[Peetwo]

Number 18. from the list completed??

Head of ATSB YBBN office, Dr Walker presents: https://www.atsb.gov.au/media/news-items...d-practice

737 freighter failed to pressurise due to normalised but unauthorised practice



A 737 freighter aircraft failed to pressurise after a cargo depressurisation switch was left on during preflight preparations, an Australian Transport Safety Bureau report details.

The Boeing 737-36E SF (an aircraft built as a passenger airliner but subsequently converted to a freighter) was being operated by Airwork on a flight from Darwin to Brisbane on 4 November 2021.

After take-off, the flight crew observed the aircraft did not pressurise as expected. After stopping the climb at 11,000 ft, the flight crew began to descend to 10,000 ft, during which time a cabin altitude warning alert occurred.

Once at 10,000 ft, the crew completed required checklist actions, but were unable to establish control of the pressurisation. Subsequently the equipment cooling fan failed, the electronic flight information system reverted to a monochrome display output, and the weather radar failed.

The crew made the decision to return to Darwin for an uneventful landing.

“On arrival it was identified that the guarded cargo/depress switch was on,” ATSB’s Dr Michael Walker said.

“This switch was normally only used in the event of a main cargo deck smoke event, when it will depressurise the aircraft to assist smoke removal.”

The ATSB found the switch had been turned on by a maintenance engineer during pre-flight preparation, in an attempt to cool the flight deck. The engineer omitted to turn the switch off prior to completing their duties, and this was not identified by the flight crew.

“Using the switch in this manner was not authorised, but it had become normalised by the operator’s staff in Darwin, where there was no ground support equipment to provide external cooling,” Dr Walker said.

“Even though this practice had become normalised, there were insufficient risk controls in place to ensure that the aircraft would be returned to the correct configuration prior to departure.”

Additionally, the ATSB investigation found a pre-flight check of the switch was not incorporated into the operator’s flight crew operating manual, despite the aircraft’s cargo conversion operations manual stipulating it as a requirement.

Since the incident, the operator issued communications to its staff to immediately cease the unauthorised practice, and remind staff to only operate equipment in accordance with approved documentation.

Additionally, the operator commenced a review of operational documentation and completed incorporating the requirements of the operations manual supplement.

“This incident highlights the risks associated with undertaking unauthorised practices and using equipment in a manner other than for its intended purpose,” Dr Walker said.

“Without formal assessment of its efficacy or its potential for unintended consequences, combined with no documentation of training, there is no assurance that an unauthorised practice would be carried out consistently or safely.”

Read the final report: Cabin pressurisation issue involving Boeing B737-36E SF, ZK-FXK, near Darwin Airport, Northern Territory, on 4 November 2021

Publication Date
16/05/2023

On the face of it this was a relatively straight forward investigation, which besides the crew etc interviews, probably relied on a copy and paste review of the internal operator SMS investigation.

Although this investigation was listed as 'Defined' it did not have an associated preliminary report or an interim report on the anniversary date of the incident (IE Non-compliant with ICAO Annex 13). The investigation took 18 months and thirteen days.

The ATSB Aviation accident investigations webpage no longer brings an update to an investigation to the top of the page. Nor do the individual investigation webpages now have a date for the latest update or a share link.

So if it hadn't been for the Dr Walker media blurb you would have to troll back through 5 pages of ATSB AAIs to find out that the AO-2021-047 investigation had been completed to a final report. 

While on page 5 of the ATSB AAI webpages I discovered that recently (15/03/2023) there had been a discontinued investigation: 

Overview of the investigation

On 30 November 2021, a Boeing 777-300ER aircraft, registration A7-BED, was being operated by Qatar Airways on a scheduled passenger flight from Auckland, New Zealand, to Brisbane, Queensland. During the landing at Brisbane Airport, the aircraft veered off the runway.

The flight crew were conducting an instrument approach to runway 01R at night and the captain was the pilot flying. During the approach, the aircraft encountered heavy rain and turbulence. The crew reported that, at about 300 ft above the runway level and still in rain, they established and maintained clear visual reference to the runway lighting and surrounds, including the runway centreline and edge lights.

The crew stated that, passing about 200 ft, the first officer announced the aircraft was drifting right of the runway centreline. The captain corrected the deviation. As the aircraft was about to touchdown, under the influence of a variable and gusting crosswind, the aircraft drifted right again and the captain was unable to correct the drift before touchdown.

The aircraft landed to the right of the runway centreline and drifting to the right. Shortly after touchdown, the right main landing gear contacted and destroyed 4 runway edge lights positioned on the sealed runway strip, before the aircraft returned towards the runway centreline.

After the landing was completed and the aircraft had exited the runway, aircraft systems alerted the flight crew of low pressure in one on the right main landing gear tyres. The flight crew stopped the aircraft on the taxiway and requested an external inspection of the aircraft. Damage to 4 right main landing gear tyres was observed, and the aircraft was towed to the international terminal. There were no injuries to passengers or crew.

The ATSB received an initial occurrence report on 1 December 2021 and commenced an investigation on the same date.

As part of the investigation, the ATSB interviewed the flight crew and reviewed:

• data from the aircraft's flight data recorder and quick access recorder
  
• weather information
  
• recorded air traffic control audio and surveillance data
  
• information provided by the aircraft operator, including flight crew rosters and the fatigue risk management system.
  

[*]

The investigation identified the following:

• runway 01R is 45-m wide with a grooved surface and runway centreline lighting and runway edge lighting, and there were no problems noted with the runway lighting
  
• there were no notable faults with aircraft systems
  
• there were no notable concerns regarding the flight crew’s decision-making
  
• the flight crew likely maintained sight of the runway centreline and edge lights throughout the landing, and were able to detect the aircraft’s drift before touchdown
  
• there was a substantial lateral wind gust that changed direction and intensity when the aircraft was below 100 ft above ground level
  
• the captain reported feeling between ‘a little tired’ and ‘moderately tired’ after having less than normal sleep quantity and quality in the 2 nights before the flight
  
• the captain was probably experiencing a level of fatigue known to adversely influence performance due to limited sleep obtained in the previous 48 hours
  
• the flight crew’s flight and duty times and rest periods met the operator’s fatigue risk management requirements for at least the preceding 28 days and they had significant rest opportunity prior to a flight from Brisbane to Auckland on 29 November and the occurrence flight from Auckland to Brisbane on 30 November.
  

Reasons for the discontinuation

The ATSB strives to use its limited resources for maximum safety benefit, and considers that in this case it was unlikely that further investigation would identify any systemic safety issues or important safety lessons from this specific occurrence.

Consequently, the ATSB has discontinued this investigation. The evidence collected during this investigation remains available to be used in future investigations or safety studies. The ATSB will also monitor for any similar occurrences that may indicate a need to undertake a further safety investigation.

[*]
Next from Popinjay HQ, courtesy of this week's DTS Stewie McLeod :

Parking brake likely not fully released prior to rejected take-off



Key points

• Parking brake likely wasn’t fully released prior to taxiing for departure.
  
• Residual pressure in the braking system led to heat build-up and further application of the brakes.
  
• The flight crew’s swift decision to reject the take-off demonstrated their effective monitoring of the aircraft’s performance.
  

The flight crew of a Saab 340 rejected the take-off after experiencing handling and acceleration issues likely due to the parking brake not being fully released, an ATSB investigation details.

The Pel-Air operated Saab 340B, with 2 pilots, a cabin attendant and 25 passengers on board, was departing Flinders Island for Wynyard, Tasmania, as part of a multi-flight charter tour on 4 November last year.

As it accelerated, the aircraft veered to the left of the runway centreline and the crew detected a decrease in acceleration before rejecting the take-off.

Afterwards, the pilots observed significant tyre marks on the runway, a flat spotted tyre, and that all main landing gear tyres were flat.

“The ATSB investigation found that the parking brake handle had likely not been completely seated in the panel when released by the pilot, resulting in residual pressure remaining in the brake system,” ATSB Director Transport Safety Stuart Macleod said.

During the taxi to the runway, the residual pressure provided a partial application of the brakes, which allowed heat to generate within the brake system, resulting in further increased pressure and a continual increase in brake application.

“As the aircraft accelerated for take-off, this heat generation increased significantly, resulting in further application of the brakes.”

Since the occurrence, the operator has taken a number of safety actions to prevent a reoccurrence, including disseminating a Notice to Aircrew to its pilots with detailed information of the operation of the parking brake.

“This occurrence demonstrates the importance of completing routine tasks in accordance with manufacturer’s instructions,” Mr Macleod said.

“The outcome of this event, no passenger injuries and minimal aircraft damage, was a result of the flight crew’s effective monitoring of the aircraft’s performance and prompt action to reject the take-off when the expected performance was not achieved.”

Read the final report: Rejected take-off involving SAAB 340, VH-ZRC, Flinders Island Airport, Tasmania, 4 November 2022

Publication Date 17/05/2023

MTF...P2