Aviation safety investigations & reports

Flight path management and descent toward the lower limit of controlled airspace involving Airbus A320, VH-VND, on approach to Melbourne Airport, Victoria, on 11 February 2015

Investigation number:
AO-2015-018
Status: Completed
Investigation completed
Phase: Final report: Dissemination Read more information on this investigation phase

Final Report

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What happened

On 11 February 2015, an Airbus A320 aircraft, registered VH‑VND and operated by Tiger Airways, was conducting a scheduled passenger service from Hobart Airport, Tasmania to Melbourne Airport, Victoria.

At about 1750 Eastern Daylight-saving Time, about 9 NM (17 km) north of Melbourne Airport, and after the flight crew had been cleared by air traffic control to conduct a visual approach, the aircraft descended below the minimum safe altitude, though the aircraft remained in controlled airspace.

During the descent, both flight crew became pre-occupied with other tasks inside the flight deck, which had the effect of increasing their workload and distracting them from monitoring the aircraft’s flight path and altitude. About two minutes after commencing descent on the visual approach, the flight crew levelled the aircraft after realising that it appeared to be low on profile. A safety alert issued by air traffic control soon followed, where in response, the aircraft was climbed to intercept the recommended visual approach descent profile. The remainder of the flight was uneventful and the aircraft landed on runway 16 at Melbourne Airport.

What the ATSB found

The ATSB found that after being vectored off the expected pre-planned shortened arrival route, and then cleared for a visual approach, a combination of increased workload and distraction diverted the flight crew’s attention from monitoring the aircraft’s descent. During the descent, the captain elected to intercept the final approach course by entering a radial intercept waypoint into the aircraft’s auto-flight system, which differed from the first officer’s more familiar plan to conduct a localiser intercept. This had the effect of diverting both crew members’ attention to inside the flight deck, as they discussed and demonstrated the intercept and resulting flight mode reversions. The aircraft continued to descend below the normal approach profile and entered the 500 ft vertical buffer at the base of the control area step. This reduced separation with terrain and any aircraft operating outside controlled airspace.

The flight crew’s mental model of the approach was not consistent with the actual flight path of the aircraft. This affected their ability to fly a normal descent profile and remain within the required control area step.

The flight crew miscalculated and did not adequately communicate the aircraft’s descent from 3,000 ft during the conduct of a visual approach. This limited their awareness of the descent rate and the below-profile altitude of the aircraft during a critical phase of flight.

Safety message

Flight crew should be mindful that during higher workload phases of flight, such as during approach and landing, introducing tasks that divert both flight crew members’ attention from monitoring the aircraft’s flight profile and altitude should be minimised. Further, if tasks that bring attention into the flight deck are required to be completed during a visual approach, pilots must ensure that at least one pilot monitors the aircraft’s flight path profile and energy state. Setting an appropriate lower altitude limit may be an effective risk control to alert flight crew and/or prevent the aircraft’s descent below a desired altitude. Communication and confirmation of any changes to the aircraft’s flight modes are also important during this period.

Download final report
[Download  PDF: 1.23MB]
 
 
 

The occurrence

Context

Safety analysis

General details
Date: 11 February 2015   Investigation status: Completed  
Time: 17:52 ESuT   Investigation level: Complex - click for an explanation of investigation levels  
Location   (show map): 17 km NE of Melbourne Airport   Investigation phase: Final report: Dissemination  
State: Victoria   Occurrence type: Flight below minimum altitude  
Release date: 23 February 2018   Occurrence class: Operational  
Report status: Final   Occurrence category: Incident  
  Highest injury level: None  

Aircraft details

Aircraft details
Aircraft manufacturer Airbus  
Aircraft model A320-232  
Aircraft registration VH-VND  
Serial number 3296  
Operator Tiger Airways Australia  
Type of operation Air Transport High Capacity  
Sector Jet  
Damage to aircraft Nil  
Departure point Hobart, Tas.  
Destination Melbourne, Vic.  
Last update 14 November 2018