What happened
On 20 January 2022, a Windlass Aquilla 912 microlight, registered as ZU-IMN, departed Groutville Private Airstrip in KwaZulu-Natal for a scheduled crop-spraying mission. The flight was being conducted under visual meteorological conditions as part of a commercial operation. After completing a previous spraying task, the pilot had refilled the aircraft with both fuel and chemical supplies.
During the takeoff roll from the departure airstrip, the pilot noted that the aircraft was failing to accelerate at the expected rate despite applying full power. Although the pilot observed the sluggish speed, the takeoff continued. Shortly after becoming airborne, the engine's revolutions per minute (RPM) began to decrease, and the aircraft's climb profile deteriorated rapidly. Realizing the engine was losing power and the aircraft was losing altitude, the pilot attempted an air turn back but was forced to execute an emergency landing in an open field at a golf driving range. The aircraft struck an embankment, resulting in substantial damage to the Windlass Aquilla 912, while the pilot sustained minor injuries.
The investigation
An investigation into the incident examined the aircraft's maintenance history and mechanical condition. The aircraft had undergone a 50-hour annual inspection approximately ten days prior to the accident. Following the event, an approved person and a Rotax engine agent inspected the engine's carburetor bowls. They discovered an imbalance in fuel levels, with one bowl full and the other only half-full. However, subsequent testing showed the engine could reach full power and operate normally.
Findings
- The investigation could not find conclusive evidence of a mechanical engine failure, leading investigators to suggest that vapour lock in the fuel line may have occurred. This was potentially caused by heat rising from the engine to the fuel pipes during the refueling and chemical replenishment process.
- The aircraft was operating at its maximum takeoff weight, carrying 100 litres of chemical.
- The loss of engine RPM, combined with the high drag associated with the maximum weight and balance configuration, prevented the pilot from maintaining sufficient lift and airspeed to continue flight.