What happened
On 10 November 2018, a Yak 52, registration ZU-FRN, was conducting a private flight from Rand Aerodrome with the intention of returning to the same location. While cruising at approximately 7,000 feet near the Heineken factory in Vereeniging, the pilot experienced what was perceived as an uncommanded loss of engine power. After unsuccessful attempts to recover power, the pilot executed a forced landing in an open field on a private farm.
During the landing sequence, the aircraft's nose landing gear collapsed. This caused the propeller blades to strike the ground while the engine was still rotating, resulting in the blades shattering. The impact also caused damage to the nose section of the fuselage. Both the pilot and the passenger were able to exit the aircraft unassisted, and no injuries were reported.
The investigation
SACAA AIID investigators examined the wreckage and the engine components to determine the cause of the perceived power loss. A post-engine inspection revealed no evidence of mechanical failure, system malfunctions, or airframe issues. Furthermore, the investigation found that the engine was actually operating at a high-power setting during the impact. This was evidenced by the shattered state of the three wooden propeller blades and the manifold pressure gauge, which was found stuck at 660mmHg—a reading indicative of power levels just above cruise settings.
Findings
- The aircraft was landed on uneven terrain, which triggered the collapse of the nose landing gear.
- There was no evidence of any engine power loss or any other mechanical system failure prior to the landing.
- The engine was operating at a high-power setting at the moment the propeller struck the ground.
- The pilot did not follow the specific emergency procedures for preparing the aircraft for a forced landing on unknown ground, which typically involves retracting the undercarriage.