Southern Airways Flight 246

During initial climb, the flight crew began to feel a vibration and loss of engine power. They declared an emergency and turned back toward the departure airport. Upon realizing they would not be able to return to the departure airport, they landed on a road, resulting in minor damage to the airplane. Postincident examination of the airframe and engine found no preincident mechanical malfunctions or failures that would have precluded normal operations. Postincident photographs taken of the airplane by first responders shortly after the incident show contamination buildup on some of the airplane’s lift-generating surfaces (that is, the wings and horizontal and vertical stabilizers). Weather before and around the time of the incident included light snow and below freezing temperatures. When the flight crew checked the airplane for contamination during their preflight inspection, they did not observe any ice or snow accumulation, but the airplane appeared wet. Neither crewmember performed a tactile check of the airplane’s lift generating surfaces, and the captain chose not to deice the airplane. He reported that the company had deicing services available and that it would normally be applied at the gate. Company procedures stated that the only acceptable deice fluid was Type 1. The operator’s standard operating procedures dictated that a visual contamination check was required to be performed within five minutes before takeoff. The same guidance left the decision to perform a tactile check of the airplane’s lift-generating surfaces to the captain. This directly contradicted the airplane manufacturer’s guidance, which stated that a tactile check must be completed when the outside air temperature is below 10°C. The second-in-command (SIC) reported that before entering the runway, they looked out at the wing and did not observe any contamination, stating that it was “just wet.” Due to contradictory guidance on when a tactile versus visual check must be performed, it is likely the crew believed they had completed an appropriate contamination check before departing. Based on the weather conditions at the time, reports that another airplane—which had been on the ground for a similar amount of time—was observed with ice accumulation, and the failure of the crew to perform a tactile contamination check within 5 minutes before takeoff; it is likely that ice had accumulated on the airframe before takeoff. Based on the taxi time of about 6 minutes and a holdover time of 11 minutes, it is also likely that had the crew chose to deice, any accumulated ice would have been removed, and the airplane subsequently would not have accumulated additional ice. Review of ADS-B data showed that during initial climb the airplane’s groundspeed (after accounting for the prevailing 8 knot headwind component) decreased below the stall speeds listed in the airplane pilot’s operating handbook. The vibration the crew felt was likely the beginning stages of an aerodynamic stall that was likely exacerbated by the degraded performance associated with structural icing.

Verbatim NTSB analysis and probable cause from the NTSB dataset