b767_flight_controls

Copyright Smartcockpit.com Ludovic ANDRE / version 00

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BOEING 767 SYSTEMS REVIEW

FLIGHT CONTROLS 1. GENERAL ¡ There is NO manual reversion (Flight controls are powered from 3 airplane hydraulics system). ¡ Spoilers assist the ailerons in providing roll control and also operate as speedbrakes. ¡ Six guarded Flight Control Shutoff switches control hydraulic fluid to the flight controls :

- Tail switches = Hydraulic power to the Elevators & Rudder - Wing switches

¡ Flight control system overrides protect against control column or flight control jams. Overrides bypass the restricted

portion of the control system when higher than normal control forces are applied. There is protection against system damage when applying high control forces . When a restricted portion of the flight controls are bypassed, some control effectiveness may be lost.

¡ RAT gives sufficient pressure above 130 kt.

2. YAW CONTROL ¡ Rudder is hydraulically powered through displacement of either pilots rudder pedals. ¡ 2 Independent Yaw dampers operate through the rudder control system to improve directional stability. Ô Each Yaw has a Yaw damper controller Ô Electrical self test occurs when power is initially established. Ô Yaw damper test switches on GRND (with at minimum 1 aligned IRS + Hydraulic power) : - INOP light ON + EICAS msg. after the test if a fault exists - Anytime a failure occurs = auto removal of hydraulic power from Yaw controller Ô 1 yaw damper = 50% authority. ¡ Displacement of either set of rudder pedals sends a signal to 3 hydraulic actuators (C, L, R) Ô Displacement limited with 1 or 2 systems U/S Ô Position on the EICAS STATUS display. ¡ Rudder trim provides signals to an electric motor that repositions the rudder neutral point. ¡ Trim control = reposition the Rudder and the pedals through a rudder ration system. Ô Rudder displacement function of airspeed :

- LOW SPEED = FULL displacement - HIGH SPEED = LIMITED displacement

Ô Information provided Actuator powered by LEFT hydraulic system + ADC ¡ RUDDER RATIO light + EICAS msg. = Control input to the rudder not correctly modified : Ô Auto depressurization of the LEFT hydraulic system rudder actuator Ô Limits in high speed Ô Full deflection only available at low speed Ô Avoid abrupt movement > 160 kt Ô If the LEFT hydraulic system is providing normal pressure (NOT depressurized), a fault may result in limited

displacements of the rudder at all speeds : - Limitations in crosswind (15 kt) - NO AUTOLAND


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3. PITCH CONTROL Pitch control is provided by 2 elevators & a movable horizontal stabilizer. • ELEVATOR ¡ 2 hydraulically powered elevators Ô 3 actuators on each elevator (L,C + R hydraulics system) ¡ If 1 control column should jam, applying significant forward or aft force to the other causes the 2 columns to override

Column Ô Pitch control is then available using the free control column path. ¡ Position visible on the EICAS STATUS display. ¡ 2 Elevator feel systems provide artificial feel forces to the pilots control columns. Mechanical springs provide feel following a loss of L + C hydraulics system. • STABILIZER ¡ 2 trim switches use hydraulic power to reposition the stabilizer through 1 motor and 1 brake mechanism which send

signals to the 2 trim control modules : Ô One release the brakes Ô The other actuates the motor. ¡ Powered by the LEFT and CENTER hydraulic systems. ¡ Rate varies with airspeed. ¡ Moving the column opposing the trim direction cuts off electric and auto trim signals to the modules. ¡ There are 3 modes of stabilizer trim control :

1) ELECTRIC TRIM : dual electric trim switches are located on each control wheel Ô actuating both switches provides electrical arming & direction signals to the 2 trim control modules 2) ALTERNATE TRIM : back-up trim control. Moving both switches provides electrical arming & direction signals to

both trim control modules. The signals neutralize any other conflicting trim inputs 3) AUTOMATIC TRIM : 3 FCCs provide autotrim input signal to the 2 Stabilizer trim & Aileron lockout Modules

(SAM). Automatic stabilizer trim uses only one trim control module & trims at ½ the electric or alternate trim rate. ¡ STAB TRIM CUT OUT switches = shuts off hydraulic power to the trim modules if necessary. (AOM 13.20.06) ¡The SAM associated with the first engaged A/P is always selected initially :

- Left FCC on Left SAM and Right FCC on Right SAM - Center FCC on Left SAM (automatically switched on the Right SAM if Left SAM fails)

Ô 1 module = 50% of the normal rate Ô Electric Trim causes the A/P in case of single A/P ops Ô Electric Trim switches are inhibited in case of multiple A/Ps ops

Ô Alternate trimming overrides any number of A/Ps but does not cause disengagement Ô During a LAND 2 approach, if both SAMs are valid, stab trim bias is applied at ≈ 55 ft RA thru the use of both SAMs : automatic stab trim speed is ≈ twice the normal. ¡ MACH TRIM SYSTEM provides a nose up trim signal thru the stab trim system to compensate for the normal pitch down characteristics that is encountered at high Mach numbers (system is fully automatic as soon as the aircraft is airborne (airspeed signal from the 2 ADCs are fed from the SAM which in turn actuates the 2 stab trim modules to provide the Mach trim compensation.


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¡ NON NORMAL OPS UNSCHD STAB TRIM Ô Uncommanded stabilizer movement Ô A/P trim direction opposes stabilizer displacement Ô also when ALTERNATE used with A/P engaged

STAB TRIM Ô BRAKE fails to release

Ô MOTOR fails to operate Ô 50% of the rate

- If one brake fails > full rate is available using the alternate trim - If both brakes fails > NO stab trim will be available

Ô Automatic stab trim failures = AUTOPILOT amber light + EICAS msg PITCH ENHANCEMENT SYSTEM Ô activated in case of loss of BOTH L and C hydraulics systems

- RIGHT system operates the PES with the LEFT fluid - Trim available ONLY with ELECTRIC TRIM at ¼ the rate

• FLAPS ¡ Altitude Limitation : 20 000 ft ¡ Maneuvering speeds = VREF 30 + 20 kt for Flaps 15/20

+ 40 kt………….…….5 + 60 kt………….…….1 + 80 kt ….……………0

(These speeds allow a normal 25° bank + an additional 15° bank safety factor before initial buffet) ¡ 3 Power Drive Units (PDU) are actuated when the Flap lever is moved Ô Powered by the Center hydraulics system Ô One PDU drives LE INBD Slats (1 each side mechanically linked) Ô Second PDU drives OUTB Slats (5 each side mechanically linked) Ô Third PDU drives TE FLAPS (2 each side mechanically linked) ¡ Indicator = 1 Left + 1 Right pointer ¡ Flap lever position 1 to 20 = SLATS in T/O position ¡ Flap lever position 25 to 30 = SLATS in LDG position ¡ TE Flaps extension inhibited until the slats extend to 1 ¡ ALTERNATE operation ÔÔ PDUs are operated by electric motors instead of hydraulic. Ô With ALT switches activated, FLAPS and SLATS hydraulic SOV are closed. Ô From UP to 20, extension time is about 3'. Ô "LE" acts on drive 1 & 2 and associated SOV

"TE" acts on drive 3 & associated SOV

LE TE ALTN = arms the selected TE flap / LE slat alternate drive unit & shuts off hydraulic power to the selected flap or slat drive unit(s)

ALTN

ALTN


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¡ FLAP LOAD RELIEF is armed by selecting Flap position 25 or 30° Ô below 180 kt, flaps extend to 25° Ô below 170 kt, flaps extend to 30° Ô SLATS remain in LDG CONFIG if the lever is in 25° or 30° position Ô NO LOAD RELIEF = FLAP LD RELIEF EICAS msg + TRAILING EDGE amber light illuminated : - Flap load relief system fails to operate (flaps will NOT retract automatically to 20°) ¡ LE (TE) DISAGREE = LE (TE) not in position Ô use the Alternate system (an LE SLAT DISAGREE or TE FLAP DISAGREE may also occur if the Flap lever is not in a detent for an extended period of time. In this case the light + msg may be removed by moving the Flap lever to the desired detent. ¡ LE SLAT (TE FLAP) ASYM = use the ASSYM procedure ¡ Hydraulic Driven Generator (HDG) is supplying electrical power, hydraulic flow to the flap/slat mechanism is

mechanically reduced, resulting in increased flap/slat operating time

4. ROLL CONTROL Roll control is provided by 4 ailerons & 12 spoilers. • AILERONS ¡ Control wheels are connected so that, if 1 Control Wheel jams, using significant force causes the Control Wheels to

override. Roll control then available using the Free Control Wheel ¡ 2 ailerons on each wing on either side of the Outboard TE side. Rotating either Control Wheel sends a signal to the

aileron hydraulics actuator (2 actuators are used for each aileron) ¡ INBOARD ailerons droop with the flaps. ¡ Aileron trim available by pushing both Aileron trim switches in the desired direction :

- switches provide arming & direction signals to 1 electrical motor that repositions the aileron neutral (trimmed) position

- Hydraulic power from 1 of the 3 hydraulics system is necessary Caution ! If the crew inadvertently activates aileron trim while an A/P is engaged, the repositioning of the aileron

Neutral point is NOT APPARENT. When the A/P is disengaged, the Control Wheels & ailerons move to to the new (possibly undesired) neutral point and the airplane will roll proportional to the amount of trim

input. ¡ LOCKOUT SYSTEM Ô At high speed, OUTBOARD ailerons are LOCKED Ô AILERON LOCKOUT EICAS msg + light failure in the lockout system :

- Fault in the Ailerons LOCKOUT system - At High airspeeds (around cruise speeds), 1 or BOTH Outboard ailerons failed to LOCKOUT - At Low airspeeds (around approach speeds), 1 or BOTH Outboard ailerons failed to UNLOCK

• SPOILERS / SPEEDBRAKES ¡ 6 spoilers panels on each upper wing surface

- GND = all the panels extend (ground speedbrakes) - FLT = idem except N°4 and N°9

¡ Control Wheels & Speedbrake lever send signals to the spoiler controller which determines the required spoiler

panel deflection


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¡ Speedbrake lever moves to UP when Speedbrake lever is armed & all the following conditions are met :

- there is hydraulics pressure to both landing gear truck tilt actuators - Both Tilt sensors detect a ground condition - BOTH T/L to idle

idem in DOWN DETENT but with either reverse thrust raised to its interlock stop (NO need to be ARMED) Following automatic Speedbrake extension, if any of the 3 conditions are no longer met, the Speedbrake lever moves to the DOWN position & the Speedbrake lever moves to the DOWN position ¡ SPEEDBRAKES EXT EICAS msg + SPEEDBRAKES light when :

- the lever is beyond the ARMED position - and RA between 800' and 15' - or FLAPS in landing condition and above Captain’s RA > 15 ft

¡ SPOILERS EICAS msg + SPOILERS light when :

- 1 or more panel(s) disagree with the lever position Ô reduced roll and speed control

Ô reduced capability of auto speedbrakes system ¡ AUTO SPEEDBRAKE EICAS msg + AUTO SPEEDBRAKE light when :

- FLIGHT = may extend when the lever is in ARMED position - GROUND = will not extend automatically after landing

5. FAULTS (amber) : Rudder ratio system failed and pilot inputs to Rudder may be increased or decreased in sensitivity. L R

(amber) : Yaw damper switch OFF or Yaw Damper INOP

- Uncommanded stabilizer movement (amber) - (A/P) engaged) : stabilizer moving opposite the direction signaled (amber) : stabilizer trimming at ½ rate signaled by the electric trim switches - Speedbrake lever > ARMED detent + RA between 800 ft & 15 ft. (amber) or - Speedbrake lever > ARMED detent + Landing flaps extended & RA > 15 ft. - If Spdbrake lever is ARMED or DOWN, Spdbrake will not extend auto after landing. (amber) or

- If Spdbrake lever is ARMED, Spdbrake may extend inflight if additional fault occur (amber) : 1 or more spoiler system faults have been detected

RUDDER RATIO

INOP

INOP

ON ON

UNSCHED STAB TRIM

STAB TRIM

SPEED BRAKES

AUTO SPDBRK

SPOILERS


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(amber) : aileron lockout actuator not in signaled position LE : Slat position disagrees with the position selected (slat asymmetry) ( amber) TE : Flap position disagrees with the position selected : - Flap asymmetry exists or Flap load

AIL LOCK

LEADING EDGE

TRAILING EDGE


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ELEVATORS SYSTEM


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STABILIZER CONTROL DIAGRAM


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RUDDER LOGIC

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