Description

On 7 June 2022, when a Boeing 737-400F (ZK-TLL) operated by Airwork on a scheduled night freight service from Sydney to Auckland was being used for line training overseen by a 73 year old Training Captain. After landing at Auckland, a fuel low pressure warning indicated that only minimal fuel remained in the wing tanks because the crew had forgotten to select the centre tank prior to takeoff or subsequently notice the oversight. It was also found that despite adverse forecast meteorological conditions at both Auckland and at nominated alternates resulting in a requirement to operate the flight in accordance with the applicable ‘Extended Diversion Time Operations’ EDTO, this had not happened.

Investigation

The aircraft operator did not notify the Serious Incident to the New Zealand Transport Accident Investigation Commission (TAIC) directly and took two days to report it to the New Zealand CAA and the Australian Transport Safety Bureau (ATSB). The TAIC remained unaware of it until advised of it by the ATSB a week after it had occurred by which time the relevant CVR and FDR data had been overwritten.

It was noted that the 73 year-old Training Captain in command had a total of 29,000 hours flying experience, the most recent ten years of which had been night cargo flights for their current airline. Their total flying experience included 10,000 hours on type and they were nominated by the Operator as “the senior person for competency assessment”. The 37 year-old First Officer had a total of 4,500 hours flying experience and, although new to the Boeing 737-400, this experience included 700 hours on another variant of the type. He was re-commencing line training after failing a Final Line Check with the same Captain six days earlier since when he had been off sick for one day and had then had four days off.  

What Happened

The Operator’s OCC Dispatcher generated a weather briefing and flight plans for the Auckland-Sydney-Auckland night rotation an hour prior to the flight crew report time. The Flight Plan for the return sector gave Palmerston North as the alternate and Sydney and Auckland as the EDTO alternates.

The outbound flight left Auckland early but arrived at Sydney late due to strong headwinds en-route with just under an hour remaining before an Australian Government-imposed curfew came into effect at 0100. During the turnround, an email from the OCC advised of fog forecast at Auckland but did not provide updated TAFs for Auckland or the FPL alternates. The Captain decided to add 1,000kg additional fuel to the previously planned departure uplift.

On requesting pushback, ATC advised that departure would be from 16R rather than the expected and planned for 16L due to noise abatement priorities which slightly delayed departure and interrupted the running of the ‘Before Start’ Checklist and the switching on of the centre tank fuel pumps was missed. The flight eventually got airborne two minutes after the start of the curfew. The return sector flight time was reduced by a significant tailwind component to 1 hour 38 minutes and the flight was able to make an approach without any weather-related delay after an improvement from the conditions which had resulted in the aircraft ahead to land making two unsuccessful approaches before diverting to Christchurch. En-route fuel checks were conducted but were based on the FMC rather than the fuel tank contents gauges which was reportedly “normal practice”. It was noted that the OM specified that fuel checks should be carried out but did not make any mention of fuel distribution (this 737 variant does not have an EICAS).

At the time of the first and only approach by the flight under investigation was made, the fluctuating visibility was improving but given that the Captain’s recollection of only 640 kg of fuel had remained in the main tanks on engine shutdown, and that typical go around and immediate further approach would use that amount of fuel, it was clear that had a go around been flown, fuel exhaustion and engine failure would have been “very likely” as the workload during such a manoeuvre would probably have precluded recognition of the centre tank fuel pump error. The Captain involved recognised this and commented that “the risk that we put ourselves in by not turning those pumps on was that had we had to do a go-around we’d put ourselves in a situation that may have been critical”.

B737-400 overhead panel with fuel panel highlighted [from final report]

Why It Happened

The immediate cause of a potential accident was the unintentional failure to facilitate use of the centre tank fuel primarily attributable to a failure to perform routine checklists properly. That this occurred during a flight being used for line training was not highlighted by the Investigation, nor was the advanced age of the Captain given New Zealand is a jurisdiction where there is no age limit if a Class 1 Medical can be successfully renewed.

The wider issue, however, was that the flight plan involved was not in accordance with the applicable EDTO regulations and the fact that this was unlikely to have been a ‘one-off’. The Operator was, on the evidence collected, quite clearly at fault in not supporting the flight crew with sufficient current weather-related information to determine an appropriate fuel load and to validate both the intended destination and the FPL alternates against the latest available weather reports and forecasts. Quite apart from the crew checklist failures, the evidence collected on what actually happened compared to EDTO regulations in respect of determining the basis for the departure fuel load was flawed. The OCC flight support reality simply did not match the Operator’s corresponding regulatory filing. Nevertheless, it was noted that the commander of an aircraft remains ultimately responsible for the procedural compliance of their flight regardless of any deficiencies in Operator support.

The Findings of the Investigation were formally documented as follows:

1. The flight crew omitted to turn on the centre fuel pumps before starting the aircraft and did not detect that the fuel in the centre tank had not been used until after landing in Auckland when a main fuel pump low pressure light illuminated.
2. The requirement to re-programme and re-plan their departure due to a runway change and the approaching 0100 (Australian) government (flight) curfew added to the pressure the flight crew were under and very likely contributed to distraction when they were completing the ‘Before Start’ checklist.
3. If the aircraft had flown a go-around from the approach into Auckland, it is likely that the fuel (remaining) in the main tanks would have been exhausted during the manoeuvre.
4. The Operator’s OCC staff did not provide updated weather forecasts or flight plans to the crew prior to Extended Diversion Time Operation (EDTO) sectors as required by the operator’s OCC Manual.
5. The flight under investigation and one of the Operator’s’ other flights that night both departed for Auckland with flight plans in which nominated destination and EDTO alternates that were not compliant with regulatory or company flight planning requirements.
6. A Regulatory Audit identified deficiencies in the operator’s SMS both before and after the occurrence. The New Zealand CAA is monitoring the implementation of the corrective actions taken by the Operator to progressively address these deficiencies.

Safety Issues 
Four Safety Issues were documented by the Investigation as follows:

1. Centre Tank Fuel Pumps not switched on
   The centre (tank) fuel pumps were not switched on as required by the ‘Before Start Checks’ and this omission was not captured by the crew completing the Checklist. If not detected, this omission has the potential to cause fuel starvation in the engines, increasing the risk of an accident occurring. 
   In response, the Operator has amended the corresponding Checklist and added EDTO elements to FFS training exercises.
2. Flight operations support by their OCC not in accordance with the Operator’s declaration
   OCC staff did not provide flight support in the form of updated weather forecasts for aerodromes or flight plans in accordance with the operator’s declaration. The absence of current and relevant information can affect a flight crew’s performance and the safety of a flight.
   Early in 2023, the Operator enhanced the provision of new weather forecasts and NOTAMS to the OCC which facilitated timely advice of same to flight crew.
3. Flight crew responsibility 
   The flight crew on the operator’s two flights departing Sydney on 7 June 2022 (which included the one under investigation) did so on flight plans that did not comply with either the Operator’s or the Regulator’s alternate and EDTO fuel and planning requirements. 
   An aircraft commander is ultimately personally responsible for ensuring that their submitted flight plans meet both Company and Regulatory requirements. 
4. Regulatory Oversight
   The Regulator’s oversight and auditing of the Operator identified deficiencies in the Operator’s SMS that have yet to be fully addressed. The Regulator has a role in ensuring that deficiencies in an Operator’s SMS are addressed to reduce the risk of accidents occurring.  
   The New Zealand CAA created a detailed monitoring programme for the operator for 2024 which outlined suggested monitoring activities covering the management of safety, en-route audits, EDTO operations and other operational aspects which allowed it to review ongoing work to resolve previous audit findings with the Operator.

Three ‘Key Lessons’ from the Investigation were documented as follows:

• Pilots need to devote their full attention to ensuring that procedures, checklists and en-route checks involving critical aircraft systems are completed with rigour and be aware of potential distractions.
• Ground-based operational staff provide essential support to flight crew on extended range flights and need to be skilled and proficient in following the procedures detailed in their manuals (so as) to provide the support that flight crew require.
• Pilots should ensure that submitted flight plans for their flights are compliant with Operator and Regulatory procedures for alternate aerodrome nominations so that they adhere to this critical safety factor in the planning process.

The Final Report was approved for publication by the Commission on 26 September 2024 and published on 27 November 2024. On the basis of the responses to all four Safety Issues, the Investigation concluded that no Safety Recommendations were required.

Related Articles

• Aircraft Fuel Systems
• Extended Range Operations
• Fuel Exhaustion
• Fuel - Diversion to Weather Alternate
• Weather Forecast
• Checklists - Purpose and Use
• Flight Plan
• Flight Plan Completion