Method of monitoring the effectiveness of a damper, and a device for implementing said method

1. A method of monitoring the effectiveness of a damper system for damping the movement components of equipment of an aircraft that result from the lead-lag resonant frequency (ω δ ) of said equipment, said damper system including two strength members that are movable relative to each other and that are connected together by a damper member, the method comprising:

a) measuring, with a movement sensor, the relative movements of the two strength members;

b) filtering, with an electronic filter, the measurements to isolate those that relate to the lead-lag resonant frequency of the equipment;

c) rectifying, with an electronic circuit, the signal that results from the filtering;

d) recording the rectified signal (S);

e) comparing, with a comparator circuit, the rectified signal (S) with a predetermined threshold value (S L ) and returning to step a) so long as the rectified signal (S) does not exceed said threshold value (S L );

f) determining an initial time instant T 0 as soon as the rectified signal exceeds the threshold value (S L );

g) calculating, with an integrator circuit, an integral I 1 of the rectified signal from T 0 to T 0 +δ, where δ is a predetermined time interval characteristic of the damped equipment;

h) calculating, with the integrator circuit, an integral I p of the rectified signal from T 0 to T 0 +pδ, where p is an integer equal to 2, 3, 4, or 5;

i) calculating a ratio R where R=I p /I 1 ;

j) comparing the ratio R with a predetermined limit value R L ;

k) returning to step a) if the ratio R is less than the limit value R L ;

l) activating and delivering an alert instruction (V 1 ) if the ratio R is greater than or equal to the limit value R L , said alert instruction corresponding to a failure of the damper system; and

m) using an electrical power supply to operate at least the filter and the circuits.

2. An effectiveness monitoring method according to claim 1 , further comprising using an integer p=3.

3. An effectiveness monitoring method according to claim 1 , that is implemented continuously on equipment while in operation.

4. An effectiveness monitoring method according to claim 1 , further comprising using pre-established and recorded values for the lead-lag resonant frequency (ω δ ), for the threshold value (S L ), for the limit value R L , and for the characteristic time δ.

5. An effectiveness monitoring method according to claim 1 , wherein the aircraft equipment is a rotor blade.

6. An effectiveness monitoring method according to claim 1 , further comprising monitoring the operating state of the means implementing said monitoring method and delivering at least one additional alert signal (V 2 ) in the event of malfunction.

7. An effectiveness monitoring method according to claim 1 , wherein the limit value R L is initially determined theoretically and is subsequently corrected as a function of experimental results from flight testing.

8. A method of monitoring the effectiveness of a damper system for damping the movement components of equipment of an aircraft that result from the lead-lag resonant frequency (ω δ ) of said equipment, said damper system including two strength members that are movable relative to each other and that are connected together by a damper member, the method comprising:

a) measuring, with a movement sensor, the relative movements of the two strength members;

b) filtering, with an electronic filter, the measurements to isolate those that relate to the lead-lag resonant frequency of the equipment;

c) rectifying, with an electronic circuit, the signal that results from the filtering;

d) recording the rectified signal (S);

e) comparing, with a comparator circuit, the rectified signal (S) with a predetermined threshold value (S L ) and returning to step a) so long as the rectified signal (S) does not exceed said threshold value (S L );

f) determining an initial time instant T 0 as soon as the rectified signal exceeds the threshold value (S L );

g) calculating, with an integrator circuit, an integral I 1 of the rectified signal from T 0 to T 0 +δ, where δ is a predetermined time interval characteristic of the damped equipment;

h) calculating, with the integrator circuit, an integral Ip of the rectified signal from T 0 +pδ to T 0 +(p+1)δ, where p is an integer equal to 2, 3, 4, or 5;

i) calculating a ratio R where R=I p /I 1 ;

j) comparing the ratio R with a predetermined limit value R L ;

k) returning to step a) if the ratio R is less than the limit value R L ;

l) activating and delivering an alert instruction (V 1 ) if the ratio R is greater than or equal to the limit value R L , said alert instruction corresponding to a failure of the damper system; and

m) using an electrical power supply to operate at least the filter and the circuits.

9. An effectiveness monitoring method according to claim 8 , further comprising using an integer p=3.

10. An effectiveness monitoring method according to claim 8 , that is implemented continuously on equipment while in operation.

11. An effectiveness monitoring method according to claim 8 , further comprising using pre-established and recorded values for the lead-lag resonant frequency (ω δ ), for the threshold value (S L ), for the limit value R L , and for the characteristic time δ.

12. An effectiveness monitoring method according to claim 8 , wherein the aircraft equipment is a rotor blade.

13. An effectiveness monitoring method according to claim 8 , further comprising monitoring the operating state of the means implementing said monitoring method and delivering at least one additional alert signal (V 2 ) in the event of malfunction.

14. An effectiveness monitoring method according to claim 8 , wherein the limit value R L is initially determined theoretically and is subsequently corrected as a function of experimental results from flight testing.

15. A device to monitor the effectiveness of a damper system for damping the movement components of equipment of an aircraft resulting from the lead-lag resonant frequency (ω δ ) of said equipment, said damper system including two strength members that are movable relative to each other and connected together by a damper member, the device comprising:

a self-contained power supply unit;

a movement sensor for measuring the relative movements of the strength members;

a bandpass filter for isolating the movement components of the strength members that result from the lead-lag resonant frequency (ω δ );

a diode bridge for rectifying the signal delivered by the bandpass filter;

recording means including a memory for storing the rectified signal;

a comparator circuit for determining the time T 0 at which the value of the rectified and filtered signal exceeds a predetermined threshold value (S L ), making use of an additional memory and a clock;

an integrator circuit for calculating the integral I 1 of the signal from time T 0 to T 0 +δ and the integral I p from T 0 to T 0 +pδ or from T 0 +pδ to T 0 +(p+1)δ, where p is an integer equal to 2, 3, 4, or 5, and where δ is a predetermined time interval characteristic of the damped equipment;

another comparator circuit for calculating the ratio R where R=I p /I 1 , and for comparing said ratio R with a predetermined limit value R L ; and

means for activating or deactivating a visual indicator as a function of the signal coming from the other comparator circuit.

16. A device according to claim 15 , including means for monitoring the operating state of said device and means for activating or deactivating at least one additional visual indicator.