Throttle Communication Module (TCM)

The Throttle Communication Module (TCM) is an ABS plastic constructed box, that is mounted directly to the forward edge of the throttle quadrant. The TCM contains all the components required to facilitate communicate between the Throttle Interface Module (TIM) and the throttle quadrant. It also enables functionality and power for the operation of the speedbrake.

Although rudimentary in function, the TCM also includes a system of three LED lights that can be used for basic troubleshooting concerning the throttle connection and speedbrake operation.

The TCM is attached to the front side of the throttle bulkhead. Access to the module is by removing the triangular side panel immediately forward of the trim wheels on the Captain-side. To access the inside of the module, 4 screws are removed to remove the cover plate.

The module accommodates three 12-Volt busbars and a Phidget 0/0/8 relay card (four relays).

One 12-Volt busbar connects directly with the speedbrake motor located above the TCM on the firewall of the throttle quadrant. This enables power for the movement of the speedbrake lever. The other two busbars are used to segregate and direct power to the motors that power the throttle and trim wheels.

The wires from the busbars are connected to five D-Sub connectors which are mounted to the front of the module. The five D-Sub connectors are individually labelled and colour coded to connect with the five straight-through cables that are connected to the Throttle Interface Module (TIM).

The four relays (on/off) are part of the logic that controls the functionality of the speedbrake. The logic being as follows:

(i) Speedbrake stowed;

(ii) Speedbrake armed;

(iii) Speedbrake armed annunciator (located on MIP); and,

(iv) Speedbrake deployed/engaged.

The inside of the TCM is essentially wiring, busbars and relays). Installing the busbars and wiring in the TCM makes more space available in the Throttle Interface Module

TCM - Interface Alert System

The TCM has a very basic Interface Alert System. This system forms part of the Interface Alert System which also includes the Throttle Interface Module (TIM).

The system comprises three coloured LEDS located on the forward side of the TCM. The coloured lights provide a reference to determine correct operation of the throttle.

TCM showing 3 leds and straight-through cables

A solid red coloured LED indicates that there is a complete connection between the throttle unit and the Throttle Interface Module (TIM). If the red light is not solid, this indicates that there is a connection/continuity problem located between he TCM and TIM. If the red light is solid – the flight can commence.

A solid green coloured LED indicates that the speedbrake logic is correct without a problem. Whenever the speedbrake lever is placed in the armed position or is in the UP position, the green LED will be solid. Failure of this light indicates that the speedbrake logic is not operating correctly.

The third purple coloured LED, which has the capacity to flash, indicates the status (on/off) of the 12-Volt actuator. The actuator, located on the captain-side of the throttle quadrant, controls the parking brake lever.

For additional information on the Interface Alert System Interface Alert System (IAS).