Embraer ERJ 170 FMS Error & Fatigue

An error programming the Flight Management System (FMS) on a flight to a zinc mine in the Northern Territory has been highlighted by the Australian Transport Safety Bureau (ATSB).

ATSB reports that Embraer ERJ 170 VH-ANO, operated by Airnorth, was flying from Darwin to the Glencore McArthur River Mine, Northern Territory. Shortly after passing navigational waypoint SNOOD, 125nm north-west of McArthur River Mine, the aircraft’s flight path started diverging from its planned track. Air traffic control detected this, advised the crew.  The aircraft landed safely at Arthur River Mine.  ATSB report that:

…while updating the aircraft’s flight management system for the descent into McArthur River Mine, the crew unintentionally omitted entering an intended navigational waypoint that was located 25nm north-west of McArthur River Mine. This omission resulted in the aircraft’s autopilot tracking the aircraft direct to the initial approach fix instead of first tracking to the intended waypoint. The crew’s crosschecking processes were not effective in identifying the data input error.

ATSB explain that:

The omission of the 25nm waypoint when entering data into the Multifunctional Control Display Unit (MCDU) was almost certainly a skill-based error. Omitting a step in a task is one of the most common types of human error (Reason 2002). There was insufficient information to determine if the omission on this occasion was due to a slip (error of execution) or a lapse (error of memory).

A range of conditions may have increased the likelihood of the crew not initially detecting the data input error on this occasion. These included:

    • The crew had flown the sector many times before without any similar problems, and probably had a high degree of expectancy that the programming task had been completed successfully.
    • The crew’s focus of attention was probably on the approach being used, which is something that can vary, rather than the 25nm waypoint, which is always the same. Similarly, when the captain conducted the approach briefing, the focus appeared to be on the approach rather than the flight path to the start of the approach.
    • The waypoint check when passing SNOOD was done soon after updating the FMS flight plan. This may have resulted in the crew having a high level of confidence at that time of the correctness of the waypoints. If there had been a longer delay before passing the next waypoint there may have been an increased level of vigilance associated with the waypoint check.

Fatigue / Alertness

ATSB also found that, the crew had restricted sleep in the previous 24 hours and so were probably experiencing a level of fatigue that is known to have an effect on human performance and alertness.  While the operator’s rostering was consistent with regulations, the ATSB say there were limited processes in place to proactively minimise the risk of fatigue, reporting that:

Airnorth advised that since the occurrence, the number of E170 flight crew has been augmented, increasing its rostering flexibility. Furthermore, due to schedule changes, the operator no longer used any roster pattern that resulted in planned rosters with flight crews receiving less than 10 hours time off duty overnight.

Although not in response to this occurrence, the Civil Aviation Safety Authority has released revised fatigue management and flight and duty time requirements in Civil Aviation Order (CAO) 48.1 Instrument 2013. These new requirements either require operators to have a fatigue risk management system, or operate to more restrictive requirements regarding minimum time off duty than those which previously applied.

Final Comment

ATSB also comment that:

This occurrence reinforces the importance of all pilots and operators conducting systematic and comprehensive checks of all data entered into flight management systems, and the importance of continually monitoring the effects of data input on an aircraft’s flight path.

UPDATE December 2014: A320 FMS Incident

ATSB has also now reported on another incident, involving an Airbus A320, VH-VNQ, on 15 February 2014, preparing to depart Hobart, Tasmania, for a flight to Melbourne, Victoria. In trying to clear an anomaly (the FMS was showing a RH turn after departure rather than the published LH turn), the take-off reference speeds and the flex temperature previously entered were inadvertently removed.  Attempts to replicate the anomaly seen in a simulator with same database were unsuccessful.  In this case fatigue was not a factor.  ATSB comment:

The operator’s investigation into the incident identified issues relating to the consistency of their before take-off checklist with that published by the aircraft manufacturer, and the status of the FMGS [Flight Management Guidance System] software installed in the flight simulators used by the operator. In response to the incident, the operator implemented a number of initiatives, including alignment of the before take-off checklist with that published by the aircraft manufacturer, implementation of a revised crew briefing format, provision of relevant educational material to flight crew and implementation of a flight simulator software upgrade.

For operators, this incident highlights the need for robust checklists and checklist management procedures that effectively cater for a wide range of operational scenarios, the importance of ensuring that the performance of training equipment accurately reflects the performance of operational equipment, and the importance of consistently accurate FMGS aeronautical data. For flight crew, this incident serves to highlight the importance of careful attention to FMGS aeronautical data and highlights the need for extra caution following an interruption to the normal sequence of events during preparation for departure. The incident also reinforces the importance of Airbus ‘Golden Rules for Pilots’, particularly the first rule: Fly, navigate and communicate (in this order and with appropriate task sharing).

UPDATE 20 October 2015: IATA have published a guide to: FMS Data Entry Error Prevention Best Practices

They say:

A total of 309 air safety reports (ASRs) involving FMS data entry error were identified in the IATA Global Aviation Data Management (GADM) / Safety Trend Evaluation, Analysis & Data Exchange System (STEADES) program between 2007 and 2011. …[equivalent to] approximately 2,377 global industry events over five years or one (1) event per day.

Analysis of the reports showed that errors related to navigational data, potential for a Mid Air Collision or Controlled Flight Into Terrain (CFIT) accident, accounted for 80% of the reports, while 20% were related to performance data and associated LOC-I or Runway Excursion accident. The analysis also shows that Air Traffic Control (ATC) related threats, cited in 27% of the reports, were the top contributor to FMS entry errors.

Other reported threats such as aircraft malfunction, cabin events, ground events and dispatch/paperwork provided further evidence that flight crew distraction during FMS programing, and in particular during the busy pre-flight phase, frequently contribute to data entry errors.

Significantly, in 44% of the reports these errors went unnoticed by the pilots due to failures in monitoring and cross-checking.

In 35% of all reports, flight path deviations were first recognized by ATC rather than by the pilots, indicating inadequate error recognition and management.

UPDATE 16 February 2017: Aerossurance is delighted to be sponsoring an RAeS HFG:E conference at Cranfield University on 9 May 2017, on the topic of Staying Alert: Managing Fatigue in Maintenance.  This event will feature presentations and interactive workshop sessions.

Aerossurance has extensive air safety, risk, accident analysis, human factors and regulation experience.  For practical advice you can trust, contact us at: enquiries@aerossurance.com