History of Flight
On January 19, 2024, at 1247 eastern standard time, Southern Airways Express flight 246, a Cessna 208B airplane, N1983X, was involved in an incident near Dulles, Virginia. The two commercial pilots and five passengers were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 135 scheduled domestic passenger flight from Washington Dulles International Airport (IAD) to Lancaster Airport (LNS), Pennsylvania.
The incident flight was the second flight of the day for the pilots; they flew the airplane into IAD from Dubois Regional Airport about an hour before the incident. The pilot-in-command (PIC) stated that when he and the second-in-command (SIC) performed a preflight inspection at IAD, there was no ice or snow on the airplane, so he decided not to deice it. The SIC noted that it started snowing around the time of startup. Review of surveillance video from IAD showed that neither flight crew member performed a tactile inspection of the airplane’s lift-generating surfaces.
Before entering the runway for takeoff, the flight crew performed a visual contamination check of the wing; there was no accumulation, only wet surfaces. As engine power was increased for takeoff, engine instruments were normal. The flight proceeded normally until about 400 ft above ground level, when the engine started vibrating. The PIC, who was flying, stated that the vibration was accompanied by a loss of engine power, so he began a turn to return to IAD. The SIC declared an emergency. The flight crew realized they would not reach a runway, saw a highway with a break in traffic, and decided to land on the highway.
After landing on the highway, due to a slight turn in the road, the airplane contacted the right guard rail during the landing roll-out, resulting in minor damage. After communicating with air traffic control, the pilots and passengers egressed.
ADS-B data indicated that the airplane began taxiing at about 1239, took off at 1244:30, and became airborne at 1245:06. At 1246:09, it reached 900 ft pressure altitude and 94 kts ground speed. At 1246:38, it climbed to 1,100 ft but decelerated to 72 kts. At 1246:50, it was at 1,100 ft and 40 kts. At 1246:58, it descended to 900 ft at 91 kts. The last data point, at 1247:14, showed 400 ft and 47 kts near a roadway outside the airport perimeter.
Personnel Information
At the time of the incident, the PIC was current in the Cessna 208 and had accumulated 287.3 hours of PIC flight time in the type.
Aircraft Information
The pilot’s operating handbook (POH) for the Cessna 208B stated that if the outside air temperature (OAT) is below 10°C (50°F), a tactile check of the wing leading edge and upper surface is required in addition to a visual inspection. During ground icing conditions, takeoff must be accomplished within 5 minutes of completing the tactile inspection unless operated per FAR 135.227(b)(3). Ground icing conditions are defined as OAT at or below 2°C with visible moisture, or OAT at or below 5°C with conditions conducive to active frost formation. Takeoff is prohibited if frost, ice, or snow may reasonably be expected to adhere between the tactile check and takeoff.
The incident airplane was equipped with wing, wing strut, and horizontal and vertical stabilizer leading edge deicing boots, as well as propeller heat. It was rated for flight into icing conditions. The PIC reported takeoff with 20° flaps. The POH stall speed table showed indicated airspeed for a stall at incident weight and 20° flaps between 53 and 54 kts. The SIC reported flaps retracted to Up between 400 and 500 ft msl; the POH stall speed for flaps up was 63 kts. The POH stated that even small amounts of snow, ice, or frost contamination may cause dangerous performance degradation.
Meteorological Information
METAR for IAD began reporting light snow and below freezing temperatures starting at 1117 and continued through the incident. The gate agent reported that the captain chose not to deice, and that she noticed ice had formed on another airplane that had been on the ground less time. It was snowing heavily while airplanes were on the ground. FAA guidance for holdover times for Type I fluid on aluminum surfaces was 11 to 18 minutes with light snow and OAT -3°C or above. About the time of the accident, wind was 330° true at 10 knots, resulting in a quartering right headwind during takeoff with a headwind component of about 8 knots.
Wreckage and Impact Information
Postincident photographs taken by first responders showed contamination buildup on some lift-generating surfaces. Postincident examination of the turboprop engine revealed no preimpact external or internal damage that would have precluded normal operation. A test cell run found power levels met specifications with no fluctuations. Propeller blades showed evidence of power at impact: gouges, missing material, and bending opposite the direction of rotation. The propeller manufacturer concluded that damage was consistent with significant rotational energy at impact, and internal witness marks were consistent with the blades in the forward thrust operating range.
Additional Information
FAA Advisory Circular 61-67C states that just before a stall, buffeting, uncontrollable pitching, or vibrations may begin. FAA Safety Alert for Operators 06002 recommended procedures to ensure lift-generating surfaces are completely free of contamination before flight through a tactile check when feasible. The operator’s standard operating procedures defined icing conditions as visible moisture with OAT 5°C or less. The operator’s flight operations manual (FOM) provided guidance on ground icing conditions and pre-takeoff contamination checks, including visual inspections within 5 minutes prior to takeoff and tactile checks if unsure of contamination. The FOM stated that accepted means for deicing include Type I fluid, heated forced air, heated hangar, or a soft brush. The winter operations guidance did not contain a definition for “active icing.”