Flight Controls

Question 1

Which hydraulic system(s) can power all primary flight controls?

Answer 1

All the primary flight controls are connected mechanically to their respective control input and hydraulically actuated. Normally, hydraulic system A and B power the flight controls redundantly; however, the primary flight controls may be operated with only system A or B.

Question 2

How are the primary flight controls operated in manual reversion?

Answer 2

With the loss of hydraulic system A and B, the ailerons and elevators are operated manually and the rudder is operated using the standby hydraulic system. This is referred to as manual reversion.

Question 3

Which hydraulic system(s) power the trailing edge flaps and leading edge devices?

Answer 3

The TE flaps and Leading Edge Devices (LEDs) are normally powered by hydraulic system B. If system B has failed, the LEDs may be operated by the standby hydraulic system and the TE flaps may be operated using an electric motor.

Question 4

How is roll controlled with a jammed aileron?

Answer 4

Using the spoilers. In the event of a lateral system jam, force applied to the Captain’s and the First Officer’s control wheels will identify which system, ailerons or spoilers, is usable and which control wheel can provide roll control. NOTE: The force applied to actuate control is against a torsion spring. The force required to move the controls is significant. If the aileron control system is jammed, force applied to the First Officer’s control wheel provides roll control from the spoilers. The ailerons and the Captain’s control wheel are inoperative. If the spoiler control system is jammed, force applied to the Captain’s control wheel provides roll control from the ailerons. The spoilers and the First Officer’s control wheel are inoperative.

Question 5

How is pitch controlled with a jammed elevator?

Answer 5

In the event of an elevator jam, an override mechanism allows the control columns to be physically separated from one another. Applying force against the jam will breakout either the Captain’s or First Officer’s control column, freeing one to provide adequate elevator control. Although total available elevator travel is significantly reduced, there is sufficient travel available for landing flare. The force required is higher than the force required for elevator movement in manual reversion; however, stabilizer trim is available to counteract the sustained control column force. Further Info: If a jam occurs in the elevator control mechanism, both control columns have a limited range of motion. During approach and landing, the Elevator Jam Landing Assist System uses the flight spoilers for small changes to the flight path. To activate the system, the ELEVATOR JAM LANDING ASSIST switch must be selected ON and the actual TE flap position must be 1 or greater with the autopilot disengaged. Activating the system will deploy six of the eight flight spoilers to a preset position. A push on the control column causes the spoilers to extend farther, increasing descent rate. A pull on the control column will retract the spoilers, decreasing the descent rate.

Question 6

What does the illumination of the SPOILERS light indicate?

Answer 6

SPOILERS light (amber) on the Flight Control panel indicates the SCE unit has identified a spoiler system fault.

Question 7

What happens when placing a FLT CONTROL switch to STBY RUD?

Answer 7

• STBY RUD activates the standby hydraulic system pump and opens the standby rudder shutoff valve to pressurize the standby rudder power control unit NOTE: With the FLT CONTROL switch in STBY RUD, the associated FLT CONTROL LOW PRESSURE light is deactivated, and the STANDBY HYD LOW PRESSURE light is armed.

Question 8

How is the Elevator Jam Landing Assist activated?

Answer 8

Positioning the ELEVATOR JAM LANDING ASSIST switch ON will activate the system and illuminate the ASSIST ON light.

Question 9

How is horizontal stabilizer trim operated?

Answer 9

The horizontal stabilizer is positioned by a single electric motor controlled by either stabilizer trim switches on the control wheel, or by autopilot trim. The stabilizer may also be positioned by manually rotating the stabilizer trim wheel.

Question 10

How is MCAS inhibited?

Answer 10

MCAS may be overridden by the control wheel main electric trim switches, or by either stabilizer trim wheel (manual trim). MCAS may be inhibited by positioning either stabilizer trim cutout switch to CUTOUT or by forward control column cutout switches. AOA Split-Vane Monitoring (SVM) and Mid-Value Select (MVS) algorithms are implemented in the MCAS to provide additional signal processing should an erroneous AOA occur, thus reducing the probability of an erroneous MCAS activation.

Question 11

How is a failure of the Speed Trim or MCAS function indicated?

Answer 11

SPEED TRIM FAIL light will illuminate. A single AOA vane failure will be indicated by a SPEED TRIM FAIL light on recall, which is independant of the PFD AOA disagree.

Question 12

Can the Speed Trim System be overridden? If so, how?

Answer 12

Speed Trim may be overridden by actuation of the control wheel trim switches (inhibits further Speed Trim operation for 5 seconds) or manual rotation of either stabilizer trim wheel. Autopilot engagement disables speed trim because normal autopilot trim commands are used.

Question 13

Which system(s) help in identifying stalls and assist in control should one occur?

Answer 13

Stall identification and control is enhanced by the yaw damper, the Elevator Feel Shift (EFS) module, and the STS by helping identify and prevent further movement into a stall condition. The Stall Management/Yaw Damper (SMYD) computer calculates and sends commands for stall management and yaw dampening functions. The SMYD also calculates performance data to provide Pitch Limit Indicators (PLIs) and minimum and maximum operating speeds. The SMYD inputs include AOA sensor and ADIRU outputs, as well as wing configuration and air/ ground sensing. During high AOA operations, the SMYD reduces yaw damper commanded rudder movement. The STS operates the control column stick shakers to alert the Flight Crew when airspeed is at a minimum operating speed and is close to a wing stall condition. When close to a stall, the SMYD operates the EFS. The EFS module increases hydraulic system A pressure to the elevator feel and centering unit during a stall. This increase in pressure approximately doubles the control column forces. The EFS module is inhibited when on the ground, radio altitude less than 100 ft, or autopilot engaged; however, if the EFS is active when descending through 100 ft RA, it remains active until AOA is reduced below approximately stick shaker threshold. There are no Flight Deck indications that the system is properly armed or activated. As airspeed decreases toward stall speed with flaps extended, the Speed Trim System uses the Speed Trim function to trim nose down above stick shaker AOA. The normal Speed Trim schedule is replaced by a stall-specific schedule where Speed Trim function is active until horizontal stabilizer trim units are greater than 9 units, regardless of Mach and N1. With Flaps UP, as AOA approaches stick shaker, the stabilizer nose-down trim commands transition from the Speed Trim function to MCAS function. These trim schedules produce a predictable and increasing column force with increasing aft column displacement. With the column aft, the amount of column force increase is more pronounced with the onset of EFS. With the autopilot engaged, the autopilot will automatically disengage at stick shaker activation.

Question 14

When is rudder limiting active?

Answer 14

With both engines operating and airspeed above approximately 135 kts, both hydraulic system A and B pressure are reduced within the main PCU by approximately 25% each. This function limits full rudder authority in flight after takeoff and before landing. It operates the same in the air and on the ground.

Rudder pressure will return to normal system operating pressure when:
• an engine failure is detected, or
• airspeed is reduced below approximately 132 kts with both engines operating.

Question 15

What is required for the main yaw damper to operate?

Answer 15

Stall Management Yaw Damper Computers.

Question 16

What is the purpose of the Landing Attitude Modifier?

Answer 16

The Landing Attitude Modifier (LAM) system performs two functions: nose gear clearance and drag. When flaps are in positions 15 through 30 and the thrust levers are near idle, the speedbrakes symmetrically deploy to create additional drag for slowing. At flap positions 30 and 40, LAM symmetrically deploys flight spoilers on approach to reduce lift and force the aircraft to have a higher angle of attack. LAM maintains an acceptable nose landing gear contact margin. The amount of spoiler deflection depends on the approach speed and begins at approximately VREF+10.

Question 17

When is emergency descent speedbrake active?

Answer 17

EDS is armed when above 30,000 ft and the cabin altitude warning is active. EDS is activated automatically by moving the SPEED BRK lever when the system is armed. EDS raises the speedbrakes to a higher than normal position when the SPEED BRK lever is in the FLIGHT DETENT. EDS is deactivated when the spoilers are stowed, or when the cabin altitude warning is no longer active.

Question 18

Under what conditions will the speedbrakes stow automatically?

Answer 18

After RTO or landing, if either thrust lever is advanced, the SPEED BRK lever automatically moves to the DOWN detent and all spoilers retract. The spoilers may also be retracted by manually moving the SPEED BRK lever to the DOWN detent.

Question 19

When does the SPEEDBRAKES EXTENDED light illuminate?

Answer 19

The SPEED BRAKE EXTENDED light only illuminates for abnormal speedbrake operation.

The light illuminates in flight if the SPEED BRK lever is beyond the ARMED detent and any of the following conditions exist:
• A thrust lever is greater than 40° for more than 3 seconds or idle for more than 15 seconds, or
• TE flaps extended more than Flaps 10, or
• Radio altitude less than 800 ft The light illuminates on the ground if the SPEED BRK lever is in the DOWN detent and hydraulic pressure (750 psi or greater) is sensed in the ground spoiler extend line, suggesting the spoiler panel may not be stowed. NOTE: This light does not illuminate if total system pressure of hydraulic system A is below 750 psi.

Question 20

When does the PFD warning SPEEDBRAKE along with an aural alert activate?

Answer 20

If the speedbrakes do not deploy after landing or rejected takeoff above 80 kts, the EGPWS provides a SPEEDBRAKE warning on the PFD as well as an aural “SPEEDBRAKE, SPEEDBRAKE” alert.

Question 21

When does the LE FLAPS TRANSIT light illuminate?

Answer 21

During extension of the LE devices, the amber transit lights of the associated LE device illuminates while the device is in motion. The LE FLAPS TRANSIT light also illuminates any time the LE devices are in motion or do not agree with the scheduled flap position.

Question 22

Which system(s) powers the alternate flap system?

Answer 22

A dedicated electric motor. The ALTERNATE FLAPS position switch controls an electric motor that extends or retracts the TE flaps.

Question 23

Are there flap protective systems available during an alternate flap extension?

Answer 23

There is no asymmetry, LE uncommanded motion, or skew protection during an alternate flaps extension.

Question 24

What is the purpose of the flap load relief system?

Answer 24

Flap load relief protects the TE flaps from excessive air loads. Flap load relief is a function of the Flap Slat Electronic Unit (FSEU), which receives data from the left Air Data Inertial Reference Unit (ADIRU). The left ADIRU is also the source for the Captain’s airspeed indication. When the Captain’s indicated airspeed exceeds the load relief speed (see below), the TE flaps will retract one flap setting below the selected FLAP lever position. When the airspeed is reduced below a re-extend speed, the flaps will re-extend to the FLAP lever position. Flap load relief is available when flaps are selected to 10, 15, 25, 30, or 40. Flap load relief is not available during alternate flap extension operations. When the flap load relief function activates, the FLAP lever does not move; however, the flap position indicator shows flap retraction and re-extension.