MARK II COMMUNICATIONS
MANAGEMENT UNIT (CMU)

P/N 965-0758-001

LINE MAINTENANCE GUIDE

Also Installed on the Aircraft.

Data Message Routing

Between 1 to 3 ARINC 739 CDUs (MCDUs or MIDUs) ARINC
ARINC

Annunciation (429 / Discrete)
Various Discrete and ARINC 429 Inputs Such as Doors Closed & Strut Switch (Varies with  A/C type)

Concept of Operation

The ACARS unit is used to send and receive data messages from the ground. The primary data link used by the ACARS is the VHF3 radio. The ACARS may also be connected to a Satellite Data Unit (SDU) as well as to an HF Data Unit (both of which are optional).
Avionics on board the aircraft such as DMU, CMC, FMC and Cabin terminals may be connected to ACARS for the purpose of sending messages to the ground. In addition, ACARS displays MCDU screens to the crew for the purpose of sending REQUESTS and Reports to the ground.
The ACARS also receives information such as Registration Number, from other avionics devices on the ARINC 429 bus as well as from discrete inputs.
Messages from the ground are sent to the ACARS unit. The ACARS unit will examine the message and either store the message or route it to other avionics depending on the destination encoded in the message. Uplink messages maintained by the ACARS unit are displayed on a RECEIVED MESSAGES MCDU screen. The crew can display or print the messages.
Typical ACARS configurations require little or no maintenance activity once installed with the appropriate software downloaded into memory. Software is downloaded using either the Airborne data Loader or Portable Data Loader or PCMCIA media.
Additional detailed information can be found in the ACARS CMU Component Maintenance Manual and the CMU Requirements Document.
CMU On-Aircraft Installation
The installation of the CMU should be performed in two stages:
1.
First Stage – install the hardware in the electronic bay.

2.
Second Stage – verify that the unit performs its power up and the green light is activated.

Following installation of the CMU, an inspection of the CMU configuration using the MCDU screen should be performed as follows:
1.
Review CMU part numbers on maintenance MCDU screens (see Software Configuration Check)

2.
If software part numbers are incorrect, load new software (see Software Installation)

An optional, functional check can be performed to ensure the VHF link is operational.  This test is performed by conducting a link test (see Link Test).

CMU Front Panel

Reset button (cold start)
Reset switch is used to restart the CMU. It will result in a cold start which will delete any existing messages store in the CMU memory.
Mark II CMU front panel LED definitions
　
中國航空網 www.k6050.com
航空翻譯 www.aviation.cn
本文鏈接地址：MARK II COMMUNICATIONS MANAGEMENT UNIT (CMU) 通訊管理裝置 LINE MAINTENANCE GUIDE 航線維護指南