List Control Laws
- Normal Law
- Alternate Law
- Direct Law
- Abnormal Attitude Law
- Mechanical Backup
Normal Law
Normal sequence of modes
- Ground mode
- Rotation mode (A321 only)
- Flight mode
- Flare mode
- Ground mode
What happens after recovery from abnormal attitude law?
Reverts to alternate law
When can alternate law have flare mode?
If the cause of alternate law was abnormal attitude law.
When does alternate law switch to direct law?
Gear down
&
Autopilot off
How is normal law depicted?
Green equal signs on PFD for bank angle limits.
(There are more, this is just the most obvious)
How is alternate law depicted?
Amber Xs on PFD where bank angle limits usually are.
(There are more, this is just the most obvious)
How is direct law depicted?
Amber Xs on the PFD
&
Amber “USE MAN PITCH TRIM” on PFD
How is mechanical backup depicted?
Amber Xs on the PFD
&
Red “MAN PITCH TRIM ONLY” on PFD
What controls do you have in mechanical backup?
- Manual stabilizer trim
- Rudder
- Thrust levers
(Hydraulics required)
When is it possible to be in mechanical backup and still have SOME normal roll flight controls working?
ELAC 1 fail
ELAC 2 fail
SEC 1 fail
SEC 2 fail
If the four computers above fail, there will not be any elevator control. This puts you in mechanical backup.
However, SEC 3 still controls one ground and one flight spoiler on each wing. Specifically spoiler 1 and 2 (1 is most inboard).
So you’ll still have roll control using spoiler 2 via the SEC 3.
Normal Law Protections
List them
- Bank
- Pitch
- Angle of Attack
- Load Factor
- High Speed:
Normal Law Protections
Describe BANK protections
67°: Max bank
45°: FD out of view, AP disconnects, max bank when high speed or alpha prot protections are active
33°: Max with neutral sidestick (letting go and bank returns to 33° - Positive static spiral stability). Max bank for autotrim
Yaw Damping & Turn Coordination
Which control laws have them?
Normal Law:
* Yaw damping
* Turn coordination
Alternate Law:
* Yaw damping only (depending on failures)
Direct Law: NO
Abnormal attitude law: NO
Normal Law Protections
Describe ANGLE OF ATTACK protections
Low energy warning: “SPEED, SPEED, SPEED”. Thrust is required.
Vls:
Lowest selectable speed with autothrust & AP engaged. Min maneuvering.
Vα Prot - Alpha Prot:
* Max bank: 45°
* Autopilot disconnects
* Speed brakes retract
* Sidestick controls AOA - NOT LOAD FACTOR
* Pitch trim inhibited nose up
Vα Floor - Alpha Floor:
* Not depicted. Predictive energy state.
* Autothrust engages at TOGA thrust (if avail)
Vα Max - Alpha Max:
* Max AOA with full aft sidestick
Normal Law Protections
Describe HIGH SPEED protections
Vmo + 6 or Mmo + 0.01:
* Max bank: 45°
* Autopilot disconnects
* Pitch up induced (can override some)
If sidestick released:
* Wings level
* Return to Vmo / Mmo
Normal Law Protections
Describe PITCH protections
Flaps 0 - 3:
-15° to +30°
Flaps Full:
-15 to +25°
Pitch up limit gradually reduces by 5° at low speeds.
Normal Law Protections
Describe LOAD FACTOR protections
Flaps Up:
+2.5G to -1.0G
Flaps Down:
+2.0G to 0G
What protections and stabilities does direct law have?
None
What protections and stabilities does alternate law have?
- Load factor protection
- Low speed stability
- High speed stability
What protections and stabilities does abnormal attitude law have?
Load Factor
(same as normal law)
Nothing else
Alternate Law
Describe HIGH SPEED stability
Nose up pitch moment at Vmo. Can override.
Might not have stability depending on failures.
Alternate Law
Describe LOW SPEED stability
- Activated 5-10 knots above stall warning.
- Gentle nose-down command initiated. Can be overriden.
- No Vα prot or Vα max speed tape indications.
What is positive static spiral stability?
In normal law, if the bank angle is exceeded, constant control input is required to maintain bank. If less than the spiral stability bank angle, the plane will maintain that bank angle (roll rate).
Normally: 33°
If high speed protection is active: 0°
