Flight Control Laws Flashcards
Normal law protections
Load factor limitation
Nose up and nose down demands from sidestick are filtered through flight control computers and are restricted to maintain the aircraft within its structural G limits at all times. (+2.5 to -1 clean and -2 to 0 configured)
Normal law: Pitch angle protection
Pitch angle is limited to
30 degrees nose up (25 degrees at low speed)
15 degrees pitch down.
Small green bars on PFD show the pitch limits.
PFD displays only speed and speed trend arrow when outside certain limits.
SRS Mode: Take off
Managed vertical mode used during take off and go around.
Controls speed via the elevators
Speed target on ground: V2
Speed target in air: V2 + 10kts
Speed target in air with OEI: current aircraft speed as long as V2<X<V2+15kts.
Guidance law also ensures
Climb slope of 0.5 degrees
A pitch angle protection to reduce the aircraft nose up to 17.5 degrees max or 22.5 degrees max during windshear.
Normal Law:
Angle of attack protection
When angle of attack gets to Alpha Prot: side stick deflection becomes proportional to angle of attack.
Auto pilot disengages and back pressure on stick is required to lift nose towards Alpha max. Releasing the stick will return pitch to alpha prot.
Alpha floor commands TOGA.
Alpha max protection prevents angle of attack advancing further.
To disengage alpha floor
When engaged ALPHA FLOOR is displayed in the thrust mode window of the FMA even if the auto thrust is armed or off.
To disengage: The side stick must be pushed forward when above alpha max or at neutral when above alpha prot.
When aircraft AOA falls back below Alpha floor TOGA LK is displayed on the FMA in the place of ALPHA FLOOR.
Pilot then has to set the thrust levers to the thrust value required and presses the ATHR disconnect button.
Normal Law Protections: High speed protection
Depending on the flight conditions high speed protection is activated at or above VMO/MMO (indicated by barbers pole)
High speed protection indicated by two green bars at VMO + 4kts
Exceeding this or MMO +0.006 results in nose up pitch and continuous aural warning.
Bank angle is limited to 45 degrees.
Auto Pilot will disconnect at VMO + 12kts MMO +0.03
Normal Law Protection: Bank Angle Protection
Below 33 degrees no back pressure required to maintain level flight.
Bank angle limited to a maximum of 67 degrees.
If angle of attack or high speed protection is active then max bank angle is limited to 45 degrees and aircraft will return to wings level when sidestick released.
Above 45 degrees AP disconnects and the FD bars disappear.
During flight with the engine failed beta target.
The pilot must maintain the beta target. Step on the rudder in the direction of the target to centralise it.
When this is centred the optimum climb performance will be achieved.
Beta target appears when flaps are extended, one engine MCT and difference between THR values is 30%.
When the beta target is centralised total drag is minimised.
Once auto pilot is engaged no requirement to apply rudder. AP will center Beta target
Normal law protection: low energy warning
Between 100ft and 2000ft in config 2 , 3 and FULL. Low energy warning SPEED SPEED SPEED indicated to the pilot speed must be increased.
Low energy warning usually triggered before ALPHA FLOOR
Normal Law Protections: Manoeuvre Load Alleviation.
Deflects ailerons and spoilers upwards if sidestick pulled more than 8 degrees upwards aft and loads are greater than 2 G.
Turbulence damping works in the same way and can be turned off on the overhead panel if no failure is detected and comfort is being degraded instead of being improved.
Alternate Law1: Summary
ALT law 1 and 2 provide different protections.
Load factor protection still available.
In most cases high and low speed stability are still available.
Low speed stability can be overridden by a pilot and a stall induced.
With loss of pitch angle and high speed protection small Amber Xs are displayed in their place on the PFD.
High speed master warning and aural message are still available.
Lateral laws are the same as in normal law except that positive static stability will not occur.
Alternate Law 2: Summary
With failure of 2 ADRs there is no low speed stability.
Failure of 3 ADRs there is no high speed stability.
Load factor stability, high speed and stall warnings are always available in alternate law.
ALT 2: bank angle protection lost.
Spoilers 2,3 and 6 inhibited in most cases.
Max roll rate is 20-25 degrees
Dutch roll damping provided in a limited capacity.
Direct Law summary
No Protections
No Autopilot
No ALPHA FLOOR
No AUTO TRIM: use man pitch trim displayed in amber
AURAL STALL and OVERSPEED warnings still exist.
Mechanical back up.
MAN PITCH TRIM ONLY displayed in red.
Happens during complete loss of electrical power, complete loss of all 5 Flight Control Computers or complete loss of elevator aileron and spoiler control.
FULL elevator control lost pitch control can only be achieved through pitch wheel.
Side-stick control maybe lost
Lateral control achieved electrically through Backup Control Module.
Abnormal attitude law
Pitch above 50 degrees or below -30
Bank angle above 125 degrees
Angle of attack an ice 30 degrees below -10.
Airspeed 440kts or Mach .96 and above
Airspeed below 60 kts or Mach 0.1
Works like alt 1 in pitch
No auto trim
Load factor protection still available.
In roll direct law
Alternate yaw.
