14 Flight Controls
Terms in this set (122)
What are the seven flight control computers that operate the flight control system?
2 - Elevator Aileron Computers (ELACs)
3 - Spoiler Elevator Computers (SECs)
2 - Flight Augmentation Computers (FACs)
What are the functions of the ELACs?
Control of the elevators, ailerons, and THS.
They also compute the need for roll spoiler movement (sent to SECs) and rudder yaw movement (sent to FACs)
What happens in the event a single ELAC fails?
The other ELAC is capable of providing complete control of the ailerons, elevators and THS.
If both ELACs fail, what backups do you have and what is lost?
SEC 1 or 2 can provide backup pitch control with the elevators and THS and roll control via the spoilers. Aileron control is lost and the ailerons streamline.
Note: SEC 3 does not provide backup pitch control
What do the SECs directly control?
Can one SEC control all spoiler pairs?
No. Each SEC controls only one or two pair of spoilers.
What happens to the spoiler control if an SEC fails?
It's associated spoilers are inoperative
What do the FACs primarily control?
What are the functions of the FACs?
1. Automatic turn coordination
2. Yaw damping
3. Rudder limiting
4. Rudder trim
1. Flight envelope limits
2. Provides speed information (characteristic speeds) to the PFDs
3. Computations for Autothrust Alpha Floor
4. Computations for windshear warnings
5. Computations for low energy warnings
What happens in the event a single FAC fails?
Only one FAC is active at a time. The other FAC is capable of providing complete backup.
What happens if you select a FAC pb to OFF?
Deactivates the rudder functions of the FAC. If the FAC is still operable, it continues to compute all flight envelope functions and speeds.
How many hydraulic servos are installed on each elevator?
How many servos are active at a time on each elevator?
In the event of a dual servo failure, what happens to the elevator?
The servos revert to a centering mode to hold the elevator streamlined with the horizontal stabilizer.
Which hydraulic systems provide hydraulic power to the elevators?
All three systems
If both ELACs fail, what provides backup control of the elevators and THS?
Either SEC 1 or 2
In what direction is the leading edge of the horizontal stabilizer deflected for nose up trim?
The THS will lower the leading edge of the horizontal stabilizer thus resulting in nose up trim.
The THS screwjack is powered by how many hydraulic motors?
Two hydraulic motors. One powered by the green system and one powered by the yellow system. Only one is active at a time.
What happens to the THS in the event of a loss of hydraulic pressure from both the green and yellow systems?
Loss of the THS
The THS servo valve is normally controlled by one of three electrical motors. What happens in the event of electrical failure (multiple ELAC and SEC failures)?
As long as hydraulic power is available, the servo valve can be controlled through mechanical linkage from the cockpit trim wheels.
Is THS control possible with the failure of both ELACs and SEC 1 and 2?
Yes, through mechanical linkages to the pitch trim wheels as long as hydraulic power is available.
How many hydraulic servos are on each aileron?
How many servos are active at a time on each aileron?
Which hydraulic systems power the aileron servos?
One blue servo and one green servo on each side.
For increased lift, what happens to each aileron as the flaps are extended?
They droop slightly
If both ELACs fail, what provides backup control of the ailerons?
Nothing. Both ailerons will be inoperative. The ailerons will revert to a damping mode and automatically center.
What happens to the ailerons if both the blue and the green hydraulic systems fail?
Both ailerons will be inoperative.
How many hydraulic servos move each spoiler panel?
Each spoiler panel has a single dedicated hydraulic servo controlled by a specific SEC.
What happens to the spoiler panel if either its associated SEC or hydraulic source fails?
The spoiler panel is inoperative. If an SEC fails the associated spoilers will retract. If hydraulic pressure is lost, the associated spoilers will remain at the current deflection.
If one spoiler panel fails, what happens to prevent control asymmetry?
The corresponding spoiler panel on the opposite wing is deactivated.
If both ELACs fail, what processes and provides roll?
The SECs will process the roll commands and roll is provided by the spoilers.
How many spoilers are on each wing?
Which spoilers are used as turn spoilers to augment roll rate commands?
2, 3, 4 & 5
During flight, which spoilers are used as speed brakes?
The three center spoilers. 2, 3 & 4
When will the speed brakes automatically retract?
1. Flaps FULL is selected
2. Airspeed decreases to Alpha Prot
3. TOGA thrust is selected
If the speed brakes are automatically retracted, will the speed brake lever automatically retract?
No. The speed brake lever is incapable of automated movement and must always be manually positioned.
On the A320, when the autopilot is engaged, what is maximum deployment capability of the speed brakes?
1/2 the maximum
Which spoilers are used as ground spoilers?
Once armed, when are the ground spoilers automatically deployed after an aborted takeoff or upon landing?
When the following conditions are met:
1. main gear speed of 72 knots or greater
2. both thrust levers at idle
If the ground spoilers are not armed, will automatic deployment occur for and aborted takeoff or upon landing?
Yes, if the following conditions are met:
1. main gear speed of 72 knots or greater
2. at least one thrust lever in reverse and the other at idle thrust
How does the pilot control aileron trim?
The pilot has no ability to make aileron trim inputs.
Under Normal Law, what does ELAC 1 control?
Primary - Aileron control (roll)
Standby - Elevator / THS control
Under Normal Law, what does ELAC 2 control?
Primary - Elevator / THS control (pitch)
Standby - Aileron control
Which hydraulic systems power the rudder servos?
All three hydraulic systems simultaneously power three associated hydraulic servo.
Can the rudder be mechanically controlled?
Yes, through the rudder pedals. The pedals are mechanically interconnected and are symmetrically displaced with the rudder trim inputs.
What happens to the autopilot if the rudder pedals are displaced?
The autopilot disconnects
How many yaw dampers are installed?
How are the yaw dampers controlled and powered?
Yaw Damper 1 - FAC 1, Green hydraulic
Yaw Damper 2 - FAC 2, Yellow hydraulic
Explain rudder travel limiting.
Available rudder travel is gradually restricted as airspeed increases
Is there a rudder trim tab?
No. Rudder trim is accomplished by displacing the entire rudder surface.
Is the RUD TRIM knob available with autopilot engaged?
No. With the autopilot engaged, the manual RUD TRIM knob and rudder trim reset pb are deactivated.
What happens if both sidesticks are operated simultaneously?
The commands are summed by the computers
How can a pilot take sole control of the flight controls?
By pressing and holding the red autopilot disconnect/takeover pb on their sidestick.
What happens if the autopilot disconnect/takeover pb is pressed for 40 seconds or more?
The deactivation logic is latched and the pilot may release the takeover pb without losing sidestick priority.
If sidestick priority is latched, can it be overridden?
Yes. The other pilot can reactivate their sidestick by depressing their takeover pb.
Is there any cockpit indication of side stick priority?
Yes, the side stick priority indicator. A red arrow illuminates on the deactivated side pointing to the pilot who has taken priority. A synthesized voice also states the priority. "Priority Left" or "Priority Right".
What are the four major flight control laws?
1. Normal Law
2. Alternate Law
3. Direct Law
4. Mechanical Backup Law
Note: Abnormal Law is considered a subset of alternate law
In normal law, changing the pitch with the sidestick commands what?
A change in load factor. Pitch control is a "load factor demand" law.
In normal law, returning the sidestick to neutral commands what?
To maintain the current attitude
In normal law, left and right changes in the sidestick command changes in what?
The commanded roll rate. Roll control is a "roll rate demand" law.
In normal law, full sidestick deflection right or left commands what roll rate?
15 degrees per second, regardless of aircraft speed
What are the three normal law modes?
1. Flight mode
2. Ground mode
3. Landing mode
In normal law ground mode, what is the relationship between stick and rudder displacement and flight control surfaces?
There is a direct relationship, proportional to the stick and rudder displacement.
In normal law, after takeoff when will the ground mode blend into the flight mode?
About 5 seconds after liftoff
What happens as the aircraft descends into landing mode?
In normal law landing mode, at 50' RA the ELACs "memorize" pitch attitude. Beginning at 30', the ELACs add a gentle nose down command to that pitch. This requires an aft movement of the stick, similar to a landing flare.
If both RAs are inoperative, can normal law landing mode function?
No, the flight controls change to direct law when the landing gear is extended.
What is the highest priority for pitch protection?
Alpha (AOA) Protection
What protections are provided in normal law?
- High Speed
- Bank Angle
What are the maneuvering limits in normal law?
Flaps 0 or 1 - +2.5 to -1.0G
Flaps 1+F to Full -- +2.0 to 0G
In normal law, what are the pitch attitude protection limits? Do they ever change?
30 degrees nose up and 15 degrees nose down in the clean configuration, noted by equal signs on the PFD. The limits are reduced when flaps are extended but the marks do not move.
What changes occur on the PFD with excessively high or low pitch attitudes?
The flight directors are removed and red arrows are displayed to indicate the proper direction of attitude movement toward normal flight.
In normal law, when does high speed protection activate?
Just above Vmo/Mmo and is depicted by a green equal sign
In normal law, what happens when high speed protection activates?
1. A gentle pitch up is produced to limit further acceleration.
2. Nose down trim is deactivated, nose up trim is still available
3. If on, AP will disconnect
4. If active, the autothrust will limit thrust so that Vmo/Mmo is not exceeded. If it is exceeded, the autothrust reduced thrust to idle.
When high speed protection is active, are there any additional bank angle protections?
Yes. Bank angle is limited to 45 degrees
Is there any way to determine the current angle of attack in the cockpit?
Yes. On the PFD, the angle of attack is the difference between the FPA and the yellow "nose of the aircraft" square.
What is alpha protection?
The flight control computers will command the control surfaces to move to prevent the angle of attack from reaching or maintaining a stall.
What flight control computers compute the various alpha protection values?
What is VLS and how is it depicted?
Lowest safe airspeed. Top of the amber "hook"
What protections occur at VLS?
1. If active, autothrust will now allow the airspeed to decrease below VLS.
2. If the pilot inadvertently selects an airspeed below VLS, the autothrust will maintain a minimum of VLS.
3. If the FD is on, it will not display a pitch command that will result in an airspeed below VLS.
What is Alpha Prot and how is it depicted?
The angle of attack where alpha protection is activated. Depicted by the range that begins at the top of the black and amber band. Pitch command logic changes from load factor demand to alpha demand.
What protections occur in Alpha Prot?
1. Sidestick commands change from load factor demand to alpha demand.
2. AP will disengage
3. Speed brakes will automatically retract
4. Additional nose up trim is inhibited, nose down trim is still available
For the aircraft to further slow below Alpha Prot, the stick must be pulled further aft. If it is released, the airspeed returns to Alpha Prot.
What is Alpha Max and how is it depicted?
The maximum angle of attack. Solid red bar at the bottom of the black and amber band.
How does the pitch reach Alpha Max?
If the autothrust is not available, holding full aft stick allows the aircraft to slow to Alpha Max. This is the highest alpha that the ELACs will allow and the aircraft will descend at Alpha Max. If the stick is neutralized, airspeed will return to Alpha Prot.
What is Alpha Floor?
Approximately halfway between Alpha Prot and Alpha Max is Alpha Floor. It is not depiected on the airspeed display. If autothrust is available, when Alpha Floor is reached, the engines will be commanded to TOGA.
In normal law, can the pilot command an angle of attack that will cause a stall?
No. Alpha Protections prevent a stall from occurring.
In Normal Law, what is the maximum bank angle?
67 degrees as indicated by the green equal signs on the PFD
In Normal Law, what happens if the bank angle exceeds 45 degrees?
1. The autopilot disconnects
2. Flight director displays are removed from the PFD
When is neutral spiral stability active?
In normal law at bank angles from 0 to 33 degrees. If the sidestick is released, the attitude is maintain and a zero roll rate is commanded.
When is positive spiral stability active?
If the bank angle exceeds 33 degrees and the sidestick is released, the aircraft will return to 33 degrees of bank.
When Alpha or High Speed Protection is active at any bank angle, the aircraft will return to wings level if the sidestick is released.
At what bank angle is Auto Trim inhibited?
above 33 degrees
In general, what is required to change the normal law to alternate law?
At least a dual failure in a specific system. A single failure of a flight control computer, ADIRU or hydraulic system will not change the flight control law.
What are the easiest ways to determine you are in Alternate Law?
1. Amber "X"s replace the green equal sign pitch and roll protection limits of Normal Law
2. ECAM message "F/CTL ALTN LAW (PROT LOST)"
How is pitch controlled in Alternate Law?
Pitch control is still load factor demand with automatic pitch trim.
How is roll controlled in Alternate Law?
There is a direct relationship between stick position and control surface deflection.
What are the major changes in yaw control in Alternate Law?
Automatic turn coordination is lost, manual rudder is required. Yaw damping usually remains functional but with limited authority.
While in Alternate Law, what happens when the landing gear is extended?
Direct Law becomes active. In the event of a go-around, Alternate Law becomes active when the landing gear is retracted.
How does the airspeed tape change in Alternate Law?
Alpha Prot and Alpha Max are no longer displayed. Vls is still displayed and the top of the barber pole is Vsw.
In Alternate Law, when does low speed stability activate?
Low speed stability activates a few knots above Vsw commanding elevator movement to lower the pitch attitude. This stability can be overridden with aft stick and the aircraft will stall.
In Alternate Law, when does high speed stability activate?
High speed stability activates slightly below Vmo/Mmo commanding elevator movement to raise the pitch attitude, preventing further speed increase. High speed stability can be overridden if additional forward stick is applied.
When does Alternate Law not have stabilities?
When malfunctions prevent the flight control computers from receiving reliable airspeed information.
When does Abnormal Attitude Law become active?
If the protection limits of normal law are exceeded due to outside forces (turbulence, windshear, etc.)
What is the purpose of Abnormal Attitude Law?
It equates to Alternate Law w/o stabilities. It ensures that the computerized flight control laws do not prevent or interfere with the recovery from an abnormal flight condition.
Once the aircraft is back within the Normal Law attitude limits, will Normal Law be restored?
No. Automatic pitch trimming and yaw damping are restored. But the aircraft will remain in Abnormal Law until landing.
Explain Direct Law.
Pilot commands are sent, unmodified by the flight control computers, directly to the flight control surfaces. There are no protections or stabilities. The aircraft can stall and overspeed with the appropriate warnings. Automatic pitch trim is not available, manual pitch trim must be used. Rudder trim and limiting should be available unless the causing Direct Law occurred in the rudder system.
How can you determine you are in Direct Law?
1. An amber "USE MANUAL PITCH TRIM" message is displayed just below the FMA.
2. ECAM message "F/CTL DIRECT LAW (PROT LOST)"
What is the most likely cause of Direct Law?
Landing gear extension when in alternate law
How do you get into Mechanical Backup?
No flight control computers or no electrical power.
How can you determine you are in Mechanical Backup Law?
A red "MAN PITCH TRIM ONLY" message is displayed below the FMA
What flight controls are available in Mechanical Backup Law?
As long as hydraulic pressure is available, manual pitch trim and rudder are available via mechanical linkages. Sidesticks are inop.
How many leading edge slats are there per wing?
How many trailing edge flaps are there per wing?
What happens if one hydraulic motor in a PCU fails?
The associated PCU and flaps or slats operate at half speed
If both hydraulic motors in a PCU fail, how does this affect the slats and flaps?
The PCU will not operate, resulting in a flaps or slats failure.
What controls the flaps and slats?
Two Slat Flap Control Computers (SFCCs). Each SFCC sends control signals to one hydraulic motor in the Flap PCU and one hydraulic motor in the Slat PCU.
If one SFCC fails, how does this affect the slats and flaps?
The flaps and slats operate at half speed.
If the Flaps Channel of one SFCC fails, how does this affect the slats and flaps?
The flaps will operate at half speed.
If the Slats Channel of one SFCC fails, how does this affect the slats and flaps?
The slats will operate at half speed.
What happens if the SFCC detects an asymmetry, un-commanded movement or a runaway?
The Wingtip Brakes (WTBs) lock the appropriate drive train to prevent further movement.
Can the flight crew reset a locked Wingtip Brake?
No. Once applied the Wingtip brakes can only be released on the ground.
What is the slat Alpha Lock?
If the angle of attack is excessive, or airspeed to low, the Alpha Lock prevents the slats from retracting, even though the pilot has selected the flap handle UP.
When is the slat Alpha Lock removed?
Once the angle of attack and airspeed are normal.
When does flap automatic retraction occur?
If the flaps are at 1+F and the aircraft accelerates to 210 knots or above, the trailing edge flaps will automatically retract.