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RCM-based risk criteria

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Devices that meet the following five criteria are potentially hazardous and could cause a serious, life-threatening injury if they are not subjected to timely periodic maintenance. The Task Force calls such devices PM Priority 1 devices. Because they are critical, high-risk devices they should be maintained according to the manufacturer’s recommendations and not included in an AEM program.

  1. The device could cause a serious, life-threatening injury if it stops working completely while it is in use. (Since this failure should be completely obvious to the user this is called an evident or overt failure). And
  2. The device has one or more components that must be periodically restored or replaced to prevent the device from stopping working completely. And/or
  3. The device could cause a serious, life-threatening injury if it develops a hidden failure (one that may not be obvious to the user but is detected when the device fails a safety test during a PM). And
  4. One or more of the device’s critical failure modes that has a PM-preventable cause has the potential to result in a serious, life-threatening injury. And
  5. This serious, life-threatening, PM-preventable failure is quite likely to occur within 75 years (i.e. with an MTBF <75 years).

The fifth criterion is important because, according to modern reliability and risk management theory, "risk" has two components;

  1. the severity of the outcome of the event (in this context a PM-preventable device failure); and
  2. the likelihood that the event (the PM-preventable device failure) will actually occur.

This is why traveling on a commercial airliner is considered to be safe. While there is a theoretical potential for a high-severity outcome if the plane should crash, the likelihood that this will actually happen is very low. And so, the level of risk when flying on a commercial airliner is also very low - relative to other ways of traveling.

There are four other defined levels of PM criticality (see Table 12) that have lower levels of PM-related risk. At this time, the Task Force recommends that devices showing these lower levels of PM-related risk be considered candidates for inclusion in an Alternative Equipment Management (AEM) program.

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