Flight Control Laws

Question 1

How many flight control law do we have?

Answer 1

• Normal law
• Alternate law(with reduced protection or without reduced protection)
• Direct law
• Mechanical backup
• Abnormal attitude law

Question 2

What protections do you have in Normal Law?

Answer 2

• High-Speed Protection

• High-Angle-of-Attack (AOA) Protection
VLS -> Vaprot -> Vamax

• Load Factor Limitation
(+2.5 / -1.0) in clean
(+2.0 / 0) in other than clean

• Pitch Attitude Protection
Conf 0-3=30° UP reducing to 25° at low speed
Conf FULL = 25° UP reducing to 20° at low speed
15° DN

• Bank Angle Protection (67° max)

Question 3

In alternate law, what happens to pitch, roll and yaw?

Answer 3

Pitch : load factor demand with auto trim (like normal law but with reduced protections)
Roll : direct law (no bank angle protection)
Yaw : yaw damping only (limited to +/-5° rudder)

Question 4

When do we expect the flight controls to refer to direct law? What protection or warnings are available?

Answer 4

Most likely when selecting gear down with alternate law.

Pitch direct law is a direct stick to elevator relationship.
No automatic trim
No alpha floor protection
Overspeed and stall warning still available

Roll is a direct stick to surface relationship
When clean max roll rate is 30°per second. With slats, the max roll rate is 25° per second. To limit the roll rate, only ailerons, and spoilers 4 and 5 used.

Yaw is through rudder pedals.
Yaw damping and turn coordination is lost.

Question 5

If angle of attack (AOA) is active, what is the bank angle limit?

Answer 5

Maximum 45 degrees’ and if released it goes back to 33 degrees

Question 6

If high speed protection is active, what is the bank angle limit?

Answer 6

Maximum bank is 40 degrees. With sidestick released, bank angle reduces to 0°.

Question 7

How does the High Speed Protection operate?

Answer 7

Depending on flight conditions (high acceleration/low pitch attitude), High Speed Protection activates at or above VMO/MMO.
THS setting locked from entry value to 11° UP. Bank spiral stability reduces to 0°. Bank limit reduces from 67° to 40°.
As speed increases above VMO/MMO, nose down authority progressivly reduced and nose up order is applied.
AP disconnects at VMO+15kts or MMO +0.04

Question 8

Can the pilot override pitch-up from High Speed Protection in Normal Law?

Answer 8

No

Question 9

What is Alpha Max?

Answer 9

The maximum angle of attack allowed in Normal Law, indicated by the top of the red strip on the airspeed
scale. Alpha Floor should activate before ever reaching Alpha Max.

Question 10

How does High Angle of Attack Protection operate?

Answer 10

This protection has priority above all other protections because it prevents the A/C from stalling and ensures optimum performance in extreme maneuvers like wind-shear and EGPW recovery.

When the angle of attack exceeds α prot, pitch trim ceases and angle of attack is now proportional to sidestick deflection, not to exceed α max even with full aft side-stick deflection.

Question 11

How many types of Alternate law, what protection is available for each one?

Answer 11

1- Alternate law with reduced protection:
• Load factor
• High speed stability (nose up demand made when above VMO/MMO wich can be overridden)
• Low speed stability (a floor is inoperative. Introduces nose down signal when active between 5-10kts above stall warning speed which can be overridden)

2- Alternate law without reduced protection:
• Load factor

Question 12

Can you override the high or low stabilities in Alternate Law?

Answer 12

yes

Question 13

What protections do you have in Direct Law?

Answer 13

None

Question 14

If you are in Pitch Alternate Law, what law would Roll be?

Answer 14

Direct Law

Question 15

When the landing gear is extended, what happens to Pitch Alternate Law?

Answer 15

Degrades to Pitch Direct Law

Question 16

How would you get into Abnormal Law?

Answer 16

By exceeding approximately double the Normal Law limits:

Bank angle above 125°
Pitch attitude above 50° UP or below 30° down
Speed below 70-90kts (depending on aircraft pitch attitude), or above 440 kts
Mach above 0.91
Angle of attack above 40°

Question 17

Can you stall the aircraft in Normal Law?

Answer 17

Not in Normal Law, but the aircraft can be stalled in all other laws.

Question 18

What is the purpose of Abnormal Alternate Law?

Answer 18

Allows the aircraft to be recovered from an unusual attitude

Question 19

After recovery from an unusual attitude, what law will you be in?

Answer 19

When back in the normal flight envelope, abnormal law disengages and the aircraft remains in Alternate law.

Perhaps older aircraft remained in abnormal law.

Question 20

In abnormal attitude law, do we refer to direct law when selecting landing gear down?

Answer 20

Unknown. You will be in alternate, and in alternate law, you will revert to direct law on gear down. But with no computer failure, perhaps it does not do this.

No, this mode last until landing (official GACA assumes abnormal law all throughout landing)

Question 21

What PFD indications indicate Normal Law?

Answer 21

• Green = for pitch, bank, and overspeed limits

* Amber/black (alpha prot) airspeed tape

Question 22

What is indicated if the PFD pitch and bank limits are amber X’s?

Answer 22

You are not in Normal Law

Question 23

What would cause you to revert to another law?

Answer 23

Multiple failures of redundant systems

Generally:
normal law = single failure
alternate law = dual failure
direct law = triple failure

with plenty of exceptions!

Question 24

What law are you in when you perform the flight control check on the ground?

Answer 24

Normal Law, Ground Mode

Question 25

Can the aircraft be flown with a loss of all flight control computers?

Answer 25

Yes, with Mechanical Backup

Question 26

How is the airplane controlled in Mechanical Backup?

Answer 26

• Pitch – Trim wheel (horizontal stabilizer)
• Yaw – Rudder pedals (rudder) (Roll is achieved through secondary effect of rudder)
• Speed – Thrust levers