Pilot indicator for predicting changes in the speed of rotation of the main rotor of a rotorcraft
View Patent ↗The present invention relates to a pilot indicator for a rotorcraft provided with a main rotor and at least one gas turbine engine. The indicator has first and second sensors delivering information relating respectively to a first speed of rotation Nr corresponding to said main rotor, and a second speed of rotation NTL corresponding to the free turbine of said engine. The indicator is also provided with display means provided with a display screen for displaying the first and second present values respectively for the first and second speeds of rotation Nr and NTL. In addition, said processor means determines an estimated value for the first speed of rotation Nr.
1. A pilot indicator for a rotorcraft provided with a main rotor and at least one gas turbine engine, the indicator comprising:
first and second sensors delivering information relating respectively to a first speed of rotation Nr corresponding to the main rotor and a second speed of rotation NTL corresponding to the free turbine of said engine;
processor means for processing the information from said first and second sensors; and
display means provided with a display screen for displaying the first and second present values respectively of the first and second speeds of rotation Nr and NTL,
wherein said processor means determines an estimated value for the first speed of rotation Nr, and
wherein, during acceleration of the engine, said processor means determines said estimated value from the following predictive relationship in acceleration, in which IPT, Nr, k, and dNr/dt correspond respectively to said estimated value of said first speed of rotation, said first present value of said first speed of rotation, a multiplier coefficient, and the variation of said present first value during a time interval:
IPT
=
Nr
+
(
k
ⅆ
Nr
ⅆ
t
)
4
.
2. A pilot indicator according to claim 1 , wherein, during deceleration of the engine, said processor means determines said estimated value from the following predictive relationship in deceleration, in which IPT, Nr, k′, and dNr/dt correspond respectively to said estimated value of said first speed of rotation, said first present value of said first speed of rotation, a second multiplier coefficient, and the variation of said present first value during a time interval:
IPT
=
Nr
-
[
[
(
k
ⅆ
Nr
ⅆ
t
)
4
]
]
(
k
′
ⅆ
Nr
ⅆ
t
)
4
.
3. A pilot indicator according to claim 2 , wherein said second multiplier coefficient k′ lies in the range 0 to 0.5.
4. A pilot indicator according to claim 1 , wherein said multiplier coefficient k lies in the range 0 to 0.5.
5. A pilot indicator according to claim 4 , wherein said multiplier coefficient k is substantially equal to 0.082.
6. A pilot indicator according to claim 1 , wherein said processor means limits said estimated value by determining a maximum estimated value.
7. A pilot indicator according to claim 6 , wherein said maximum estimated value is equal to said first speed of rotation Nr, plus:
10 rpm when the first speed of rotation Nr is less than 360 rpm;
20 rpm when the first processor means Nr lies in the range 360 rpm to 410 rpm; and
10 rpm when the first speed of rotation Nr is greater than 410 rpm.
8. A pilot indicator according to claim 1 , wherein said processor means issues an audible warning signal when said estimated value crosses a limit threshold.
9. A pilot indicator according to claim 1 , wherein said processor means issues a visual warning signal when said estimated value crosses a limit threshold.