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(2) Pitch control law
**ON A/C 001-049, 051-099, 101-149, 201-299,
(Ref. Fig. 008)
R **ON A/C 151-199, 301-399, 401-499,
(Ref. Fig. 008A)
**ON A/C ALL
Three phases are considered:
-flight,
-flare,
-ground.
These phases are determined by the computers and consolidated by the
information below :
-radioaltimeter altitude,
-R and L L/G compressed signals from the LGCIUs,
-Pitch attitude from the ADIRS,
-wheel speed and spoiler activation from the SECs.
(a) Flight law (Ref. Fig. 009) The C* law is activated. It combines the elevator control and the THS controls (AUTOTRIM function). It generates a load factor demand as a function of the position of the side sticks and inertial feedbacks. The gains depend on the speed (Vc) and center of gravity. The main characteristics of the C* law are:
-load factor demand,
-inclusion of the AUTOTRIM function,
-compensation of the lateral attitude up to 33.,
-A/C response independent from the speed, weight and center of gravity. The maximum surface deflection controlled by the computers are: Elevator deflection: +15, -30 deg THS deflection: +3.5, -11 deg.
Flight Control Laws Figure 008
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Flight Control Laws Figure 008A
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Flight Normal Law Figure 009
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**ON A/C 001-049, 051-099, 101-149, 201-299,
(b)
Flare law (Ref. Fig. 010) This law generates a longitudinal attitude value as a function of the side stick demand, Nz feedbacks and pitch rate. The gains are function of the speed (Vc) and center of gravity. The purpose of this law is to restore the behaviour of a conventional aircraft down to the ground.
(c)
Ground law The side stick outputs directly control the surface position. Elevator kinematics on ground:
-
ELACs "on" , 2 or 3 ADIRUs "on" and SECs "off".
*
If Vc < 70 kts, the deflection is + 15, - 30..
*
If Vc > 70 kts, the deflection is + 15, - 20..
-
ELACs "on" , ADIRUs "off" and SECs "off".
* Fixed Vc = 80 kts, the deflection is + 15, - 20..
-SECs "on" and ELACs "off", the deflection is + 15, - 30..
(d) Not Applicable
R **ON A/C 151-199, 301-399, 401-499,
(b)
Flare law (Ref. Fig. 010) This law generates a longitudinal attitude value as a function of the side stick demand, Nz feedbacks and pitch rate. The gains are function of the speed (Vc) and center of gravity. The purpose of this law is to restore the behaviour of a conventional aircraft down to the ground.
(c)
Ground law The side stick outputs directly control the surface position. Elevator kinematics on ground:
-
ELACs "on" , 2 or 3 ADIRUs "on" and SECs "off".
*
If Vc < 70 kts, the deflection is + 15, - 30..
*
If Vc > 70 kts, the deflection is + 15, - 20..
-
ELACs "on" , ADIRUs "off" and SECs "off".
* Fixed Vc = 80 kts, the deflection is + 15, - 20..
-SECs "on" and ELACs "off", the deflection is + 15, - 30..
Flare Normal Law Figure 010
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(d) Pitch rate law at rotation (theta.) To limit the pitch rate for take-off in order to avoid tail strike in normal operation, a positive (nose-down) demand reduces the direct law order. This demand is function of the pitch rate and side stick position.
**ON A/C ALL
(3)
THS control The elevator orders are progressively transferred to the THS through a low-speed integrator to decrease the drag. This is the AUTOTRIM function. The THS movement is inhibited:
-under 50 ft in manual mode (100 ft in AP mode),
-when the high-speed and Mach protection is active,
-in case of manual action on the hand wheel,
-when the load factor is lower than 0.5 g,
-in case of abnormal condition law.
The THS movement is limited in up direction:
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