Aircraft Maintenance Systems Quiz

On Board Maintenance System (ATA 45)

• The system is a component of the aircraft's integrated digital avionic system
• It aids in troubleshooting and maintaining the avionic system
• The system ranges from basic indicators to intricate setups that link laptops to system parameters and fault data
• The system includes central maintenance computers, data loading systems, electronic libraries, and printing capabilities
• Structure monitoring (damage tolerance) is another element of the system
• Health Usage Monitoring System (HUMS) is also a component

Maintenance Definition

• Aircraft service and safety depend on task certificates
• Maintenance involves seven tasks: Modification, Overhaul, Repair, Replacement, Inspection, and Testing

Aircraft Types

• Old generation Boeing aircraft: B737-200 (Jurassic), B737-300/400/500 (Classic)
• New generation Boeing aircraft: B737-600/700/800/900, B737-8/9/10 (MAX)

Purpose of Onboard Maintenance System (OMS)

• Aims to troubleshoot and maintain the aircraft's integrated digital avionic system
• Includes a diverse array of systems, from basic magnetic indicators on Line Replaceable Units (LRUs) to complex systems enabling engineers to download system parameters and fault data using laptops

Acquisition of Aircraft System Data

• Electronic Centralized Aircraft Monitoring (ECAM) system monitors operational data and displays warnings/system info
• Flight Data Recording System (FDRS) records aircraft operational parameters for incident investigation
• Central Maintenance System (CMS) monitors and records the system's Basic In-test Equipment (BITE) data and failures
• Aircraft Condition Monitoring System (ACMS) records significant operational parameters for engine and aircraft performance analysis and problem detection

Consolidation

• In normal operation, the ECAM shows normal aircraft parameters, while ACMS and FDRS log aircraft system parameters
• When an anomaly occurs, the ECAM displays the abnormal parameter and the CMS records the failure with the BITE report

Analysis of Maintenance Operations

• Maintenance is categorized into three groups:
  • Minor troubleshooting is performed using the ECAM/CMS via MCDU and printed/downlinked ACARS reports
  • In-depth troubleshooting utilizes the CMS and ACMS through MCDU and printed reports
  • Long-term maintenance employs the ACMS/FDRS, incorporating printed, downlinked ACARS, and downloaded reports/recorded tapes

Central Maintenance Computing System (CMCS)

• Collects and stores maintenance data for most airplane systems
• The Maintenance Access Terminal (MAT) or Portable Maintenance Access Terminal (PMAT)/Laptop provides access to maintenance functions based on task type

CMCS Functions

• Includes fault processing, testing, and data loading
• Facilitates fault history, input monitoring, configuration reporting, shop faults, engine balancing, proximity sensor electronic unit functions, and air/ground rigging report generation
• Monitors Flight Deck Effect (FDE) activity
• Matches applicable FDEs and maintenance messages

Flight Deck Effects (FDEs)

• Visual cues on the primary displays inform flight and ground crews about system or function loss requiring repair or deferral

Fault Isolation Manual (FIM)

• Includes tables of fault codes and corresponding tasks for troubleshooting

Data Loading

• The Central Maintenance Computing Function (CMCF) in the AIMS cabinets provides data load display formats for selection of the data source and destination.
• The source can be a hard disk file or disk in the disk drive.
• Data destinations include ARINC 429 LRU, LRU on a system or flight controls 629 bus, or LRM in the AIMS cabinet.
• Data is transmitted from the MAT to the appropriate component through the Ethernet interface to the Core Processor Module/Communication (CPM/COMM) in the left AIMS cabinets.

Built-In Test Equipment (BITE)

• BITE is a system composed of Line Replaceable Units (LRUs), which can be computers, sensors, actuators, or probes.
• Most LRUs are controlled digitally.
• BITE permanently monitors LRUs, allowing for testing and troubleshooting.
• In each system, a computer component is dedicated to these functions, thereby becoming BITE.
• BITE continually monitors systems, recording faults for recall by flight crew or maintenance personnel.
• After repairs, the BITE system can be reset.
• Most BITE systems accurately isolate system faults on the first attempt with a 95% likelihood.
• BITE conducts two types of testing: Operational and Maintenance tests.

BITE Forms

• Power-Up BITE (PUBIT): Checks power supplies, processors, RAM, and loads operating software
• Interruptive BITE (IBIT): Inject signals into system channels to detect malfunctions, also known as Ground Test.
• Continuous BITE (CBIT): Monitors system components (command & monitor, or standby channels); if error, reports data to aircraft main computer

Status Message

• Displays system function status.
• Aircrew will not have immediate access, but will do so when alerted.
• Necessary for dispatch.

Maintenance Message

• Set by the CMC (Central Maintenance Computer) after a fault is detected.
• Indicates the ATA chapter of the fault, and is not displayed to aircrew, but only to ground engineers.

Fault Code

• Indicates the failed LRU and related correlation procedures.
• Not displayed to aircrew.

Memo Message

• Allows the aircrew to see reminders of operational systems (e.g., APU running, parking brake on).

Maintenance Memo

• Issued for insignificant failures with sufficient backups, allowing flight to continue until next scheduled maintenance.
• Airbus uses the term "Fault Message"

ATA 45 - Central Maintenance System (CMS)

• The latest BITE technology is centralized to a computer, the Central Maintenance Computer (CMC), as the foundation for all on-board maintenance systems.
• This centralization led to ATA 45, focusing on Central Maintenance Systems (CMS). Airbus uses a similar approach called Centralized Fault Display System (CFDS).

Fault Correlation

• Fault correlation involves linking together Flight Deck Effect (FDE) and maintenance messages.
• Ground engineers must associate the FDE with CMC-generated messages.

Fault Processing

• The Central Maintenance Computing Function (CMCF) can process up to 5,000 fault reports per second, storing and processing reports.
• The CMCF verifies the fault reports' accuracy and whether the relevant LRUs are active.
• Filters handle fault reports during power-up/engine start/shutdown.

Cascade Effect

• If a key component, like the IRS, fails, it can trigger cascading failures throughout other systems.
• Fault data processing groups fault reports into categories and links them to single maintenance messages for convenient troubleshooting.

Categories of Defect

• Immediate Effect; requires immediate resolution
• Delayed Effect; requires moderate speed repair
• No Effect; can be corrected during next hangar schedule

System Failure Classes

• Class 1: Operational consequences during current flight, displayed as warnings on ECAM and MCDU; potential "no-go" or "go" status based on MEL (Minimum Equipment List).
• Class 2: No operational impact on current flight; identified on ECAM status page.
• Class 3: Neither operational nor safety consequences; visible only on ground through the MCDU.

Aeroplane Condition Monitoring System (ACMS)

• Collects all system data, monitors performance, records abnormalities, and distributes data for analysis
• ACMS reports aid in system trend analysis, identifying and preventing component deterioration.

Data Management Unit (DMU)

• A powerful data processor that lets airlines customize their ACMS programs.
• Collects data from diverse aircraft systems and onboard computers (e.g., flight/central management computers, air data computers, fuel, navigation).
• Processes data into reports based on user requests for various output destinations (quick access recorder, control display unit, data loader, multi-input printer, ACARS).

Standard Reports

• Includes various reports like weather, engine/APU start/fail/trend, ground run-ups, EGT divergence, maintenance reports, and more.

Health and Usage Monitoring System (HUMS)

• A system designed to enhance helicopter airworthiness, reliability, and effective maintenance management.
• Identifies detected/diagnosed operating and external environmental data.
• Monitors critical components, providing warnings before failures occur and collects data for routine maintenance.
• Data processing can be done onboard, remotely, or both.

HUMS Main Functions

• Detects damage areas (rotor, engine, transmission, gear box)
• Rotor Track & Balance (RTB)
• Rotor vibration health & monitoring
• Drive train/transmission vibration health & monitoring
• Engine & airframe vibration monitoring
• Logbook accuracy and improved flight hour management
• Data analysis and diagnostics/prognosis on ground after flight

HUMS Main Components

• DAPU (Data Acquisition and Processing Unit)
• CQAR (Card Quick Access Recorder)
• PIP (Pilot Interface Panel)
• GS (Ground Station)
• PBT (Permanent Blade Tracker)
• Sensors

System Operation

• HUM System monitors parameters like engine speed, temperature, pressure, torque, acceleration, vibration levels, and stress to gearboxes and transmission train.
• Sensor output is digitally formatted and stored in non-volatile memory until the end of flight.
• Data is extracted by a Data Transfer Unit (DTU).
• The processed data is sent to a Ground Station for analysis and potential maintenance action.
• Condition-based servicing can identify potential issues before failure occurs.

Test your knowledge on key aircraft maintenance systems such as the Flight Data Recording System (FDRS) and the Central Maintenance Computing System (CMCS). This quiz covers their functions, interactions, and vital components. Ideal for aviation students and professionals seeking to deepen their understanding of aircraft maintenance operations.