Incident Details
On April 24, 2018, at approximately 1000 mountain daylight time, a Cessna T303 airplane, registration N9746C, impacted terrain during an emergency off-airport landing near Pine Ridge, South Dakota. The flight had departed Aberdeen Regional Airport (ABR) at about 0930 central daylight time, destined for Pine Ridge Airport (IEN). The aircraft was operated by Aberdeen Flying Service under Title 14 Code of Federal Regulations Part 135 as an on-demand air taxi flight. Day instrument meteorological conditions (IMC) prevailed, and an instrument flight rules flight plan was filed.
The commercial pilot and two passengers sustained minor injuries, while one passenger was not injured. The airplane sustained substantial damage to the wings and fuselage. The pilot reported no preaccident mechanical malfunctions or failures that would have precluded normal operation, and the aircraft was below its maximum gross weight.
Sequence of Events
Before the flight, the pilot obtained a weather briefing via the company computer system and reviewed it with the company chief pilot. The briefing did not include icing conditions, but the pilot was aware of the forecast weather along the route and at the destination.
After takeoff, during the climb to 12,000 feet mean sea level (msl), the airplane encountered light rime ice. The pilot activated the de-ice equipment, which functioned without issues. After crossing over Pierre Regional Airport (PIR), Pierre, South Dakota, the pilot heard radio reports of better weather at a lower altitude and requested a descent to between 5,000 and 6,000 feet. During the descent, the airplane encountered light to moderate icing conditions. Prior to the descent, the airplane was clear of ice accumulation. The pilot considered turning back to PIR but could not obtain clearance due to poor radio coverage until the airplane was closer to IEN.
Shortly thereafter, the pilot reported that it felt "like a sheet of ice fell on us" as the airplane encountered severe icing conditions. The pilot applied full engine power to maintain altitude. The airplane exited the overcast cloud layer about 500 feet above ground level (agl). Unable to maintain altitude, the pilot decided to execute an off-airport emergency landing. The airplane touched down in a field about 25 miles from IEN. During the landing, the landing gear separated, and the airplane came to rest upright.
Weather Conditions
The Automated Surface Observation System (ASOS) at IEN, located 19 miles west-southwest of the accident site, reported conditions at 0852 as wind from 350° at 15 knots gusting to 22 knots, visibility 5 miles in unknown precipitation and mist, ceiling overcast at 1,200 feet agl, temperature 2° C, dew point 1° C, and altimeter 30.43 inches of mercury (Hg). At 0952, conditions were wind from 360° at 11 knots gusting to 20 knots, visibility 6 miles in unknown precipitation and mist, ceiling overcast at 1,300 feet agl, temperature 2° C, dew point 1° C, and altimeter 30.45 inches of Hg.
The National Weather Service Aviation Weather Center Current Icing Products, available online for preflight briefing, indicated a greater than 75% probability of icing over South Dakota from below 5,000 feet through 9,000 feet. Icing intensity was depicted as light to moderate, with a high threat of Supercooled Large Droplets at 5,000 and 7,000 feet.
The preflight weather briefing did not include inflight weather advisories. An AIRMET Zulu issued at 0700 and valid for 0900 included moderate ice between 5,000 feet and flight level 180, with conditions continuing beyond 0900. The briefing did include a pilot report of light rime icing encountered by a commercial airplane climbing between 3,500 and 10,000 feet in IMC. No SIGMET was current at the time of the accident.
Post-Accident Observations
Photograph images obtained by the operator confirmed that the airplane retained structural icing after the landing.
The Federal Aviation Administration's Instrument Flying Handbook (FAA-H-8083-15B) notes that flight in IMC involves operating in visible moisture, which can freeze on aircraft, causing increased weight, degraded performance, and unpredictable aerodynamic characteristics. The handbook emphasizes that avoidance and early recognition followed by prompt action are critical, and that structural icing can only worsen.