What happened
On 18 July 2014, a Bombardier Q400, registration ZS-NMO, departed Cape Town International Airport on a scheduled commercial flight to Bloemfontein. While the aircraft was climbing through flight level 160, a passenger alerted the cabin crew that a piece of the engine cowling appeared to be missing from the left side of the number 2 engine.
Upon verification by the cockpit crew, it was determined that the cowling had likely separated from the engine during the takeoff roll or shortly after liftoff. Despite the incident, the flight crew consulted with maintenance and operations control centers and elected to proceed to Braam Fischer Aerodrome. The aircraft landed safely in Bloemfontein, though the separation had caused substantial damage to the engine's leading edge and the outer de-icing boot.
The investigation
An investigation by the SACAA AIID examined the sequence of events and the maintenance history of the aircraft. The investigation found that the cowling was located by airport fire services approximately 660 meters from the threshold of Runway 01 at Cape Town. Inspection of the detached part revealed that while two side latches were secured, the two lower latches remained unlatched.
Investigators reviewed the maintenance activities performed during a "night-stop inspection" the previous evening. It was established that an assistant had performed engine oil uplifts during this period under rainy conditions. The certified maintenance technician involved could not confirm whether they had performed a spot check on the work completed by the assistant.
Findings
- The right hand engine inboard cowling was not properly latched and locked.
- The pre-flight inspection was not adequately performed by either the maintenance personnel or the flight crew.
- The separation of the cowling occurred during the takeoff sequence due to the improper securing of the lower latches.
- Maintenance work involving engine oil levels was performed by an assistant who was not qualified to perform aircraft maintenance.
Safety action
Following the investigation, it was recommended that the Director of Civil Aviation implement regular and ad-hoc oversight to ensure that maintenance tasks at Aircraft Maintenance Organisations are not performed by unqualified personnel.