A Tropicair de Havilland DHC-6-300, registration P2-BBM performing a flight from Tapini to Port Moresby (New Guinea) with 19 passengers and 2 crew, was departing Tapini's runway 09 on a wet, muddy grass strip when the aircraft skidded to the right, the crew corrected but the aircraft now drifted to the left and, already airborne, impacted the airport fence causing the Nose Wheel and Lower Fork assembly to separate from the Nose Landing Gear (NLG) shock strut assembly. The crew was informed about the separation and continued the flight to Port Moresby for an emergency landing on runway 32L without nose wheels. The aircraft came to rest on the runway, there were no injuries.
Papa New Guinea's AIC released their final report concluding the probable causes of the accident were:
The investigation identified that the occurrence resulted from a combination of environmental, aerodrome, and human factors. The severely reduced runway surface friction resulting from heavy overnight rainfall, which left the grass runway surface at Tapini Airstrip wet, muddy, and slippery. Poor drainage at the airstrip contributed to water accumulation and deterioration of the runway surface condition, significantly reducing braking effectiveness, steering authority, and tyre traction during the take-off roll.
Contributing aerodrome factors included the approximately 4.5% downhill gradient and lateral slope of Runway 09, which increased the aircrafts tendency to slide on the contaminated surface and reduced the effectiveness of directional control inputs. The presence of overgrown vegetation and perimeter fencing adjacent to the runway also increased the likelihood and severity of damage during the runway excursion.
Contributing human factors included the control inputs applied by the pilot-in-command in response to the developing loss of directional control. As the aircraft was already skidding on a low-friction surface, the use of rudder, nose wheel steering (tiller), and asymmetric power increased the loading and structural stresses acting on the nose wheel assembly. These stresses contributed to the damage sustained by the assembly; however, the subsequent failure resulted from the combined effects of these stresses, entanglement with perimeter fencing wire, and overload during the runway excursion sequence.
The investigation also identified that limited runway condition information available prior to departure reduced the crews ability to fully assess the operational suitability of the airstrip under the prevailing wet-season conditions. The absence of a structured runway condition assessment, including surface condition and braking action reporting, increased the operational risk associated with conducting a take-off from the contaminated runway surface.
Papa New Guinea's AIC released their final report concluding the probable causes of the accident were:
The investigation identified that the occurrence resulted from a combination of environmental, aerodrome, and human factors. The severely reduced runway surface friction resulting from heavy overnight rainfall, which left the grass runway surface at Tapini Airstrip wet, muddy, and slippery. Poor drainage at the airstrip contributed to water accumulation and deterioration of the runway surface condition, significantly reducing braking effectiveness, steering authority, and tyre traction during the take-off roll.
Contributing aerodrome factors included the approximately 4.5% downhill gradient and lateral slope of Runway 09, which increased the aircrafts tendency to slide on the contaminated surface and reduced the effectiveness of directional control inputs. The presence of overgrown vegetation and perimeter fencing adjacent to the runway also increased the likelihood and severity of damage during the runway excursion.
Contributing human factors included the control inputs applied by the pilot-in-command in response to the developing loss of directional control. As the aircraft was already skidding on a low-friction surface, the use of rudder, nose wheel steering (tiller), and asymmetric power increased the loading and structural stresses acting on the nose wheel assembly. These stresses contributed to the damage sustained by the assembly; however, the subsequent failure resulted from the combined effects of these stresses, entanglement with perimeter fencing wire, and overload during the runway excursion sequence.
The investigation also identified that limited runway condition information available prior to departure reduced the crews ability to fully assess the operational suitability of the airstrip under the prevailing wet-season conditions. The absence of a structured runway condition assessment, including surface condition and braking action reporting, increased the operational risk associated with conducting a take-off from the contaminated runway surface.
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