Understand your FMS and cross-check instrument indications

The ATSB is reminding pilots of the need to fully understand their flight management systems and ensure they cross-check their flight instrumentation indications to remain on assigned flight path.

Cairns Airport, Queensland

The ATSB has completed the investigation into an operational non-compliance incident involving a GIE Avions De Transport Regional ATR72 at Cairns Airport.

On 4 September 2017, PNG Air charter flight CG950 was cleared for departure from runway 33 with via the CAIRNS TWO standard instrument departure (SID). This SID included an assigned heading component. The captain had not previously used a SID with an assigned heading component for a departure and selected the lateral navigation mode of the flight management system (FMS) for their initial departure.

The aircraft was cleared for take-off with an assigned heading of 335°M. The captain selected the heading bug to 335. The take-off was conducted as normal and as the aircraft climbed through 500 ft, the FMS, in lateral navigation mode, directed a right turn past the assigned heading. As the aircraft turned to 335°M, the FMS continued to command a right turn. The captain followed the FMS and reached a heading of 013°M.

To use an FMS effectively, flight crews need to have a thorough understanding of the system and the effect of each input and selection.

Upon identifying the deviation, the flight crew and air traffic control took immediate action to return the aircraft to its assigned flight path. The flight continued without further incident.

ATSB Executive Director of Transport Safety, Mr Nat Nagy, said the incident was a reminder to flight crews to ensure they use their FMS effectively and to cross-check their flight instrumentation.

“To use an FMS effectively, flight crews need to have a thorough understanding of the system and the effect of each input and selection,” Mr Nagy said.

“Flight crews also need to continuously cross-check their flight instruments and remain aware of the overall flight situation.

“You can never assume that an FMS route or course will be free from error.  Always remember to cross-check the instrument displays to ensure that all indications agree.”

Read the final report, AO-2017-091: Operational non-compliance involving GIE Avions De Transport Regional ATR72, P2-ATR, Cairns Airport, Queensland, 4 September 2017

For more information on the effective use of flight management system read the United States Federal Aviation Authority’s publication: Advanced Avionics Handbook, Chapter 4: Automated Flight Control.

Last update 04 May 2018