Flight Control Laws

Question 1

In Normal Law describe pitch in Ground mode and Flight mode?

Answer 1

Pitch Ground mode - Direct relationship between elevator and side stick input (during TO roll elevator authority may reduce from 30deg to 20deg weight/cg dependent

Pitch Flight mode - Pitch is based on a load factor demand and the elevator & THS is set accordingly

Question 2

In normal law when will auto-trim stop functioning?

Answer 2

-Flight crew sets a manual trim order
-Radio height is below 50ft
-Load factor goes below 0.5g
-Aircraft is in high speed protection

Question 3

What is Flare mode and when does it activate?

Answer 3

Activates when the aircraft passes 50ft
THS frozen and a direct stick to elevator relationship
System memorises attitude at 50ft and it becomes reference for pitch control
At 30ft system reduced pitch to -2deg over 8 seconds causing the pilot to flare

Question 4

In Normal Law describe Lateral control in Ground Mode and Flight mode?

Answer 4

Ground mode - Direct side stick to aileron and roll spoiler relationship. As speed increases max permitted deflection reduces

Flight mode - Side stick input commands a roll rate (max 15deg/sec). Turns are coordinated automatically through ailerons, spoilers & rudder

Question 5

Name the 5 normal law protections

Answer 5

High AOA
High Speed
Bank Angle
Load factor
Pitch Attitude

Question 6

Explain High AOA protection

Answer 6

Can set 100kts minimum but with A/THR speed won’t reduce below VLS
With A/THR disengaged speed will reduce below VLS to Alpha prot (orange & black bars)
Beyond alpha prot side stick commands AOA directly
Alpha floor commanded somewhere between alpha prot and alpha max
Side stick released AOA return to Alpha Prot
Alpha max can only be reached with constant sidestick back pressure

Question 7

Describe High Speed protection

Answer 7

VMO +4 kts Overspeed warning
VMO +6kts Two green dashes = overspeed protection becomes active
As speed increases beyond VMO/MMO nose down authority is reduced and a permanent nose up authority is applied to aid recovery
If sidestick is maintained full forwards at approx VMO+16 the pitch down nose authority will reduce to zero
The PF therefore has ability to perform escape manoeuvre
A/p disconnects at VMO +15kt/MMO +.04

Question 8

Describe load factor protection

Answer 8

Load factor limited to:
+2.5g -1g clean
+2g 0g other configs

Question 9

Describe Bank Angle protection
Normal flight
AOA or Pitch attitude protection active
High Speed protection active

Answer 9

Normal flight envelope
Bank angle limited to 67deg
Returns to 33deg when sidestick release
Auto pitch trim up 33deg

If AOA or pitch attitude prot active
Bank angle limited to 45deg
No return to 0

If High Speed prot active
Bank angle limited to 40 deg
Return to 0 when sidestick release

Question 10

What bank angle does the auto-pilot disconnect and the FDs disappear?
When do you get them back?

Answer 10

AP Disconnects and FDs disappear at 45deg
Get them back at less than 40deg

Question 11

Describe Pitch Attitude protection
When do you lose the FDs?

Answer 11

Config 0-3 - +30deg -15deg
Config full - +25deg -15deg

Lose FDS +25deg -13deg

Question 12

What is Load Alleviation Function?

Answer 12

Available in clean flight in normal law, loads on the wing can unloaded by inverting the ailerons and deploying the spoilers

Question 13

What does centering the BETA target during single engine operations do?

Answer 13

Provides minimum drag and best climb performance

Question 14

What is the low energy warnings and when is it available?

Answer 14

An aural ‘SPEED SPEED SPEED’ alert repeated every 5s warning the pilot of low energy situations before alpha prot and alpha floor are triggered

It is available below 2000ft RA in config 2,3 & Full

Question 15

When is the Low energy warning inhibited?

Answer 15

Above 2000ft RA
TOGA
Below 100ft RA
Alpha floor or GPWS triggered
Alternate or Direct law
Dual RA failure

Question 16

In Alternate law, describe pitch control in Ground mode, Flight mode & Flare mode

Answer 16

Ground mode - Identical to Normal law
Flight mode - Identical to Normal law but without protections
Flare mode - Changes to flare mode when L/G is selected down & A/c enter direct law. Pitch is a direct stick to elevator relationship

Question 17

In Alternate law, describe lateral control in Ground mode & Flight mode

Answer 17

Ground mode - Same as normal law
Flight mode - A/c is in Roll Direct Law I.e direct sidestick to surface relationship

Question 18

What is the difference between Alternate law with and without reduced protections?
What reduced protections are available?

Answer 18

Depending on system downgrades the a/c may still have some reduced protections know as stabilities

Load factor limitation = same as normal
Low speed stability - 5-10kts above Vsw gentle and progressive nose down is introduced which can be overridden, stall warning & crickets are activated
High speed stability - Above VMO/MMO a nose up demand is introduced which can be overriden, aural overspeed warning is still available

Question 19

How will the PFD appear differently in alternate law?

Question 20

In Direct law, explain pitch control & lateral control?

Answer 20

Pitch is a direct stick to elevator relationship, the pilot must trim manually

Lateral control is a direct stick to surface position relationship, yaw damping and turn coordination functions are lost

Question 21

How does the PFD announce Direct Law?

Answer 21

“Use Man Pitch Trim” on PFD

Question 22

What is Mechanical Backup and how is the aircraft controlled in this condition?

Answer 22

Results from a loss of all fly by wire computers most likely as a result of a total electrical failure

Meant as a temporary condition where pitch is controlled through THS and roll controlled through the rudder pedals