The deployment of an emergency exit's ditching dam in-flight highlights to flight crews that not every system in an aircraft is controllable or monitored, an ATSB investigation reinforces.
The 8 August 2019 incident occurred when a QantasLink Dash 8-300 aircraft was operated on a scheduled passenger flight from Adelaide to Whyalla, South Australia. The flight had proceeded normally until just after top of descent when a loud repetitive banging noise was heard in the cabin.
The two cabin crew members initially suspected the sound was due to ice coming off the propellers and hitting the aircraft fuselage, but the volume and intensity of the noise did not align with their previous experience of flying in icing conditions, and they decided to break the sterile cockpit protocols in place for the descent and landing in order to inform the flight crew of the situation via the interphone.
Further investigation by the cabin crew identified that the noise was coming from the vicinity of the right rear emergency exit at seat row 10. They then identified a yellow object flapping on the outside of the aircraft, just below the exit. The flight crew concluded that the right-hand ditching dam - an inflatable device that activates on operation of the exit hatch after a ditching or landing on water, in order to minimise water ingress into the cabin - had inadvertently deployed. They elected to continue to Whyalla, where an uneventful landing was conducted.
Cabin crew should not hesitate to inform flight crew of abnormal conditions within or external to the cabin.
ATSB Director Transport Safety Stuart Macleod said that the cabin crew had acted appropriately in breaking the sterile cockpit environment - where non-essential activities and communications on the flight deck are not permitted to minimise distraction during safety critical phases of flight - and alerting the flight crew to the situation.
"Not every system in an aircraft is controllable or monitored by the flight crew," Mr Macleod said.
"Cabin crew should not hesitate to inform flight crew of abnormal conditions within or external to the cabin, as flight crew may be unaware of the situation."
QantasLink subsequently determined that the ditching dam had not inflated but rather, for reasons that could not be determined, its cover had opened in flight, allowing the uninflated dam bag to unfurl into the slipstream.
The bag, cover and inflation hose then hit the fuselage repeatedly, which was the loud noise heard by the occupants of the aircraft.
"Management of the unexpected deployment was controlled through the use of non‑normal checklists and effective resource management," Mr Macleod said.
You can find here the report AO-2019-044: In-flight deployment of ditching dam involving De Havilland Aircraft of Canada DHC-8, VH-SCE, near Whyalla, South Australia, on 8 August 2019
