What happened
On 5 March 2013, a Taylor monoplane, registration ZS-UHI, departed Wonderboom aerodrome for a private flight to Panorama aerodrome. During the flight, the pilot noticed that the airspeed readings seemed inconsistent with expected performance. To verify the speed, the pilot coordinated with another aircraft flying in formation.
While performing the approach to runway 01 at Panorama, the pilot extended full flaps and reduced the airspeed to an indicated 65 knots. However, due to a technical error, the actual airspeed was significantly lower. This caused the aircraft to stall, leading to a left-wing drop and a developed spin. The aircraft struck a barbed wire fence surrounding the Panorama cemetery before impacting the ground. The aircraft was destroyed, and the pilot sustained serious injuries.
The investigation
SACAA AIID investigators examined the wreckage and the aircraft's maintenance history. The investigation focused on why the aircraft entered a spin during a standard approach. Analysts found that the aircraft's airspeed indicator was providing an erroneous, higher-than-actual reading.
Upon inspecting the pitot-static system, investigators discovered that a flexible hose in the static line had been improperly routed and was kinked. This kink trapped static pressure within the system, causing the instrument to over-read by approximately 21 knots. Consequently, when the pilot believed the aircraft was flying at 65 knots, it was actually traveling at only 44 knots, which was below the aircraft's stalling speed.
Findings
- The primary cause of the accident was the failure to maintain sufficient flying speed, resulting in a stall.
- A kinked flexible hose in the static line caused the airspeed indicator to provide an incorrect, higher reading.
- Improper maintenance practices led to the incorrect installation of the static line and the lack of proper securing clamps.
- The pilot was flying the aircraft under visual flight rules in clear weather conditions.