N1983X – CESSNA 208 – 2024-01-19 NTSB Accident Report

HISTORY OF FLIGHTOn 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), Dulles, Virginia, to Lancaster Airport (LNS), Lancaster, Pennsylvania.

The incident flight was the second flight of the day for the pilots; they flew the airplane into IAD from Dubois Regional Airport (DUJ), Dubois, Pennsylvania, about an hour before the incident. The pilot-in-command (PIC) stated that when he and the SIC performed a preflight inspection of the airplane at IAD, there was no ice or snow on it, so he decided not to deice the airplane. The SIC stated, “It started snowing basically right about the time that we did our startup. And it may have been snowing lightly before that, but I really didn't notice the snow until we were actually on startup.” Review of surveillance video from IAD showed that neither member of the flight crew performed a tactile inspection of the airplane’s lift-generating surfaces.

The SIC stated that before entering the runway for takeoff, the flight crew performed a visual contamination check of the wing. At that time, there was no accumulation; it was “just wet.” The SIC further reported that as engine power was increased for takeoff, she checked the engine instruments and “everything was in the green.”

The SIC reported that the flight proceeded normally until about 400 ft agl, when the engine started vibrating “like a flat tire.” The PIC, who was the pilot flying, stated that the vibration was accompanied by a loss of engine power, so he began a turn to return to IAD. The SIC then declared an emergency. In the turn, the flight crew realized that they would not be able to reach a runway, saw a highway in front of them with a break between traffic, and decided to land on the highway.

After the PIC landed the airplane 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 to the airplane. After communicating with the IAD air traffic control tower regarding their position and the disposition of their passengers, the pilots and passengers egressed the airplane.

Review of ADS-B data indicated that the airplane began taxiing on the terminal ramp for takeoff about 1239. The takeoff roll commenced at 1244:30. The airplane became airborne at 1245:06. At 1246:09, the airplane reached a pressure altitude of 900 ft and a ground speed of 94 kts. At 1246:38, the airplane continued to climb to 1,100 ft but had decelerated to a ground speed of 72 kts. At 1246:50, the airplane was at 1,100 ft but had decelerated to 40 kts ground speed. At 1246:58, the airplane had descended to 900 ft and its ground speed was 91 kts. The last ADS-B data point, at 1247:14, showed that the airplane was at a pressure altitude of 400 ft with a ground speed of 47 kts near a roadway just outside the IAD airport perimeter. PERSONNEL INFORMATIONAt the time of the incident, the PIC was current in the 208 and had accumulated 287.3 hours of PIC flight time in the airplane type. AIRCRAFT INFORMATIONThe pilot’s operating handbook (POH) for the Cessna 208B stated the following regarding visual and tactile checks of the wing:

If the OAT is below 10°C (50°F) a tactile check of the wing leading edge and upper surface per Section 4 of the Pilot Operating Handbook (POH) 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 the airplane is operated per FAR 135.227(b)(3).

Ground icing conditions are defined as:

1. The Outside Air Temperature (OAT) is 2°C (36°F) or below and visible moisture is present (i.e. rain, drizzle, sleet, snow, fog, water is present on the wing, etc.), or

2. The OAT is 5°C (40°F) or below and conditions are conducive to active frost formation (e.g. clear night with a dew point temperature/OAT difference of 3°C (5°F) or less). Takeoff is prohibited if frost, ice or snow may reasonably be expected to adhere to the airplane between the tactile check and takeoff (e.g. snow near freezing temperature with no deicing/anti-ice fluid application).

The incident airplane was equipped with wing, wing strut, and horizontal and vertical stabilizer leading edge deicing boots, as well as propeller heat. The airplane was rated for flight into icing conditions

The PIC reported that during the incident flight, the flight crew took off with 20° of flaps set. A review of the POH stall speed table showed the indicated airspeed for a stall at the incident weight and 20° of flaps was between 53 and 54 kts, depending on the center of gravity. The SIC reported that they retracted the flaps to the Up position between 400 and 500 ft msl. The POH stall speed table showed the indicated airspeed for a stall at the incident weight and flaps up was 63 kts. The POH also stated, “Even small amounts of snow, ice or frost contamination may cause a potentially dangerous degradation of aircraft performance and unexpected flight characteristics.” METEOROLOGICAL INFORMATIONThe meteorological aerodrome report (METAR) for IAD began reporting light snow and below freezing temperatures starting at 1117 and continued to report these conditions through the time of the incident. The gate agent for the flight reported that the captain chose not to deice the airplane. She also reported that she noticed ice had formed on another airplane that had been on the ground for a shorter amount of time than the incident airplane, and that it was snowing heavily while the airplanes were on the ground.

FAA guidance on holdover times for the 2023-2024 winter season stated that the holdover time for Type I fluid on critical aircraft surfaces composed predominately of aluminum was 11 to 18 minutes with light snow and an outside air temperature of -3°C or above.

About the time of the accident the reported wind was 330° (true) at 10 knots. This would have resulted in quartering right headwind during the takeoff with a headwind component of about 8 knots. AIRPORT INFORMATIONThe pilot’s operating handbook (POH) for the Cessna 208B stated the following regarding visual and tactile checks of the wing:

If the OAT is below 10°C (50°F) a tactile check of the wing leading edge and upper surface per Section 4 of the Pilot Operating Handbook (POH) 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 the airplane is operated per FAR 135.227(b)(3).

Ground icing conditions are defined as:

1. The Outside Air Temperature (OAT) is 2°C (36°F) or below and visible moisture is present (i.e. rain, drizzle, sleet, snow, fog, water is present on the wing, etc.), or

2. The OAT is 5°C (40°F) or below and conditions are conducive to active frost formation (e.g. clear night with a dew point temperature/OAT difference of 3°C (5°F) or less). Takeoff is prohibited if frost, ice or snow may reasonably be expected to adhere to the airplane between the tactile check and takeoff (e.g. snow near freezing temperature with no deicing/anti-ice fluid application).

The incident airplane was equipped with wing, wing strut, and horizontal and vertical stabilizer leading edge deicing boots, as well as propeller heat. The airplane was rated for flight into icing conditions

The PIC reported that during the incident flight, the flight crew took off with 20° of flaps set. A review of the POH stall speed table showed the indicated airspeed for a stall at the incident weight and 20° of flaps was between 53 and 54 kts, depending on the center of gravity. The SIC reported that they retracted the flaps to the Up position between 400 and 500 ft msl. The POH stall speed table showed the indicated airspeed for a stall at the incident weight and flaps up was 63 kts. The POH also stated, “Even small amounts of snow, ice or frost contamination may cause a potentially dangerous degradation of aircraft performance and unexpected flight characteristics.” WRECKAGE AND IMPACT INFORMATIONPostincident photographs taken of the airplane by first responders shortly after the incident showed contamination buildup on some of the airplane’s lift-generating surfaces.

Postincident examination of the turboprop engine revealed no indications of preimpact external or internal damage that would have precluded normal operation. A test cell run was performed, and power levels were found to meet the engine overhaul manual performance specifications with no fluctuations in engine speed or torque during testing. The propeller blades showed evidence of power at impact, including gouges on the leading edge, material missing from the blade tips, and blade bending opposite the direction of rotation. A propeller examination performed by the propeller manufacturer did not identify indications of preimpact failure and concluded that the propeller blade damage was consistent with significant rotational energy at impact. Propeller blade internal witness marks were also consistent with the blades being in the forward thrust operating range at impact. ADDITIONAL INFORMATIONFAA Advisory Circular 61-67C (Stall and Spin Awareness Training) states, “Just before the stall occurs, buffeting, uncontrollable pitching, or vibrations may begin.”

FAA Safety Alert for Operators 06002 (Ground Deicing Practices for Turbine Aircraft in Nonscheduled 14 CFR Part 135 Operations and in Part 91), issued March 29, 2006, recommended that operators review their standard operating procedures to ensure they include, “procedures to ensure that the aircraft’s lift-generating surfaces are COMPLETELY free of contamination before flight through a ta...