What happened
On 15 September 2013, a Piper Cherokee 235, registration ZS-DWJ, departed from Runway 04 at Mabaling and was en route to Vryburg Aerodrome. The flight was being conducted under visual meteorological conditions with four people on board. During the initial climb, the pilot experienced a significant loss of altitude and the aircraft's stall warning activated. While attempting to turn into the wind, the aircraft struck trees at an altitude of approximately 10 to 15 meters before impacting the ground. The accident resulted in two serious injuries, involving the pilot and one passenger, while the aircraft sustained substantial damage.
The investigation
The investigation examined the aircraft's performance under the prevailing environmental conditions and the pilot's actions during the departure. Investigators noted that the aircraft was operating on an up-slope runway (+1% gradient) toward a mountain. The high surface temperature of 35°C had resulted in a density altitude of 6,750 feet, significantly reducing engine and aerodynamic performance.
Evidence showed that the pilot did not perform a weight and balance calculation prior to departure, nor did they consult the Pilot Operating Handbook (POH) to assess performance requirements for the high density altitude and runway slope. Furthermore, the pilot selected 25 degrees of flaps after the aircraft was already airborne, a configuration the POH suggests should only be used for obstacle clearance and selected before take-off.
Findings
- The primary cause of the accident was that the pilot stalled the aircraft during the climb phase following take-off.
- The aircraft's performance was severely degraded by high density altitude caused by high ambient temperatures.
- The pilot maintained a high nose attitude, which may have obscured the view of the mountain at the end of the runway.
- The selection of 25-degree flaps during the climb, combined with a left-hand turn at low airspeed, contributed to the loss of lift.
- The pilot failed to calculate the aircraft's weight and balance or verify performance data for the specific environmental conditions.