What happened
On 23 April 2023, a Pel-Air Aviation Saab 340A, registered VH-KDK, was operating a revenue cargo flight from Wagga Wagga, New South Wales, to Charleville, Queensland. Approximately one hour into the mission, the crew identified an in-flight fire. The aircraft subsequently diverted to Cobar, New South Wales.
During the diversion, thick smoke filled both the cabin and the cockpit. The fire caused damage to underfloor insulation and air conditioning ducting, which eventually weakened the fuselage structure, resulting in a cabin depressurisation. Despite the intense smoke and loss of pressure, the crew managed to perform a safe landing at Cobar. There were no injuries to the flight crew, though the aircraft sustained substantial damage.
The investigation
The ATSB traced the fire to the right recirculating fan assembly, specifically identifying an electrical failure within the control circuit boards of the external box sub-assembly. This failure ignited the underfloor area.
Investigators found that several factors allowed smoke to penetrate the flight deck. The cockpit door was left open, contrary to operating limitations, and a required smoke barrier curtain had not been installed for this cargo configuration. The crew was unaware of the requirement to fit this curtain, as they were more accustomed to passenger-configured aircraft. Furthermore, a technical fault in the first officer's oxygen mask microphone caused significant communication difficulties between the pilots, delaying emergency procedures by nearly a minute.
Findings
- An electrical component failure within the recirculating fan control board triggered the fire.
- The failure to install the smoke barrier curtain and keep the flight deck door closed allowed smoke to migrate from the cabin to the cockpit.
- The crew lacked familiarity with the specific requirements of the cargo configuration, including the location of the cross-valve handle.
- Discrepancies in training and documentation contributed to the risk, as Rex Airlines had not provided specific training for freight operations, and Saab's pre-flight documentation omitted instructions regarding the smoke curtain.
Safety message
- Rex Airlines must ensure flight crews receive adequate training regarding the operational differences between passenger and freight configurations of the Saab 340A.
- Maintenance and operational documentation should be updated to include specific requirements for cargo-specific safety equipment, such as smoke curtains.