Aviation safety issues and actions

Guidance information on the limitations of FAID

Issue number: AO-2014-190-SI-16
Who it affects: All operators and flight crew: Air transport and general aviation
Issue owner: InterDynamics
Transport function: Aviation: Air transport
Background: Investigation Report AO-2009-072
Issue release date: 23 November 2017
Current issue status: Adequately addressed
Issue status justification:

The ATSB is satisfied that the safety action will reduce the risk associated with this safety issue.

Safety issue description

Guidance material associated with the FAID bio-mathematical model of fatigue did not provide information about the limitations of the model when applied to roster patterns involving minimal duty time or work in the previous 7 days.

Proactive Action

Action number: AO-2014-190-NSA-045
Action organisation: InterDynamics
Date: 23 November 2017
Action status: Closed

In October 2017, InterDynamics (the provider of FAID) published a document titled BMM Warning’ on its website (www.interdynamics.com). The document included the following statements:

Warning – know your biomathematical model and use it appropriately!

Not all biomathematical models are the same and will differ in their sensitivity to different work patterns and other parameters. The user of a biomathematical model should be familiar with how it works, what it is sensitive to, its strengths and weaknesses and suitability for evaluating the work context in question.


One of the strengths of the FAID biomathematical model is the inclusion of the accumulated contribution of work hours for the past 7 days. This component of the model is particularly helpful in highlighting the increasing fatigue exposure over consecutive work periods, particularly night work, as shown below.

FAID biomathematical model

However, this is also a weakness when evaluating very intermittent work periods or work periods immediately after a long break. As shown above the first night shift after multiple days break has a low score.

The document also noted the usefulness of another biomathematical model (provided by the same company) for evaluating intermittent work or work after long breaks.

InterDynamics advised the warning document would also be provided to all new licence holders.

Last update 02 December 2019