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white background.
The maximum TPR limit is indicated by an amber line at the top of the TPR dial.
The TPR indication does not change color when maximum TPR is reached. The
reference/target TPR indication displays the FMS reference or target TPR. The
commanded TPR indication displays the EEC calculated TPR commanded by
thrust lever position.
Electronic Engine Control (EEC)
Each EEC has full authority over engine operation. The EEC uses thrust lever
inputs to automatically control forward thrust and reverse thrust. The EEC has two
control modes: normal and alternate. In the normal mode, the EEC uses TPR as
the parameter for setting thrust. In the alternate mode, the EEC uses N1 RPM as
the controlling parameter.
787 Flight Crew Operations Manual
Engines, APU -
Engine System Description
7.20.4 Boeing Proprietary
EEC Normal Mode
In the normal mode, the EEC sets thrust by controlling TPR based on thrust lever
position. TPR is commanded by positioning the thrust levers either automatically
with the autothrottles, or manually by the flight crew.
Maximum TPR represents the maximum rated thrust available from the engine.
The EEC continuously computes maximum TPR.
Maximum rated thrust is available in any phase of flight by moving the thrust
levers to the full forward positions.
EEC Alternate Mode
If the required signals are not available to operate in the normal mode, the EEC
automatically uses the alternate mode. In the alternate mode, the EEC schedules
N1 as a function of thrust lever position. The alternate mode provides soft and
hard levels of control:
• Soft – When the EEC automatically switches an engine to the alternate
mode and the EEC mode switch remains in NORMAL, the EEC is in the
soft alternate mode (the switch position is NORMAL, the EEC mode is
alternate). At a fixed thrust lever position, thrust does not change.
• Hard – When ALTERNATE is manually selected on an EEC mode
switch, that engine is switched to the hard alternate mode (the switch
position is ALTERNATE, the EEC mode is alternate). Reference and
target N1, and maximum and commanded N1 values are displayed on the
N1 indication during the hard alternate mode. Thrust may change to set
the commanded N1 when ALTERNATE is manually selected.
For the normal, soft alternate, and hard alternate modes, the following TPR and
N1 information is displayed:
Automatic reversion or manual selection to the alternate mode is indicated by the
EICAS advisory message ENG EEC MODE (L, R) and illumination of the EEC
alternate light on the associated EEC mode switch. Selecting the alternate mode
on both engines eliminates thrust lever stagger at equal thrust settings, or
asymmetric thrust when the thrust levers are operated together.
EEC mode switch –
NORMAL
EEC mode – NORMAL
EEC mode switch –
NORMAL
EEC mode – SOFT
ALTERNATE
EEC mode switch –
ALTERNATE
EEC mode – HARD
ALTERNATE
• TPR: actual,
command,
reference/target,
maximum
• N1: actual, red
line.
• TPR: blank
• N1: actual, red
line.
• TPR: blank
• N1: actual,
command,
reference/target,
maximum, red
line.
787 Flight Crew Operations Manual
Engines, APU -
Engine System Description
Boeing Proprietary 7.20.5
The autothrottles remain engaged whenever the EEC automatically switches to
the alternate mode. The alternate mode N1 reference/target values are computed
by the FMC.
Note: Autothrottles remains engaged in the soft or hard alternate mode.
The alternate mode schedule (N1 schedule) provides equal or greater thrust than
the normal mode for the same thrust lever position.
Thrust protection is not provided in the alternate mode and maximum rated thrust
is reached at a thrust lever position less than full forward. As a result, thrust
overboost can occur at full forward thrust lever positions. The EICAS caution
message ENG LIMIT PROT (L, R) is displayed if the thrust lever position
commands an N1 greater than the maximum rated thrust (maximum N1). N1 and
N2 red line protection is still available in the alternate control mode.
Overspeed Protection
The EEC also provides N1, N2 and N3 red line overspeed protection. If N1, N2 or
N3 approaches overspeed, the EEC commands reduced fuel flow. The EICAS
advisory message ENG RPM LIMITED (L or R) is provided when overspeed
protection is provided.
If the EECs are in alternate mode, advancing the thrust levers full forward
provides some overboost and should be considered only during emergency
　
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