What happened
On November 24, 2017, a SpiceJet Bombardier DHC8-400, registration VT-SUM, was operating a scheduled flight from Hyderabad to Jabalpur when the crew reported smoke in the cabin while cruising at 25,000 feet. The flight crew confirmed the presence of smoke and initiated an emergency diversion to Nagpur.
During the descent, the situation escalated as the crew received aft baggage cargo smoke and fire warnings. In response, the crew activated the aft cargo fire extinguisher. Smoke subsequently entered the cockpit, prompting the pilots to don oxygen masks and follow emergency procedures for fuselage fire and smoke. During the final approach, a low oil pressure warning for the number two engine was triggered. The aircraft landed safely at Nagpur, where an emergency response was initiated. Following the landing, the crew evacuated all 59 passengers and 4 crew members via the left side of the aircraft.
The investigation
AAIB India investigators examined the aircraft's maintenance records and the engine components. The investigation focused on the engine's bearing compartments and the presence of metallic particles found during a chip detector test. The engine was subsequently removed and sent to the original equipment manufacturer (OEM) for a detailed teardown inspection.
Investigators reviewed existing Service Bulletins (SB) regarding bearing seals. It was noted that while the engine had undergone previous maintenance, the No. 3 bearing carbon seal had not yet been replaced with the updated version specified in SB 35341, as the necessary access was only available during specific shop visits.
Findings
- The primary cause of the incident was the failure of the No. 3 bearing carbon seal during flight.
- This failure allowed engine oil to leak into the gas path, which then entered the aircraft cabin via the bleed off valves.
- The resulting oil loss eventually led to the low oil pressure warning observed during approach.
- The investigation identified that the failure of the No. 3 bearing carbon seal was the direct cause of the oil fumes entering the cabin and cockpit.