|FLIGHT CONTROL LAWS SUMMARY
|Normal operating configuration of the
system. Failure of any single computer does not affect normal law.
Covers 3-axis control, flight envelope protection, and load alleviation.
Has 3 modes according to phase of flight.
- Active when aircraft is on the ground.
- Direct proportional relationship between the
sidestick deflection and deflection of the flight controls.
- Is active until shortly after liftoff.
- After touchdown, ground mode is reactivated and
resets the stabilizer trim to zero.
- Becomes active shortly after takeoff and remains
active until shortly before touchdown.
- Sidestick deflection and load factor imposed on the
aircraft are directly proportional, regardless of airspeed.
- With sidestick neutral and wings level, system
maintains a 1 g load in pitch.
- No requirement to change pitch trim for changes in
airspeed, configuration, or bank up to 33 degrees.
- At full aft/fwd sidestick deflection system
maintains maximum load factor for flap position.
- Sidestick roll input commands a roll
- Roll rate is independent of airspeed.
- A given sidestick deflection always
results in the same roll rate response.
- Turn coordination and yaw damping are
computed by the ELACs and transmitted to the FACs.
- No rudder pedal feedback for the yaw
damping and turn coordination functions.
- Transition to flare mode occurs at 50' RA during
- System memorizes pitch attitude at 50' and begins
to progressively reduce pitch, forcing pilot to flare the aircraft
- In the event of a go-around, transition to flight
mode occurs again at 50' RA.
||Load factor Limitation
- Prevents pilot from overstressing the
aircraft even if full sidestick deflections are applied.
- Pitch limited to 30 deg up, 15 deg
down, and 67 deg of bank.
- These limits are indicated by green =
signs on the PFD.
- Bank angles in excess of 33 deg
require constant sidestick input.
- If input is released the aircraft
returns to and maintains 33 deg of bank.
High Angle of Attack Protection
- When alpha exceeds alpha prot,
elevator control switches to alpha protection mode in which angle of
attack is proportional to sidestick deflection.
- Alpha max will not be exceeded even if
the pilot applies full aft deflection
High Speed Protection:
- Prevents exceeding VMO or MMO by
introducing a pitch up load factor demand.
- The pilot can NOT override the pitch
Low Energy Warning:
- Available in CONF 2,3, or FULL between
100' and 2,000' RA when TOGA not selected.
- Produces aural "SPEED SPEED
SPEED" when change in flight path alone is insufficient to
regain a positive flight path (Thrust must be increased).
|If Multiple Failures of
Redundant Systems occur, the flight controls revert to Alternate
The ECAM displays the message: ALTN LAW:
|The ground mode is identical to Normal
- In pitch alternate law the flight mode
is a load factor demand law similar to the Normal Law flight mode,
with reduced protections.
- Pitch alternate law degrades to pitch
direct law when the landing gear is extended to provide feel for
flare and landing, since there is no flare mode when pitch normal
law is lost.
- Automatic pitch trim and yaw damping
(with limited authority) is available.
- Turn coordination is lost.
- When pitch law degrades from normal
law, roll degrades to Direct Law - roll rate depends on airspeed.
- All protections except for load factor
maneuvering protection are lost.
- The load factor limitation is similar
to to that under Normal Law.
- Amber XX's
replace the green = attitude limits on the PFD.
- A low speed stability function
replaces the normal angle-of-attack protection
- System introduces a progressive
nose down command which attempts to prevent the speed from
- This command CAN be overridden by
- The airplane
CAN be stalled in Alternate Law.
- An audio stall warning consisting
of "crickets" and a "STALL" aural message is
- The Alpha Floor function is
- The PFD airspeed scale is modified:
- VLS remains displayed
- VALPHA PROT and VALPHA
MAX are removed
- They are replaced by a red and
black barber pole, the top indicating the stall warning speed VSW
- A nose up command is introduced any
time the airplane exceeds VMO/MMO to keep the
speed from increasing further, which CAN be overridden by the
- Bank angle protection is lost.
- Certain failures cause the system to
revert to Alternate Law without speed stability.
- Yaw damping is lost if the fault is a
triple ADR failure.
|Abnormal Alternate Law is activated if the
airplane enters an unusual attitude, allowing recovery from the unusual
- Pitch law becomes Alternate (without
autotrim or protection other than Load Factor protection).
- Roll law becomes Direct law with
mechanical yaw control.
- After recovery from the unusual
attitude, the following laws are active for the remainder of the
- Pitch: Alternate law without
protections and with autotrim.
- Roll: Direct law
- Yaw: Alternate law
- There is no reversion to Direct law
when the landing gear is extended.
|Direct law is the lowest level of computer
flight control and occurs with certain multiple failures.
- Pilot control inputs are transmitted unmodified to
the control surfaces, providing a direct relationship between
sidestick and control surface.
- Control sensitivity depends on airspeed and NO
autotrimming is available.
- An amber message USE MAN
PITCH TRIM appears on the PFD.
- If the flight controls degrade to Alternate Law,
Direct Law automatically becomes active when the landing gear is
extended if no autopilots are engaged. If an autopilot is engaged,
the airplane will remain in Alternate Law until the autopilot is
- There are no protections provided in Direct Law,
however overspeed and stall aural warnings are provided.
- The PFD airspeed scale remains the same as in
|In case of a complete loss of electrical
flight control signals, the aircraft can be temporarily controlled by
- Pitch control is achieved through the horizontal
stabilizer by using the manual trim wheel.
- Lateral control is accomplished using the rudder
- Both controls require hydraulic power.
- A red MAN PITCH TRIM ONLY
warning appears on the PFD.