When the asset data is plotted as a line chart or bar chart, it is a simple representation of the description of the event. The accompanying figure shows the variation in the temperature of air, overlaying the different parts of the jet engine. In its simple form, this would be just a line graph without the asset. A slight variation can be a threshold to indicate that the value of temperature is above or below the expected range. APM often uses this form of descriptive analytics to alert an M&D center analyst when some asset behavior is drifting from the normal range. While this form of analytics is good for human-supervised scenario such as the M&D center, it may not often be high value addition, as it focuses on what happened, as it typically does not answer how and why questions.

Source: Transportation Safety Board of Canada (http://www.bst-tsb.gc.ca/eng/rapports-reports/aviation/2012/a12o0074/a12o0074.asp)