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Functional Resonance Accident Model (FRAM)

Functional Resonance Accident Model – for the analysis of accidents

The functional resonance accident model (FRAM) is used for accident investigation to find the combination of conditions, actions and events that contributed to the accident. This method specifically focuses on a combination of events, actions and conditions. Thereby interconnected variations of normal functions are seen as cause of an accident rather than a real function failure. The variability of multiple functions can combine in unexpected ways. It goes also with an understanding that normal activities can never be prescribed or regulated completely. Conditions of work are always underspecified to allow a flexible and efficient working. So a good coping with situations is related much to the adjustment and ability of anticipating risks by organizations and individuals.

Starting the analysis requires the identification of the essential system functions. Base could be existing task analysis, procedures and expert knowledge. For each function the following characteristics are described:

  • Input (I)— start of the function
  • Output (O) — result of the function
  • Precondition (P) — conditions that must be fulfilled before the function starts
  • Resource (R) — needed by the function to produce the output
  • Time (T) — temporal constraints
  • Control (C) — monitoring and control of the function

Dependent on the function it may is described in several aspects each with the characteristics. The functions can be characterized in a table. Visualized the analysis could look like this for one function:


Source: Erik Hollnagel, Shawn Pruchnicki, Rogier Woltjer and Shawn Etcher, International Symposium of the Australian Aviation Psychology Association, 2008

In the second step the variability of the function in case of the accident is described. Also the interconnection of functions needs to be described, e.g. if the input for a function was not adequate then the function giving input must also be described.

Step three considers the couplings and dependencies between the functions. Graphically it is shown through linking the output of one function with the input of another function, see Figure below.


Source: Erik Hollnagel, Shawn Pruchnicki, Rogier Woltjer and Shawn Etcher, International Symposium of the Australian Aviation Psychology Association, 2008

Step four is more outcome related for the analysis, it identifies barriers for performance variations, comparable to quality checks that help to avoid unwanted events from happening. A barrier thereby can be an organizational structure or a physical structure, e.g. for cabling of a computer on the organizational level a checklist that needs to be during the cabling to ensure the correct cabling or on a physical level different types of cables so that no wrong ones can be connected. In the outcome of the analysis it may suggests barriers dependent on found couplings.

As an example for accident analysis the above introduced FRAM method is applied on the accident analysis of the Comair flight 5191. Comair flight 5191 was the first flight to start at the specific morning in 2006 at Lexington Airport. The airplane crashed after an unsuccessful takeoff. Unintentionally the pilot took the wrong runway, did not recognize it that this runway was shorter and not suitable for the type of airplane.

Usual functions involved before the turn into runway and takeoff:

  1. review of weather and airport data
  2. taxi briefing
  3. takeoff briefing
  4. clearance(s) from air traffic control (ATC)
  5. perform a taxi checklist
  6. taxi to runway
  7. perform a before takeoff checklist
  8. turn onto the runway

Pilot error was soon assumed as error, but other factors contributed which in another combination of events maybe could have avoided the accident.

Step one the review of weather and airport data reportedly was done by the pilot. The variance analysis revealed a deviation in this step. Due to constructions the usual taxi way to the runway (where the airplane speeds up and takes off) was not available and the taxi way changed. This information was part of a so called NOTAM (Notice To AirMan). A NOTAM is a notification of potential safety critical events along a flight route or at a location. It is distributed via telecommunication means to airman. Government agencies and airport operators generate and distribute them. One reason for a NOTAM is e.g. a closed runway. NOTAMs important for the specific flight are included in the flight release procedure. However in this case they were missing. A second source for this information failed as well, the NOTAMs are usually broadcasted by the terminal service information available on the special radio frequency. But this specific NOTAM of the taxiway closure was not part of the broadcast.

Graphically the function “review of weather and airport data” gets input at least from three sources, it looks like this:


Source: Erik Hollnagel, Shawn Pruchnicki, Rogier Woltjer and Shawn Etcher, International Symposium of the Australian Aviation Psychology Association, 2008

There was only one person at the tower and not two like an internal policy advises it. Usually when there are two operators in the tower one supervises the radar and the other one does the takeoff planning and communication with the airplanes, like checklists above. One person has more workload. He did not check during talk through of the checklists if the airplane was really at the transmitted position.

The pilot drove the airplane and the co-pilot (also called first officer) was busy meanwhile with the conversation with the tower as they went through the before takeoff check-list. At the stop line of the runway the first officer was not able to recheck the correct runway marking, he was not able to see from his position.

Another contributing factor was that the pilots used an outdated map of the airport. The changed taxiway was not correctly presented, even that would make the identification of the correct position at the airport difficult. Additionally resulting from the construction some of the taxiway and runway lighting systems were not functioning.

 Source: Erik Hollnagel, Shawn Pruchnicki, Rogier Woltjer and Shawn Etcher, International Symposium of the Australian Aviation Psychology Association, 2008

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