Flight Controls - Flaps and Slats Show Schematic only

Flaps and Slats Spoilers Spoilers Aileron

The trailing edge flaps and leading edge slats are high lift devices that increase wing lift and decrease stall speed during takeoff, approach, and landing.

The flaps and slats are normally operated with hydraulic power from the Left Hydraulic system.

An Alternate system allows the flaps and slats to be operated by electric motors.

Flap and slat position is controlled with the Flap Lever. Moving the lever provides a signal to the flap Power Drive Unit (PDU) which moves the flaps to the selected position. As the flaps move toward their selected position a signal is sent to the Slat PDU which drives the leading edge slats.

The Flap PDU is located in the left wheel well. The Slat PDU is located in the left wing root.

Flap and Slat Position Indicator Flap and slat positions are indicated by two pointers in the flap position indicator. There are L and R pointers for the left and right wing flaps and slats. The right pointer is normally hidden from view by the left pointer.

In the flaps 1 position, the flaps and slats move. Flaps 1, 5, 15, 20 are takeoff flap positions. Flaps 25 and 30 are landing flaps positions. Flaps 20 is used for some non-normal landing conditions.


Flap and Slat Sequencing

Flaps UP

When the flap lever is in the UP detent, all flaps and slats are commanded retracted and the flap position indicator points to UP. Moving the flap lever aft allows selection of flap detent positions 1, 5, 15, 20, 25, and 30.

Flaps and Slats - UP

Takeoff Positions

Flaps And Slats Takeoff.

Flaps 1
Starting from flaps UP, selection of flaps 1 commands:

The position indicator pointers move mid-way between UP and 1 when the flaps and slats are in transit. The pointers move to the 1 indication when all slats are in the midrange position and flaps reach position 1.

Flaps 5, 15 and 20
Selection of the flaps 5, 15, or 20 positions commands:

The position indicator provides only trailing edge flap position indications for all flap settings greater than 1.


Landing Positions

Flaps And Slats Landing.

Flaps 25
Selection of flaps 25 commands both the flaps and slats to move to landing positions.

Flaps 30
Selection of flaps 30 commands the flaps to extend to the primary landing position.

During retraction flap and slat sequencing is reversed.

Flap Gates

The flap gate at the flaps 20 detent prevents inadvertent retraction of the flaps past the go-around position. The flap gate at flaps 1 prevents inadvertent retraction of the slats.

Flap Maneuvering Speeds

The flap maneuvering speeds allow a normal 25° bank for maneuvering plus an additional 15° of bank safety factor before initial buffet is encountered.

Flap Load Relief

The flap load relief system protects the flaps from excessive air loads. If the flap airspeed placard limit is exceeded with the flaps in the 30 position, the flaps automatically retract to position 25. The Flap Lever does not move. When airspeed is reduced, the flaps automatically re-extend.

Auto-Slats

Fully extended autoslats.

The autoslat system enhances airplane stall characteristics. Upon receiving a signal from the stall warning system, the slats automatically extend from the midrange position to the fully extended landing position. The slats retract a few seconds after the signal is removed.

Flap/Slat Non-Normal Operation

Alternate Flap Operation

The alternate mode allows direct manual operation of the flaps and slats through electric motors.

Alternate Flap Switches

Alternate Flap Selector The alternate flaps switches:

Alternate Flap Selector

The alternate flaps selector extends and retracts the flaps and slats. Alternate mode flap and slat extension is limited to flaps 20. Trailing edge flap asymmetry protection, autoslats, and flap load relief are not available in the alternate mode; however, slat asymmetry is available. Because autoslats are unavailable, the slats are fully extended at flaps 20 to improve stall handling characteristics.

Slat and flap operation time in the alternate mode is greatly increased - extension of the flaps and slats to position 20 requires approximately 2 minutes.

Leading Edge Disagreement

Leading Edge Disagreement The LEADING EDGE light illuminates and the EICAS caution message LE SLAT DISAGREE displays when the leading edge slat positions disagree with commanded position. The disagree indicates that the slats are not driving toward their new commanded position. Hydraulic power to both slats and flaps Power Drive Units is automatically shut off.

Note: This message may also occur if the Flap Lever is not in a detent for an extended period of time.

Leading Edge Asymmetry

Leading Edge Asymmetry The LEADING EDGE light illuminates and the EICAS caution message LE SLAT ASYM displays when the leading edge slats are not symmetrically extended. Hydraulic power to both slats and flaps Power Drive Units is automatically shut off.

Note: The leading edge Slats should not be operated using the Alternate system.

Slat Loss Sensing System

AMM The loss of slats 2-5 and 6-9 [all except outboard slats] is detected by switches in the fixed wing leading edge. Loss of any or all of the affected slats will cause the EICAS caution message LE SLAT ASYM to display and the LEADING EDGE light to illuminate.

Trailing Edge Disagreement

Trailing Edge Disagreement The TRAILING EDGE light illuminates and the EICAS caution message TE FLAP DISAGREE displays when the trailing edge flap positions disagree with commanded position. The disagree indicates that the flaps are not driving toward their new commanded position. Hydraulic power to both slats and flaps Power Drive Units is automatically shut off.

A 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 and message can be removed by moving the flap lever to the desired detent.

Trailing Edge Asymmetry

Trailing Edge Asymmetry The TRAILING EDGE light illuminates and the EICAS caution message TE FLAP ASYM displays when the trailing edge flaps are not symmetrically extended. Hydraulic power to both slats and flaps Power Drive Units is automatically shut off.

Note: The trailing edge Flaps should not be operated using the Alternate system.

Load Relief Inoperative

Load Relief Inoperative The TRAILING EDGE light illuminates and the EICAS advisory message FLAP LD RELIEF displays when the flap load relief system fails to operate when required.

Hydraulic Driven Generator

ETOPs fitted
When the hydraulic driven generator is supplying electrical power, hydraulic flow to the slats and flaps Power Drive Units is reduced, resulting in increased slat and flap operation time.

Flaps and Slats Electronic Units

AMM The Flaps and Slats Electronic Unit (FSEU) consists of three physically and functionally isolated identical units. The three FSEUs monitors the output of the flap system to obtain flap system position information. Position data is used by the FSEU for asymmetry detection, uncommanded motion detection, fault annunciation, position indication, control in the alternate mode, protection in the normal mode, and flap/slat position information to other systems.

FSEU 1 performs all primary flap/slat drive protection, fault annunciation, and automatic control operations. Specifically, FSEU 1 provides:

  1. Uncommanded motion detection/protection of the flaps under normal control.
  2. Asymmetry detection/protection of the flaps under normal control.
  3. Trailing edge flap load relief.
  4. Autoslat control.
  5. Flaps up depressurization.
  6. Logic for flap needles halfway between UP and 1.
  7. Fault annunciation from EICAS and TRAILING EDGE light.
  8. Signals to other components.

FSEU 2 performs alternate flap/slat drive protection and annunciation. Specific functions are:

  1. Uncommanded motion detection under alternate control.
  2. Asymmetry detection under alternate control.
  3. Autoslat control.
  4. Logic for flap needles halfway between UP and 1.
  5. Fault annunciation from EICAS and TRAILING EDGE light.
  6. Signals to other components.

FSEU 3 performs alternate flap/slat drive control. Specific functions are:

  1. Alternate electric drive motor control.
  2. Signals to other users

EICAS Messages