(a) One TMC is installed in the main electrical/electronic equipment compartment E2-3 shelf. Two EPR thrust limits are continuously computed by the TMC. Maximum EPR and reference EPR are functions of pressure altitude, Mach number, total air temperature, and engine air extraction. The TMC uses this data for control of the servomotor generator, which drives the thrust levers.
(2)
Thrust Mode Select Panel (TMSP)
(a) The TMSP allows the crew to select thrust limit computation modes. A thrust rating mode and corresponding limit is selected on the panel for each stage of the flight profile. Selected thrust modes and limits are displayed on the EICAS display unit.
(3)
Autothrottle Servomotor Generator
(a) The autothrottle servo provides the interface between the TMC and thrust levers. The servo drives the thrust levers and linkage through a gearbox and no-back clutch pack assembly.
(4)
Clutch Pack Assembly
(a) The clutch pack assembly provides the interface between the autothrottle servo and the thrust levers. The clutches slip when the thrust levers are moved by the pilot. This allows the pilot to override the TMS without backdriving the autothrottle servo.
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MAINTENANCE MANUAL
THRUST MODE SELECT PANEL
Thrust Management System
Figure 1
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MAINTENANCE MANUAL
F. TMS Control Inputs
(1) The AFCS Mode Control Panel (MCP) allows manual selection of autothrottle control modes. The EPR (or THR) and SPD select controls are operable when the autothrottle switch on the MCP is in the ARM position. The SPD mode is operable only when the airplane is airborne. The Flight Management Computer (FMC) automatically selects autothrottle modes to follow the flight paths and speed profiles defined by FMC performance and vertical navigation functions.
G. Sensor Inputs
(1)
The Air Data Computing System (ADCS) (34-12-00) consists of left and right Air Data Computers (ADCs), which provide environmental data to the airplane.
(2)
The Inertial Reference System (IRS) (34-21-00) consists of left, right, and center IRUs which provide pitch and roll attitude; and longitudinal and vertical acceleration.
(3)
The Electronic Engine Control (EEC) (Ref 73-21-00) provides thrust limiting for engine protection as measured by EPR.
(4)
The autothrottle Power Lever Angle (PLA) transducer is a rotary variable differential transformer that provides an ac signal output proportional to thrust lever position. One sensor is installed on each engine. The autothrottle PLA is driven by inputs from the engine to strut control rod, which is connected to the control cables from the thrust levers (Ref 22-33-00).
H. TMS Outputs
(1) A fast/slow indicator is on the EADI. This gives the crew a cue for speed control by indicating whether airspeed is above or below the target speed. The TMC computed thrust reference limits and maximum limits are displayed on the upper EICAS display unit.
I. TMC/Systems Interface Inputs (Fig. 2)
(1) Digital Data Bus Inputs
(a) Digital data bus inputs are received by the TMC from the following components. 1) Thrust Mode Select Panel (TMSP) 2) AFCS Mode Control Panel (MCP) 3) Maintenance Control Display Panel (MCDP) 4) Left and Right Air Data Computers (ADCs) 5) Left and Right Flight Management Computers (FMCs)
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