Method and device for reducing on an aircraft the effects of a vertical turbulence
View Patent ↗Disclosed is a method and device for attenuating vertical turbulence on an aircraft. The method and device involve calculating, by a calculating unit, based on a determined vertical wind component a first control order to control movement of at least one first controllable movable member that acts on aircraft lift, and a second control order that controls movement of at least one second controllable movable member to act on aircraft pitch. A verification unit verifies that activation conditions evidencing severe turbulence are in effect, the vertical turbulence being attenuated.
1. A method for attenuating vertical turbulence on an aircraft during flight, the method comprising the steps of:
a) determining, by a wind determining unit, a vertical wind component existing outside the aircraft at a current position of said aircraft;
b) calculating, by a calculating unit, based on the determined vertical wind component:
a first control order to control movement of at least one first controllable movable member to act on aircraft lift, said first control order minimizing amplitude of vertical turbulence load factors on the aircraft due to vertical turbulence; and
a second control order to control movement of at least one second controllable movable member to act on aircraft pitch, said second control order compensating for pitch moment of the aircraft due to the movement control of said first movable member;
c) verifying, by a verification unit, activation conditions evidencing severe turbulence are in effect; wherein
said first control order is transmitted to at least one actuator of said first controllable movable member;
said second control order is transmitted to at least one actuator of said second controllable movable member, and
in the course of the flight, the following series of successive steps is carried out:
α) determining, based on the determined vertical wind component, a standard deviation of the wind;
β) comparing the determined standard deviation with a predetermined threshold value, said threshold value being such that, when the determined standard deviation is greater than or equal to said threshold value, the frequency of the wind is less than that of an oscillation of the incidence of the aircraft, due to the wind;
γ) calculating, based on current flight parameter values, a second auxiliary control order to control said second controllable movable member to act on the aircraft pitch, said second auxiliary control order acting indirectly on the aircraft lift at a center of gravity of the aircraft to increase the load factor amplitude; and
δ) transmitting, when said standard deviation is greater than or equal to said threshold value, said second control order to the actuator of said second movable member so that said second movable member is subjected to a global control order corresponding to a sum of said second control order and of said second auxiliary control order.
2. The method as claimed in claim 1 ,
wherein in step α), the standard deviation of the wind σ(k) is calculated according to the following expressions:
σ
(
k
)
=
σ
max
(
k
)
/
3
σ
max
(
k
)
=
pA
·
Wzo
(
k
)
+
(
1
-
pA
)
·
Wzo
(
k
)
-
Wzo
(
k
-
2
)
/
2
·
Te
in which: pA is a predetermined constant;
k is an integer;
Te is the sampling period;
Wzo(k) is the vertical component of the wind in a geographical reference frame at an instant k.Te;
σ(k) is the standard deviation of the wind at the instant k.Te; and
σ max(k) is the maximum of the wind at the instant k.Te.
3. The method as claimed in claim 1 ,
wherein in step γ), said second auxiliary control order δqαwd is calculated according to the following expression:
δ qαwd=K .( s−mq ).α wd 1/ mδq
in which: K is a predetermined constant;
mq and mδq are predetermined coefficients; and
αd1 is the derivative of the incidence of the aircraft, induced by the wind.
4. The method as claimed in claim 1 ,
wherein in step c):
c1) the vertical component of the wind, taken in a reference frame tied to the aircraft, is translated into an angle of incidence, and a dynamic component of the angle of incidence is determined;
c2) a current threshold value which depends on mass, current speed and current altitude of the aircraft is determined; and
c3) said dynamic component of the angle of incidence is compared with said current threshold value, and it is concluded that activation conditions evidencing severe turbulence are fulfilled, when said dynamic component of the angle of incidence is greater than said current threshold value.
5. The method as claimed in claim 1 , wherein:
said first controllable movable member is an aircraft spoiler;
an initial deflection of said spoiler is carried out so as to bring the spoiler to an intermediate deflection position; and
said first control order is applied to said spoiler with respect to the intermediate deflection position.
6. The method as claimed in claim 1 ,
wherein, when at activation conditions evidencing severe turbulence are fulfilled, authority of an automatic piloting system is limited.
7. The method as claimed in claim 1 ,
wherein, when activation conditions are terminated, said control orders that are transmitted to said actuators are canceled.
8. A device for attenuating vertical turbulence on an aircraft during flight, said device ( 1 ) comprising:
at least one first controllable movable member that acts on aircraft lift;
at least one second controllable movable member that acts on aircraft pitch;
wind determining unit that determines a vertical wind component existing outside the aircraft at a current position of said aircraft;
calculation unit that calculates, based on said vertical wind component:
a first control order to control movement of at least one first controllable movable member to act on aircraft lift, said first control order minimizing amplitude of vertical turbulence load factors on the aircraft due to vertical turbulence; and
a second control order to control movement of at least one second controllable movable member to act on aircraft pitch, said second control order compensating for pitch moment of the aircraft due to the movement control of said first movable member;
verification unit that verifies activation conditions evidencing severe turbulence are in effect; and
transmission unit that transmits:
said first control order to at least one actuator of said first controllable movable member; and
said second control order to at least one actuator of said second controllable movable member,
wherein:
said device further comprises:
standard deviation determination unit that determines, based on said vertical wind component, a standard deviation of the wind;
standard deviation comparison unit that compares the this standard deviation with a predetermined threshold value, said threshold value being such that, when said standard deviation is greater than or equal to said threshold value, wind frequency is less than that of an oscillation of the incidence of the aircraft, due to the wind; and
control order calculator that calculates, based on current flight parameter values, a second auxiliary control order for said second controllable movable member, said second auxiliary control order acting indirectly on the aircraft lift at a center of gravity of the aircraft to increase the load factor amplitude; and
said transmission unit transmits, when said activation conditions are fulfilled and said standard deviation is greater than or equal to said threshold value, said second control order to the actuator of said second movable member so that said second movable member is subjected to a global control order corresponding to a sum of said second control order and of said second auxiliary control order.
9. An aircraft, which comprises the device of claim 8 .