What happened
On 2 December 2023, a Pakistan International Airlines (PIA) Boeing 777-200ER, registration AP-BMH, experienced a serious incident shortly after departing Jinnah International Airport (JIAP), Karachi, for Madinah. During the climb phase at approximately 300 feet above ground level, the flight crew received a right engine overheat message, which was immediately followed by the activation of the engine fire warning system.
The crew declared a "MAYDAY" and initiated emergency fire suppression procedures. After the immediate threat appeared to be mitigated, the crew downgraded the emergency status to "PAN PAN" and executed an emergency return to Karachi. The aircraft landed safely at JIAP at 02:00 UTC with no injuries reported to the 288 occupants on board.
The investigation
The Bureau of Aircraft Safety Investigation (BASIP) Pakistan conducted an investigation into the event. While a fire warning was triggered, post-flight inspections revealed no evidence of actual fire or thermal damage to the engine core or fan sections.
Investigators discovered that a high-pressure (HP) pneumatic duct connection near the High-Pressure Compressor (HPC) case had disconnected. The associated duct clamp was found displaced in the lower section of the engine. This disconnection caused a significant bleed air leak from the 14th stage of the HPC, which triggered the overheat and fire warnings.
Findings
- The incident occurred during the first flight following a right engine replacement.
- The HP pneumatic duct clamp was found to be improperly torqued, with no threads visible beyond the nut, making it susceptible to loosening due to vibration.
- Maintenance tasks were performed under challenging night-shift conditions using suboptimal tools, such as ladders instead of platforms, which increased the risk of error.
- No pneumatic leak checks were conducted on the right engine following the installation, contrary to Aircraft Maintenance Manual (AMM) requirements.
- The clamp was likely loosened during a separate task involving HP bleed valve removal/installation, but the error went undetected because the procedure did not explicitly require checking adjacent components.
- Contributing factors included inadequate communication during shift handovers and a maintenance culture that prioritized task completion over procedural verification.