ON BOARD MAINTENANCE SYSTEM (OBMS)

ON BOARD MAINTENANCE SYSTEM (OBMS)

This is a system found in modern larger commercial aircraft that integrates all required information forming the basis of generating maintenance guidance, trouble shooting information on faults.

System has a panel, called Maintenance Panel, normally located behind the first officer (also called Lateral Panel). The complete lateral/maintenance panel is divided into different system panels. Each system maintenance panel has dedicated bite/test knobs, system instruments, anunciator lights.

OBMS computers centralizes data from system sensors, processes those data to find faults/failure ranges and keep the fault in non-volatile memory. Centrally there displays a BITE light whenever there is a FAULT light in the local panel of any system. This display of BITE light in the OBMS panel, in conjunction with FAULT light in the local panel means that the fault has been codified by the OBMS and stored in the BITE software. Now, when BITE switches in the corresponding maintenance panel is to be positioned to the test and BITE position. DBMS computer will then send codes on the dedicated CRTs or ECAM CRTs. The codes are to be taken out to decode and follow the trouble shooting manual.

This panel is primarily intended to be used by maintenance personnel as an assistance in the performance of system maintenance. Normally only component condition memory indicator lights are installed. The memory indicators are illuminated if the maintenance panel switch ANN LT is in the READ position and if a signal has been stored.

For example, in a typical engine with FADEC system, there is a FADEC BITE panel in the OBMS panel (Figure 1.10). When ever there is a FADEC fault, OBMS BITE light comes on, meaning that a fault on FADEC has been stored in the NVM. To trouble shoot the fault (including normal test), FADEC BITE test is carried out.

Placing the BITE switch of any engine to test position, status data received by the EEC of FADEC system is transmitted to the ECAM CRTs. Placing the BITE switch to the BITE Display position causes maintenance words in hexadecimal code on the L CRT (Figure 1.11, 1.12).

Hexadecimal words are taken to convert into label-bit through conversion chart and ultimately fault code will be obtained that helps tracing a trouble shooting tree in the trouble shooting manual.