What happened
On November 28, 2017, at approximately 12:00 LMT, a student pilot was conducting a training flight following a route from Dęblin to Nowe Miasto, Warka, and back to Dęblin. After reaching the initial waypoint, establishing cruise power, and transitioning to level flight, the pilot noticed an anomaly on the engine power indicator. The power percentage indicator changed from white to yellow, with values fluctuating between 70% and 90%.
In addition to the power fluctuations, the pilot observed unusual readings from the twist grip, which caused the Guimbal Cabri G2 to deviate from its intended flight path. Due to these irregularities, the pilot decided to terminate the flight and return to the departure airfield. Upon landing and transitioning the engine to idle, the power indicator continued to fluctuate between 2% and 5%. Following an engine shutdown and a subsequent power-on self-test, a throttle malfunction alert appeared on the cockpit display, an error that had not been present prior to the flight.
The investigation
The investigation focused on the mechanical integrity of the engine control systems and the cockpit instrumentation. The operator's maintenance organization conducted a thorough inspection of the throttle position measurement system. The inspection identified a malfunction within the throttle position sensor.
Findings
- The primary cause of the incident was a failure of the throttle position sensor.
- The faulty component (p/n: HG70-2308, s/n: 125234) was replaced with a new unit.
- Following the replacement and subsequent adjustment according to the maintenance manual, a ground test was performed, and no further irregularities were detected.