Regional Express amends procedures after incidents in which pilots took manual control to restore flightpath.
Australian operator Regional Express is amending flight procedures following incidents in which Saab 340B turboprops drifted off their planned departure course after take-off.
One of these involved an aircraft departing Townsville for Hughenden on 19 November last year. It was supposed to fly the CATEY ONE instrument departure from runway 01, which requires passing the waypoint AGSIR and turning left to AVMAT.
The captain had programmed the flight-management system with the CATEY ONE pattern.
But the Australian Transport Safety Bureau says that, when the autopilot was engaged after take-off, the aircraft immediately attempted to deviate left from the intended track.
The crew disengaged the autopilot and operated the aircraft manually.
While the first active waypoint should have been AGSIR, some 2nm ahead after take-off, the first officer noticed that the flight-management system was instead indicating CATEY – the final waypoint in the pattern, located far behind the aircraft.
The crew also observed that, although the departure pattern waypoints were in the system, they had a “different appearance” and were “greyed out”, says the inquiry.
Attempts to re-sequence the departure pattern were unsuccessful.
The aircraft had passed beyond ASGIR and the crew requested radar vectors from air traffic control to return to the correct course, continuing to climb and re-engaging the autopilot in ‘heading’ mode for navigation.
Visual conditions prevailed throughout the incident and the flight – which had 18 occupants – safely proceeded to Hughenden.
But the inquiry has been unable to determine the reason for the deviation.
It says the the departure pattern “likely appeared as invalid data” within the flight-management system, which caused the unexpected turn towards CATEY – the first route waypoint for the flightpath to Hughenden.
Several scenarios were proposed, but ultimately discarded as improbable. There was no fault with the departure pattern in the operator’s flight-management system database and the system’s manufacturer could not replicate the symptoms.
The inquiry considered whether data entry into the flight-management system – which was programmed under external power – might not have been fully completed before the system was powered down during engine start.
“Without a download of the [flight-management system] or cockpit-voice recorder, further analysis was not possible,” says the inquiry.
It points out that Regional Express did not require verification of the programmed flightplan after engine start. The operator is amending its procedures in the aftermath of the incident.
Regional Express experienced a similar event in May this year, during a Saab 340B departure from Perth to Esperance.
Although the crew was issued with the LENVU ONE area navigation departure pattern – with the first waypoint HOVEA – the aircraft turned towards a different waypoint, LENVU, when the autopilot was engaged.
The captain has not realised before take-off that the flight-management system was not sequenced to HOVEA, after the first officer programmed it with the flightplan from LENVU to Esperance.
“The crew immediately intervened to correct the tracking,” says the safety bureau, adding that the pilots then sequenced the system to HOVEA.
“Data errors happen for many varied reasons,” it adds. “The [flight-management system] cannot identify data entry errors in all cases, and therefore it is the responsibility of the pilots to perform this critical function.”
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