone N 2 , slightly ahead of the main rotor ( 3 ) of said rotorcraft ( 1 ); and
in a third zone N 3 behind said main rotor ( 3 ); and
b) at each of the ends of horizontal tail plane ( 12 ) of said reference rotorcraft.
19. A method according to claim 1 , characterized in that said plurality of noise levels includes at least the following noise levels whose values are measured by sensors (C) disposed:
a) on the side of the fuselage ( 2 ) of the reference rotorcraft corresponding to the blade advance side:
in a first zone N 1 at the front of the fuselage ( 2 );
in a second zone N 2 , slightly ahead of the main rotor ( 3 ) of said rotorcraft ( 1 ); and
in a third zone N 3 behind said main rotor ( 3 ); and
b) on a pole situated in the plane of the tail rotor ( 4 ).
20. A method according to claim 1 , characterized in that the plurality of noise levels includes noise levels whose values are measured by sensors (C) disposed in several zones N 1 , N 2 , N 3 on the side of the fuselage ( 2 ), and further includes noise levels measured in zones M 1 , M 2 , and M 3 that are respectively symmetrical to the zones N 1 , N 2 , and N 3 about the longitudinal plane of symmetry of said reference rotorcraft.
21. A method according to claim 1 , characterized in that the plurality of noise levels includes noise levels whose values are measured by sensors (C) disposed in several zones that are situated outside said fuselage ( 2 ) of said reference rotorcraft.
22. A method according to claim 1 , characterized in that the plurality of noise levels includes noise levels whose values are measured by sensors (C) disposed in several zones that are situated inside said fuselage ( 2 ) of said reference rotorcraft.
23. A method according to claim 1 , characterized in that said number n of configurations of said reference rotorcraft comprises:
at least one mass M corresponding to m=1; and
at least one speed of rotation R 1 of the main rotor ( 3 ) corresponding to q=1.
24. A method according to claim 1 , characterized in that said number n of configurations of said reference rotorcraft comprises:
three masses M corresponding to m=3; and
three speeds of rotation R 1 of the main rotor ( 3 ) corresponding to q=3.
25. A method according to of claim 1 , characterized in that said number n of configurations of said reference rotorcraft comprises:
three masses M corresponding to m=3;
three speeds of rotation R 1 of the main rotor ( 3 ) corresponding to q=3; and
three speeds of rotation R 2 of the tail rotor ( 4 ) corresponding to r=3.
26. A method according to claim 1 , characterized in that said maximum noise level BMA corresponds to the minimum noise level in level flight at nominal speed of said rotorcraft ( 1 ).
27. A method according to of claim 1 , characterized in that said sensors (C) are microphones.
28. A method according to claim 1 , characterized in that it is implemented for a rotorcraft ( 1 ) selected from the group consisting of: a helicopter, a rotorcraft combining a rotary-wing and a fixed-wing, a convertible rotorcraft.