The aircraft can be flown in normal law, alternate law (with and without reduced protections), direct law and mechanical back up.
NORMAL LAW
There are three modes of normal law; ground mode, flight mode and flare mode.
Ground mode
. Direct control of elevator, spoilers, ailerons and rudder. This is progressively blended out when airborne so that flight mode becomes effective.
Flight mode
.
Side-stick movement in the pitch axis commands a change in "g". Zero displacement is a positive command for 1g flight. 1g flight means no change in flight path. So once the correct flight path has been established, in the short term it will be maintained, despite any changes to thrust or speed. Hence there is no need to trim.
.
Side-stick movement in the roll axis commands a given rate of roll. Zero displacement is a positive command for zero roll rate flight. Once the required bank angle has been established, release the side-stick to neutral and it will be maintained.
.
Resist the temptation to "overcontrol" the aircraft. Make a small input then gently release to neutral and leave the stick alone unless a further adjustment is required. All turns may require some side-stick and power adjustments.
Flare mode
. A change in pitch control below 50 ft only, requiring a gentle pull on the sidestick during the flare in order to maintain a progressive flare.
Protections :
Full flight envelope protection is provided in normal law using the following individual
protections.
.
Load factor limitation
.
Attitude protection (Pitch and Bank)
.
High angle of attack protection (between VPROT and VMAX the sidestick demands angle of attack up to MAX and the aircraft does not stall)
.
High speed protection
A319/A320/A321 FLIGHT CREW TRAINING MANUAL NORMAL OPERATION BRIEFINGS FLIGHT CONTROLS FLIGHT CHARACTERISTICS 1.02.34 Page 3
REV 21 MAY 98
ALTERNATE LAW
Depending on the particular failure that causes the degrading of the flight control laws, ECAM will indicate whether Alternate Law with or without protections is active. The indications will be ALTN LAW or ALTN LAW : PROT LOST . The main differences between these two laws and normal law are detailed below.
In alternate law pitch control is similar to normal law with some changes in the protections available.
Roll control is the same as direct law with the sidestick demanding aileron deflection rather than roll rate.
Protections :
Load factor limitation........................................ same as normal law
Pitch attitude protection ................................... not provided
High angle of attack protection ........................ - changed to low speed stability
(PFD display also changes, VSWis shown and stall warning is provided) High speed protection......................................changed to alternate high speed stability
In some failure cases alternate law without protection is available. All protections except load factor limitation are lost.
DIRECT LAW
ECAM will indicate to the crew when direct law is the active flight control law and USE MAN PITCH TRIM will be displayed on the PFD as a reminder.
In direct law, the sidestick is coupled directly to the controls, without any stabilization feedback. In effect, it becomes like a conventional aircraft. Manual pitch trim must be used. No protections are available.
MECHANICAL BACK-UP
In the unlikely event of certain multiple failures, pitch trim and rudder can be used to control the aircraft by mechanically controlling the associated hydraulic motors. If it is necessary to use the pitch trim wheel to control the aircraft in pitch, MAN PITCH TRIM ONLY will be displayed in red on the PFD. There is no turn coordination and no protections are operative.
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