History of the Incident
On 7 June 2014, Jet Airways ATR 72-212A aircraft VT-JCS operated flight 9W-2760 from Rajahmundry to Hyderabad. The flight was uneventful until after landing on runway 27 at approximately 1003 UTC. During taxi, the cabin crew noticed white smoke accompanied by a burning smell reminiscent of electrical wires, originating from the mid cabin. Simultaneously, the flight crew received an electrical smoke warning in the cockpit. The captain called an on-duty Aircraft Maintenance Engineer (AME) who was travelling as a passenger into the cockpit. The aircraft was stopped on taxiway B4, and ATC was informed. The crew performed the smoke and electrical smoke emergency checklists, including shutting down the engines. However, the smoke persisted, and the source could not be identified. The captain then directed the cabin crew to evacuate the passengers via the aft door onto the taxiway. All 62 passengers and 4 crew members evacuated safely without injury. The aircraft was subsequently towed to the bay.
Aircraft and Engine Findings
External visual inspection revealed no signs of burning or other abnormalities. Circuit breaker panels were opened, and the forward cargo compartment floor board was removed without detecting anomalies. Both air conditioning packs operated normally in auto and manual mode, but an oil smell persisted in the cockpit and cabin. No odor was observed in the bleed valve controlled air supply, and no restrictions were found in the metering plugs. Boroscopic inspection of both engines revealed dried oil stains from the leading edge to one-third of the chord on all vanes of the left-hand engine's high-pressure impeller. The left-hand engine (serial number AV0112) was removed for detailed strip examination.
Probable Cause
Inadequate air supply across the bearing seal, required for prevention of oil seepage in the airflow, due to the P2.5/P3 air switching valve being sticky and a deteriorated #4 bearing housing resulted in seepage of oil into the P2.5 air system, causing the oil smell and smoke in the cabin.
Safety Recommendations
To prevent recurrence, the investigation recommended that the operator conduct visual inspections of the air switching valve during Hot Section Inspection (HSI) and overhaul the valve during engine overhaul, given its non-functioning status as an on-condition item. Additionally, line maintenance personnel should participate in major overhaul and HSI activities to better appreciate indications of core engine deterioration during boroscope inspection.