What happened
On September 16, 2016, a Partenotomy/Vulcanair P-68TC Observer, operated by OPEGIEKA sp. z o.o., was conducting a photogrammetric flight within the Rzeszów TMA at an altitude of 4,500 ft. During the mission, the pilot identified a loss of power in the right engine, noting that the maximum manifold pressure achievable during power increases was only 30 in.Hg, significantly lower than the expected 44 in.Hg. Following this engine performance degradation, the pilot elected to return to the departure airfield, EPRZ.
The investigation
The investigation focused on the mechanical integrity of the engine's turbocharger control system. Investigators examined the control linkage (connector P/N LW14714) responsible for the turbocharger wastegate. The examination revealed that the external sheath of the control cable had become disconnected from the cable itself, causing the inner cable to protrude from the housing. This displacement prevented the linkage from functioning in the compression direction, as the protruding portion of the cable would bend rather than transmit movement.
Findings
- The primary cause of the incident was the failure of the turbocharger wastegate control linkage (connector P/N LW14714), specifically the separation of the cable from its outer sheath.
- The investigation identified that one end of the linkage is positioned within an area of the engine compartment subject to high temperatures. This heat likely degraded the lubrication within the assembly, increasing friction and resistance during the movement of the pushrod end within its sleeve, which ultimately led to the mechanical failure.
- This was noted as a recurring issue, as a previous failure of the same part number (P/N LW14714) had been recorded on July 7, 2013.