Commission says mechanical faults caused smoke incidents

THE Papua New Guinea Accident Investigation Commission (AIC) found wear and tear mechanical faults that caused “smoke incidents”, in two flights last year.
One flight was a flyover in Mt Hagen by a DHC-6-400 Twin Otter aircraft and the other by an Australian registered (VH-QOE) Bombardier DHC-8-402 aircraft on a flight from PNG to Cairns
AIC chief commissioner Hubert Namani said for the international flight, a notification was received on the same day and the aircraft had to turn mid-air and return to the Jackson International Airport.
“The flight crew identified an unusual smell entering the cockpit which intensified as the aircraft continued climbing and reportedly extended to the cabin,” he said.
“The flight crew commenced the procedure for “smoke (warning light) or fuselage fire, smoke or fumes” by its recall actions items, donning their oxygen masks, requesting for a priority return to Port Moresby.
“The flight crew landed the aircraft on runway 32R and subsequently exited the runway, stopped at Taxiway Foxtrot and shut down the engines.”
Namani said the in-flight smoke/fumes event occurred due to the failure of the No.3 bearing carbon seal located at the compressor section of the right-hand engine.
“The carbon seal had fractured allowing oil to leak into the compressor section where air is compressed and routed and bled into the cabin for air-conditioning and pressurisation,” he said.
“The leaked oil contacted hot surfaces generating smoke/fumes which contaminated the air being routed into the cabin and cockpit.”
On the Mt Hagen flight, Namani said, “the crew of a DHC-6-400 Twin Otter aircraft, registered P2-KSY, operated by Hevilift (PNG) Aviation Ltd, identified the presence of smoke in the cockpit while overflying Mt Hagen airport following a discontinued approach to runway 30”.
“The final report by the AIC stated that due to the inconsistent operation of the hydraulic pressure switch, the hydraulic relay switch remained engaged and continued operating the hydraulic pump beyond its normal operation limit and overheated.”