PC12 Icing Incident Near Saint-Étienne (LX-JFM)

Incident Overview and Aircraft Details On 23 January 2015, a PC12 aircraft with registration LX-JFM, operated and owned by Jetfly Aviation S.A. of Luxembourg, experienced an incident during an instrument flight rules (IFR) approach. The flight was a type rating renewal from Valence (LFLU) to Saint-Étienne (LFMH). The aircraft was approximately 5 nautical miles north of Saint-Étienne, France, at an altitude of 1,000 feet above ground level. ## Crew and Flight Conditions The flight crew consisted of a pilot-in-command, a French national born in 1967, and a pilot, a French national born in 1987. Both held commercial pilot licenses (CPL(A)) issued by the French Directorate General of Civil Aviation (DGAC) under EASA regulations. The pilot-in-command had 9,225 total flight hours, including 1,935 hours on the PC12 type. The second pilot had 1,906 total hours, including 1,090 hours on the type. ## Incident Description During an NDB approach to runway 18 at Saint-Étienne, the crew encountered oscillations and vibrations in icing conditions. Approximately 30 seconds before passing the EB NDB, with de-icing and anti-icing systems active, the crew felt pitch-axis oscillations with increasing amplitude. This was followed by a sudden roll movement to the right, then to the left. The crew engaged the autopilot, and the pilot flying felt strong vibrations in the pitch controls. ## Resolution and Aftermath The crew initiated a descent to regain visual conditions, increasing airspeed. At approximately 800 feet AGL, visual references were acquired, and the aircraft landed normally with a 20-knot speed surplus. On the ground, the crew verified the pneumatic de-icing boots were functioning correctly but found 4 to 5 cm of residual ice on the horizontal stabilizer in an area without boots. ## Investigation and Manufacturer Actions The incident was reported to the Swiss Safety Investigation Authority (SESE) by the French BEA on 5 March 2015, with the investigation delegated to Switzerland as the state of manufacture. Meteorological data showed 0°C at Saint-Étienne with a dew point of 1°C, and cloud cover of 2/8 to 4/8 at 800 feet AAE and 8/8 at 2,000 feet AAE. The crew estimated 4 to 5 minutes in icing conditions. In May 2016, the manufacturer updated the flight manual sections 4.24 and 4.25 regarding severe icing conditions, emphasizing the risk of residual ice on the tailplane and recommending minimum airspeeds and configuration changes to mitigate degraded flying qualities.