What happened
On 3 April 2008, a Cessna Citation 560, registration ZS-NGL, arrived at Pietermaritzburg Aerodrome following a private flight from Lanseria. After the passengers disembarked, the crew moved the aircraft to facilitate refueling. Once the 1,800-liter refueling process was complete, Air Traffic Control instructed the crew to reposition the aircraft to parking bay A4 to ensure clearance for an incoming SA Airlink flight.
While the first officer was maneuvering the aircraft, the right-hand undercarriage passed over a manhole. A loud bang occurred, and the aircraft suddenly dropped onto its right side as the manhole cover failed. The captain immediately ordered the engine to be shut down. There were no injuries to the crew or passengers, but the aircraft sustained significant damage to the right-hand wing spar, flap bell crank, hydraulic gear actuator, and the right-hand gear door. The manhole cover itself shattered, and an electrical box beneath the surface was damaged.
The investigation
SACAA AIID investigators examined the structural integrity of the airfield infrastructure and the circumstances of the movement. The investigation focused on why the pavement failed under the weight of a light jet. Metallurgical analysis of the manhole cover revealed it was constructed from a pearlitic grey cast iron. This specific material was found to be unsuitable for airport pavement applications because its strength is too low for aircraft loads.
Findings
- The manhole cover was designed for light-duty highway use rather than airfield requirements.
- The incorrect manhole cover used at the parking bay could not sustain the weight of the aircraft.
- The aircraft was properly maintained, and the first officer held a valid license and appropriate ratings.
- Weather conditions were calm with good visibility and did not contribute to the event.
- The manhole cover had been previously damaged.
Safety action
- It is recommended that the South African Civil Aviation Authority adopt the standards outlined in FAA Engineering Guidance 98-11 and incorporate them into the Civil Aviation Regulations (CARs).