A320 Flight Controls
Terms in this set (57)
What's the fly through-computer concept?
Flight control system input, made by either the pilot or the autopilot, is first processed by flight control computers. The flight control computers then process these commands and electronically signal the hydraulic servos/actuators to deflect the control surfaces accordingly.
What's the flight control law concept?
Flight control computers utilize factory preset instructions called "flight control laws". These laws define how the flight control computers control pitch, roll, and yaw.
What are the roles of the two Elevator Aileron Computers (ELACs)?
The ELACs provide control of the elevators, ailerons, and trimmable horizontal stabilizer (THS). The ELACs also serve as the master flight control computers processing the need for spoiler
input during rolls, and rudder input for yaw. Both are active during flight, and should one fail, the remaining ELAC will assume all ELAC related responsibilities.
What are the roles of the two Flight Augmentation Computers (FACs)?
The FACs provide control of the rudder. This
includes automatic turn coordination, yaw damping, rudder limiting, and rudder trimming. Only one FAC is active at a time with the other serving as a standby.
Describe the roles of the three Spoiler Elevator Computers (SECs).
The SECs provide control of the spoiler panels. All SECs are active during operations; each is responsible for a specific pair, or pairs, of panels. Should both ELACs fail, the SECs can also provide backup control of the elevators and THS.
Why are there are two separate overhead FLT CTL panels?
1.The left overhead FLT CTL panel contains the
pbs for controlling ELAC 1, SEC 1, and FAC 1.
The right overhead FLT CTL panel contains the
pbs for controlling ELAC 2, SEC 2, SEC 3, and
2. The left panel specifically defines which flight
control computers remain powered while in the
emergency electrical configuration. The
remaining computers defined by the rightpanel
are not powered in the emergency electrical
What is Normal Law?
Normal Law: defines how the flight control
computers control pitch, roll, and yaw during
normal operations. It also protects the aircraft
from exceeding the normal flight envelope. It is
active when all or nearly all systems are
Was is Alternate Law?
Alternate Law: defines how the flight control
computers control pitch, roll, and yaw after the
flt control system, or systems that support it,
experience certain multiple failures. While
alternate law still maintains a high level of
capability, some of the flt control characteristics
change, and some flight envelope
protection is lost.
What is Direct law?
Direct Law: is the least sophisticated flight control
law. It occurs as the result of more significant
system failures, or when the landing gear is
lowered while in alternate law. Control and feel is
similar to that of conventional aircraft.
List the flight characteristics associated with Normal Law?
- Load Factor Demand
- Automatic Pitch Trim
- Roll Rate Demand
- Automatic Pitch Trim
- Bank Angle Hold
- Positive Spiral Stability
- Automatic Turn Coordination
- Yaw Damping
- Rudder Limiting
What are the protections associated with Normal Law?
- Maneuver Protection
- Pitch Protection
- High Speed Protection
- Alpha Protection
- Bank Angle Protection
What is load factor demand?
For pitch control in normal law, sidestick input results in the ELACs changing the aircraft's load factor. This is referred to as load factor demand. Fore and aft sidestick input does NOT directly correspond to the position of the elevators. Instead, pulling the stick aft requests a positive change in load factor while pushing the stick forward results in a negative request in load
factor. The ELACs then deflect the elevators accordingly to provide the requested change in load factor. Leaving the sidesticks neutral requests a zero change in load factor.
Describe automatic pitch trim as it pertains to pitch and roll.
In normal law, no manual trimming is required. The ELACs automatically trim the aircraft during changes in pitch and for bank angles up to and including 33°.
What is manuever protection?
Maneuver protection prevents a pilot from overstressing the aircraft. It prevents additional flight control surface movement if those movements would cause the aircraft to exceed structural G load limits.
The load limits are:
- +2.5 Gs/-1.0 G w/trailing edge flaps retracted
- +2.0 Gs/0 G w/trailing edge flaps extended
What is pitch protection?
Pitch protection prevents excessive nose-up and nose-down attitudes. The ELACs will not allow attitudes greater than 30º nose-up, or 15º nose-down even if the sidestick is held full aft/forward.
What is high speed protection?
High speed protection prevents aircraft damage due to excessive speed. When activated, the ELACs automatically pitch the aircraft up to limit further acceleration even if the sidestick is held full forward.
What is Alpha Protection?
During low speed/high angle of attack flight, load factor demand is not sufficient for precisely controlling pitch. Therefore, the system has a built-in feature called alpha protection (alpha prot).
If angle of attack, or alpha, becomes greater than alpha prot, pitch logic changes from load factor demand to alpha demand to provide for more precise pitch control. Sidestick input then commands specific angles of attack. This feature is particularlyuseful during windshear, GPWS, or TCAS recoveries.
How is alpha prot is depicted on the airspeed tape?
Alpha prot is represented at the top of the amber and black "barber pole" band of the airspeed tape. This band is only present if the aircraft is in normal law.
What is alpha max and how it is depicted on the airspeed tape?
Alpha max is the highest alpha that the flight control computers will allow for a given configuration and weight; it provides the max lift coefficient. Since alpha max occurs just prior to stall, theoretically the aircraft cannot be stalled while in normal law. Alpha max is achieved by continuously holding full aft sidestick
Alpha max is the top of the red solid band found on the airspeed tape.
Describe roll rate demand.
There is not a direct relationship between the position of the sidestick and the ailerons in normal law. Instead, left or right sidestick movement command rates of roll.
- Full sidestick deflection yields the maximum
allowable roll rate of 15º per second regardless
of airspeed or configuration.
- Deflecting a sidestick only halfway yields a roll
rate half of the maximum allowable rate.
- Neutral sidestick commands a "zero" change in
What is bank angle hold?
If the sidestick is neutralized at bank angles ≤33º, a zero roll rate is commanded and the bank angle does not change; the bank angle is held.
Describe positive spiral stability.
At bank angles >33º, if the sidestick is released, the aircraft will automatically roll back to 33º. Continuous pressure must be applied to the sidestick to hold the desired level of bank when itexceeds 33º.
Describe the role of automatic trim during turns.
At bank angles ≤33º, the ELACs automatically introduce the necessary back pressure through the use of automatic pitch trim. At bank angles above 33º, this feature becomes inhibited, and aftsidestick will be necessary to maintain a level turn.
What is bank angle protection?
In normal law, the ELACs will not allow the aircraft to exceed 67º of bank. Even if full left or right sidestick is maintained, the bank angle is limited to 67º. This limit is further reduced if other protections are active.
Know the indications associated with normal law.
The presence of green equal signs located throughout the PFD indicates the aircraft is in normal law. The green equal signs are at:
- the 67º bank angle limits
- the +30º and -15º pitch attitude limits
- the high speed protection limit (several knots
Describe the Ground Mode of Normal Law.
Ground Mode: active when on the ground.
- Since load factor demand and roll rates aren't
practical during takeoff, there is a direct
relationship between the placement of the
sidestick/rudder and the flight control surfaces
while in ground mode.
- Ground mode also better accommodates full
flight control checks.
Descibe the Flight Mode of Normal Law.
Flight Mode: Flight mode becomes active shortly after takeoff; this allows all of the flight characteristics and protection sassociated with normal law to take effect.
Describe the Landing Mode of Normal Law.
- Landing mode gives the aircraft a conventional
feel during landings.
- As the aircraft descends through 50' AGL, the
ELACs "memorize" the pitch attitude. Beginning
at 30' AGL, the ELACs add a gentle nose down
command, referencing the "memorized" attitude
as a starting point. To counter this nose down
command requires aft movement on the
sidestick. This, in turn, provides an artificial feel
in a manner similar to the landing flare of
List the flight characteristics associated with Alternate Law.
- Load Factor Demand
- Automatic Pitch Trim
- Roll Direct
- Yaw Damping*
- Rudder Limiting*
*Provided at least one FAC is functional.
List the protections available in Alternate Law.
- High Speed Stability
- Low Speed Stability
How is roll control maintained while in
In alternate law, roll control is similar to that of conventional aircraft. Unlike in normal law, there is now a direct relationship between the sidestick and the roll control surfaces. Additionally, all of the remaining roll control flight characteristics and protections are lost.
Describe how high and low speed stabilities differ from protections (in Alt Law).
Unlike a protection, the pilot can override stabilities.
-High Speed Stability (replaces high speed protection): Slightly below VMO/MMO, high speed stability automatically commands the elevators to increase the aircraft's pitch thus preventing any
additional increase in speed. However, if forward sidestick is applied, high speed stability will be overridden, and the aircraft will accelerate.
-Low Speed Stability (replaces alpha prot): At a speed slightly faster than stall, low speed stability automatically commands the elevators to lower the aircraft's pitch thus preventing additional loss of airspeed. However, if aft sidestick is applied, low speed stability will be overridden. The aircraft will continue to decelerate, AND EVENTUALLY STALL!
What's the stall warning speed presented on the airspeed tape while in alternate and direct laws?
Stall warning speed is presented at the top of the red and black "barber pole" band on the airspeed tape while in alternate and direct laws.
Know the indications associated with alternate law.
- All green equal signs associated with normal
law are replaced with amber "X"s.
- An E/WD message stating: "F/CTL ALTN LAW
(PROT LOST)" is also presented.
List the flight characteristics direct law.
*Provided at least one FAC is functional.
List the protections available in direct law.
What are the indications associated with direct law?
- The amber "X"s presented with alternate law
are still present.
- "USE MAN PITCH TRIM" appears in amber
above the artificial horizon on the PFD.
- An E/WD message stating: "F/CTL DIRECT
LAW (PROT LOST)" is also presented.
Describe backup control (mechanical control).
Backup control provides for mechanical control of the aircraft in the event all flight control computers fail or there is a complete electrical failure. It is intended to be used only for as long as it takes to restore computer flight control or electrical power.
Which flight control surfaces contain
backup mechanical systems for controlling pitch, roll, and yaw?
Hydraulic power must be available for backup control to function.
-Pitch is controlled by using the pitch trim wheels;
there is a mechanical connection between the
pitch trim wheels and the THS hydraulic servos.
-Roll and yaw is controlled using the rudder
pedals; there is a mechanical connection
between the pedals and the rudder hydraulic
Since there is no mechanical connection to either sidestick, they will be inoperative.
What is the primary indication associated with backup control?
Assuming there is electrical power, "MAN PITCH TRIM ONLY" appears in red above the artificial horizon on the PFD alerting you that the aircraft is in backup control.
What is Abnormal Attitude law?
Abnormal attitude law ensures that the flight characteristics and protections associated with normal law do not interfere with recovery from an abnormal flight condition. It's essentially alternate law without automatic pitch trim. Also, yaw control is the same as backup control. After the recovery has been made, the aircraft remains in alternate law for the remainder of the flight. It will not degrade to direct law once the landing gear is extended.
Describe the rudder and rudder trim indications presented on the F/CTL page.
- The rudder is depicted on the bottom of the
F/CTL page similar to an overhead shot.
- The rudder trim indication is presented as a
small cyan "tick" against the rudder deflection
What does a blue pulsing "A-LOCK"
represent on the E/WD?
"A-LOCK" is displayed on the E/WD when slat retraction is inhibited due to excessive angle of attack or airspeed that is too low. Once alpha and airspeed are normal, the inhibition is removed and the slats retract. The "A-LOCK" indication also extinguishes.
What is the sidestick priority system?
The sidestick priority system allows either pilot's sidestick to have sole control of the aircraft in the event of a failure of the other sidestick, the autopilot(s), or if the other pilot were to become incapacitated and displace his/her sidestick.
What are the priority order of the sidestick priority system?
Sidestick priority is engaged as follows:
- The pilot seeking control presses and holds the
autopilot disconnect/priority pb located on their
respective sidestick. As the pb is held, the
opposing sidestick is deactivated. This action
will also disengage the autopilot.
1. A synthesized voice states "priority left" or
"priority right" as appropriate.
2. A red SIDE STICK PRIORITY arrow
illuminates in front of the pilot losing control.
3. If the opposing sidestick is not sensed in
the neutral position, a light in front of the
pilot with priority illuminates green:
a. "CAPT" illuminates if the CA is
seeking priority and the FO's sidestick
is out of neutral.
b. "F/O" illuminates if the FO is seeking
priority and the CA's sidestick is out of
4. After 40 seconds, the sidestick priority pb
may be released, and the opposing sidestick
will be deactivated.
a. If the sidestick priority pb is released
prior to 40 seconds, the opposing
sidestick will reactivate.
b.The deactivated sidestick can be
reactivated at any time by pressing its
Describe what occurs if dual inputs are made to both sidesticks.
If both sidesticks are simultaneously displaced, the ELACs will process the sum of their inputs.
- If the CA's sidestick is fully displaced to the left
while the FO's is fully displaced to the right, the
resultant command will be neutral ailerons.
- If both the CA's and FO's sidesticks are
displaced halfway forward, the resultant
command will yield FULL forward elevator.
a. commands are summed up to a maximum
of one stick's full deflection
As dual inputs are made, a synthesized "dual inputs" is heardover the loudspeakers.
Describe how the hydraulic systems that
power flight control surface actuation are
depicted on the F/CTL page.
- The flight control hydraulic servos and
servojacks for each control surface are depicted
on the F/CTL page. "G" is presented for servos
powered by the GREEN hydraulic system, "Y"
for the YELLOW system, and "B" for the BLUE
system. When the hydraulic system is
functioning normally, the letter is displayed in the
- The letter changes to amber if the respective
hydraulic system fails.
Describe how the flight control computers are depicted on the F/CTL page.
- The two ELACs and the three SECs are
depicted. The words "ELAC" and "SEC" are
shown separately in white. The corresponding
computer number is shown in green when
functioning normally. Each computer
representation (ELAC 1, ELAC 2, SEC 1, SEC
2, and SEC 3) are also bordered by a grey half-
- If a flight control computer fails or has been
selected OFF, the computer number and the half-
box turn amber. Additionally, an amber half-box
appears around the respective hydraulic system
letter that is controlled by the failed computer.
- The FACs are not depicted on the F/CTL page.
How are PITCH TRIM indications presented on the F/CTL page?
- A digital readout for PITCH TRIM is presented
on the F/CTL page. It specifically shows the
angle of the THS on the F/CTL page. for
nose "UP" or nose "DN" trimming. For example:
a. a reading of "-0.6º UP" means the THS is
set at -0.6º for nose up trimming
b. a reading of "1.2º DN" means the THS is
set at 1.2º for nose down trimming
**Note: as a backup, analog pitch trim settings can
also be referenced by using the markings
adjacent to the pitchtrim wheels.**
Why are there two different references for neutral ailerons presented on the F/CTL page?
For added lift, the ailerons droop when the flaps are extended.
- The "=" indication represents the neutral position
of the ailerons when the flaps are retracted.
- The "" indication below represents the neutral
position of the ailerons when the flaps are
Describe how speed brake indications are
presented in the memo section of the E/WD.
- When the speed brakes are deployed with
engines at idle, the words "SPEED BRK" are
presented in green in the memo section.
- When the speed brakes are deployed with the
engines above idle, "SPEED BRK" appears in
Explain how the speedbrakes respond on the A320 with the autopilot engaged vs. disengaged.
- On the A320, when the autopilot is engaged, the
speed brakes are limited to ½ their maximum
capability. Placing the speed brake lever beyond
the 1/2 position will yield no further deployment.
- If the autopilot is off, the speed brakes can then
be used in their full range of capability.
**NOTE: This autopilot limitation does not apply to
the A319; the speed brakes will respond
to all lever positions.**
Where can you monitor speed brake and ground spoiler deployment?
-The positioning of the spoiler panels can be
monitored on both the F/CTL and WHEEL pages.
- On landing, the ground spoilers are specifically
monitored on the WHEEL page because that
page is automatically displayed upon gear
Know the conditions that will cause the speed brakes to automatically retract if they're deployed.
The speed brakes will automatically retract under the following conditions:
- FLAPS FULL is selected
- Airspeed decreases to alpha prot
- TOGA power is applied
List the requirements for the ground spoilers to deploy during landing or a rejected takeoff.
- both main gear are compressed
- main gear wheel speed is 72 knots or greater
If the ground spoilers are armed:
- both thrust levers are retarded to the IDLE stop
If the ground spoilers are not armed:
- at least one thrust lever is in the REVerse
range and the other is at the IDLE stop
If the slats fail do you still have flaps
All of the slats are operated as a group via torque tubes, and likewise for the flaps. The slat torque tubes are rotated by a dedicated slat Power Control Unit (PCU), and the flap torque tubes have their own Flap PCU. Each PCU is powered by two motors powered by different hydraulic systems. Dual Slat Flap Control Computers (SFCCs), two PCUs, and dual PCU hydraulic motors, prevent any single failure from disabling either the slats or flaps. If one hydraulic motor in a PCU fails, the PCU and its associated slats or flaps will operate at half speed. If both hydraulic motors in a PCU fail, that PCU will not operate, resulting in a failure of either the slats or flaps.
What happens if you accelerate and forget to clean up?
If the flaps are at 1+F and the aircraft accelerates to 210 kts or above, the trailing edge flaps will automatically retract. The leading edge slats remain extended.