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TRAILING EDGE FLAPS -LOAD RELIEF -FUNCTIONAL DESCRIPTION
General
The flap load relief function prevents damage to the flaps and their support structures from large aerodynamic forces.
Flap load relief limits the position of the flaps as a function of airspeed. This function initiates when the airspeed is more than one knot more than the flap placard speeds.
Flap load relief operates only in the primary mode. It compares the flap lever command position to the airspeed.
Load relief is active if the airspeed increases above the load relief limit for more than one half second. Load relief then retracts the flaps or prevents the flaps from extending to the commanded position. Flap load relief retracts the flaps to these positions:
*
25
*
20
*
15
*
5.
The flap load relief command resets when the airspeed decreases below a set value. The load relief command also resets when the pilot moves the flap lever to or below the flap load relief position.
EFFECTIVITY
BEJ ALL
Load Relief -25
Load relief retracts the flaps to 25 if the flap lever is at 30 and the airspeed is more than 171 knots. The load relief command resets if the airspeed decreases to less than 165 knots.
Load Relief -20
Load relief retracts the flaps to 20 if the flap lever is at 30 or 25 and the airspeed is more than 181 knots. The load relief command resets if the airspeed decreases to less than 175 knots.
Load Relief -15
Load relief retracts the flaps to 15 if the flap lever is at 30, 25, or 20 and the airspeed is more than 191 knots. The load relief command resets if the airspeed decreases to less than 185 knots.
Load Relief -5
Load relief retracts the flaps to 5 if the flap lever is at 30, 25, 20, or 15 and the airspeed is more than 201 knots. The load relief command resets if the airspeed decreases to less than 195 knots.
Indication
When flap load relief is active, the LOAD RELIEF message shows on the EICAS display or on the EICAS compacted engine display.
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TRAILING EDGE FLAPS -LOAD RELIEF -FUNCTIONAL DESCRIPTION
The flap position indication shows the position of the flaps. During load relief, the command bar and detent number change to magenta and do not agree with the flap position.
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TRAILING EDGE FLAPS -LOAD RELIEF -FUNCTIONAL DESCRIPTION
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777 AIRCRAFT MAINTENANCE MANUAL
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TRAILING EDGE FLAPS -FUNCTIONAL DESCRIPTION -SECONDARY MODE CONTROL
General
Only one FSEU commands the flaps in the secondary mode.
The FSEU controls:
*
Secondary mode engage
*
Retraction and extension
*
Flap/slat sequence
*
Cruise Inhibit
*
Secondary mode auto test.
For redundancy, both channels in the FSEU must agree on the flap command.
In the secondary mode, the FSEUs energize relays. The relays control the electrical power to the electric motor, clutch, and bypass solenoid. The alternate mode operation also uses these relays.
Secondary Mode Engage
When the FSEU engages the secondary mode, it energizes the bypass/clutch relay.
See the high lift control section for more information about the mode selection (SECTION 27-03).
EFFECTIVITY
BEJ ALL
This relay has three functions. First, the bypass/clutch relay supplies power to the bypass solenoid in the primary control valve. This prevents hydraulic operation in the primary mode.
Second, this relay supplies power to the clutch in the electric motor. This permits the electric motor to move the flap drive system.
Third, the bypass/clutch relay supplies power to the extend and retract relays. These relays do not energize until the FSEUs supply the grounds for them.
Retraction and Extension
The FSEU compares the flap lever position to the flap position. The flaps retract if the flap lever position is less than the flap position. The flaps extend if the flap lever position is greater than the flap position.
Either FSEU can energize the extend and retract relays to move the flaps. These relays supply 115v ac power to the electric motor.
Flap/Slat Sequence
This function controls the sequence of the retraction and extension of the flaps and slats. See the high lift control section for more information about the secondary mode flap and slat sequence (SECTION 27-03).
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