(10)
During takeoff or go-around, a throttle lever prediction is used to preposition the throttle levers to the approximate rated power position. The prediction is based on engine type, temperature, commanded N1, altitude, and PMC status.
(11)
When takeoff or go-around is engaged, the throttles drive forward towards a position 5 degrees short of the predicted position, at a rate of 13.5 degrees/second.
(12)
When rate compensated N1 error is within 8 percent of the target N1, the throttle letters move to match the N1 target at a rate of approximately 5 degrees/second.
(13)
Each engine N1 is monitored. If either N1 value falls below 12.5 percent or exceeds 120 percent, the N1 INVALID logic is enabled.
(14)
If N1 is invalid during takeoff, the A/T disengages. If N1 becomes invalid during other modes, the A/T reverts to a throttle position limit, rather than an N1 limit.
B. N1 Mode Logic
(1)
During N1 mode, the Autothrottle controls throttle position to maintain the selected N1 target or limit.
(2)
When takeoff mode is set, N1 is enabled. There are no inhibits for the N1 mode, when enabled by takeoff.
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737-300/400/500MAINTENANCE MANUAL
(3)
N1 mode is also enabled by a N1 request from the Autopilot, if not inhibited by Autothrottle go-around, airspeed less than 60 knots (or 80 knots for airplanes with A/T computers P/N 10-62017-25 and subsequent), throttle hold, or squat.
(4)
Maximum go-around also enables the N1 mode, if not inhibited by airspeed less than 60 knots or throttle hold (or 80 knots for airplanes with A/T computers P/N 10-62017-25 and subsequent).
19. TO/GA Modes and Logic_____________________
A. Takeoff Mode Logic
(1)
Takeoff mode provides thrust control during the initial phase of the takeoff roll (0 to 60 knots) (or 0 to 80 knots for airplanes with A/T computers P/N 10-62017-25 and subsequent).
(2)
The takeoff mode is set by the takeoff/go-around switch, with the A/T armed for takeoff. The A/T is armed for takeoff when the airplane is on the ground, the Autothrottle is engaged, and the FMC takeoff mode is executed. If the A/T is engaged in go-around, the takeoff mode is inhibited. The takeoff mode is reset when the throttle hold logic is set, or the Autothrottle is disengaged.
B. Go-Around Logic (Fig. 11)
(1)
Fig. 11 describes go-around (GA) logic interface. Tables defining GA related logic follow the block diagram.
(2)
A/T GA is armed below 2000 feet radio altitude (15000 feet baro altitude if the LRRA is invalid) and remains armed until two seconds after touchdown. The GA mode is initiated by pressing either TO/GA switch. The GA mode is divided into three submodes: reduced GA, reduced GA (maintaining) and maximum GA. GA operation is terminated by a DFCS request, or disengaging the A/T.
(3)
Pressing either TO/GA switch once initiates the reduced GA mode, provides REDUCED GA logic, sets the reduced GA latch, starts the GA timer, and arms reduced GA (maintaining).
(4)
The timer (8 seconds) is reset when the N1 error is within 3% of computed N1, the reduced GA latch is reset when the timer is reset and the GA latch is reset when radio altitude is greater than 100 feet.
(5)
The reduced GA (maintaining) latch is set when the GA timer expires. It remains set until the DFCS requests a mode change or the A/T is disengaged.
(6)
Pressing either TO/GA switch a second time initiates maximum GA mode (sets the maximum GA latch). The maximum GA latch was armed during the first 0.5 seconds of reduced GA. This latch provides MAXIMUM GA logic and is reset if the GA latch has been reset by the timer and altitude (greater than 100 feet R/A) and the DFCS requests a mode change (N1 or speed).
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