Incident Details
On the morning of 23 April 2023, a Saab 340A, registered VH-KDK and owned by Pel-Air Aviation, was operated by Regional Express Airlines (Rex) on a non-revenue flight from Wagga Wagga, New South Wales, to Charleville, Queensland. While cruising at 22,000 ft east of Cobar, the flight crew received a cargo smoke indication on the central warning panel. They donned oxygen masks and smoke goggles as a precaution, and shortly after, the cockpit filled with smoke. The captain initiated a diversion to Cobar while the first officer made a PAN-PAN call to Melbourne Centre. Thick smoke filled the flight deck, impairing visibility of external references and flight instruments. During emergency checklist actions, additional warnings appeared: avionics smoke, cabin depressurisation, and a right engine fire detection fail indication. The crew landed at Cobar and stopped on the runway to evacuate the aircraft. Fire and Rescue New South Wales personnel arrived and located a heat source at the air cycle machine and associated wiring. The heat source was doused with water, and an internal inspection revealed fire damage around the right recirculating fan. The aircraft was substantially damaged; the crew were not injured.
ATSB Investigation Findings
The ATSB determined that a likely failure of the right recirculating fan electronic box sub-assembly caused an in-flight fire under the cabin floor. The fire filled the cabin with smoke, which entered the flight deck because a smoke barrier curtain was not installed and the flight deck door was open. When the crew donned their oxygen masks, the first officer's mask microphone malfunctioned, delaying the execution of emergency checklists. The fire caused substantial structural damage and a fuselage breach, resulting in cabin depressurisation. The ATSB also found that the Rex flight crew had not received training on differences specific to the cargo-configured Saab 340, including unfamiliarity with certain systems, which prevented them from completing some steps in emergency checklists. The operator's flight crew operating manuals did not reflect differences in cargo-configured aircraft interior checklists. Additionally, the manufacturer's pre-flight checklists did not include a specific check for correct fitment of the smoke barrier curtain in cargo-configured aircraft.
Safety Actions Taken
On 13 May 2023, Rex issued an Operations Notice highlighting guidance on the cross-valve handle from the Saab Aircraft Operating Manual, which was later incorporated into the Rex Flight Crew Operating Manual. On 13 November 2024, Rex amended the internal inspection checklist in their Saab 340 FCOM to include verification of the cross-valve handle position during pre-flight checks. Rex also updated ground school training to include the cross-valve system for cargo-configured Saab 340 aircraft. Rex plans a fleetwide inspection of recirculating fan assemblies at the next heavy maintenance cycle, focusing on the electronic sub-assembly module. Pel-Air revised their flight crew operating manual to include a caution that the smoke barrier curtain must be installed whenever combustible material is carried in the cargo compartment. Due to contract completion, Pel-Air ceased freight operations with the Saab 340 and sold the aircraft. Saab revised their preparatory and walk-around pre-flight checklists to include fitting of the smoke barrier curtain when carrying cargo in cargo-configured aircraft.