B737 NG Flight controls

B 737 NG Ground School.
See the aircraft study guide at www.theorycentre.com
The information contained here is for training purposes only. It is of a general nature it is
unamended and does not relate to any individual aircraft. The FCOM must be consulted for
up to date information on any particular aircraft.

Introduction
The primary flight control system uses conventional control wheel, column and
pedals linked mechanically to hydraulic power control units which command the
primary flight control surfaces; ailerons, elevators and rudder. The flight controls
are powered by redundant hydraulic sources; system A and system B. Either
hydraulic system can operate all primary flight controls. The ailerons and
elevators may be operated manually if required (Manual Reversion). The rudder may
be operated by the standby hydraulic system if system A and system B pressure is
not available.
The secondary flight controls, high lift devices consisting of trailing edge (TE)
flaps and leading edge (LE) flaps and slats (LE devices), are powered by hydraulic
system B. In the event hydraulic system B fails, the TE flaps can be operated
electrically. Under certain conditions the power transfer unit (PTU) automatically
powers the LE devices. The LE devices can also be extended using standby
hydraulic pressure.

Fully powered
rudder
Hydraulic
systems A-B
and Stby.
No tab
Power assisted
Elevators
Hydraulic systems
A and B
Manual reversion
Aerodynamic
balance tab.
Power assisted Ailerons.
Hydraulic systems A and B.
Manual reversion
Aerodynamic balance tab.
Primary Flight Controls

Movable horizontal stabiliser
powered by an electric motor for
manual trim or by the Autopilot.
Manual via cables from the trim
wheels in the cockpit.
Four flight spoilers on each wing
symmetrical pairs powered by hydraulic
systems A and B
Secondary Flight Controls
Inboard and outboard
double slotted T.E Flaps
Normally Hydraulic
system B
Alternate Electric motor
Outboard and
Inboard spoilers
Ground only
Hydraulic system A
4 slats on each wing .
Hydraulic system B Normal
Standby Hydraulic Alternate
2 Krueger flaps
On each wing
inboard of the
engines move
with the slats

Blended winglets provide enhanced performance, extended range and increased
fuel efficiency.
Blended winglets offer operational and economic benefits to 737-800 customers.
Mission block fuel is improved approximately 4 %.
Range capability is increased by as much as 130 nm on the 737-800.
The reduction in takeoff flap drag during the second segment of climb allows
increased payload capability at takeoff-limited airports.
Environmental benefits include a 6.5% reduction in noise levels around airports
on takeoff and a 4% reduction in nitrogen dioxide emissions on a 2,000-nm flight

FLIGHT CONTROL Switches
STBY RUD - activates standby
hydraulic system pump and
opens standby rudder
shutoff valve to pressurize
standby rudder power control
unit.
OFF - closes flight control
shutoff valve isolating ailerons,
elevators and rudder
from associated hydraulic
system pressure.
ON (guarded position) - normal
operating position.

Flight Control LOW
PRESSURE Lights
Illuminated (amber) -
• indicates low hydraulic
system (A or B) pressure to
ailerons, elevator and
Rudder (< 1200 PSI)
• deactivated when associated
FLIGHT CONTROL switch is
positioned to STBY RUD and
standby rudder ON light
illuminates.

Flight SPOILER Switches
ON (guarded position) – normal
operating position.
OFF – closes the respective
flight spoiler shutoff valve.
Note: Used for maintenance
purposes only.

Roll Control
The roll control surfaces consist of hydraulically powered ailerons and flight spoilers,
which are controlled by rotating either control wheel.
Ailerons
The ailerons provide roll control around the airplane’s longitudinal axis. The ailerons are
positioned by the pilots' control wheels.
The Captain’s control wheel is connected by cables to the aileron power control
units (PCUs) through the aileron feel and centring unit.
The First Officer’s control wheel is connected by cables to the spoiler PCUs through the
spoiler mixer.
The two control wheels are connected by a cable drive system which allows actuation of
both ailerons and spoilers by either control wheel.
With total hydraulic power failure the ailerons can be mechanically positioned by rotating
the pilots' control wheels. This is called manual reversion. Control forces are higher due
to friction and aerodynamic loads.

Aerodynamic
Balance tab to
assist during
manual reversion.

Aileron Transfer Mechanism
If the ailerons or spoilers are jammed, 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, Captain’s or First Officer’s, can provide roll control.
If the spoiler 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.
If the aileron control system is jammed, force applied to the First Officer’s control
wheel provides roll control from the spoilers. There is a 12 degree lost motion
device in the spoiler controls which must be exceeded before any spoiler
movement will occur.
The ailerons and the Captain’s control wheel are inoperative in this case.

Torsion Spring
To Spoiler Mixer Unit.
Transfer Mechanism
If the right control wheel cannot move, the captain can operate the left wheel and
override the force of the torsion spring and the force of the feel and centering
mechanism. This allows control of the ailerons only.
If the left control wheel cannot move, the first officer can operate the right control wheel
and override the force of the torsion spring and the spring cartridge. This allows control of
the flight spoilers only.
To Aileron Feel
and Centring unit
Captain Control F/O Control.
Aileron Transfer
mechanism
12⁰ lost motion device

Spoiler mixer Main Wheel well Right side forward
FO’s Control wheel input

Left Main Gear Captains control wheel input
System B
Aileron PCU’s
System A
Aileron feel and
centring unit and
trim actuator

Aileron PCU’s Main
Wheel well
Aileron Transfer Mechanism
Connects Both control wheels
Aileron Trim Electric
motor repositions
Feel unit and control
wheel neutral
Aileron Feel and
centering unit Simple
spring feel that holds
control wheels neutral
Spoiler mixer controls
spoiler deflection
proportionally to
control wheel and
speed brake
commands.

The A and B FLT CONTROL
switches control hydraulic shutoff valves.
These valves can be used to isolate each aileron, as well as the
elevators and rudder, from related hydraulic system pressure.

Aileron Trim
Dual Aileron trim switches, located on the aft electronic panel, must be pushed
simultaneously to command trim changes. The trim electrically repositions the
aileron feel and centring unit, which causes the control wheel to rotate and
redefines the aileron neutral position. The amount of aileron trim is indicated on
a scale on the top of each control column.
If aileron trim is used with the autopilot engaged, the trim is not reflected in the
control wheel position. The autopilot overpowers the trim and holds the control
wheel where it is required for heading/track control. Any aileron trim applied
when the autopilot is engaged can result in an out of trim condition and an abrupt
rolling movement when the autopilot is disconnected.

LIMITATIONS
Autopilot/Flight Director System
# Use of aileron trim with the autopilot engaged is prohibited.

Flight Spoilers
Four flight spoilers are located on the upper surface of each wing. Each hydraulic
system, A and B, is dedicated to a different set of spoiler pairs to provide isolation
and maintain symmetric operation in the event of hydraulic system failure.
Hydraulic pressure shutoff valves are controlled by the two flight SPOILER
switches.
Flight spoiler panels are used as speed brakes to increase drag and reduce lift,
both in flight and on the ground. The flight spoilers also supplement roll control in
response to control wheel commands. A spoiler mixer, connected to the aileron
cable-drive, controls the hydraulic power control units on each spoiler panel to
provide spoiler movement proportional to aileron movement.
The flight spoilers rise on the wing with up aileron and remain faired on the wing
with down aileron. When the control wheel is displaced more than approximately
10 , spoiler deflection is initiated.

Flight SPOILER Switches
ON (guarded position) – normal operating position.
OFF – closes the respective flight spoiler shutoff valve.
Note: Used for maintenance purposes only.

• Spoilers
• 4 Flight spoilers on each wing.
• Spoiler rise on down-going wing with 10° control
wheel rotation
(equates to 1.6 trim units of rotation)
NOTE; Trim indication is in units not degrees on
Boeing aircraft

Flight spoiler movement depends on
Roll command and Speed Brake lever position.
Ground Spoilers UP or DOWN
Position controlled by the SPOILER MIXER.
Controlled by Ground Spoiler
Control Valve and Ground
Spoiler Bypass Valve.

2 3 4 5 8 9 10 11
FLIGHT SPOILER ROLL CONTROL
1.6 Units 10º
Spoilers 4&5 or 8&9 begin to rise

2 3 4 5 8 9 10 11
Control Wheel 2, 3. 10, 11 4, 5, 8, 9
30 Degrees
4.8 Units
2 or 11 UP 3.5
3 or 10 UP 5.5
UP 10.5
70 Degrees
11.2 Units
UP 33 UP 38
4.8 Units 30º
2 or 11 UP 3.5º 3 or 10 UP 5.5º
4 & 5 or 8 & 9 UP 10.5º

2 3 4 5 8 9 10 11
Control Wheel 2, 3. 10, 11 4, 5, 8, 9
30 Degrees
4.8 Units
2 or 11 UP 3.5
3 or 10 UP 5.5
UP 10.5
70 Degrees
11.2 Units
UP 33 UP 38
11.2 Units 70º
2 & 3 or 10 & 11 UP 33º
4 & 5 or 8 & 9 UP 38º

PITCH CONTROL
Pitch Control
The pitch control surfaces consist of hydraulically powered elevators and an
electrically powered stabilizer. The elevators are controlled by forward or aft
movement of the control column. The stabilizer is controlled by autopilot trim or
manual trim.

Elevators
The elevators provide pitch control around the
airplane’s lateral axis. The elevators are
positioned by the pilots control columns. The A
and B FLT CONTROL switches control hydraulic
shutoff valves for the elevators.
Cables connect the pilots’ control columns to
elevator power control units (PCUs) located in the
tail compartment and powered by hydraulic
system A and B. The elevators are interconnected
by a torque tube.
With loss of hydraulic system A and B the
elevators can be mechanically positioned by
forward or aft movement of the pilots’ control
columns. Control forces are higher due to friction
and aerodynamic loads.

Elevator Neutral Shift
The stabilizer controlled elevator neutral shift function changes the neutral position of the
elevators during stabilizer movement. The stabilizer moves elevator neutral shift rods.
The neutral shift rods provide an input to the elevators through the Mach trim actuator
and the feel and centring unit, When the feel and centring unit moves it also back drives
the control cables which move the control columns to their new neutral position.
The elevator is drooped 4 degrees when the stabilizer is at the neutral trim position
indicated as 4 units of trim. When the stabilizer moves in either direction from neutral
position, The elevators move up this is true with flaps UP.
FCC Controlled Neutral Shift Functional
The primary function of the flight control computer (FCC) controlled neutral shift is to
reduce the pilot column force necessary to trim the airplane during initial climb out after
takeoff with a forward CG and both engines operating. The FCCs provide inputs to the
Mach trim actuator. The incremental elevator input commanded by the FCC controlled
neutral shift varies with flap and stabilizer position.
Very simply with flaps not up the combined FCC and stabiliser neutral shift function
moves the elevators down with the stabiliser set between 0 and about 7 units.
From 7 units to 16.9 units or maximum Nose up trim the elevators move UP
Note. Trim 0 is maximum stabiliser L.E. Up or Nose down trim for Aft C. G.
Trim 16.9 is maximum L.E Down or Nose UP trim for forward CG.
Note. Manual trim wheel inputs, autopilot, and speed trim will not command elevator
movement by the FCC controlled neutral shift function.

Elevator Tab Control Mechanism
The elevator tab mechanism changes the function of the elevator tab. When the TE
flaps are up, the elevator tab operates in the balance mode. When the TE flaps are
not up, the elevator tab operates in the anti-balance mode which aids nose up control
with the flaps not up.
The elevator tab control mechanism attaches to the aft edge of each elevator.
Functional Description
When the flaps are up, the elevator tab operates in the balance mode. As the elevator
moves, the tab moves in the opposite direction to elevator movement. In the balance
mode, the tab moves 0.75 degrees for each degree of elevator movement.
When the flaps are not up and hydraulic power is on, the elevator tab operates in the
anti-balance mode. The actuator extends, moves the crank and repositions the
elevator balance tab rods. When the elevator moves, the elevator tab moves in
the same direction that the elevator moves. In the anti-balance mode, the tab moves
0.50 degrees for each degree of elevator movement.
When the TE flaps are not up, and the FCCs send signals to the left solenoid control
valve. This connects system A pressure to the actuator for the left tab.
When the TE flaps are not up, there is a 10-second delay before the right actuator
moves. The purpose of the 10-second delay is to improve autopilot performance.
When power goes to operate the control valve it connects system B pressure to the
right actuator.
NOTE: With Both hydraulic system A and B failed in Manual reversion mode there is
no pressure and the tabs remain in the balance mode to assist the pilot.

Elevator Torque tube
Elevator control rod
Elevator
Elevator Tab.
Elevator
Elevator tab control mechanism
Flaps UP balance mode
Single acting actuator extended in
Anti-Balance mode
Elevator Hinge point

Elevator Control Column Override Mechanism
In the event of a control column jam, an override mechanism allows the
control columns to be physically separated. Applying force against the jam
will breakout either the Captain’s or First Officer’s control column. Whichever
column moves freely after the breakout can provide adequate elevator
control.
Although total available elevator travel is significantly reduced, there is
sufficient elevator travel available for landing flare. Column forces are higher
and exceed those experienced during manual reversion. If the jam exists
during the landing phase, higher forces are required to generate sufficient
elevator control to flare for landing.
Stabilizer trim is available to counteract the sustained control column force.

Elevator Feel System
The elevator feel computer provides simulated aerodynamic forces using airspeed
(from the elevator pitot system) and stabilizer position. Feel is transmitted to the
control columns by the elevator feel and centring unit. To operate the feel system
the elevator feel computer uses either hydraulic system A or B pressure,
whichever is higher. When either hydraulic system or elevator feel pitot system
fails, excessive differential hydraulic pressure is sensed in the elevator feel
computer and the FEEL DIFF PRESS light illuminates.
Elevator Feel Computer Inputs
The elevator feel computer receives pressure from hydraulic systems A and B,
pitot pressure from the pitot tubes mounted on the vertical stabiliser, and
mechanical input from the stabilizer position.
The elevator feel computer uses pitot pressure and stabilizer input to control
hydraulic pressure to the dual feel actuator in the feel and centering unit. The feel
force of the feel and centring unit increases as the airspeed increases.
Elevator Feel pitot Left and Right

Stall Warning System
Natural stall warning (buffet) usually occurs at a speed prior to stall. In some
configurations the margin between stall and natural stall warning is less than
desired. Therefore, an artificial stall warning device, a stick shaker, is used to
provide the required warning.
The stall warning “stick shaker” consists of two eccentric weight motors, one on
each control column. They are designed to alert the pilots before a stall develops.
The warning is given by vibrating both control columns. The system is armed in
flight at all times. The system is deactivated on the ground.
The SMYD computers provide outputs for all stall warning to include stick shaker
and signals to the pitch limit indicator and airspeed displays and the GPWS
windshear detection and alert.
STALL WARNING TEST Switches
Push – on ground with AC power available: each test switch tests its respective
stall management yaw damper (SMYD) computer. No.1 SMYD computer shakes
Captain’s control column, No.2 SMYD computer shakes First Officer’s control
column. Vibrations can be felt on both columns
• inhibited while airborne.
AFT OVERHEAD PANEL
Pitch limit indicator.
Displayed Flaps Not up and
variable based on current
conditions

Stall Identification
Stall identification and control is enhanced by the yaw damper, the Elevator Feel
Shift (EFS) module and the speed trim system. These three systems work together
to help the pilot identify and prevent further movement into a stall condition.
During high AOA operations, the SMYD reduces yaw damper commanded rudder
movement.
The EFS module increases hydraulic system A pressure to the elevator feel and
centering unit during a stall. This increases forward control column force to
approximately four times normal feel pressure. The EFS module is armed
whenever an inhibit condition is not present. Inhibit conditions are: on the ground,
radio altitude less than 100 feet and autopilot engaged. However, if EFS is active
when descending through 100 feet RA, it remains active until AOA is reduced
below approximately stickshaker threshold. There are no flight deck indications
that the system is properly armed or activated.
As airspeed decreases towards stall speed, the speed trim system trims the
stabilizer nose down and enables trim above stickshaker AOA. With this trim
schedule the pilot must pull more aft column to stall the airplane. With the column
aft, the amount of column force increase as the EFS module increases pressure to the
elevator feel and centering unit.

These are the components of the stall warning system:
* Stall management yaw dampers (SMYDs)
* Control column shakers
* Elevator feel shift module (EFSM)
* Stall warning test panel.
The stall warning system shakes the control column when the airplane gets close to
a stall.
During a stall, the FCCs command the stabilizer to trim the airplane nose down. The
EFSM and column cut-out switch modules operate to make sure the pilot cannot
easily stop this automatic stabilizer movement with the elevator control column nose
up input
During a stall, the elevator feel shift module (EFSM) provides 850 psi system A
pressure to the elevator feel computer and the dual feel actuator. This causes the
feel force of the control column and the feel and centering unit to increase to
approximately four times greater than high speed feel forces.

Flight control computer Nose
down trim and nose up trim
inhibit
Elevator feel pitot system
Stabiliser trim position input
Feel computer adjusts hydraulic
pressure according to speed and
stabiliser position.
Actual feel is provided by the
higher of A or B pressure.
During a stall System A pressure
850 psi.
With a large difference (>25% &
flaps are up.)
FEEL DIFF PRESS light
illuminates.
With no Hydraulic pressure
simple spring feel holds the
control column neutral.

Mach tuck is an aerodynamic effect, whereby the nose of an aircraft tends to pitch
downwards as the airflow around the wing reaches supersonic speeds.
As the aircraft's wing approaches its critical Mach number, typically around Mach 0.8 the
aircraft is traveling below Mach 1.0. However, the accelerated airflow over the upper
surface of the wing exceeds Mach 1.0 and a shock wave is created at the point on the
wing where the accelerated airflow returns from supersonic to subsonic airflow. While the
air ahead of the shock wave is in laminar flow, a boundary layer separation is created aft
of the shock wave, and that section of the wing fails to produce lift.
In most aircraft susceptible to Mach tuck, the camber at the wing root is more
pronounced than that of the wing tip. This means that when an aerofoil exceeds its
critical Mach number, the shock wave, and resulting stall condition, will begin to form at
the root.
A second design element that leads to Mach tuck is that many aircraft which will
approach the speed of sound are designed with swept wings. When the wing root stalls,
the centre of pressure is shifted towards the wing tip. With a swept wing, this also means
that the centre of pressure travels aft compared to the unmoving centre of mass of the
aircraft which will generate a nose down pitching moment this is “Mach tuck."

Mach Trim System
A Mach trim system provides speed stability at the higher Mach numbers. Mach
trim is automatically accomplished above Mach .615 by adjusting the elevators
with respect to the stabilizer as speed increases. The flight control computers use
Mach information from the ADIRU to compute a Mach trim actuator position.
The Mach trim actuator repositions the elevator feel and centering unit which
adjusts the control column neutral position.
As the speed of the airplane increases, the nose starts to drop. This is called Mach
tuck. When the airplane airspeed is more than Mach 0.615, the Mach trim function
of the FCC gives an up elevator command to keep the nose of the airplane level.
This function operates with or without the autopilot or flight director.
Limit airspeed to 280 knots/.82 Mach.

Stabilizer
The horizontal stabilizer is positioned by a single electric trim
motor controlled through either the stab trim switches on the
control wheel or autopilot trim. The stabilizer may also be
positioned by manually rotating the stabilizer trim wheel.
Trim motor used by
both Autopilot and Trim
switches.
Gear box
Cable Drum turned by
moving trim wheels
and back drives trim
wheels when trim
moves electrically
Screw jack turned by the motor or trim wheels

Stabiliser Trim Screw Jack.
Attachment arm to the
L.E. of the stabiliser
As the trim actuator
turns the screw jack
a nut in the
attachment arm runs
up or down the screw
thread moving the
stabiliser Leading
Edge.

Stabilizer Trim
Stabilizer trim switches on each control wheel actuate the electric trim motor
through the main electric stabilizer trim circuit when the airplane is flown
manually. With the autopilot engaged, stabilizer trim is accomplished through the
autopilot stabilizer trim circuit. The main electric and autopilot stabilizer trim
have two speed modes: high speed with flaps extended and low speed with flaps
retracted. If the autopilot is engaged, actuating either pair of stabilizer trim
switches automatically disengages the autopilot. The stabilizer trim wheels rotate
whenever electric stabilizer trim is actuated.
Trim switches. Captain Left hand,
FO Right hand. 2 switches both
must be moved for trim.

The STAB TRIM MAIN ELECT cut out switch and the STAB TRIM
AUTOPILOT cut out switch, located on the control stand, are provided to allow the
autopilot or main electric trim inputs to be disconnected from the stabilizer trim motor.
Main Electric and
Auto pilot cut out
switches

Manual Trim Auto pilot Cut out

Control column actuated stabilizer trim cut
out switches stop operation of the main
electric and autopilot trim when the control
column movement opposes trim direction.
i.e. If the pilot is pulling nose up nose down
trim is inhibited.
When the STAB TRIM override switch is
positioned to OVERRIDE, electric trim can
be used regardless of control column
position. The control column activated cut
out switches are bypassed.

Column Cut out Switches
The column cut out switches
contain a set of cam-operated
switches. When the control
column moves in the opposite
direction from the stabilizer trim
direction, electric trim stops.

Manual stabilizer control is accomplished through cables which allow the pilot to
position the stabilizer by rotating the stabilizer trim wheels. The stabilizer is held
in position by two independent brake systems. Manual rotation of the trim wheels
can be used to override autopilot or main electric trim. The effort required to
manually rotate the stabilizer trim wheels may be higher under certain flight
conditions. Grasping the stabilizer trim wheel will stop stabilizer motion.
Captains Stabiliser Trim wheel
Folding Handle

Stabilizer Trim Operation with Forward or Aft CG
In the event the stabilizer is trimmed to the end of the electrical trim
limits, additional trim is available through the use of the manual trim
wheels. If manual trim is used to position the stabilizer beyond the
electrical trim limits, the stabilizer trim switches may be used to
return the stabilizer to electrical trim limits.
Stabilizer Position Indication and Green Band
Stabilizer position is displayed in units on two STAB TRIM indicators
located inboard of each stabilizer trim wheel. The STAB TRIM indicators
also display the TAKEOFF green band indication.
The trim authority for each mode of trim is limited to:
• Main Electric Trim
• flaps extended 0.05 to 14.5 units
• flaps retracted 3.95 or 4.30 to 14.5 units (Aircraft option)
• Autopilot Trim 0.05 to 14.5 units
• Manual Trim -0.20 to 16.9 units.
The green band range of the STAB TRIM indicator shows the
takeoff trim range.
An intermittent horn sounds if takeoff is attempted with the stabilizer
trim outside the takeoff trim range.

Speed Trim System
The speed trim system (STS) is a speed stability augmentation system designed to
improve flight characteristics during operations with a low gross weight, aft centre
of gravity and high thrust when the autopilot is not engaged. The purpose of the
STS is to return the airplane to a trimmed speed by commanding the stabilizer in
a direction opposite the speed change. The STS monitors inputs of stabilizer
position, thrust lever position, airspeed and vertical speed and then trims the
stabilizer using the autopilot stabilizer trim. As the airplane speed increases or
decreases from the trimmed speed, the stabilizer is commanded in the direction to
return the airplane to the trimmed speed. This increases control column forces to
force the airplane to return to the trimmed speed. As the airplane returns to the
trimmed speed, the STS commanded stabilizer movement is removed.
STS operates most frequently during takeoff, climb and go-around.
Conditions for speed trim operation are listed below:
• STS Mach gain is fully enabled between 100 KIAS and Mach 0.60 with a fadeout to zero
by Mach 0.68
• 10 seconds after takeoff
• 5 seconds following release of trim switches
• Autopilot not engaged
• Sensing of trim requirement

QRH Procedure to deal with a runaway trim condition

Yaw Control
Yaw control is accomplished by a hydraulically powered rudder and a digital yaw
damper system. The rudder is controlled by displacing the rudder pedals. The yaw
damping functions are controlled through the stall management/yaw damper (SMYD)
computers.

Rudder (with Rudder System Enhancement Program (RSEP) installed)
The rudder provides yaw control about the airplane’s vertical axis. The A and B
FLT CONTROL switches control hydraulic shutoff valves for the rudder and the
standby rudder.
Each set of rudder pedals is mechanically connected by cables to the input levers
of the main and standby rudder PCUs. The main PCU consists of two independent
input rods, two individual control valves, and two separate actuators; one for
Hydraulic system A and one for Hydraulic system B. Either system A or B will move
the rudder with limited authority. The standby rudder PCU is controlled by a separate
input rod and control valve and powered by the standby hydraulic system. All three
input rods have individual jam override mechanisms that allows input commands to
continue to be transferred to the remaining free input rods if an input rod or
downstream hardware is hindered or jammed.
Pre Rudder system enhancements only 2 lights.
After Enhancement program addition of STBY RUD ON light
Indicating Standby rudder shutoff valve open. All aircraft
should have been modified by 2008.

System A and B PCU’s and
input control rods.
Standby system PCU with
input control rod

Rudder Pressure Limiter.
At speeds above approximately 135 knots, both hydraulic system A and B pressure
are each reduced within the main PCU control valve to approximately 2,200 psi.
This function reduces the PCU output force by approximately 25% this limits full
rudder authority in flight after takeoff and before landing. If either system A or B is
low pressure the other system operates at full pressure.
The main rudder PCU contains a Force Fight Monitor (FFM) that detects opposing
pressure (force fight) between A and B actuators. This may occur if either system
A or B input is jammed or disconnected. The FFM output is used to automatically
turn on the Standby Hydraulic pump, open the standby rudder shutoff valve to
pressurize the standby rudder PCU, and illuminate the STBY RUD ON, Master
Caution, and Flight Control (FLT CONT) lights.

The standby rudder PCU is powered by the standby hydraulic system. The standby hydraulic
system is provided as a backup if system A and/or B pressure is lost.
With the standby PCU powered the pilot retains adequate rudder control capability. The
Standby rudder PCU can be powered manually through the FLT CONTROL switches or
automatically.
An amber STBY RUD ON light illuminates when the standby rudder hydraulic system is
pressurized. The standby rudder system can be pressurized with either Flight Control switch, or
automatically during takeoff , landing and automatically by the Force Fight Monitor. The STBY
RUD ON light illumination activates Master Caution and Flight Control warning lights on the
Systems Annunciation Panel.

Rudder Trim
The RUDDER trim control, located on the aft electronic panel, electrically
repositions the rudder feel and centering unit which adjusts the rudder neutral
position. The rudder pedals are displaced proportionately. The RUDDER TRIM
indicator displays the rudder trim position in units. There is no tab on the rudder.
Rudder Trim control
Rudder Trim
Indicator

Rudder control cables
Rudder input rod with force transducer
Rudder trim actuator
Repositions control
neutral and pedals
move
Centring spring
Main PCU control rods
Standby PCU control rod

Yaw Damper
The yaw damper keeps the airplane stable around the vertical axis. When
engaged, the yaw damper system gives input to the main or the standby rudder
PCUs. The yaw damper system consists of a main and standby yaw damper. Both
yaw dampers are controlled through Stall Management/Yaw Damper (SMYD)
computers. During normal operation, SMYD 1 controls the rudder through the main
rudder PCU.
The SMYD computers receive inputs from both ADIRUs, both control
wheels and the YAW DAMPER switch. SMYDs provide yaw damper inputs to the
main rudder power control unit (PCU) or standby rudder PCU, as appropriate.
YAW DAMPER Light
Illuminated (amber) – yaw damper is not engaged.
YAW DAMPER Switch
OFF – disengages yaw damper.
ON – Electrically held. Releases to OFF if Yaw
Damper light illuminates
• engages main yaw damper to main rudder power
control unit if the B FLT CONTROL switch is in the
ON position
• engages standby yaw damper to standby rudder
power control unit if both the A and B FLT CONTROL
switches are in the STBY RUD position.

When engaged, the yaw damper system gives input to the main PCU yaw
damper solenoid valve. The solenoid valve moves and sends pressure from
system B to the electrohydraulic servo valve (EHSV). When the EHSV moves, it
sends pressure to move the yaw damper actuator. The yaw damper actuator
input mechanically adds to the pilot rudder pedal input. Then the control valve
moves and sends pressure to the tandem actuator. This moves the PCU piston
and the rudder. Rudder input from the yaw damper does not back drive the
rudder pedals.
The Yaw damper indicator show Main
Yaw damper only inputs to the rudder
system.

During normal operation the main yaw damper uses hydraulic system B and the
SMYD computers provide continuous system monitoring. The YAW DAMPER
Switch is held ON by an electro magnet and automatically moves to OFF, the amber YAW
DAMPER light illuminates and the YAW DAMPER switch cannot be reset to ON when
any of the following conditions occur:
• SMYD senses a yaw damper system fault,
• SMYD senses that the yaw damper does not respond to a command,
• B FLT CONTROL switch is positioned to OFF or STBY RUD.
During manual reversion flight (loss of hydraulic system A and B pressure), both
FLT CONTROL switches are positioned to STBY RUD. In this case, the YAW
DAMPER switch can be reset to ON when on the standby hydraulic system powers the
standby yaw damper. SMYD 2 commands rudder movement for the wheel to rudder
interconnect system (WTRIS) Standby yaw damping and turn coordination. During
Standby Yaw Damper operation, The WTRIS commands a small amount of rudder
movement as a function of the captains control wheel aileron input to help assists turns
during flight control manual reversion operations.

Flight control surface position display.
Option on some aircraft.
Rudder position indicator shows both Main
and standby Yaw damper inputs and the
main yaw damper indicator may not be fitted.
The flight spoiler position sensors
are on panels 4 and 9 and send
spoiler position to the FCC’s

Speed Brakes
The speed brakes consist of flight spoilers and ground spoilers. Hydraulic system A powers
all four ground spoilers, two on the upper surface of each wing. The SPEED BRAKE lever
controls the spoilers. When the SPEED BRAKE lever is actuated all the spoilers extend
when the airplane is on the ground and only the flight spoilers extend when the airplane is
in the air.
The SPEEDBRAKES EXTENDED light provides an indication of spoiler operation in-flight
and on the ground. In-flight, the light illuminates to warn the crew that the speed brakes are
extended while flaps are more than 10 or below 800 feet AGL. On the ground, the light
illuminates when hydraulic pressure is sensed in the ground spoiler Bypass valve with the
speed brake lever in the DOWN position.

In-Flight Operation (All Aircraft)
Operating the SPEED BRAKE lever in flight causes all flight spoiler panels to rise
symmetrically to act as speed brakes. Caution should be exercised when
deploying flight spoilers during a turn, as they greatly increase roll rate. When the
speed brakes are in an intermediate position roll rates increase significantly.
Moving the SPEED BRAKE lever beyond the FLIGHT DETENT causes
buffeting and is prohibited in flight.

•Speed Brakes
Flight Spoilers
• Speed Brake Lever has 4 or 5
positions
DOWN, ARMED, (50%), FLIGHT
DETENT & UP
Note: the 50% position is on later
aircraft only.

In Flight Operation with optional Load alleviation.
The speed brake load alleviation feature limits the deployment of the speed brakes
under certain high gross weight/airspeed combinations. Under these conditions, if
the speed brakes are deployed to the FLIGHT DETENT, they automatically retract
to 50 percent of the FLIGHT DETENT. The SPEED BRAKE lever moves to
reflect the position of the speed brakes. Manual override is available. Increased
force is needed to move the SPEED BRAKE lever beyond the 50 percent position
with load alleviation active. The SPEED BRAKE lever must be held in place
when manual override is used between 50 percent and the UP position. The
SPEED BRAKE lever will remain stationary if moved to UP with load alleviation
active. When load alleviation deactivates, the speed brakes can be manually
returned to the FLIGHT DETENT position.
OPTION.
A lever stop feature is incorporated into the SPEED BRAKE lever mechanism.
The lever stop prevents the SPEED BRAKE lever from being moved beyond the
FLIGHT DETENT when the airplane is in flight with the flaps up. In the event of
the loss of electrical power the lever stop is removed and full speed brake lever
movement is available.

Speed Brakes
Flight Spoilers
Spoiler Mixer controls spoiler PCUs & the
Ground Spoiler Control Valve
Moving the speed brake past the Flight Detent
position opens the Ground Spoiler Control
Valve, It also causes a lot of buffet and is
prohibited in flight.

Speed Brake Lever 50%
Speed Brake Lever 50%.
And
Full Right Aileron.
Spoiler Mixer reduces Speed Brake input
on up going wing and increases the input
to the down going wing .

•Speed Brakes
Flight Spoilers
• Avoid using when flaps are extended
• Do not use below 1,000 ft RA
• Do not use with Flap 15
• During flight, do not extend lever beyond
FLIGHT DETENT

•Speed Brakes
Flight Spoilers
• Avoid using when flaps are extended
• Do not use below 1,000 ft RA
• Do not use with Flap 15
• During flight, do not extend lever beyond
FLIGHT DETENT
• SPEED BRAKES EXTENDED light:
• In flight with lever extended
beyond armed position &
800’ RA or Flap 10
• On ground with lever down
and hydraulics pressure > 750
psi at the bypass valve indicates a
fault.

Ground Operation
During landing, the auto speed brake system operates when these conditions
occur:
• SPEED BRAKE lever is in the ARMED position
• SPEED BRAKE ARMED light is illuminated
• radio altitude is less than 10 feet (Radio alt From FCC’s)
• landing gear strut compresses on touchdown or main landing gear wheels spin
up (more than 60 kts).
• both thrust levers are retarded to IDLE
• The SPEED BRAKE actuator moves the lever to the UP position and the
spoilers deploy.
If a wheel spin-up signal is not detected, when the air/ground system senses
ground mode (any gear strut compresses) the SPEED BRAKE lever moves to
the UP position and flight spoiler panels deploy automatically.
When the right main landing gear strut compresses, a mechanical linkage opens
the ground spoiler bypass valve and the ground spoilers deploy.
Note: Compression of any landing gear strut enables the flight spoilers to
deploy. Compression of the right main landing gear strut enables the ground
spoilers to deploy.

Ground Operation
If the SPEED BRAKE lever is in the DOWN position during landing or rejected
takeoff, the auto speed brake system operates when these conditions occur:
• main landing gear wheels spin up (more than 60 kts)
• both thrust levers are retarded to IDLE
• reverse thrust levers are positioned to revers idle.
The SPEED BRAKE lever actuator automatically moves to the UP
position and spoilers deploy.
After an RTO or landing, if either thrust lever is advanced, the SPEED
BRAKE lever automatically moves to the DOWN detent and all spoiler
panels retract. The spoiler panels may also be retracted by manually
moving the SPEED BRAKE lever to the DOWN detent.

• Auto Speed Brakes
• When armed, lever moves to UP &
flight spoiler panels extend with main
wheel spin-up or a MLG strut
compressed
• The ground spoilers deploy with
right MLG compression
• With the lever DOWN (landing or RTO),
all spoilers will deploy if thrust Revers
is selected
Note: If either thrust lever is advanced after landing or RTO all spoilers will retract
Ground Spoilers
• Extend when lever in UP position &
right main gear is compressed
• If Ground Spoiler Bypass Valve fails
do not operate speed brake lever in
flight

SPEED
BRAKE
LEVER
2, 3. 10, 11 4, 5, 8, 9 1 6 7 12
Flight Detent UP 19.5º UP 24.5º
UP UP 33º UP 38º 1 &12 52º
6 & 7 60º
SPOILER SPEED BRAKE CONTROL
1 2 & 3 4 & 5 6 7 8 & 9 10 & 11 12

High lift wing with Short field performance modification.
Includes a Triple slotted flap.

Airplane Flight Manual has a limitation restricting the use of flaps above 20,000 feet.
The reason for the limitation is simple; Boeing does not demonstrate or test (and
therefore does not certify) airplanes for operations with flaps extended above 20,000
feet.
There is no Boeing procedure that requires the use of flaps above 20,000 feet. Since
flaps are intended to be used during the takeoff and approach/land phases of flight,
and since Boeing is not aware of any airports where operation would require the use of
flaps above 20,000 feet, there is no need to certify the airplane for this.
Flap Manoeuvring Speeds
Flap - Speed Schedule/Manoeuvring Speeds
The following tables contain flap manoeuvring speeds for various flap settings.
The flap manoeuvring speed is the recommended operating speed during takeoff
or landing operations. These speeds guarantee at least full manoeuver capability or
at least 40 of bank (25 of bank and 15 overshoot) to stick shaker within a few
thousand feet of the airport altitude. While the flaps may be extended up to 20,000
feet, less manoeuver margin to stick shaker exists for a fixed speed as altitude
increases.
Note:
The flap manoeuvring speeds should not be confused with the minimum manoeuver
speed which is displayed as the top of the lower amber band on the airspeed display.

Flap Extension
During flap extension, selection of the flaps to the next flap position should be
made when approaching, and before decelerating below, the maneuver speed for
the existing flap position. The flap extension speed schedule varies with airplane
weight and provides full maneuver capability or at least 40 of bank (25 of bank
and 15 overshoot) to stick shaker at all weights.
Note VREF 40 depends on current gross weight. VREF 40 + -- therefore varies
accordingly.

Begin flap retraction at V2 + 15 knots, except for a flaps 1 takeoff. For a flaps 1
takeoff, begin flap retraction when reaching the flaps 1 manoeuvre speed.
With airspeed increasing, subsequent flap retractions should be initiated when
airspeed reaches the manoeuvre speed for the existing flap position. The
manoeuvre speed for the existing flap position is indicated by the numbered flap
manoeuvre speed bugs on the airspeed display.
For flaps up manoeuvring, maintain at least:
• “UP”
Takeoff Flap Retraction Speed Schedule
MCP speed is normally set
to V2 for take off. The
white bug represents V2 or
MCP +15. The flight
director will command
MCP + 20 during initial
climb. This is a flap 5 TO
When speed is above V2
+15 flap 1 can be selected.
Flaps should not be
selected to UP until the
speed is at least -1 with
airspeed increasing.
Minimum Manoeuvre
speed is the top of the
amber about 128 knots.

Leading edge Kruger flaps Extended Any time T.E. Flaps are not up.

L.E. Kruger Flaps.
Kruger flaps are either retracted into the wing or extended there is no
intermediate position. There is a Go around gate at Flap 1 position.
This is used for single engine Go around. It also ensures that the L.E.
devices are not inadvertently retracted.
Flaps Up Retracted.
Flaps 1 or more Extended.

Flaps and Slats
The flaps and slats are high lift devices that increase wing lift and decrease stall
speed during takeoff, low speed manoeuvring and landing.
LE devices consist of four flaps and eight slats: two flaps inboard and four slats
outboard of each engine. Slats extend to form a sealed or slotted leading edge
depending on the TE flap setting. The TE devices consist of double slotted flaps
inboard and outboard of each engine.
TE flap positions 1–15 provide increased lift; positions 15–40 provide increased
lift and drag. Flaps 15, 30 and 40 are normal landing flap positions. Flaps 15 is
normally limited to airports where approach climb performance is a factor.
Runway length and conditions must be taken into account when selecting a
landing flap position.
To prevent excessive structural loads from increased Mach at higher altitude, flap
extension above 20,000 feet should not be attempted.

Flap and Slat Sequencing (There are differences depending on aircraft)
LE devices and TE flaps are normally extended and retracted by hydraulic power
from system B. When the FLAP lever is in the UP detent, all flaps and LE devices
are commanded to the retracted or up position. Moving the FLAP lever aft allows
selection of flap detent positions 1, 2, 5, 10, 15, 25, 30 or 40. The LE devices
deployment is sequenced as a function of TE flaps deployment.
When the FLAP lever is moved from the UP position to the 1, 2, or 5 (option10,15,25)
position, the TE flaps extend to the commanded position and the LE:
• flaps extend to the full extended position and
• slats extend to the extend position.
When the FLAP lever is moved beyond the 5 (25) position the TE flaps extend to the
commanded position and the LE:
• flaps remain at the full extended position and
• slats extend to the full extended position.

The LE devices sequence is reversed upon retraction.
Mechanical gates hinder inadvertent FLAP lever movement beyond flaps 1 for
one engine inoperative go–around and flaps 15 for normal go–around.
Indicator lights on the centre instrument panel provide overall LE devices position
status. The LE DEVICES annunciator panel on the aft overhead panel indicates
the positions of the individual flaps and slats.
Flap 1 and flap 15 gates.

Leading Edge Flaps Transit (LE FLAPS TRANSIT) Light
Illuminated (amber) –
• any LE device in transit
• any LE device not in programmed position with respect to TE flaps
• a LE uncommanded motion condition exists (two or more LE flaps or
slats have moved away from their commanded position)
• during alternate flap extension until LE devices are fully extended and TE
flaps reach flaps 10.
Note: Light is inhibited during autoslat operation in flight.
Leading Edge Flaps Extended (LE FLAPS EXT) Light
Illuminated (green) –
• all LE flaps extended and all LE slats in extended (intermediate) position
(TE flap positions 1, 2 and 5)
• all LE devices fully extended (TE flap positions 10 through 40).

Flap Load Relief (Some aircraft differ)
The flaps/slat electronics unit (FSEU) provides a TE flap load relief function which
protects the flaps from excessive air loads. This function is operative at the flaps 30 and
flaps 40 positions only. The FLAP lever does not move, but the flap position indicator
displays flap retraction and re–extension.
When the flaps are set at 40, the TE flaps:
• retract to 30 if airspeed exceeds 163 knots ( 1 knot above placard limit)
• re–extend when airspeed is reduced below 158 knots.
When the flaps are set at 30, the TE flaps:
• retract to 25 if the airspeed exceeds 176 knots (Placard plus 1 Knot)
• re–extend when airspeed is reduced below 171 knots.
On some aircraft this function is operative at the flaps 10, 15, 25, 30 and flaps 40
positions. The FLAP lever does not move, but the flap position indicator displays flap
retraction and re–extension.
On some aircraft the FLAP LOAD RELIEF light illuminates when the TE flap load relief
function is activated.
Forward Right Panel when fitted.

Flap position Indicator shows
position of the Left and Right T.E
flaps and can show flap skew and
asymmetry.
Asymmetry and Skew Detection, Protection and Indication
The FSEU monitors the TE flaps for asymmetry and skew conditions. It also
monitors the LE devices for improper position and skew conditions on slats 2 through 7.
If a flap on one wing does not align with the symmetrical flap on the other wing, there is
a flap asymmetry condition.
A skew condition occurs when a TE flap or LE slat panel does not move correctly
causing the panel to twist during extension or retraction.

Trailing Edge Flap Asymmetry and Skew
When the FSEU detects a trailing edge asymmetry or
skew condition the FSEU:
• closes the TE flap bypass valve
• displays a needle split on the flap position indicator.

Leading Edge Device Improper Position or Skew
When the FSEU detects a LE device in an improper
position or a LE slat skew condition, the LE FLAPS
TRANSIT light remains illuminated and one of the
following indications is displayed on the LE DEVICES
annunciator panel:
• amber TRANSIT light illuminated
• incorrect green EXT or FULL EXT light illuminated
• no light illuminated.
There is no skew detection of the outboard slats, 1 and 8,
or for the LE flaps.
Slat skew detection is inhibited during autoslat operations.

Uncommanded Motion Detection, Protection and Indication
The FSEU provides protection from uncommanded motion by the LE devices or
TE flaps.
Leading Edge Uncommanded Motion
Uncommanded motion is detected when no TE flap position or autoslat command
is present and:
• two LE flaps move on one wing, or
• two or more slats move on one wing.
The FSEU shuts down the LE control and illuminates the amber LE FLAPS
TRANSIT light.
In addition, to prevent uncommanded motion from occurring on the LE devices
during cruise, the FSEU maintains pressure on the retract lines and depressurizes
the extend and full extend lines. ( L.E. Cruise depressurisation.)
Trailing Edge Uncommanded Motion
Uncommanded motion is detected when no FLAP lever or flap load relief
command is present and the TE flaps:
• move away from the commanded position
• continue to move after reaching a commanded position, or
• move in a direction opposite to that commanded.
The FSEU shuts down the TE drive unit by closing the TE flap bypass valve. The
TE flap shutdown cannot be reset by the flight crew and they must use the
alternate flap system to control TE flaps. The shutdown is indicated by the flap
position indicator disagreeing with the FLAP lever position.
There is no flap needle split.

Flap Placard speeds
are displayed below
the Landing Gear lever.
These are T.E flap load
limits.
Flap Load Relief. If the
Flaps are at 30 and speed
exceeds 176 Knots the
flaps will move to Flap 25.
If the flaps are at 40 and
speed exceeds 163 Knots the
flaps will move to Flap 30.
It is possible to have the flap
lever at position 40 and the
flaps at 25.

L.E. Devices are indicated individually
by LED’s on the Aft Overhead panel.
Amber in transit or not in commanded
position.
Green for extended or Fully extended.
The Test button allows a test of all
LED’s on the panel.

Flap lever via
cables controls to
main wheel well
moves the TE flap
control Valve.

Hydraulic system B
pressure drives a hydraulic
motor on the T.E Flap drive
unit.

As the T.E Flaps move a
mechanical linkage sends
position information to the
T.E control valve and also
the L.E. control valve which
allows the L.E. devices to
move to the correct position

F.S.E.U.
Flap Slat Electronics Unit.
T.E. Flap Position Information.
T.E. Flap Load Relief.
T.E. Flap Skew and Asymmetry detection. ( Closes Bypass Valve)
T.E. Uncommanded Motion detection. (Closes Bypass Valve)
L.E. Flap and Slat Position Information.
L.E. Cruise Depressurisation.
L.E. Flap and Slat Uncommanded motion detection.

F.S.E.U.
Flap Slat Electronics Unit.
Rudder PCU for load limiter function.
PSEU for T/O Configuration Warning.
Ground Proximity warning module for Ground
Proximity warnings.

NOT HERE
This is what you
asked for!
WHEN FLAPS ARE PART OF
A CHECKLIST.
The response is:
FLAP 10 GREEN LIGHT.
This is what the FSEU is
indicating you have!

Autoslats
Autoslat operation is normally powered by hydraulic system B. An alternate
source of power is provided by system A through a power transfer unit (PTU) if a
loss of pressure is sensed from the higher volume system B engine driven pump.
The PTU uses system A pressure to power a hydraulic motorized pump,
pressurizing system B fluid to provide power for the autoslat operation.
Most Aircraft
At flap positions 1, 2 and 5 slats extended an autoslat function is available that
moves the LE slats to full extended if the airplane approaches a stall condition.
NOTE: No auto slat with flaps UP.
The autoslat system is designed to enhance airplane stall characteristics at high
angles of attack during takeoff or approach to landing. When TE flaps 1 through
5 are selected, the LE slats are in the extend position. As the airplane approaches
the stall angle (within 1⁰ of stick shaker), the slats automatically begin driving to the
full extended position. The slats return to the extend position when the pitch angle
is sufficiently reduced below the stall critical attitude. The L.E FLAPS TRANSIT
light is inhibited during autoslat operation.
Alternative on some aircraft.
At flap positions 1, 2, 5, 10, 15, and 25 an autoslat function is available that moves
the LE slats to full extended if the airplane approaches a stall condition.

L.E. Slat fully Retracted.
Slat Extended.
Sealed position
Flap 1 to 5.
Slat Fully Extended Forming
Aerodynamic slot for improved
boundary layer control at high
AOA.
Flap 10 to 40 or Auto slat.
Also Standby Hydraulic
Alternate flap operation

Alternate Extension
In the event that hydraulic system B fails, an alternate method of extending the
LE devices and extending and retracting the TE flaps is provided.
The TE flaps can be operated electrically through the use of two alternate flap
switches. The guarded ALTERNATE FLAPS master switch closes a flap bypass
valve to prevent hydraulic lock of the flap drive unit and arms the alternate flaps
position switch. The ALTERNATE FLAPS position switch controls an electric
motor that extends or retracts the TE flaps. The switch must be held in the
DOWN position until the flaps reach the desired position. No asymmetry or skew
protection is provided through the alternate (electrical) flap drive system.
When using alternate flap extension the LE flaps and slats are driven to the full
extended position using power from the standby hydraulic system. In this case
the ALTERNATE FLAPS master switch energizes the standby pump and the
ALTERNATE FLAPS position switch, held in the down position momentarily,
fully extends the LE devices.
Note: The LE devices cannot be retracted by the standby hydraulic system.

Lifting the guard and moving the
Alternate flap arming switch to
ARM
Closes the T.E. Flap Bypass valve
Commands the Standby Hydraulic
pump to run.

Lifting the guard and moving the
Alternate flap arming switch to
ARM
Closes the T.E. Flap Bypass valve
Commands the Standby Hydraulic
pump to run.
Arms the Alternate Flap control
switch.

The Alternate Flap control switch.
Commands the T.E. Flap electric
motor to move the T.E. Flaps.
Opens the L.E. Alternate Shutoff
valve and allows Stby Hydraulic
pressure to fully extend the L.E
Flaps and slats.

Hydraulic motor.
Normal flap extension.
Hydraulic System B
Electric Motor.
Alternate flap extension and
Retraction
Trailing edge Flap power drive unit. Main Wheel well aft wall.

Black and Red torque tube transfers power drive unit force to
the Wing mounted flap actuators. Inboard flap inboard drive is in
each wheel well.
Torque tube. Ball screw. Flap attachment. Transmission 4 each wing.

LIMITATIONS
Flight Controls
Max flap extension altitude is 20,000 ft.
Holding in icing conditions with flaps extended is prohibited.
Alternate flap duty cycle:
• When extending or retracting flaps with the ALTERNATE FLAPS position switch, allow
15 seconds after releasing the ALTERNATE FLAPS position switch before moving the
switch again to avoid damage to the alternate flap motor clutch
• After a complete extend/retract cycle, i.e., 0 to 15 and back to 0, allow 5
minutes cooling before attempting another extension.
QRH
LOSS OF SYSTEM B
Hydraulic system B pressure is low.
Plan a flaps 15 landing.
Set VREF 15 or VREF ICE.
Note: VREF ICE = VREF 15 + 10 knots:
The trailing edge flaps can be operated with the alternate electrical system. Alternate
flap extension time to flaps 15 is approximately 2 minutes.

QRH
LEADING EDGE FLAPS TRANSIT
Light(s) for only one leading edge device is illuminated:
Limit airspeed to 300 knots (280 knots for turbulent air penetration) or 0.65 Mach, whichever
is lower.
Light(s) for more than one leading edge device is illuminated:
Limit airspeed to 230 knots maximum.

Flap Placard speeds
are displayed below
the Landing Gear lever.
These are T.E flap load
limits.
Alternate Flap Extension
speed is 230 Knots as all
L.E. devices will extend to
the full extend position.
This is the structural load
limit for the L.E devices.
During Alternate extension the LE FLAPS TRANSIT light will
be illuminated until the flaps go past 5 (25 on some aircraft)
Because the LE Slats are not in their correct sequenced
position.

Elevator feel force is provided by the elevator feel computer. The
computer receives inputs from where?

Elevator feel force is provided by the elevator feel computer. The
computer receives inputs from where?
Elevator Feel System
The elevator feel computer provides simulated aerodynamic forces using airspeed (from the
elevator pitot system) and stabilizer position. Feel is transmitted to the
control columns by the elevator feel and centering unit. To operate the feel system
the elevator feel computer uses either hydraulic system A or B pressure,
whichever is higher. When either hydraulic system or elevator feel pitot system
fails, excessive differential hydraulic pressure is sensed in the elevator feel
computer and the FEEL DIFF PRESS light illuminates.

The system that detects opposing hydraulic pressure in the
main rudder PCU is called the?

The system that detects opposing hydraulic pressure in the main
rudder PCU is called the?
The main rudder PCU contains a Force Fight Monitor (FFM) that detects opposing
pressure (force fight) between A and B actuators. This may occur if either system
A or B input is jammed or disconnected. The FFM output is used to automatically
turn on the Standby Hydraulic pump, open the standby rudder shutoff valve to
pressurize the standby rudder PCU, and illuminate the STBY RUD ON, Master
Caution, and Flight Control (FLT CONT) lights.

How many flight spoilers are on each wing?

The flight spoilers begin extension with a control wheel deflection of approximately:
a) 10°
b) 15°
c) 20°
d) 25°

What happens when the ALTERNATE FLAPS Master switch is armed?

The amber LE FLAPS TRANSIT light is inhibited under what conditions?

Max flap extension altitude is?

Max flap extension altitude is?
20,000 ft.

What is the maximum duty cycle for the alternate flap electric motor?

What is the maximum duty cycle for the alternate flap electric motor?
LIMITATIONS.
Alternate flap duty cycle:
• When extending or retracting flaps with the ALTERNATE FLAPS
position switch, allow 15 seconds after releasing the ALTERNATE
FLAPS position switch before moving the switch again to avoid damage
to the alternate flap motor clutch.
• After a complete extend/retract cycle, i.e., 0 to 15 and back to 0, allow 5 minutes
cooling before attempting another extension.

L.E. Indicator
FLIGHT CONTROL PANEL
MACH and
STALL warning
test switches
The END of FLIGHT CONTROLS.
Now take the test at www.theorycentre.com
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B737 NG Flight controls

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