Flight control system Flashcards
1
Q
What are the main components of the primary flight control system?
A
Elevators, ailerons, multifunction roll spoilers, rudder
These components are responsible for pitch, roll, and yaw control.
2
Q
What does the secondary flight control system consist of?
A
Horizontal stabilizer, inboard and outboard flaps, slats, multifunction spoilers, dedicated ground spoilers
These components enhance the performance and control of the aircraft.
3
Q
What type of system is the flight control system?
A
Electronic closed-loop fly-by-wire system
This system uses electrically commanded and hydraulically powered actuators.
4
Q
What is the function of the dedicated computers in the fly-by-wire system?
A
Operate in normal and direct modes, provide enhanced flight control laws and protections
These computers ensure the safety and efficiency of the flight control system.
5
Q
What happens if one actuator of a control surface fails?
A
The remaining actuator can control the surface
This redundancy is crucial for flight safety.
6
Q
How many hydraulic systems provide redundancy to the flight control system?
A
Three independent hydraulic systems
This redundancy enhances reliability.
7
Q
What are the benefits of computer-regulated fly-by-wire technology?
A
Enhanced flight control laws, envelope protection, reduced workload, efficient fuel burn, weight savings
These benefits improve overall aircraft performance.
8
Q
What inputs are used by the flight crew for the flight control system?
A
Conventional control wheel, control column, pedals, flight condition data
These inputs allow for precise control of the aircraft.
9
Q
How many flight control computers (FCCs) are in the system?
A
Three flight control computers
Each FCC controls primary surfaces and spoilers for roll control.
10
Q
What is the purpose of the horizontal stabilizer control unit (HSCU)?
A
Controls the horizontal stabilizer surface
The HSCU operates in an active/standby configuration.
11
Q
What happens during a loss of normal electrical power in the fly-by-wire system?
A
A backup battery system activates automatically
This system provides power for essential functions for at least 30 minutes.
12
Q
What are the two basic modes of operation for the flight control system?
A
Normal mode and direct mode
These modes determine how the flight control surfaces respond.
13
Q
What defines the normal flight envelope?
A
Bank angle less than 33°, angle of attack below shaker, speed below VMO/MMO, pitch angle between +30° and -15°
These parameters ensure safe flight conditions.
14
Q
What functions are featured in the normal flight envelope?
A
- Turn compensation
- Neutral spiral stability
- Automatic compensation for configuration changes
- Elevator offload pitch and yaw damping
- Thrust asymmetry compensation
These functions enhance the aircraft’s stability and control.
15
Q
What occurs when the airplane enters the limit flight envelope?
A
The flight control system gradually pushes the airplane back to the normal flight envelope
This process helps maintain safe operational limits.
16
Q
Can direct mode be engaged automatically?
A
Yes, after the loss of minimum set sensors needed for normal mode
Direct mode can also be manually engaged.
17
Q
What are the functions available in direct mode?
A
- Command computation
- Pitch and yaw dampers
- Multifunction spoiler functions
- Turn coordination
These functions allow for direct control based on crew inputs.
18
Q
What does the NORMAL MODE button do on the FLIGHT CONTROLS MODE panel?
A
Manually transitions between flight modes
The button indicates the current mode with a white striped bar when in direct mode.
19
Q
What is the maximum bank angle limit in the limit flight envelope?
A
There is no hard limit unless high-speed protection is active, limiting bank angle to 33°
This limitation is crucial for aircraft safety during high-speed maneuvers.
20
Q
The system allows up to _____ transitions, after which only direct mode is available.
A
5
21
Q
Structural limits and safety aspects, which define the limit flight envelope hard limits include:
A
maximum load factor
maximum angle of attack
maximum dive speed (Vd)
maximum sideslip angle.
22
Q
Actuators are also commonly referred to as ___________
A
power control units (PCUs).
23
Q
flight control system includes the following dedicated electronic control units:
A
Three flight control computers (FCCs), Four slat/flap control units (FSCUs), One horizontal stabilizer control unit (HSCU)
24
Q
Where are the flight control crew interfaces primarily located?
A
On the central pedestal
Interfaces include control columns, control wheels, and various levers and switches.
25
What does the pitch trim switch on the control wheel do?
Manually trims the airplane around the pitch axis when the autopilot is not engaged
26
How must both parts of the split switch be moved to actuate the pitch trim?
Up or down simultaneously
27
What happens if the pitch trim switch is actuated for more than seven seconds?
The switch is automatically deactivated
28
What is the function of the SLAT/FLAP lever?
Activates and controls movement of the slats and flaps
29
How many positions does the SLAT/FLAP lever define?
Seven positions
30
What distinct feature does lever position 4 have?
A stop mechanism to prevent inadvertent movement
31
What is the speed brake lever used for?
To deploy the multi-function spoilers during flight
32
What happens when the speed brake lever is in the fully forward position?
The spoilers are in the stowed position
33
What does the TRIM panel include?
A rotary knob, split switches, and guarded switches for trim functions
34
What does the rotary YAW trim knob enable?
Manual left or right position adjustments
35
When is yaw trim inhibited?
While the airplane is on the ground
36
What does the PITCH BACKUP switch do?
Enables up or down pitch trim adjustments
37
What happens if the pitch trim switch is used while autopilot is engaged?
Results in the disengagement of the autopilot
38
What do the guarded pitch trim SYS 1 and SYS 2 CUTOUT buttons do?
Enable and disable the respective HSCU channels
39
What does the flight control system monitor?
Control surface deflections and separate surfaces
40
What information is displayed on the flight control system synoptic page?
Position, status, and failure information of primary flight controls
41
What does the SURFACE AWARENESS window indicate?
Surface commands as a percentage of total authority
42
What do MODE indicators identify?
The surface operating mode as NORMAL or DIRECT
43
What is the purpose of the elevator and aileron disconnect mechanisms?
To enable separation of control columns or wheels in case of a jam
44
What is the validity period for a successfully executed PBIT?
50 flight hours
45
What do the ELEC and HYDR PBIT digital readouts display?
Elapsed time remaining before PBITs expire
46
What does the EICAS message FLT CTRL BIT EXPIRED indicate?
The PBIT has expired
47
When is the electrical PBIT performed?
During power-up after being powered by any AC source
48
What aborts the electrical PBIT?
Any of the following: electric hydraulic pump is turned ON, AC power is interrupted, engine starts running, pilot moves any flight control surface
49
What does the hydraulic PBIT test?
Elevator, rudder, and aileron control actuators
50
What does the SLAT/FLAP/SPOILER indicator display?
Graphical and digital representation of flap, slats, spoilers, and speedbrake positions
51
What do the TRIMS indicator scales represent?
Aircraft roll, yaw, and pitch trim positions
52
What do cyan bugs indicate in slat/flap indications?
The commanded position
53
What does the TRIMS positions tick marks represent?
-100%, -50%, 0%, 50%, and 100% of trim command
54
What happens if the pitch trim pointer displays in red?
It indicates the pitch trim is outside the allowable position for takeoff
55
What do Flight Control Computers (FCCs) process for pitch control?
Pilot inputs and airplane flight condition
56
How are the actuators for pitch control configured?
In active-active configuration
57
What happens if one actuator fails?
The remaining actuator can control the elevator surface with a smaller rate of movement
58
What is automatically commanded during the takeoff run as thrust levers are moved towards TO/GA?
A nose-down elevator offset to increase steering controllability
59
What function is activated during takeoff roll to facilitate pitch attitude capture?
Rotation function
60
In flight control, what does control column displacement relate to?
Proportional to a rate of change in the flight path angle
61
What does the normal mode load factor protection ensure?
The commanded load factor never exceeds maximum allowable by control laws
62
What must be done to trim the airplane in a new trim airspeed?
Control column or trim inputs are required
63
What happens if the airplane is trimmed in a determined airspeed?
The offload function activates if the elevator position exceeds a given threshold
64
What does pressing the trim switch represent in flight?
A change in the speed target for the control laws
65
On ground, what do pitch trim switches directly command?
The horizontal stabilizer surface
66
What does the lift compensation feature do during turns in the air?
Partially compensates the natural loss of lift due to airplane roll
67
What does the de-rotation function control during touchdown?
The airplane rotation rate
68
What is direct mode pitch control?
A degraded mode of operation with limited functions and no envelope protection
69
How is direct mode engaged manually?
By pressing the NORMAL MODE button on the FLIGHT CONTROLS MODE Panel
70
What does the elevator do in direct mode?
Moves as a direct function of the column position
71
What activates the pitch protection?
When the pitch angle is lower than 15° pitch down or higher than 30° pitch up
72
What does the horizontal stabilizer control system do?
Trims the aircraft around the pitch axis
73
What is the function of the HSCU?
Drives the HSTA to move the horizontal stabilizer surface
74
What happens if the FCCs are not available?
The HSCU receives commands directly from the backup trim switch
75
How is manual trim commanded?
Through switches on the control wheels or a PITCH BACKUP switch
76
What happens if only one side of the dual split trim switch is actuated?
An aural warning 'TRIM' annunciates for six seconds
77
What is the priority order for processing trim inputs?
1. Backup switches, 2. Left seat switches, 3. Right seat switches
78
What occurs during an electrical emergency regarding trim commands?
Trim commands are inhibited for two seconds
79
What triggers a takeoff configuration warning?
The airplane is not in a suitable takeoff condition
80
What does the Tail Strike Avoidance (TSA) function do?
Controls airplane pitch angle by reducing control column authority in the nose up direction
81
At what altitudes is the TSA function enabled during takeoff and landing?
Takeoff: less than 30 ft, Landing: less than 25 ft
82
What does the high-speed protection prevent?
Exceeding maximum dive speed
83
What happens when high-speed protection is activated?
Reduction of pitch down column authority
84
What is the purpose of the maneuver load alleviation (MLA) function?
Automatically compensates for disturbances by moving the elevators
85
What does the stall protection system provide to the pilot?
Warning when approaching stall speed
86
What does the AOA limiting function do in flight controls normal mode?
Reduces authority of control column in the nose up direction
87
What activates the stick shaker?
When the top warning range of the LSA is reached
88
True or False: The AOA limiting function is available in direct mode.
False
89
What type of configuration do the aileron actuators operate in?
Active-active configuration
90
What happens if a jam is detected in one of the aileron actuators?
The respective aileron surface remains fixed at the position where the jam occurred and an EICAS message AILERON LH (RH) FAIL is displayed
91
What is the role of the multifunction spoiler panels?
Each is equipped with a single actuator for roll control and compensations based on pilot inputs and flight conditions
92
What occurs if a spoiler panel becomes inactive due to failure?
The symmetric panel on the opposite wing is deactivated
93
In normal mode on the ground, how is the surface deflection of ailerons and multifunction spoilers determined?
It is a direct function of the control wheel position
94
What do the lateral control laws provide in normal mode?
Turn coordination, eliminating the need to apply the pedals
95
What happens as the airplane gains speed on the ground?
The direct relationship between inceptor and surface position remains with an active yaw damper
96
What does the standard lateral control law in air convert?
Wheel deflection to a roll rate demand
97
What do the control laws command when the control wheel is kept in the neutral position?
They command the surfaces to maintain zero roll rate up to 33° of bank
98
What activates when a high bank angle or high-speed condition is reached?
Two additional protections in normal mode
99
In direct flight mode, how is aileron displacement determined?
It is a direct function of control wheel displacement, scheduled and limited with airspeed and flap position
100
What happens to roll trim commands after three seconds?
They must be released and then reengaged for further displacement
101
What do roll trim commands generate?
Aileron, roll spoilers, and rudder commands
102
What is the purpose of the control law regarding roll trim?
To artificially provide neutral spiral stability
103
When is roll trim inhibited?
While the airplane is on the ground or in flight with the AP engaged
104
How does roll trim command perform in normal mode?
Like a small wheel command
105
How do roll trim commands correspond in direct mode?
Directly to aileron surface displacement
106
What activates if the airplane bank angle is greater than 33°?
Bank protection function
107
What does bank protection provide?
Positive spiral stability to gradually return to a bank angle of 33°
108
What authority does the pilot have over bank angle protection?
The pilot can maintain a constant bank angle greater than 33° by moving the control wheel out of neutral
109
What is generated with the control wheel at maximum deflection?
The maximum available roll rate
110
What happens if the wings are not leveled in a high-speed situation?
Lateral commands are generated to bring the airplane back to a maximum bank angle of 33°
111
What is the maximum bank angle allowed in high-speed mode with maximum wheel deflection?
33°
112
What is unique about the bank angle limit in high-speed mode?
It is the only condition where a hard limit on bank angle is imposed
113
What technology does the yaw control system use?
Fly-by-wire technology
## Footnote
This technology allows for precise control of the rudder surface.
114
What are the two components used to control rudder movement in the yaw control system?
Hydraulically-powered active-active actuators
## Footnote
These actuators receive commands based on pilot inputs and flight conditions.
115
What happens if one hydraulic system fails in the yaw control system?
Hydraulic power is still available from the other system
## Footnote
Hydraulic system 1 powers the upper actuator and hydraulic system 3 powers the lower actuator.
116
What occurs if a pedal assembly becomes jammed?
The rudder remains active for FCCs compensation functions
## Footnote
These functions include yaw damper and turn coordination.
117
How do flight characteristics in the yaw axis compare to conventional airplanes?
Similar, with improved handling qualities and disturbance rejection
## Footnote
This is due to feedback from inertial, air data, and airplane configuration.
118
What is the behavior of the rudder on the ground?
Moves as a direct function of pedal deflection
## Footnote
It is scheduled with airspeed and flap position.
119
What activates the on-ground yaw damper?
When the airplane reaches approximately 50 kt
## Footnote
This is when control surfaces become more aerodynamically efficient.
120
In normal mode, what do pedal deflections correspond to?
A sideslip demand
## Footnote
Control laws send commands to achieve the desired sideslip.
121
What does maximum pedal deflection correspond to?
Maximum sideslip allowable by control laws
## Footnote
This is to avoid structural damage.
122
In direct mode, how is rudder displacement determined?
Direct function of pedal displacement
## Footnote
Scheduled and limited with airspeed and flap position.
123
What functions are not available in direct mode?
Thrust asymmetry function, limited sideslip, best beta function
## Footnote
These are critical for optimized flight handling.
124
How is the rudder control system trimmed manually?
Using the YAW trim switch
## Footnote
It operates similarly to conventional airplanes.
125
What does the yaw trim command result in during normal mode?
A sideslip demand to the control laws
## Footnote
This generates appropriate aileron and rudder commands.
126
How long is the rudder trim function limited to?
Three seconds
## Footnote
Further displacement requires reengaging the switches.
127
When is the yaw trim function inhibited?
While the airplane is on the ground
## Footnote
This ensures safe ground operations.
128
What does the thrust asymmetry compensation (TAC) function do?
Supplies roll-yaw tendency corrections during thrust asymmetries
## Footnote
It activates during single engine conditions.
129
What is produced automatically when TAC is activated?
A one-second rudder input
## Footnote
This anticipates the pilot's response.
130
What happens to yawing caused by thrust asymmetry when an engine failure occurs in the air?
TAC counteracts most of the yawing
## Footnote
A slight roll tendency towards the failed engine is also created.
131
What is the Best beta function used for?
To maintain a certain sideslip and optimize climb performance during OEI conditions
## Footnote
This applies to any phase of flight including takeoff and go-around.
132
What conditions must be met for the Best beta function to activate?
FCS in normal mode, thrust asymmetry, TLA > 57°, flaps < 5, landing gear UP
## Footnote
These conditions ensure proper functioning.
133
What does the roll pointer slip-skid indicator change to when the Best beta function is activated?
Cyan
## Footnote
It becomes proportional to the difference between current and target sideslip angles.
134
What is required to center the sideslip indication when the Best beta function is active?
A slight pedal deflection
## Footnote
This helps maintain the optimal sideslip angle.
135
What does the high lift control system consist of?
Electrically powered flap and slats actuator systems
136
How many slat surfaces does the slat actuator system control?
10 slat surfaces (5 per wing)
137
How many flap surfaces does the flap actuator system control?
4 single slotted flap surfaces (2 per wing)
138
What provides surface position commands to electrical actuators?
Flap/slat control units (FSCU) inputs from the SLAT/FLAP control lever
139
In what mode does the system operate if it is using a single engine generator or without any FSCU?
Low-rate mode
140
What do electronic sensors monitor in the flap/slat system?
The status of flap/slat system
141
What happens if a fault is detected in a flap or slat?
Emergency shutoff protection sends a command to stop the movement of flap/slat panels
142
What messages are displayed on the EICAS upon activation of the emergency shutoff protection?
SLAT FAIL and FLAP FAIL messages
143
What message may display if the respective surface has not reached the selected position on the SLAT/FLAP lever?
SLAT-FLAP LEVER DISAG
144
What can be done to release a jam on any flap or slat?
Setting the selector lever to the previous position and again to the desired position
145
How many further releases of jams are allowed after the first jam?
Two further releases
146
What happens if the jam monitor trips for a third time?
Emergency protection function deactivates the surface actuators
147
What does the flight control system use flap and slat position for?
To schedule surface commands
148
What happens if the FCCs lose flap or slat position information?
The flap/slat control system is locked with the current flap or slat position
149
How do flaps and slats operate during an electrical emergency with only the RAT as the power source?
In sequential actuation and half speed
150
What is prevented when the RAT is the only source of electric power?
Deployment of flaps and slats beyond position three
151
What occurs if the RAT is deployed after the flaps and slats have extended beyond position three?
The surfaces do not retract automatically
152
What does the system continue to command if a flap or slat fails?
The non-affected surface based on SLAT/FLAP LEVER movement
153
What is the limitation for flap deflection when slats are below 20°?
FSCU does not command the flaps beyond 10° (SLAT/FLAP lever in position 2)
154
What happens if the SLAT/FLAP lever is commanded beyond position 2 when slats are below 20°?
FSCU limits the flap deflection to 10° and displays SLAT-FLAP LEVER DISAG
155
What is enabled on the ground regarding the slat/flap interlock?
Extension or retraction of either surface to any valid position regardless of the position of the other surface
156
What is the number of spoiler panels in the spoiler control system?
Twelve panels
## Footnote
Six panels on each wing
157
How are the spoiler panels numbered on the left wing?
L1 to L6
## Footnote
Right wing panels are numbered R1 to R6
158
What are the two types of spoiler panels located on each wing?
Ground spoilers and multifunction spoilers
## Footnote
Two ground spoilers inboard, four multifunction spoilers outboard
159
What happens to the symmetric spoiler panel on the opposite wing if one panel becomes inactive?
It is deactivated
160
How many modes do the multifunction spoilers operate in?
Three modes
161
What are the three modes of operation for multifunction spoilers?
* Roll control
* Ground spoilers
* Speed brakes
162
In roll control mode, how are the multifunction spoilers deployed?
Asymmetrically
163
What is the purpose of deploying multifunction spoilers in ground spoiler mode?
To aid in deceleration
164
When are multifunction spoilers deployed symmetrically during flight?
In speed brakes mode
165
What is the maximum limit of panel displacements in speed brakes mode?
30°
166
What does the speed brakes mode do?
Increases aerodynamic drag to reduce airspeed or increases rate of descent
167
Under what conditions do speed brakes automatically retract if extended?
* Airspeed below 180 KIAS
* Thrust lever angle beyond 76°
* Slat/flap lever at position 1 and airspeed above 230 KIAS
* Slat/flap lever at position 2 or above
* Stall protection function is active
168
What advisory message displays if there is a disagreement between the speed brake handle position and the actual surface position?
SPBRK LEVER DISAG
169
During ground operation, how do all twelve spoiler panels function?
As ground spoilers
170
What commands the deployment of dedicated ground spoilers and multifunction spoilers after touchdown?
FCCs
171
What must occur for full deployment of all spoilers as ground spoilers?
* Weight on wheels on ground
* Wheel speed above 45 kt or airspeed above 60 KIAS
* Thrust lever angle (TLA) below 26°
172
How do ailerons assist in the deployment of spoilers after touchdown?
They are symmetrically deflected upwards
173
What is the effect of deploying all spoilers and deflecting the ailerons after touchdown?
Increases wheel braking efficiency and aerodynamic drag
