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detent, the speedbrakes automatically extend. The speedbrake lever does not need
to be in the ARMED position. If either thrust lever is advanced to a takeoff
position, the speedbrake lever is driven to the down position.
Automatic speedbrakes are not available in the secondary and direct modes.
There is no limitation for extension of speedbrakes in a landing configuration.
Flaps and Slats
The flaps and slats are high lift devices that increase wing lift and decrease stall
speed during takeoff, approach, and landing.
The airplane has an inboard and an outboard flap on the trailing edge of each wing,
and one inboard and five outboard slats on the leading edge. A two-position
Krueger flap provides a seal between the inboard slat and engine nacelle on each
wing.
787 Flight Crew Operations Manual
Flight Controls -
System Description
9.20.18 Boeing Proprietary
In the flaps 1 position, only the slats move. Flaps 5, 15, and 20 are takeoff flap
positions. Flaps 25 and 30 are landing flaps positions. Flaps 20 is used for some
non–normal landing conditions.
To protect against inadvertent deployment during cruise, flap and slat extension
from the UP position is inhibited when speed is more than 250 knots or altitude is
above approximately 20,000 feet.
Flap and Slat Sequencing
When the flap lever is in the UP detent, all flaps and slats are commanded
retracted. Moving the flap lever aft allows selection of flap detent positions 1, 5,
15, 20, 25 and 30. The flaps and slats sequence so that the slats extend first and
retract last.
Starting from flaps UP, selection of flaps 1 commands the slats to move to the
midrange position. The flaps remain retracted.
Selection of the flaps 5, 15, and 20 positions commands the flaps to move to the
position selected. The slats remain in the midrange position.
Selection of flaps 25 commands both the flaps and slats to move to landing
positions. First the slats extend to the fully extended position, then the flaps extend
to the landing flaps 25 position.
Selection of flaps 30 commands the flaps to extend to the primary landing
position.
During retraction, flap and slat sequencing is reversed.
The mechanical gate at the flaps 20 detent prevents inadvertent retraction of the
flaps past the go–around flap setting. The mechanical gate at flaps 1 prevents
inadvertent retraction of the slats past the midrange position.
Flap and Slat Modes
Three modes of flap and slat operation are possible:
• primary (hydraulic)
• secondary (hydraulic or electric)
• alternate (electric).
The flaps and slats can operate independently in either the primary or secondary
mode. However, independent flap and slat operation in the alternate mode is not
possible.
Primary mode hydraulic power is supplied by the center hydraulic system.
Secondary and alternate mode electrical power is supplied by the left and right AC
busses.
787 Flight Crew Operations Manual
Flight Controls -
System Description
Boeing Proprietary 9.20.19
The secondary mode is automatically engaged whenever the primary mode fails
to move the flaps or slats to the selected position. Once engaged, the secondary
mode remains engaged until the affected system surfaces are fully retracted or
center hydraulic system pressure is restored.
In the secondary mode, the flaps and slats are positioned by hydraulic or electric
motors. Because autoslats are unavailable, the slats are fully extended at all flap
positions (if airspeed is less than 215 knots) to improve stall handling
characteristics. If airspeed exceeds 215 knots, the slats retract to the midrange
position (the midrange index on the slat position indicator), or do not extend
beyond the midrange position.
If the slats are in the midrange position (flaps 1 through 20) when the secondary
mode is engaged, they remain in that position until the flaps are retracted to UP,
or extended beyond 20.
On the ground, secondary electric mode extension or retraction is inhibited when
groundspeed is less than 40 knots, center hydraulic system pressure is low, and
two of the following three items are true:
• left engine N2 is less than 50 percent,
• right engine N2 is less than 50 percent,
• primary external power is available.
The alternate mode allows direct manual operation of the flaps and slats through
the secondary drive electric motors. The alternate flaps ARM switch:
The three–position alternate flaps selector extends and retracts the flaps and slats.
The flaps and slats extend simultaneously, but slat retraction is inhibited until the
flaps are up. Alternate mode flap and slat extension is limited to slats midrange
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787机组操作手册Flight Crew Operations Manual 2(75)
