DH2 Beaver Accident ATSB Prelim Report

General stuff that gets thrown about when Pilots shoot the Breeze.
ozloadie
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DH2 Beaver Accident ATSB Prelim Report

Postby ozloadie » Wed Jan 03, 2018 11:06 am

ATSB Investigation number: AO-2017-118
The above report is now published, the intentions of the recovery team being to lift the wreckage as wholly as possible towards the end of this week.
There are no obvious indications at this stage as to why the accident occurred.
Hopefully the reasons will be established.
Thoughts go out to all.

Steve
ozloadie
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Re: DH2 Beaver Accident ATSB Prelim Report

Postby ozloadie » Wed Jan 31, 2018 12:56 pm

Fornal ATSB prelim Report has now been published.
ozloadie
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Re: DH2 Beaver Accident ATSB Prelim Report

Postby ozloadie » Thu May 17, 2018 1:04 am

Investigation number: AO-2017-118
Still active.
ozloadie
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Re: DH2 Beaver Accident ATSB Prelim Report

Postby ozloadie » Thu Feb 04, 2021 8:48 pm

Final report and findings:
Collision with water involving a de Havilland Canada DHC-2 Beaver aircraft, VH‑NOO, at Jerusalem Bay, Hawkesbury River, NSW on 31 December 2017
Investigation number:
AO-2017-118
Status: Completed Investigation completed
Phase: Final report: Dissemination Read more information on this investigation phase
TAB - FINAL
TAB - SAFETY ISSUES
Final
Download Final report
[Download PDF: 8.44MB]
Listen to this PDF
Alternate: [Download DOCX: 85.62MB]

What happened
On the afternoon of 31 December 2017, the pilot and five passengers of a de Havilland Canada DHC-2 Beaver floatplane, registered VH-NOO, boarded the aircraft for a return charter flight from Cottage Point to Rose Bay, New South Wales. Shortly after take-off, the aircraft conducted a 270° right turn in Cowan Water and then entered Jerusalem Bay, below the height of the terrain. The aircraft stopped climbing, continued along the bay and then made a very steep right turn. The aircraft’s nose then dropped and the aircraft collided with the water. All on board were fatally injured and the aircraft destroyed.

What the ATSB found
The ATSB found that some of the circumstances regarding the accident were unexpected given the nature of the operations and the pilot’s significant level of experience. Specifically, the aircraft entered a known confined area (Jerusalem Bay) below the height of the terrain, with no need to be operating in the bay; the aircraft did not continue to climb despite being in the climb configuration; the aircraft was capable of turning within the bay, it could have been turned earlier, and there was sufficient distance remaining to land at the position of the steep turn; and a steep turn was performed at low‑level and at a bank angle in excess of what was required. It was established that pilot control column and rudder inputs were necessary to travel at least half-way through the final steep turn as observed. However, the propeller was at a ‘lower power condition’. The aircraft likely aerodynamically stalled, with insufficient height to effect a recovery before colliding with the water. Further, the front seat passenger was regularly taking photographs, but stopped during the turn in Cowan Water, and it was very likely the middle right passenger was unrestrained at impact.

Toxicology results identified that the pilot and passengers had higher than normal levels of carboxyhaemoglobin in their blood. This was almost certainly due to elevated levels of carbon monoxide (CO) in the aircraft cabin. The ATSB’s wreckage examination established that several pre-existing cracks in the exhaust collector ring, very likely released exhaust gas into the engine/accessory bay, which then very likely entered the cabin through holes in the main firewall where three bolts were missing from the magneto access panels. In addition, the examination also found that the in situ bolts used by the operator’s external maintenance provider to secure the panels were worn, and were a combination of modified AN3-3A bolts and non-specific bolts.

A 27 minute taxi, with the pilot’s door ajar, before the passengers boarded likely exacerbated the pilot’s elevated carboxyhaemoglobin level. As a result, the pilot would have almost certainly experienced effects such as confusion, visual disturbance and disorientation. Consequently, it was likely that this significantly degraded the pilot's ability to safely operate the aircraft.

The ATSB established that, although not required, the aircraft was fitted with a disposable CO chemical spot detector, which was likely not effective on the accident flight due to sun bleaching. Commonly used in general aviation, these types of detectors have known limitations and can be unreliable at detecting CO in the cabin. Further, they are a passive device that relies on the pilot regularly monitoring the changing colour of the sensor to detect elevated levels of CO. In contrast, electronic active warning CO detectors are designed to attract the pilot’s attention through auditory and/or visual alerts, so are more likely to be effective.

While inexpensive and readily available, there was no regulatory requirement from the Civil Aviation Safety Authority for piston-engine aircraft to carry a CO detector with an active warning. Similarly, other international investigation agencies have made safety recommendations to aviation regulators to mandate the carriage of active detectors. However, despite the ongoing threat CO exposure poses to aircraft occupants, these recommendations have not been accepted. Consequently, the ATSB has recommended that the Civil Aviation Safety Authority consider mandating the carriage of active warning CO detectors in piston-engine aircraft with a maximum take-off weight less than 5,700 kg. In addition, while the aircraft carried a passive CO detector, Sydney Seaplanes had no mechanism for monitoring the serviceability of the detectors to their aircraft at the time.

The ATSB has identified a safety issue relating to the lack of requirements to fit recording devices in commercial air transport (passenger‑carrying) aircraft with a maximum take-off weight less than 5,700 kg. Given that recent advancements in lightweight recording devices have made this technologically and economically more feasible, the ATSB has recommended that the International Civil Aviation Organization and the Civil Aviation Safety Authority consider mandating the fitment of such devices.

Although not contributory, the ATSB also identified that the recommended standard passenger weights specified in Civil Aviation Advisory Publication 235‑1(1) Standard passenger and baggage weights did not accurately reflect the average weights of the current Australian population. Further, while volunteered passenger weights were commonly used by the operator and others in the charter industry, there was no regulatory advice on how these should be applied.

What has been done as a result
In July 2020, the ATSB issued two safety advisory notices to aircraft maintainers, operators and owners of piston-engine aircraft. The first notice reminded maintainers of the importance of conducting detailed inspections of exhaust systems and firewalls, with consideration for potential CO exposure. The second notice strongly encouraged operators and owners to install a CO detector with an active warning to alert pilots to the presence of elevated levels of CO in the cabin. If not provided, pilots were encouraged to carry a personal CO detection and alerting device.

In addition, as a result of this investigation, the Civil Aviation Safety Authority released the related airworthiness bulletin AWB 02-064 in July 2020 and 19 October 2020 Preventing Carbon Monoxide Poisoning in Piston Engine Aircraft.

Related to the consideration of CO exposure, the operator has implemented a range of measures and amended the DHC-2 system of maintenance, including:

The operator’s aircraft have been fitted with active electronic CO detectors.
The check of the serviceability of the CO detectors has been incorporated into the monthly emergency equipment checklist.
Directing its new maintenance provider that the removal and installation of the main firewall access panels must be classified as a critical maintenance operation task, and will require certification by a licensed aircraft maintenance engineer and a conformity inspection.
Directing its new maintenance provider that following maintenance activities on the engine exhaust system or use of the main firewall access panels, the test for the presence of CO must be conducted.
An inspection of the magneto access panels and CO testing has been incorporated into the 100-hourly ‘B’ check inspection.
The operator also recommended that their external training provider include a CO module as part of their human factors training for all pilots. This has since been incorporated, and is provided to other operators undertaking this training. Following the accident, and prior to recommencing DHC‑2 flights on 31 January 2018, the operator installed a stall warning system to their other DHC-2 aircraft. In addition, GPS tracking devices to provide real-time positioning information and flight data were installed in all their aircraft. Further, the operator’s pilots completed helicopter underwater escape training.

The operator recognised that it was impractical for them to weigh passengers immediately before a flight. However, they now include an additional 5 kg allowance on volunteered passenger weights when establishing the aircraft’s weight and balance.

Safety message
This accident highlights the insidious danger CO exposure poses to aircraft occupants. It reinforces the importance of conducting a thorough inspection of piston-engine exhaust systems and the timely repair or replacement of deteriorated components. In combination with the assured integrity of the firewall, this decreases the possibility of CO entering the cabin.

Further, the use of an attention attracting CO detector provides pilots with the best opportunity to detect CO exposure before it adversely affects their ability to control the aircraft or become incapacitated. Operators and owners of piston-engine aircraft are strongly encouraged to install a CO detector with an active warning to alert pilots to the presence of elevated levels of CO in the cabin. If not provided, pilots are encouraged to carry a personal CO detection and alerting device.

Recording devices have long been recognised as an invaluable tool for investigators in identifying the factors behind an accident, and their contribution to aviation safety is irrefutable. Such systems were generally only fitted and mandated on larger aircraft. However, advancements in technology have led the way for more cost-effective, self-contained image, audio and flight data recording systems accessible to all aircraft. This accident highlights the benefits of having these devices fitted to passenger-carrying aircraft with a maximum take-off weight less than 5,700 kg.

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