Boeing 737-476, VH-TJR

Prior to the first flight of the day, the Boeing 737 aircraft cabin was found to contain smoke and fumes. While the crew returned to the crew room, maintenance personnel inspected the aircraft and found that the auxiliary power unit (APU) had malfunctioned. The cabin was cleared of fumes and the aircraft despatched with an unserviceable APU. For a short time after take-off, some smoke and fumes were observed in the cabin but cleared.

At around 6,000 ft on approach to Sydney, fumes were again detected; most noticeably in the rear of the cabin. A fast approach and normal landing ensued. Cabin staff reported that the smell dissipated when the air conditioning packs were selected to HIGH.

Company maintenance investigation found that the APU malfunction was the result of a cooling fan shaft failure. The failure allowed APU turbine oil to leak from around the shaft seal from where it was sucked into the APU inlet prior to the APU control unit initiating an auto-shutdown. The oil then entered the air conditioning system ducting and later exited into the cabin as fumes and oily smoke during that system's normal operation.