What happened
During a scheduled international flight from London Heathrow to Cape Town, a Boeing B7 .400, registration G-BNLB, began its take-off roll on Runway 01 at Cape Town International Airport. During the acceleration, the flight crew heard a loud bang originating from the left side of the aircraft. Shortly thereafter, air traffic control informed the pilots that flames were visible trailing from the number one engine.
In response to the engine malfunction, the crew initiated an aborted take-off at an indicated airspeed of 100kt. The aircraft came to a halt on the runway approximately 1000m from the start of the take-off roll. Following the stop, emergency fire services inspected the engine and the main landing gear, including all brake assemblies, before the aircraft was cleared to taxi to its parking bay. There were 0 fatalities and 0 injuries reported, and the passengers and crew evacuated the aircraft safely from the gate.
The investigation
Investigators looked into the history of the engine's performance, discovering that the crew had encountered a compressor stall during the preceding flight leg from London to Cape Town. At that time, because all engine parameters appeared normal, the crew proceeded to the destination. Upon arrival in Cape Town, maintenance technicians performed a borescope inspection of the number one engine. This inspection revealed minor damage to a stator blade within the compressor module, though the damage was initially deemed to be within acceptable operational limits. Subsequent ground testing of the engine showed satisfactory results, and the aircraft was released for service.
Findings
- The engine surge was caused by increased compressor blade tip clearances throughout the High Pressure (HP) compressor module.
- These clearances had expanded by a margin of 0.02 to 0.04 inches.
- This mechanical deviation created conditions during engine operation that allowed for an engine surge or stall to manifest during the high-power take-off phase.