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trailing edge flaps are completely retracted.
Flap Load Relief
The flap load relief function of the FCUs operates if flap airspeed limits are
exceeded with flaps 25 or 30. Automatic retraction protects the flaps from
excessive airloads. If the airspeed limit is exceeded with flaps 30 selected, the
flaps retract to flaps 25. If airspeed is still excessive at flaps 25, the flaps retract to
20. Similary, if the airspeed limit is exceeded with flaps 25 selected, the flaps
retract to 20.
The Flap lever does not move. The flaps extend to the selected position when
airspeed is sufficiently reduced.Maximum flap speeds are placarded on the center
panel.
Flap load relief is not available in secondary or alternate modes.
Flap Indications
Flap position indications are displayed on the primary EICAS display. A single
vertical indicator displays combined leading and trailing edge flap position. The
position commanded by the flap lever is also displayed. Ten seconds after all flaps
are up, the entire indication is no longer displayed.
If flap control is in secondary or alternate mode, or if any non-normal flap position
is detected, an expanded flap indication is displayed. The position of each flap
group is separately indicated. In alternate mode, the position commanded by the
Flap lever is replaced by flap position index marks at flaps 5 and flaps 25. The
index marks are used by the flight crew as a guide to position the flaps at the
desired setting.
December 01, 1999
747 Operations Manual
Flight Controls -
System Description
Copyright © The Boeing Company. See title page for details.
D6-30151-425 9.20.15
If the standby bus is the only powered AC bus, the left wing trailing edge flap
position sensors are not powered. An expanded indication is displayed with an
amber X on the left outboard and inboard trailing edge flap indications.
During engine reverse thrust operation, automatic retraction of inboard and
midspan leading edge flaps changes the flap postion indicator to reflect flaps in
transit.
Leading Edge Flaps Control Diagram
M
AIR
BLEED
LEADING EDGE
FLAP DRIVE UNIT
(TYPICAL)
FLAPS
TO
ALTN FLAPS
RET
OFF
EXT
FLAP
CONTROL
UNITS
(3)
ARM
ALTN
INBOARD
MIDSPAN
OUTBOARD
PRIMARY MODE
(PNEUMATIC)
SECONDARY/ALTERNATE MODE
(ELECTRIC)
December 01, 1999
747 Operations Manual
Copyright © The Boeing Company. See title page for details.
9.20.16 D6-30151-425
Flight Controls -
System Description
Trailing Edge Flaps Control Diagram
RET
ALTN
ARM
EXT
OFF
ALTN FLAPS
INBD FLAP
TO RIGHT
OUTBD FLAP
TO RIGHT (3)
UNITS
CONTROL
FLAP
M
TRAILING EDGE
(TYPICAL)
FLAP DRIVE UNIT
FLAPS
TO
PRESS
HYD
HYD SYS 1
UNIT
DRIVE
INBD
FLAP
GROUP
OUTBD
DRIVE
UNIT
FLAP
GROUP
HYD SYS 4
(HYDRAULIC)
(ELECTRIC)
PRIMARY MODE
SECONDARY/ALTERNATE MODE
December 01, 1999
747 Operations Manual
Flight Controls Chapter 9
EICAS Messages Section 30
Copyright © The Boeing Company. See title page for details.
D6-30151-425 9.30.1
Flight Controls EICAS Messages
Note: Configuration (CONFIG) warning messages are described in Chapter 15,
Warning Systems.
The following EICAS messages can be displayed.
Message Level Aural Condition
AILERON
LOCKOUT
Advisory A fault has occurred in the aileron lockout
system. One or both outboard ailerons may
be unlocked at high airspeeds or locked
out at low airspeeds.
>FLAP RELIEF Advisory Flap load relief system is active.
FLAPS CONTROL Caution Beeper All three FCUs have failed in their control
function, or the Alternate Flaps Arm
switch is in ALTN.
FLAPS DRIVE Caution Beeper A trailing edge flap asymmetry condition,
or a leading or trailing edge drive failure
which cannot be corrected by use of
electric motors has occurred.
FLAPS PRIMARY Caution Beeper A flap group is in secondary mode.
>FLT CONT VLVS Advisory One or more flight control shutoff valves
are closed.
Message Level Aural Condition
RUD RATIO
DUAL
Advisory A fault has occurred in both ratio changer
systems.
RUD RATIO
SNGL
Advisory A fault has occurred in one ratio changer
system.
SPEEDBRAKE
AUTO
Advisory A fault has occurred which could result in
the loss of the automatic ground spoiler
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