2) The aft limit is at ten degrees. This position is just before the position where the engine surge bleed valves open. The limit is changed to the idle stop if the airplane is more than five knots fast since this improves deceleration capability and there is adequate margin for engine acceleration. At radio altitudes 400 feet and below, the aft limit is moved back to ten degrees to ensure rapid engine acceleration if a go-around is initiated.
(f)
EPR Equalization Engine EPR is equalized during speed control to minimize rudder trim which would increase drag. The equalization is operating anytime EPR is above
1.15 and is limited to thrust lever separation of eight degrees. In the event of an engine failure, the equalization will drive the thrust lever of the failed engine forward to the eight degree limit of the equalization.
(g)
Attitude Director Fast Slow The autothrottle drives the fast slow display in each attitude director indicator only during the automatic or manual speed control mode.
(4)
Arm Mode
(a)
The autothrottle will be in the Arm mode when the autothrottle engage (A/T ARM) switch on the AFCS MCP is in the ARM position and no mode command is being received from the AFCS. The Flight Mode Annunciator will display ARM. The pilot may adjust thrust manually without reaction from the autothrottle in the Arm mode.
(b)
The Arm mode occurs when ready for take off just prior to pressing the thrust-lever mounted (AUTO TAKE OFF & GO AROUND) switch(es). It also occurs after retard from descent or as the result of deselecting speed or EPR by pressing the SPD or EPR pushbutton (when illuminated) on the AFCS MCP. The ARM annunciation on the Flight Mode Annunciator will disappear when the A/T ARM switch moves from the ARM position to OFF.
(5)
Retard Operation
(a)
Descent Retard
1) The Descent Retard mode provides a thrust reduction for descending from cruise altitudes at autopilot request. The Flight Mode Annunciator will display RETARD when the mode is in use. The mode is terminated by the pilot stopping the thrust levers or the thrust levers driving against the idle stop. The autothrottle will then transfer into the Arm mode. The Flight Mode Annunciator will then change from RETARD to ARM.
(b)
Landing Flare Retard
580
Oct 20/85 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 22-31-01 Page 17
1) The landing flare retard provides a thrust reduction to idle during the landing flare maneuver. The retard rate is adjusted so the thrust levers will be reduced to idle in six seconds. The Flight Mode Annunciator will show RETARD. The landing flare retard will occur at 27 feet of radio altitude during landing. The landing flare retard will also occur approximately 1 second after the autopilot flare if not initiated by the radio altimeter.
(6) Go Around Operation
(a)
The Go-Around mode can be initiated for use when the autothrottle is engaged and the radio altitude is below 2000 feet. If radio altimeter has failed, selection of Go-Around is allowed until 1500 feet barometric altitude is reached. Go-Around may be engaged until the airplane has been on the ground for more than two seconds. Operating the thrust lever mounted (AUTO TAKE OFF & GO AROUND) switch(es) causes the thrust levers to advance at 15 degrees per second to the predicted thrust lever position for the PDCS go around thrust value. The thrust value provided is a reduced value depending on airplane weight and may vary between 1.75 EPR and full go-around thrust. When flaps are retracted from F15 to F5, thrust is further reduced by 0.1 EPR. A second operation of the palm switch after throttles move up will cancel reduced thrust and cause full go-around thrust to be set. The FMA drops its previously displayed mode and displays EPR.
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