Control Laws

Question 1

Control laws and their characteristics

Answer 1

• Normal law:

• Pitch: Vertical load factor
• Bank: Roll rate

• Alternate law:

• Pitch: Vertical load factor
• Bank: Roll rate in ALTN1 / Direct control of ailerons in ALTN2
• Direct law: Direct relationship between stick and flight control surfaces
• Ground law (before lift-off and after touch-down): Same as Direct law
• Flare law (allow conventional flare):
• Pitch: Stick orders a pitch attitude increment to a reference attitude
• Bank: Direct control of ailerons

Question 2

Protections in normal law

Answer 2

• Load factor protection
• High speed protection
• High angle-of-attack protection
• Pitch attitude protection
• Bank angle protection
• Low energy warning

Question 3

Protections in alternate law

Answer 3

• Load factor protection
• Bank angle protection (ALTN1 only)
• Low speed stability:
- VSW replaces αPROT and αMAX
- If speed reduces to VSW, AP disconnect and a nose down pitch input is introduced • High speed stability:
- Amber dashes replace the Green dashes on speed scale
- If speed increases to VMO, AP disconnect and a nose up pitch input is introduced
• Aural stall
• Overspeed warning

Question 4

Protections in Alternate law without stability

Answer 4

• Load factor protection
• Aural stall
• Overspeed warning

Question 5

Load factor protection

Answer 5

• Load factor limitation:
+ 2.5 g, -1 g in clean configuration
+ 2 g, 0 g when slats are extended

• Rapid pull-up to 2.5 g is immediately possible.

Question 6

High speed protection

Answer 6

• VMO + 4 kt / MMO+ 0.006, Overspeed Ecam warning
• VMO +6 kt / MMO + 0.01, Automatic pitch up applied
• VMO + 16 kt / MMO +0.04, Maximum stabilized speed stick maintained nose down

Question 7

High angle-of-attack protection

Answer 7

• VLS: Minimum allowed speed, A/THR in speed mode will not allow speed to drop below VLS even if lower speed is selected
• Vα Prot: AP disengages, Auto Pitch trim stops
• Vα Floor: TOGA thrust is set automatically
• Vα Max: Speed is maintained with full aft stick, speed brake retract if previously extended

Question 8

Pitch attitude protection

Answer 8

• Nose-down, 15°
• Nose-up,
- 30° in conf 0 to 3 reduced to 25° at low speed
- 25° in conf FULL reduced to 20° at low speed

Question 9

Bank angle protection

Answer 9

• Bank angle limited to 67°
• Above 33°:
- Stick released, aircraft rolls back to 33°
- Stick maintained, bank angle maintained
• In high speed protection:
- Spiral stability is introduced regardless of angle
- bank angle is limited to 40°
• In high angle-of-attack protection, bank angle is limited to 45°

Question 10

Low energy warning

Available between 100 ft and 2000 ft RA in Conf 2, 3 and Full

Answer 10

• Aural warning, “SPEED SPEED SPEED”

* To stop the warning, increase Thrust

Question 11

Protections in Direct law

Answer 11

• Aural stall

* Overspeed warning