BY ORDER OF THE AIR FORCE PAMPHLET 91-215 SECRETARY ...

A2.C.7. THE MULTILINEAR EVENTS SEQUENCING TOOL
A2.C.7.1. FORMAL NAME. The multilinear events sequencing tool
A2.C.7.2. ALTERNATIVE NAMES. The timeline tool, the sequential time event plot (STEP)
A2.C.7.3. PURPOSE. The multilinear events sequencing tool (MES) is a highly specialized hazard ID
procedure designed to detect hazards arising from the time relationship of various operational activities.
The MES detects situations in which either the absolute timing of events or the relational timing of events
may create risk. For example, an operational planner may have crammed too many events into a single
period of time, creating a task overload problem for the personnel involved. Alternatively, the MES may
reveal that two or more events in an operational plan conflict because a person or piece of equipment is
required for both but obviously can’t be in two places at once. The MES can be used as a hazard ID tool
or as a mishap investigation tool.
A2.C.7.4. APPLICATION. The MES is usually considered a professional loss prevention level tool, but
the MES worksheet actually simplifies the process to the point that a motivated individual can effectively
use the tool. The MES should be used any time that risk levels are significant and when timing and/or time
relationships may be a source of risk. It is almost an essential tool when the time relationships are
relatively complex.
A2.C.7.5. METHOD. The MES is accomplished using a worksheet similar to the one illustrated at Figure
A2.43. The sample worksheet displays the timeline of the operation across the top and the “actors”
(people or things) down the left side. Notice that in some operations the timeline may literally be broken
down in seconds. The flow of events is then displayed on the worksheet showing the relationship between
the actors on a time basis. Once the operation is displayed on the worksheet, the sources of risk will be
evident as the flow is examined.
Figure A2.43. Multi-linear Events Sequencing Form.
Timeline (Time units in seconds or minutes as needed)
Actors
(People or
things involved
in the process)
A2.C.7.6. RESOURCES. The best sources for more detailed information on the MES is the local safety
staff. As with the other more advanced tools, using the MES will normally involve consultation with a
safety professional familiar with its application.
A2.C.7.7. COMMENTS. The MES is unique in its role of examining the time-risk implications of
operations.
93