Virgin Australia B738 at Cairns on Oct 24th 2022, descended below minimum safe height

Last Update: February 28, 2023 / 21:00:04 GMT/Zulu time

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Incident Facts

Date of incident
Oct 24, 2022

Classification
Incident

Airline
Virgin Australia

Flight number
VA-793

Departure
Brisbane, Australia

Destination
Cairns, Australia

Aircraft Registration
VH-VUT

Aircraft Type
Boeing 737-800

ICAO Type Designator
B738

A Virgin Australia Boeing 737-800, registration VH-VUT performing flight VA-793 from Brisbane,QL to Cairns,QL (Australia), was on a RNAV HENDY 8A standard instrument approach BARIA transition to Cairns when the aircraft descended below the minimum safe height with air traffic control issuing a low altitude warning to the crew and instructing them to return to safe altitude. The crew climbed back to safe altitude, commenced a missed approach and landed sfely on second approach.

The ATSB released their preliminary report summarizing the sequence of events:

At 1945 local time, the aircraft was cruising in darkness at flight level (FL)2 380 about 215 NM to the south of Cairns. At that time, air traffic control (ATC) provided the crew with clearance to conduct the Cairns HENDO 8Y standard arrival (STAR) via the BARIA waypoint3 transition.

The flight crew entered the HENDO 8Y STAR into the flight management computer (FMC) and selected the BARIA transition. The HENDO 8Y STAR progressed into the required navigation performance (RNP) Y instrument approach for runway 33 at Cairns. While clearance for the approach had not been provided at that time, the crew anticipated the clearance and loaded the approach into the FMC. From HENDO, the minimum altitude for commencing the RNP Y approach was 6,800 ft above mean sea level (AMSL). The HENDO waypoint was located within the 6,500 ft minimum sector altitude (MSA)4 segment to the south of Cairns.

The approach procedure had two different initial approach fixes (IAF) (Figure 2) with associated paths to a common intermediate fix (IF) at waypoint CS540. From the BASIL IAF, the approach proceeded via CS520, CS521 and CS523, and from the HENDO IAF via CS522 and CS523. In order to load either path into the FMC, the flight crew needed to select one of the two approach transitions.

The flight crew did not recognise that an approach transition selection was required and consequently did not select one. As a transition had not been selected, the FMC presented a discontinuity in the entered flight path at the HENDO waypoint (see the section titled Flight management computer). The flight crew misidentified the approach IF, CS540, as the IAF and resolved the FMC discontinuity by connecting HENDO to CS540. This selection removed the 6,800 ft descent altitude constraint associated with HENDO in the RNP approach programming.

At 1954, when the aircraft was 136 nm south of HENDO, ATC cleared the flight to track direct to the HENDO waypoint and 6 minutes later the crew commenced descending the aircraft. At 2010:51, when the aircraft was about 11 NM southeast of HENDO, ATC provided the crew with clearance to conduct the RNP Y runway 33 approach.

One minute later, the aircraft approached HENDO descending through about 7,300 ft with the autopilot engaged and an altitude of 6,800 ft selected in the autopilot mode control panel. At about that time, the captain selected the approach’s minimum descent altitude of 800 ft, but sensed that this selection was incorrect and therefore reselected an altitude of 6,800 ft. The captain then reviewed the approach briefing, confirmed that the aircraft was tracking as intended and the vertical navigation autopilot mode was active and again selected 800 ft.

At 2011:38, about 7 NM prior to crossing HENDO, the aircraft descended below 6,800 ft and 9 seconds later descended below the 6,500 ft MSA. Six seconds later, at 2011:53, ATC observed that the aircraft had descended below 6,800 ft and contacted the crew to confirm the aircraft’s altitude. The captain then reselected 6,800 ft and manually arrested the descent. ATC then issued a low altitude alert to the crew and advised them to climb immediately. Three seconds later, at 2012:07, the aircraft stopped descending at about 5,920 ft and then commenced a climb. At 2012:28, the aircraft climbed back above 6,800 ft. No ground proximity warning system alerts were generated during the incident.

A missed approach was then commenced, and the crew conducted a second approach without further incident.

Aircraft Registration Data

Registration mark

VH-VUT

Country of Registration

Australia

Date of Registration

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Airworthyness Category

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TCDS Ident. No.

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Manufacturer

THE BOEING COMPANY

Aircraft Model / Type

737-8FE

ICAO Aircraft Type

B738

Year of Manufacture

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Serial Number

JAige Subscribe to unlock

Maximum Take off Mass (MTOM) [kg]

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Engine Count

G Subscribe to unlock

Engine

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Main Owner

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Main Operator

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Incident Facts

Date of incident
Oct 24, 2022

Classification
Incident

Airline
Virgin Australia

Flight number
VA-793

Departure
Brisbane, Australia

Destination
Cairns, Australia

Aircraft Registration
VH-VUT

Aircraft Type
Boeing 737-800

ICAO Type Designator
B738

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Virgin Australia B738 at Cairns on Oct 24th 2022, descended below minimum safe height

Incident Facts

Aircraft Registration Data

Incident Facts

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