Laws Flashcards
Flight Mode
of
Normal Law
Load Factor Demand in Pitch, all protections available
Load Factor Demand
Normal Law - Pitch
A specific input results in the same G change regardless of the current airspeed
Automatic Pitch Trim
Normal Law - Pitch
If the desired pitch attitude requires the elevators to remain displaced, THS movement is commanded until the elevators are centered with the THS.
Manual Pitch Trim Not Required
Ground Mode
of
Normal Law
(Normal Law - Pitch)
Direct stick to flight control relationship
Enables pilot to:
- Check Controls
- Rotate A/C for takeoff
Lost in Alternate Law
Landing Mode of Normal Law
Normal Law - Pitch
Created to give the flare and touchdown a “conventional feel”
- 50’ AGL - ELACs memorize pitch attitude
- 30’ AGL - ELACs add a gentle nose down command which the pilot counters with an aft stick input.
Lost in Alternate Law
Maneuver Protection
Normal Law - Pitch
Prevents flight control surface movement that would cause the aircraft to exceed preset G limits.
Prevents aircraft damage due to over stressing the aircraft
Pitch Protection
Normal Law - Pitch
30 degrees nose up
15 degrees nose down
Lost in Alternate Law
High Speed Protection
Normal Law - Pitch
Prevents A/C damage due to excessive speed
Activates just above VMO/MMO
Gentle pitch up is produced to limit acceleration
Acceleration limited even if full forward stick applied
Automatic pitch trim nose down deactivated
AP deactivates
Always possible to overspeed, flight computers merely limit max attainable speed to within safe limits.
Alpha Prot
Normal Law - Pitch
AOA where computers intervene to prevent alpha from reaching a stall alpha
- Logic changes from load factor demand to commanding an angle of attack
- Addt’l nose up trim inhibited, nose down available
- AP disengages
- Lowering of pitch attitude occurs
Note: Actual angles of attack that correspond with Alpha Protection and Alpha Max are computed by the ELACs based on AOA, not airspeed.
Alpha Max
Normal Law - Pitch
Highest AOA that ELACs will allow
Lower alpha than ALPHA STALL; therefore, it is nearly impossible to stall the aircraft in normal law
Note: Actual angles of attack that correspond with Alpha Protection and Alpha Max are computed by the ELACs based on AOA, not airspeed.
Alpha Floor
Normal Law - Pitch
- Predictive function of the A/THR system
- Activates based on current trend if it predicts thrust will be required
- Available rom immediately after TO throughout the flight down to 100’ RA in config 1 or greater.
- Only available in Normal Law
Uses A/THR system to automatically provide TOGA if any of the following occur:
- Excessive high angle of attack
- Indirectly as a result of windshear
- Excessive nose up attitudes combined w/specific side stick inputs
Predictive, triggered at any airspeed, not depicted on airspeed tape. Can be at airspeeds significantly higher than Alpha Prot
- TOGA thrust automatically applied regardless of lever position
- DOES NOT require A/THR to be engaged, just available
Roll Rate
Normal Law - Roll
Neutral stick - Requests zero roll rate (maintains current bank angle)
Full stick deflection - Request 15 degrees/sec roll rate
Stick slightly left/right of center - Requests between 15 and 0 degrees/sec roll rate
Lost in Alternate Law
Pitch Trim < or equal to 33 degrees
Normal Law - Roll
Automatic pitch trim available up to 33 degrees of bank
Bank Angle Hold < or equal to 33 degrees
Normal Law - Roll
If stick released to neutral, a 0 degree/sec roll rate is commanded
A/C maintains a constant bank angle, unless commanded otherwise
Lost in Alternate Law
Positive Spiral Stability
Normal Law - Roll
If bank angle exceeds 33 degrees and stick is released, bank angle returns to 33 degrees.
Returns bank angle to 0 degrees if high speed protection is active.
Lost in Alternate Law
Bank Angle Protection
Normal Law - Roll
Computers will not allow bank angles in excess of 67 degrees.
Bank angle limited to 45 degrees if high speed protection or angle of attack protection is active
Lost in Alternate Law
Turn Coordination
Normal Law - Yaw
Turn coordination is automatic, no rudder input required
No rudder pedal movement as a result
Yaw orders processed by ELACs, transmitted to the FACs which direct the hydraulic servos to move.
Lost in Alternate Law
Yaw Damping
Normal Law - Yaw
Two yaw dampers installed
Moves entire rudder as necessary to dampen oscillations
Either damper is capable of providing damping authority
No rudder pedal movement as a result
Rudder Trim
Normal Law - Yaw
Entire rudder surface is moved, no trim tabs
AP engaged: needs are computed by FACs and automatically carried out, manual trim deactivated
AP off: may be trimmed using the RUD TRIM knob
Pedals are symmetrically displaced when rudder trimmed
Manual Rudder (HYD) (Normal Law - Yaw)
Backup mechanical control always available via cables from the rudder pedals to the rudder servos if at least one hydraulic system available
Rudder Limiting
Normal Law - Yaw
rudder surface movement is limited at high speeds by FACs (inputs from ADRs) to prevent airframe loads and yaw responses
Rudder pedal travel is never restricted, only rudder surface travel
Stabilities
Alternate Law
Smoothly attempt to change pitch to prevent overspeed or a low speed (stall) condition
Can be manually overridden with stick movement causing overspeed or stall
High Speed Stab: Activates at speed slightly below VMO/MMO
Low Speed Stab: Activates if the speed decreases to within a few knots of stall warning
Roll Direct
Alternate Law
Direct stick to flight control surface relationship in roll
Direct Law
Possible to degrade from Normal Law straight to Direct Law (e.g., dual radar altimeter failure)
Primary reason reached is because A/C is in Alternate Law and the landing gear is lowered for landing because Alternate Law does not provide a landing mode
Direct stick to flight control surface relationship; carry out pilot orders exactly as signaled, computers have no authority to modify or override, thus no protections or stabilities
USE MAN PITCH TRIM
Mechanical Backup
Mech. Backup of THS & rudder always available
Only way to maintain A/C control if all flight computers fail or total loss of electrical power.
Controlled using trim wheels, rudder pedals & engine thrust
Means to maintain A/C control until higher law can be restored.
MAN PITCH TRIM ONLY
Abnormal Attitude Law
Caused by conditions that force the A/C to leave the protected envelope (e.g., severe turbulence) and exceed a normal law limit.
Alternate law without protections and stabilities except load factor protection
Safety feature: Flight control computers never prevent pilots from recovering from abnormal attitude.
After recovery, flight controls remain in alternate law without protections but with auto trim. No reversion to direct law when gear extended.
