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Aircraft Condition Monitoring System (ACMS)

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Aircraft Health Monitoring Systems (AHMS)

Condition Based Maintenance (CBM)

Central Maintenance Computer System (CMCS)

Definition

An Aircraft Condition Monitoring System (ACMS) is a Predictive Maintenance tool consisting of a high capacity flight data acquisition unit and the associated sensors that sample, monitor, and record information and flight parameters from significant aircraft systems and components.

Condition Monitoring

Condition monitoring is a critical component of predictive maintenance. It is the process by which one or more parameters of a machine are either periodically measured, or continuously monitored, to identify significant changes that usually are indicative of a failure in progress. This allows the operator to plan maintenance actions focused on avoiding failures and their consequences. Continuous condition monitoring is most often applied to rotating machinery such as fans, compressors, pumps and combustion engines.

Sensor Types

Depending upon the piece of machinery or type of component concerned, there are a number of different parameters that can be measured or monitored. There are also a number of different types of sensor with which these measurements can be accomplished. Sensor types include, but are not limited to:

  • Vibration monitors - these are particularly relevant to rotating machinery such as engines, fans, compressors and generators. An increase in vibration can be indicative of an "out of balance" condition or the progressive failure of a shaft bearing
  • Temperature monitors - in the context of aircraft systems, there are numerous potential components subject to temperature monitoring. These include items such as engine oil temperature, bleed air temperature, both at the engine extraction point and at the user components such as the anti-ice system or the Pressurisation and Air Conditioning System (PACS), and engine exhaust gas temperature monitoring, most typically measured as one of Exhaust Gas Temperature (EGT), Turbine Inlet Temperature (TIT) or Interstage Turbine Temperature (ITT). Abnormal temperatures in any of these components can be indicative of a leak, blockage or a component failure, as appropriate to the monitored system
  • Pressure monitors - measurable parameters include engine oil pressure, hydraulic system pressure, bleed air duct pressure and aircraft cabin differential pressure. A change in a pressurisation parameter can be indicative of a progressive (or catastrophic) failure of a pump, duct or valve
  • Electrical Current measurement and analysis - many components of an aircraft electrical system can be monitored. Generator output, system (or individual bus) load and battery health are all measurable parameters
  • Speed ​​Measurement - in the context of condition monitoring, speed measurement most often refers to rotational speed as would be the case in an engine, fan, motor or generator. However, there is also merit in measuring other speed related parameters such as airspeed exceedances or component extension/retraction speeds

Monitoring Methodology

Data Download and Analysis

Advantages and Liabilities

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