Tiger A320 at Melbourne on Jun 7th 2011, descended below minimum safe altitude

Last Update: November 20, 2012 / 15:20:55 GMT/Zulu time

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Photo of Tiger Airways VH-VNG, Airbus A320 — Tiger Airways VH-VNG, Airbus A320 (Photo credit: ZK-NGJ / Flickr / License: CC by-nd)

Incident Facts

Date of incident
Jun 7, 2011

Classification
Incident

Airline
Tiger Airways

Flight number
TR-5207

Departure
Brisbane, Australia

Destination
Melbourne, Australia

Aircraft Registration
VH-VNG

Aircraft Type
Airbus A320

ICAO Type Designator
A320

A Tiger Airways Airbus A320-200, registration VH-VNG performing flight TR-5207 from Brisbane,QL to Melbourne,VI (Australia), was on an instrument approach to Melbourne's runway 27 turning onto the base leg, when the aircraft descended to 2000 feet, which is below the minimum safe altitude of 2500 feet, before the aircraft climbed back to 2500 feet while turning final. The aircraft continued for a safe landing.

The Australian TSB opened an investigation into the "operational occurrence" (editorial note: suggesting the ATSB is looking into a possible ATC error).

On Jul 7th the ATSB released a first preliminary report stating, that the flight had been cleared for an Arbey One Alpha Arrival, the captain was pilot flying. For the following briefing of the approach the captain temporarily handed control of the aircraft to the first officer. The captain briefed the approach by reading the details of the approach from the MCDU, the first officer checked those details against the paper approach charts. The crew did not notice that the approach procedure's lowest descent altitude was 2500 feet while the data in the flight management system's navigation database displayed on the MCDU showed 2000 feet. The captain resumed control of the aircraft after the briefing was completed. The aircraft subsequently began the descent from FL380 and was at 2500 feet while on downwind. While turning from downwind to base the captain checked the altitude by looking at the displayed altitude at the MCDU, saw 2000 and selected an altitude of 2000 feet at the flight control unit (FCU) calling "2000", the first officer confirmed the altitude was set at 2000 feet. While the aircraft was descending to 2000 feet the first officer queried the altitude set on the FCU, the captain referred to the MCDU. When the aircraft was approaching 2000 feet ATC advised they should be at 2500 feet and instructed the crew to climb to 2500 feet. The investigation determined, that the FMS had been updated and using the current database which included a lowest descent altitude for Melbourne's Arbey One Alpha Arrival runway 27 of 2000 feet instead of the correct 2500 feet.

On Nov 19th 2012 the ATSB released their final report concluding the causes of the occurrence were:

- The aircraftÂ’s Flight Management and Guidance System database included incorrect data for the ARBEY ONE ALPHA arrival/runway 27 Instrument Landing System approach, increasing the risk that crews would descend below the published minima for the approach.

- The flight crewÂ’s pre-descent procedures did not identify the incorrect flight profile in the aircraftÂ’s Flight Management Guidance System.

- The pilot flying based the descent limit for the approach on the incorrect descent profile displayed on the Multipurpose Display and Control Unit, instead of the descent clearance that was provided by air traffic control (ATC), negating the ATC input as a safety defence.

- The inconsistent application of the operatorÂ’s safety management system to the identification and rectification of database anomalies, and intermittent notification of these anomalies to crews increased the risk of inadvertent flight crew non-compliance with published instrument approach procedures. [Significant safety issue]

- The operatorÂ’s lack of awareness of the data providersÂ’ assumption that the operator was complying with DO-200A Standards for Processing Aeronautical Data, which was not mandated in Australia, meant that the quality of the data was not assured. [Significant safety issue]

Other key finding

- Air traffic control intervened to alert the flight crew of their descent below minima, allowing them to re-establish their aircraft at the cleared altitude.

The ATSB reported the airline took immediate safety actions regarding database content and data integrity in response to the incident, the ATSB was satisfied with the actions, no safety recommendations were released.

Metars:
YMML 071300Z 26015KT 9999 VCSH FEW040 SCT055 BKN070 04/01 Q1016 FM1300 MOD TURB BLW 5000FT
YMML 071230Z 26015KT 9999 FEW040 SCT050 05/00 Q1016 FM1230 MOD TURB BLW 5000FT
YMML 071200Z 27015KT 9999 FEW040 SCT045 05/00 Q1016 RMK DIST RASH FM1200 MOD TURB BLW 5000FT
YMML 071130Z 27015KT 9999 SCT040 SCT055 05/01 Q1016 FM1130 MOD TURB BLW 5000FT
YMML 071100Z 27015KT 9999 FEW035 05/01 Q1016 FM1100 MOD TURB BLW 5000FT
YMML 071030Z 27013KT 9999 FEW035 05/01 Q1016 FM1030 MOD TURB BLW 5000FT
YMML 071000Z 28013KT 9999 FEW035 04/01 Q1016 FM1000 MOD TURB BLW 5000FT
YMML 070930Z 27014KT 9999 FEW035 SCT060 BKN140 05/01 Q1016 FM0930 MOD TURB BLW 5000FT
YMML 070900Z 27016KT 9999 FEW035 SCT120 05/01 Q1015 INTER 0900/0930 22022G36KT 3000 SHRAGS BKN015 FM0900 MOD TURB BLW 5000FT