In July 2020, the Australian Transport Safety Bureau issued a safety advisory notice to operators, owners and pilots:
The use of an attention attracting carbon monoxide detector in the cockpit provides pilots with the best opportunity to detect carbon monoxide exposure before it adversely affects their ability to control the aircraft or become incapacitated. The ATSB strongly encourages operators and owners of piston‑engine aircraft to install a carbon monoxide detector with an active warning to alert pilots to the presence of elevated levels of carbon monoxide in the cabin. If not provided, pilots are encouraged to carry a personal carbon monoxide detection and alerting device.
Additional safety action by the Civil Aviation Safety Authority
On 3 July 2020, as a result of this investigation, the Civil Aviation Safety Authority released the airworthiness bulletin AWB 02-064 (Issue 1) Preventing Carbon Monoxide Poisoning in Piston Engine Aircraft. This included the following recommendations:
The Civil Aviation Safety Authority recommends that when LAME/AMEs [licensed aircraft maintenance engineer/ aircraft maintenance engineer]. conduct visual inspections of exhaust collectors and heat exchange units, that a thorough inspection is conducted with the view of finding potential CO poisoning points/cracks. Whilst the internal condition and thickness of exhaust components is difficult to determine visually, if the component exhibits signs of thinning, cracking, bulging or any exhaust leakage the section should be removed and replaced with a new or serviceable/repaired item.
An ideal maintenance program would involve system replacement at engine change or at a predetermined interval gained from operating experience. To operate these items to a point of failure is not considered appropriate. Any modification or reduction in length of the tail pipe/exhaust system must be conducted with original equipment manufacturer approval or local Australian CASR [Civil Aviation Safety Regulations] Part 21 approval.
Secondly, approved modifications that include access panels and attachments to firewalls must be re‑sealed following all disturbances to prevent CO entering the cabin. Heating ducts and on/off valves should function correctly, particularly in the off position to allow the pilot to stop the flow of contaminated air entering the cockpit. If an access panel on the engine firewall is opened/removed during maintenance/servicing for gaining access, ensure that the access panel seals/gaskets and hardware is reinstalled correctly to prevent the flow of gases and flammable fluids entering the cockpit and cabin.
Finally, whilst not all aircraft are required to have CO detectors fitted, small electronic personal devices are available at relatively affordable prices, these devices allow for continual monitoring of CO levels with audible and visual warnings when escalated CO levels are detected.
Aircraft certified and hard-wired products are also available that can be installed by approved maintenance repair organisations. Reliance on only the visual CO indicator placard, that changes colour in the presence of CO, is considered suboptimal.
If the aircraft is only fitted with the placard type CO indicator, the operator should ensure the placard is placed in the field of view of the pilot, is regularly checked to ensure that the placard is not time expired and that the indicator is not faded from ultraviolet exposure or contamination.
On 19 October 2020, the Civil Aviation Safety Authority issued version 2 of the above airworthiness bulletin. Specifically, the bulletin strongly recommended that pilots wear personal CO detectors.
Additional safety action by Sydney Seaplanes
Following the accident, prior to recommencing DHC-2 flights on 31 January 2018, Sydney Seaplanes 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.
Carbon monoxide detection-related
- The operator reported that all of their aircraft have been fitted with active electronic carbon monoxide detectors. Due to the ambient noise of the DHC-2 aircraft, the detector has been connected to the cabin communications system so the aural alert can be heard through the headsets.
- The operator recommended that their external training provider incorporate a carbon monoxide module onto their human factors training for all This has since been included, and is also available for other operators.
Carbon monoxide maintenance-related
The operator has amended the DHC-2 system of maintenance, including:
- Directing its new maintenance provider that the removal and installation of the 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.
- Following post-installation of the firewall access panels, a test for the presence of carbon monoxide is to be conducted prior to the aircraft being returned to service.
- Directing its new maintenance provider that following maintenance being conducted on the engine exhaust system, whether scheduled or un‑scheduled work, a test for the presence of carbon monoxide must be conducted prior to the aircraft being returned to service.
- The 100-hourly ‘B’ check inspection has been amended to include an examination of the magneto access panels. At the completion of this inspection, the cabin is to be tested for carbon monoxide.
Volunteered passenger weights
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 for when establishing the aircraft’s weight and balance.