The Tiger Airways crew of a flight that descended below the minimum safe altitude on approach to Melbourne Airport on June 7 “did not notice” a disparity for that altitude between the paper approach chart they were using and the database in the aircraft’s FMGS (flight management guidance and envelope system), an ATSB preliminary report into the incident has found.
“The flightcrew did not notice that the documented arrival procedure had a lowest descent altitude of 2500ft, while the data from the FMGS’s navigational database that was displayed on the MCDU (multifunction control and display unit) had a lowest descent altitude of 2000ft,” the ATSB report, released on July 7, reads.
Tiger A320 VH-VNG was on approach to land at Melbourne at the end of a flight from Brisbane, and was conducting an ‘ARBEY ONE ALPHA’ arrival for Runway 27, with air traffic control clearing the aircraft to descend to 2500ft.
Details the report, “The PF (pilot flying) observed that the planned altitude was displayed as 2000ft on the MCDU, and set that altitude on the flight control unit (FCU) to descend the aircraft to 2000ft. The PF notified the PM (monitoring pilot) by calling ‘two thousand’ and the PM confirmed that the altitude was set to 2000ft.
“As the aircraft descended from 2500ft to 2000ft between waypoint PAULA and the Epping locator, the PM queried the altitude that was set on the FCU. The PF verified that altitude by referring to the displayed altitude in the MCDU. The aircraft was approaching 2000ft, when ATC advised the flightcrew that they should be at 2500ft and instructed them to climb to 2500ft.”
The aircraft then climbed back to its cleared altitude of 2500ft and continued its approach and landed at Melbourne without further incident.
Interestingly, the ATSB found that the “the navigational database that was current for the flight included a lowest descent altitude for the Melbourne ARBEY ONE ALPHA runway 27 arrival of 2000ft.”
The ATSB says the continuing investigation will include an “examination of the operator’s procedures” and “an investigation of the data management system for the navigational database”.
The June 7 incident was one of two where Tiger aircraft have flown lower than the minimum safe altitude on approach to land in recent times. The second incident, which took place on the evening of June 30 on approach to Avalon, was followed soon after by CASA moving to ground the airline. Media reports state that the same captain was in command during both incidents.
