What happened
On 24 November 2000, a Fokker F27 Mark 050, registration G-UKTI, was performing a non-revenue positioning flight from Teesside Airport toward Amsterdam. Shortly after climbing through 1,000 feet, the flight crew was alerted by a member of the cabin crew that the cabin was filling with smoke. The smoke was so dense that the commander could not see more than 1.5 metres past the cabin crew member. As the smoke entered the flight deck through the air vents and the open door, the pilots declared a Mayday and initiated an emergency return to land.
To manage the situation, the crew turned the aircraft into a left-hand visual circuit at 1,700 feet and deactivated both air conditioning packs, bleets, and recirculation fans. The pilots donned oxygen masks, and the cabin crew utilized smoke hoods. Once the air conditioning system was switched off, the smoke ingress ceased. The aircraft landed safely on Runway 23, where the Airport Fire Service met the aircraft.
The investigation
The investigation examined the source of the smoke and the communication breakdown between the crew members. It was discovered that the aircraft had experienced similar issues in the preceding days. Two days prior, a significant oil leak had been noted on the right engine, which was initially attributed to a failed reduction gearbox propeller shaft seal. Following repairs, a similar smoke event occurred during a takeoff on 23 November, which led to an aborted takeoff.
Technical examinations following the 24 November incident revealed that the true source of the leak was a defective propeller feathering pump. This component was leaking oil into the right engine intake. Because the oil was being ingested into the engine, it contaminated the compressor air bleed used for the air conditioning system, creating the smoke/mist effect in the cabin. Furthermore, investigators found that the interphone system's audio alert was inhibited during the takeoff phase when speeds exceeded 80 knots, preventing the cabin crew from immediately alerting the pilots via the standard intercom.