Flight Control Laws

Question 1

What are Laws in Airbus?

Answer 1

Protections that are electronically activated and hydraulically operated that operate within preset limits

The side sticks or AP sends a rate demands to the flight control computers, which process the demand and send it to the control surfaces. The process uses a pre-set of limitations called LAWS

Question 2

What are the Flight Control Laws?

Answer 2

1. Normal Law
2. Alternate Law (with and without reduced protection)
3. Direct Law
4. Mechanical Backup
5. Abnormal Attitude Laws

Question 3

What are the 3 modes of Normal Law?

Answer 3

1. Ground mode - operates on the ground when the aircraft is electrically and hydraulically powered.
2. Flight mode - operates in the air with a gradual transition from ground mode. Starts at 50’ or 8 secs after lift off and ends at 50’ for Flare mode
3. Flare mode - modifies the landing mode to introduce a conventional feel to the landing phase

Question 4

What are the protections of Normal Law?

Answer 4

1. Pitch Attitude protection
2. Load factor limitation
3. High angle of attack protection
4. High speed protection
5. Bank angle protection

Question 5

In normal law, are auto turn coordination and dutch roll damping provided?

Answer 5

Yes. Pilot inputs are not required

Question 6

Normal Law/LFL: Load Factor Limitation limits are: (clean / flaps extended)

Answer 6

Clean: 2.5g to - 1g

Flaps extended: 2.0g to 0g

Question 7

Normal Law/PAP: Pitch attitude protection nose up and down limits?

Answer 7

Nose up:
Config 0 to 3: 30deg up
Config full: 20 deg up

Nose down: 15deg

Question 8

Normal Law/PAP: In pitch attitude protection, when do the flight directors disappear and when do they come back?

Answer 8

Flight directors disappear passed 25 deg up and 13 deg down, they return passing 22 deg up and 10 deg down

Question 9

Normal Law/HAoA: Which protection is the priority among all other protections in Normal Law?

Answer 9

High Angle of Attack protection

Question 10

Normal Law/HAoA: What is the purpose of the high angle of attack protection?

Answer 10

1. Protection from a stall

2. To provide optimum performance during windshear or GPWS recovery

Question 11

Normal Law/HAoA: On the speed tape, during Normal Law, what are the 3 symbols on the lower part of the speed scale? 2 in amber and 1 in red

Answer 11

VLS
Va PROT
Vs MAX

Question 12

Normal Law/HAoA: What is VLS? Can this be exceeded down to Va PROT?

Answer 12

1. Lowest selectable speed, speed will not go down to Va PROT with the Autothrust engaged
2. With the auto thrust off, the speed may go down to Va PROT

Question 13

Normal Law/HAoA: What are Va PROT, Va MAX, Vsw (shown on the lower end of the speed tape)?

Answer 13

Va PROT
The AOA protection speed. Angle of attack where AOA protection becomes active. Autothrust not engaged.

Va MAX
Maximum angle of attack speed. Maximum AOA that may be reached under normal law. Reached using max side stick pull back. When the stick is released, speed will go back to Va Prot.

Vsw
Stall warning speed displayed on the PFD when not in normal law

Question 14

Normal Law/HAoA: With the speed at Va PROT, will the auto pilot engage?

Answer 14

No. If it were connected, it will disconnect

Question 15

Normal Law/HAoA: What are Va PROT, Va FLOOR and Va MAX based on?

Answer 15

The AOA

Question 16

Normal Law/HAoA: In other laws other than Normal Law, what will be left of the lowest speed protections?

Answer 16

In alternate, direct law, Va PROT and Va MAX are lost, instead there will be VLS then Vsw. You still get a stall warning

Question 17

Normal Law/HAoA: When is Va FLOOR activated?

Answer 17

When the speed drops between Va PROT and Va MAX

Go around thrust will be automatically set

Question 18

Normal Law/HAoA: Where is A. FLOOR shown to the pilot when it is activated?

Answer 18

On the PFD FMA and the E/WD

Question 19

Normal Law/HAoA:

Alpha Floor is available from?

Answer 19

Lift off until 100ft RA on approach

Question 20

Normal Law/HAoA: Which computer generates the signal that triggers the alpha floor mode?

Answer 20

FAC

Question 21

Normal Law/HAoA: When is Alpha Floor lost?

Answer 21

1. In either alternate or direct law

2. In an engine out with slats/flaps extended

Question 22

Normal Law/HSP: How are the symbols of the High Speed Protection displayed to the crew?

Answer 22

Via the PFD speed scale, the top part. Red and black barber pole tip and an amber equal sign beside it.

Question 23

Normal Law/HSP: How is VMO / MMO high speed protection activated? When does the AP disconnect?

Answer 23

On the speed scale, where the red and black barber pole is, the tip is where VMO / MMO is. The green amber equal sign beside it to the left is where the protection is activated (VMO+6).

AP disconnects at VMO + 15 / MMO + 0.04

Question 24

Normal Law/HSP: What happens when the speed is exceeded?

Answer 24

1. Passing the green equal sign, the autopilot will disengage (VMO+15 / Mach+0.04) and the flight control computers will give a pitch up attitude to prevent further increase in speed.
2. Max THS is limited between and the setting at the point where the aircraft entered this protection and a nose up at 11 deg
3. With the flight stick released, speed will return to VMO / MMO
4. The pilot cannot override the automatic pitch up
5. With the side stick released, the bank angle will return to 0 deg, max bank is down from 67 to 40 deg

Question 25

Normal Law/BAP: How is the bank angle protection in normal law displayed to the pilot?

Answer 25

Two green equal signs on both sides of the PFD attitude display

Question 26

Normal Law/BAP: The flight directors will disappear when the pilot exceeds XX deg of bank. They will return when?

Answer 26

45 deg and return passing 40 deg

Question 27

Normal Law/BAP: Maximum angle of bank protection is?

Answer 27

67 deg bank left or right

Question 28

Normal Law/BAP: A. What are the limits on bank when: 1. AOA protection is active or 2. High speed protection is active B. What happens when the side stick is released during a bank with high speed protection is active?

Answer 28

1. AOA: 45 deg 2. High speed: 40 deg B. Aircraft will have a spiral stability where bank will return to 0 deg

Question 29

Normal Law/BAP: What happens to the Automatic Pitch Trim when we exceed 33 deg bank?

Answer 29

It is inoperative past 33 degrees and the aircraft will start to sink

Question 30

Normal Law/BAP: What happens to the automatic turn coordinator past a bank 33 deg?

Answer 30

Automatic turn coordinator is active until 67 deg. No need to apply manual rudder

Question 31

Normal LAw/BAP: When the side stick is released and banking above “XX” deg, the aircraft will return to this angle of bank

Answer 31

33 deg

Question 32

Normal Law/BAP: In normal flight with normal bank, less than 33 deg, what can we expect when we bank?

Answer 32

1. A command for a turn is given and if less than 33 deg, the bank will maintain 2. No need to adjust for pitch 3. No need to use the rudder

Question 33

Reconfiguration Laws: What are reconfiguration laws

Answer 33

Multiple or dual system failures that degrade the flight control normal laws

Question 34

Reconfiguration Laws: | What are the 3 levels of Reconfiguration Laws?

Answer 34

``` 1. Alternate Law A. With reduced protections B. Without reduced protections 2. Direct Law 3. Mechanical Back Up ```

Question 35

Reconfiguration Laws/AL: | How does Alternate Law affect the Normal Law modes?

Answer 35

1. Ground: is the same as normal law 2. Flight mode: A. Pitch control - same as normal law B. Roll - conventional C. Yaw control - turn coordinator is lost, limited damping 3. Landing mode: with gear down, goes into direct law

Question 36

``` Reconfiguration Laws/AL: What happens to the following in alternate law with reduced protection? 1. Pitch protection? 2. Bank angle protection? 3. Load factor limitation? 4. High angle of attack protection? 5. High speed protection? ```

Answer 36

1. Pitch limits are lost but auto trim still works, aircraft will keep pitch 2. Bank angle protection is lost, limited yaw damping, roll is in direct law 3. Load Factor Limitation is the same as normal law 4. Replaced by Low Speed Stability 5. Replaced by High Speed Stability

Question 37

Reconfiguration Laws/AL: What is Low Speed Stability?

Answer 37

High angle of attack protection is replaced by Low Speed Stability. A. Loss of Va Prot and Va Max, Alpha Floor (aircraft can stall) B. Replaced by a stall warning speed Vsw which introduces a small nose down input to prevent speed loss, can be over ridden by the pilot C. Aural stall warning

Question 38

Reconfiguration Laws/AL: What is high speed stability?

Answer 38

High speed protection is replaced by High Speed Stability. 1. Reaching MMO / VMO, a slight pitch up is introduced by the aircraft to prevent further speed increase. 2. This can be over ridden by the pilots. 3. Aural warning with over speed warning chimes

Question 39

Reconfiguration Laws/AL: In summary, what are the reduced protections in Alternate Law?

Answer 39

Summary: Alternate law with reduced protections is: 1. Load Factor Limitation 2. High and Low Speed Stability

Question 40

Reconfiguration Laws/AL: | What is left when you are in Alternate Law without reduced protections?

Answer 40

1. Load Factor Limitation remains. | 2. Aural stall and high speed warnings (only the warnings)

Question 41

Difference between alternate law with reduced protections vs alternate law without reduced protection? What happens when the landing gear is brought down?

Answer 41

Alternate Law with reduced protections has high speed and low speed stability (can be overriden by the pilots) and load factor protection Alternate Law without reduced protections only has load factor protection When the landing gear is brought down, the aircraft goes into direct law

Question 42

Reconfiguration Laws/DL: | What is Direct Law?

Answer 42

1. Lowest level of computer control 2. Pilot inputs are sent directly to the control surfaces unmodified 3. Loss of all protections

Question 43

Reconfiguration Laws/DL: | What if any protections are remaining under direct law?

Answer 43

Only aural Stall and Over Speed warnings

Question 44

Reconfiguration Laws/DL: | Is there auto trim in direct law?

Answer 44

No. USE MAN PITCH TRIM is displayed on the PFD

Question 45

Reconfiguration Laws/DL: | Does the Auto turn coordination and dutch roll damping still work in direct law?

Answer 45

They are lost and all yaw control is done via the rudder pedals only

Question 46

Reconfiguration Laws/MB: | What is Mechanical Backup Mode?

Answer 46

1. Pitch is via the pitch trim wheel, adjusting the THS, provided green or hydraulic system is available 2. On the PFD, in red, MAN PITCH TRIM ONLY 3. Roll is through the rudders through a mechanical linkage with the rudder provided at least one hydraulic system is available

Question 47

Can systems be reset to bring the aircraft back to a safer state? Say from Mechanical Back Up Mode back to either alternate or direct law?

Answer 47

Yes. Depending on the type of failure, resetting systems can recover into either alternate or direct law. The idea of Mechanical Back Up Mode is to give the crew time to reset systems

Question 48

What is the Abnormal Attitude Law?

Answer 48

When the aircraft exceeds the flight envelopes, the abnormal attitude law engages to provide maximum efficiency to the PF to recover the attitude The idea is to bring back the aircraft back within the normal flight envelope. The system will revert to alternate law but no direct law transfer when the landing gear is brought down. The aircraft will remain in alternate law

Question 49

When does the abnormal attitude law engage?

Answer 49

When one of the following: 1. Bank is greater than 125 deg 2. Pitch is nose up 50 deg and nose down 30 deg 3. Speed is below 70-90kt (depending on attitude) 4. Mach above .91 5. AOA is above 40 deg

Question 50

What is the point of mechanical back up law?

Answer 50

Buy time, to be able to reset some systems and maybe get back to alternate or direct law?