Created Thursday, Aug 24th 2023 12:50Z, last updated Wednesday, Sep 30th 2026 16:33Z
An ANZ Air New Zealand de Havilland Dash 8-300, registration ZK-NEM performing flight NZ-8199 from Wellington to Timaru (New Zealand) with 33 passengers and 3 crew, was descending towards Timaru when the crew descended below minimum safe height, detected their error and corrected. The aircraft continued for a safe landing on Timaru's runway 20 at 19:12L (07:12Z).
New Zealand's TAIC reported on Aug 24th 2023, that they have opened an investigation into the occurrence stating: "The reported circumstances were that at about 1937hrs on 13 June 2023, an Air New Zealand Bombardier passenger aircraft, ZK-NEM, descended below the minimum safe altitude for a sector during its approach into Timaru, New Zealand. The crew took corrective action when they became aware of the discrepancy and the flight was completed without further incident."
On Sep 30th 2026 the TAIC released their final report concluding the probable causes were:
- The flight crew was conducting an instrument approach at night when the aeroplane descended approximately 2500 ft below the correct profile and 1000 ft below the minimum safe altitude required for the runway 20 RNAV procedure at Timaru.
- Once aware of the aeroplane’s position in relation to the airfield, the captain adjusted the flight profile and continued the approach to land, rather than executing the missed approach procedure.
- It is virtually certain that the aircraft was descending in V/S mode because VNAV was not reselected following the transition altimeter checks.
- With vigilance and communication being reduced within the flight deck, it is likely that both flight crew members were experiencing reduced levels of alertness during the flight from Wellington to Timaru.
- DHC’s modification design change to fit the FMS into the Q300 specified that it would only be supplied with a baro-corrected altitude signal from the DADC. This inhibited the full functionality of the FMS that would have calculated a smooth descent through transition. Had the FMS also been provided with a pressure altitude signal, it is very unlikely that this incident would have occurred.
- The practice used by crew to manage the aeroplane’s vertical flight path through transition did not provide an adequate level of protection against the potential consequences of an automation mode selection error.
- It is virtually certain that the combination of a degraded instrument scan and fixation with visual acquisition of the airfield lights resulted in the crew not recognising the vertical deviation below profile until the aeroplane was almost 2500 ft below the intended flight path.
- Had either of the flight crew members been appropriately monitoring and crosschecking the aeroplane’s profile, it is very likely that the flight mode error would have been discovered and corrected before the vertical deviation from the intended flight path became as significant as it did.
- Crew resource management within the cockpit was not effective; this very likely contributed to the length of time that the error remained unnoticed by the flight crew and influenced the recovery action taken.
- The Commission considers it is very likely that inadequacies in the operator’s CRM training programme contributed to the flight crew’s performance during the descent into Timaru, specifically their collective inability to recognise the situation that was developing and take appropriate action to recover.
General findings
- It is very likely that the timeframe in which Air Nelson and Mount Cook were brought onto the operator’s operating certificate, and the subsequent impact of Covid-19, impacted the operator’s ability to appropriately recognise and address the differences in organisational culture within the Q300 fleet.
- The 2020 recertification of the operator’s operating certificate did not fully assess the implementation of the airline integration as intended.
- Following the CAA’s shift from compliance-based regulation to risk-based oversight, the CAA’s maturity in conducting risk-based oversight very likely contributed to CAA’s inability to identify and respond to the Q300 safety issues in a timely manner.
- The way in which both the integration and the subsequent AOC recertification were conducted, and evidence collected from CAA staff tasked with overseeing the operator, indicated a regulatory relationship that was too close in nature. It is likely this impeded the regulator’s ability to impartially oversee the operator’s safety management system.
- Most aircraft registered in New Zealand and used to conduct passenger or cargo operations in large and medium capacity aeroplanes, only have CVRs with a two-hour capacity. Managing the preservation of CVRs with such a small recording window is problematic and increases the likelihood that invaluable safety evidence will be overwritten and not available.
- The operator’s post-incident procedures at the time of the Timaru incident were not sufficiently robust to ensure that the CVR was preserved. This reduced the evidence available to the Commission to conduct its inquiry.
- At the time of the Timaru incident, the regulator’s inability to reliably triage reported aviation occurrences, and to notify the Commission of serious incidents as soon as practicable, inhibited the Commission’s ability to fulfil its statutory obligations to conduct independent inquiries to prevent future risk to transport safety in New Zealand.
The TAIC summarized the sequence of events:
The flight to Timaru was the final sector of a four-sector duty for the captain and a five-sector duty for the first officer. The two pilots had operated together from New Plymouth to Auckland, and then to Gisborne and Wellington before departing to Timaru. The departure, climb and cruise phases of the flight were uneventful.
Prior to leaving the cruise altitude of FL180 the flight crew prepared for arrival into Timaru. This included programming the RNAV arrival for runway 20 into the onboard flight management system (FMS).
At 1846, air traffic control (ATC) instructed the crew, ‘When ready, descend 11,000 feet, Canterbury QNH 1021.’ In preparation for the descent, the first officer wound the altitude alerter8 to 11,000 feet (ft).
At about 1855, ATC cleared the aeroplane to leave controlled airspace via waypoints ELDAK and SUNPA. Given that the autopilot was engaged in vertical navigation (VNAV) mode and there were no further altitude restrictions, the captain set the altitude alerter to 400 ft. At 1856 the aeroplane commenced descent toward Timaru.
Approximately two minutes after leaving FL180, the aeroplane reached the transition level. At this point the captain engaged the Vertical Speed (V/S) function of the autopilot flight director system. The subscales on all three altimeters were then changed from 1013 hectopascals (hPa) to 1021 hPa and the approach checklist was executed.
At 1901, the aircraft passed overhead ELDAK waypoint at approximately 11,000 ft. It was around this time that the captain, who was familiar with flying over the South Island at night, visually identified the city lights of Timaru and pointed these out to the first officer. Shortly after that, the first officer informed the captain that they could see the precision approach path indicators (PAPI) and aerodrome beacon.
At approximately 7000 ft, the captain reduced thrust in order to slow the aeroplane to 160 knots indicated airspeed (KIAS). The captain had not yet identified the runway lights, PAPI or aerodrome beacon. The first officer attempted to point out the PAPI to the captain, but the captain was unable to positively identify them.
The captain, who was having difficulty slowing the aeroplane, questioned whether there was a tailwind affecting their approach speed. At approximately 3500 ft, they instructed the first officer to increase the propeller revolutions per minute (RPM) to slow the aeroplane down, as the speed was still about 170 KIAS. The captain also asked the first officer to confirm that the runway lights were on. As Timaru aerodrome is an unattended airfield with no ATC, the first officer contacted the operator’s Timaru ground staff who stated that the runway lights were on and at full intensity.
While the first officer informed the captain that they could still see the PAPI, the captain was becoming increasingly concerned that they did not yet have any visual reference to Timaru aerodrome. The captain continued the approach and selected the landing gear down at approximately 1500 ft. At this point the aeroplane was crossing waypoint BUDPA, approximately 14 NM from Timaru aerodrome and 6 NM from waypoint SUNPA.
The RNAV approach for runway 20 contained minimum altitudes that had to be adhered to in order to ensure that the aeroplane remained at a safe distance from surrounding terrain (see Aerodrome information, paragraph 2.56). While the minimum safe altitude (MSA) on the direct track between ELDAK and Timaru was 1600 ft, the minimum initial approach altitude was 2000 ft. The clearance issued by Christchurch Control meant that NZ8199 could deviate from its flight plan track to commence the approach. However, in doing so the aircraft needed to remain above 2000 ft within 25 NM of waypoint SUNPA.
Within a few seconds of the landing gear being lowered, the captain commented to the first officer that the aeroplane appeared low in relation to their distance from Timaru and requested a reference height check. Before the first officer could respond, the captain checked the aeroplane’s lateral position on the electronic horizontal situation indicator (EHSI) and realised that the aeroplane still had approximately 3.5 NM to run before crossing waypoint SUNPA. The captain immediately realised the aeroplane must have descended below the VNAV profile. A check of the advisory display unit confirmed that the aeroplane was not in VNAV mode but descending in V/S mode at a rate of 1400 feet per minute (ft/min).
Upon realising that they were below the approach profile (at this point close to 2500 ft below), the captain levelled the aeroplane. Information from the flight data recorder (FDR) shows that the autopilot was disconnected at 1908:14 and approximately two seconds later engine torque increased. The aeroplane continued to descend to a lowest recorded altitude of 1156 ft (1022 ft above ground level) and then began a gentle climb. As the aeroplane was climbing, the captain sighted the PAPI and elected to continue the approach.
During the climb to re-establish the correct descent profile, the aeroplane crossed SUNPA at an altitude of 1668 ft. The captain continued the climb to 2000 ft, where the correct profile was regained, and proceeded to land without incident, touching down at 1913.
