The Safety Board concludes that the aileron flight control surface position sensors
installed on airplanes in accordance with STC No. ST01310NY are unreliable and that
FDR functional checks every 6 months could ensure the timely identification and
correction of potentiometer malfunctions and ensure that accurate flight control data are available for accident and incident investigations. Therefore, the Safety Board believes that the FAA should require the replacement of aileron surface position sensors installed in accordance with STC No. ST01310NY with more reliable aileron surface position sensor within 1 year or at the next heavy maintenance check, whichever comes first, after the issuance of an approved STC. Until reliable aileron surface position sensors have been installed, require FDR functional checks every 6 months and replacement of faulty sensors, as necessary. Additionally, the Safety Board believes that the FAA should conduct a review of all FDR systems that have been modified by an STC to determine the reliability of all sensors used as flight control surface position sensors. If the review determines that a sensor does not provide reliable flight control surface position data,require that the sensor be replaced with a more reliable sensor.