What happened
During the climb phase of a flight, two cabin crew members noticed a chlorine-like smell in the forward galley. While they experienced mild symptoms, these initially subsided before returning upon landing. The aircraft's air-conditioning configuration at the time distributed bleed air from the left engine to the flight deck and forward galley, while the right side supplied the passenger cabin.
As the aircraft approached Hobart Airport, the flight crew detected a chlorine odour. Shortly after, the captain experienced rapid onset symptoms of incapacitation, including cognitive impairment, necessitating a handover of pilot flying duties to the first officer. As the aircraft neared the runway, the first officer also began experiencing symptoms, specifically slowed reaction times. Although the crew considered a go-around or using supplemental oxygen, they ultimately decided that continuing the landing was the safest course of action, partly due to the perceived difficulty of donning oxygen masks so close to touchdown.
Both flight crew members remained partially incapacitated during the landing and the subsequent taxi to the parking bay.
The investigation
The ATSB examined the aircraft's maintenance history and found that the same aircraft had experienced a similar cabin air quality event just two days prior. During that previous instance, the cabin crew also reported a chlorine smell and mild symptoms. Following the June 2023 incident, engineers inspected the aircraft but were unable to identify a source of the odour or reproduce the issue during ground tests or subsequent flight trials.
Findings
- The operator's specific procedure for cabin air quality events focused on reporting and maintenance but did not address the need to trigger smoke/fumes or incapacitation procedures.
- The lack of integration between air quality reporting and emergency procedures increased the risk that flight crews could be adversely affected during critical flight phases.
- Training for the crew did not sufficiently cover how to identify or respond to subtle forms of physical or cognitive incapacitation.