Flight Controls Flashcards
The flight control system uses seven flight control computers which include:
- 2 Elevator Aileron Computers (ELACs)
- 3 Spoiler Elevator Computers (SECs)
- 2 Flight Augmentation Computers (FACs)
FAC 1 becomes inoperative when the aircraft electrical supply is in a batteries-only configuration.
If both ELACs have failed or are selected OFF:
- The flight control laws degrade from normal to alternate
- Both ailerons are inoperative and roll control is provided by the spoilers
- Elevator and THS control is provided by the SECs
- Both autopilots will be inoperative
What are the purpose of the SECs?
The spoilers are controlled in pairs by the SECs so that a single failure does not result in an asymmetric flight control configuration.
SECs 1 and 2 also provide backup elevator and THS control should both ELACs fail.
SEC 3 does not provide any backup control.
If all three SECs have failed or are selected off:
- The speed brakes and spoiler panels are all inoperative and roll is controlled by ailerons only
- The ability of the SECs to provide backup pitch control is lost
- Flight control laws degrade from normal to alternate
- Autopilot remains operational since the primary flight controls are receiving inputs from the ELACs and FACs
If both FACs have failure or are selected OFF:
- Rudder control is through the rudder pedals via mechanical connection
- Rudder trim, yaw damping, and rudder limiting are lost
- Flight control laws degrade from normal to alternate
- Both autopilots will be inoperative
Only one FAC controls the rudder at a time, the other serves as a backup. All three rudder servos are powered by separate hydraulic systems.
Turn coordination is computed by the _____, which send yaw information to the controlling _____ to actuate the rudder servos.
ELACs, FAC
How is rudder travel limited at higher speeds?
The FACs use airspeed information from the ADIRUs to limit the amount of available rudder travel at higher speeds as deflection produces excessive airframe loads.
Rudder travel is unrestricted below 160 kts in the A320.
Speedbrake extension is inhibited, and any extended panels will automatically retract if:
- Flaps FULL are selected
- If TOGA thrust is applied
- If certain high AoA situations are encountered
Ground Spoilers are automatically extended during an RTO when:
- When armed, wheel speed exceeds 72 kts and thrust levers are set to idle
- Even when disarmed, wheel speeds exceed 72 kts and at least one thrust lever is set to reverse and the other lever set to idle
Ground Spoilers are automatically extended during landing when:
During landing, either armed or not in the RET position:
* Both main landing gears are on the ground
* Both thrust levers are at idle, OR reverse is selected on at least one engine, with the other lever being below MCT
During landing, disarmed:
* Both main landing gears are on the ground
* Reverse is selected on at least one engine, with the other lever being below MCT
How would the flight crew manually extend the ground spoilers on the ground?
It is possible to manually extend the ground spoilers on the ground by moving the SPEED BRAKE lever aft, however only panels 1 through 4 extend.
What is the purpose of the SFCCs?
The SFCC monitors the position of the slats and flaps which enables them to respond to asymmetry, uncommanded movement, or runaway situations.
After an SFCC failure, the remaining SFCC is able to control the remaining unaffected motors to operate the slats and flaps, but only at approximately half their normal speed.
Each SFCC controls one hydraulic motor to extend the slats and one to extend the flaps.
What is the purpose of the WTBs?
The WTBs are used to lock the appropriate drive train to prevent further movement in an asymmetry situation as well as during uncommanded movement of slats or flaps.
Slat Alpha/Speed Lock engages if the slats are extended and:
- The AoA, or alpha, becomes excessive, or
- Airspeed gets too low
All five spoiler panels on each wing are used to perform the ground spoiler function. The bracket markings on the F/CTL page remind you that:
- The 3 middle spoiler panels carry out the speedbrake function
- The outer four spoiler panels assist in roll control
What are the Normal Law pitch attitude protections?
Pitch Attitude - 30 degrees (CONF 0 to 3), reduced to 25 degrees at low speed. Or 25 degrees (CONF FULL), reduced to 20 degrees at low speed. 15 degrees nose down.
What are the Normal Law High Speed protections?
High Speed - Protection limit by green equals on speed tape. The autopilot will disconnect at VMO + 15 / MMO + 0.04. This protection does not prevent the aircraft from exceeding VMO/MMO. Bank angle limit is reduced from 67 to 40 degrees.
What is the maximum rate of roll in Normal Law?
The ELACs limit a roll to a maximum of 15 degrees per second in normal law.
What is Ground Mode in Normal Law?
Ground Mode:
* Control surface deflection is proportional to sidestick and rudder pedal movement.
* Allows for a flight control check and rotation on takeoff.
* Automatic pitch trimming is inhibited.
What is Flare Mode in Normal Law?
- Exists to give the landing flare and touchdown a conventional feel.
- At 50 feet RA, the system memorizes the current pitch attitude.
- Beginning at 30 feet, the system begins to reduce the pitch attitude to negative two degrees nose down over a period of 8 seconds.
- Shortly after landing, Ground Mode again becomes active and the THS automatically resets to 0.
- In the event of a go-around, the transition from Flare to Flight Mode occurs above 50 feet.
Can the speedbrakes be used in Direct Law?
Speedbrakes should be used with caution, allowing time to make manual pitch trim corrections.
What do the FACs provide in Direct Law?
Yaw damping no longer functions, however rudder limiting and trimming continue to function as long as one FAC is operable.
What is the purpose of Abnormal Attitude Law?
Ensures that the flight control laws do not prevent or interfere with recovery from an abnormal flight attitude.
The same as Alternate Law without automatic pitch trim, yaw damping or protections, except load-factor demand is maintained. Automatic pitch trim and yaw damping are restored after recovery.
Abnormal Attitude Law engages when:
* Bank angle exceeds 125 degrees
* Pitch attitude exceeds 50 degrees nose up or 30 degrees nose down
* Airspeed is below 60 to 90 knots (dependant on pitch attitude), or above 440 knots
* Mach exceeds 0.91
* Angle of attack above 30 to 40 degrees, or below -10 degrees
This is the only case where the flight control laws will remain in Alternate Law after the landing gear is extended.
Recognizing that the flight control computers may have been subjected to conditions that they are not normally designed for, the system is prevented from upgrading back to Normal Law.
When would Mechanical Backup Control become active?
Available in the unlikely event that a total loss of the electrical system has occurred, or significant failures have occurred in the flight control system, such as a loss of five FBW computers, a loss of both elevators, or the total loss of ailerons and spoilers.
Allows you to maintain aircraft control until a higher law can be restored.