No regulatory requirement for carbon monoxide detectors

As a result of this investigation, the Civil Aviation Safety Authority released the airworthiness bulletin AWB 02-064 (Issue 1) on 3 July 2020 that recommended the use of electronic personal CO detectors in aircraft:

4. Recommendations

… whilst not all aircraft are required to have CO [carbon monoxide] 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.

On 19 October 2020, the Civil Aviation Safety Authority issued version 2 of the above airworthiness bulletin. Specifically, the bulletin stated that:

CASA [Civil Aviation Safety Authority] strongly recommends pilots wear personal CO detectors. As not all aircraft are required to have CO detectors fitted, small electronic personal devices are readily available at affordable prices. These devices allow for continual monitoring of CO levels with audible and visual warnings when escalated CO levels are detected.

Response by the Civil Aviation Safety Authority

On 08 Oct 2021 in response to an ATSB follow-up email, the Civil Aviation Safety Authority stated that:  

Barring any new information, CASA believes its current position to strongly encourage fitment but not mandate it is the most appropriate action at this point in time. As outlined in Air Worthiness Bulletin 02-064 and its subsequent issues.  Should new information become available CASA will review in the context of this matter.

On 21 October 2020, in response to the draft ATSB report, the Civil Aviation Safety Authority stated that:

Existing OEM [original equipment manufacturer] maintenance manual advice as well as CASA airworthiness directive actions applicable to engine exhaust system for this aircraft (AD/DHC-2/33 Exhaust Collector Ring Segments http://services.casa.gov.au/airworth/airwd/ADfiles/UNDER/DHC-2/DHC-2-033.pdf) are considered appropriate for safe operations.

The fitment of detection equipment is not required by any applicable airworthiness standards.  Appropriate maintenance performed in accordance with the appropriate data ensures that the aircraft remains airworthy. i.e. in conformity with its type design and in a condition for safe operation.

The emphasis for any corrective actions should be focussed on the root cause of the accident i.e. inadequate maintenance, rather than the formal introduction of additional safety mechanisms as a belated safety defence mechanism. The existing maintenance standards and processes are considered to be adequate when conducted appropriately for preventing Carbon Monoxide entering the cabin through the firewall and cabin entry doors when closed.

CASA AWB 02-064 Preventing Carbon Monoxide Poisoning in Piston Engine Aircraft  AWB 02-064 Issue 1 - Preventing Carbon Monoxide Poisoning in Piston Engine Aircraft | Civil Aviation Safety Authority (casa.gov.au) recommending portable, personal electronic Carbon Monoxide detectors is considered appropriate in this instance and identifies a measure that can add an additional layer of safety defence to avoid future reoccurrences of this nature if appropriate maintenance data or actions are not followed.  CASA is reviewing this AWB and will further emphasise the need to conduct maintenance in accordance with appropriate maintenance data to prevent Carbon Monoxide entering the cabin as well as stating: “CASA strongly recommends pilots wear Carbon Monoxide detectors on their person”.

The ATSB acknowledges the issuance of the Civil Aviation Safety Authority’s airworthiness bulletin advising owners, operators and aircraft engineers of the potential dangers of carbon monoxide exposure. However, this, and other investigations have shown that the existing barriers for minimising the risk of carbon monoxide exposure (aircraft design and maintenance inspections) may not always be effective. Although some aircraft manufacturers are proactively installing detectors on new aircraft, without a mandate, the use remains at the pilot and aircraft owner's discretion. Therefore, as also recommended by other investigation agencies world-wide to their regulators, the Civil Aviation Safety Authority should consider the carriage of detectors in piston-engine aircraft as an additional barrier to carbon monoxide prevention. Of particular note are passenger-carrying piston-engine aircraft such as the aircraft involved in this accident.

The ATSB is issuing the following recommendation.

The Australian Transport Safety Bureau recommends that the Civil Aviation Safety Authority takes further safety action to enable it to consider mandating the carriage of carbon monoxide detectors in piston-engine aircraft, particularly passenger-carrying operations.