Accident Details
On November 15, 2022, at approximately 1500 central standard time, a Fairchild SA227-AT airplane, registration N247DH, sustained substantial damage after impacting terrain near Pewaukee, Wisconsin. The aircraft was operating under Title 14 Code of Federal Regulations Part 135 as an on-demand cargo flight. Both flight crew members received minor injuries, and the sole passenger was uninjured.
Flight Crew Account
During climb and cruise, the crew experienced occasional momentary right yaw. They opted to keep the yaw damper engaged as it was otherwise functioning normally. While performing an ILS approach to runway 10 at Waukesha County Airport (UES), the flight director command bars indicated a climbing right turn, though the autopilot remained engaged and tracking the localizer and glideslope. Airspeed was steady at about 135 knots. The crew disconnected the autopilot, after which the airplane immediately rolled to the right. Both pilots applied control inputs and increased engine power, managing to level the wings, but the aircraft struck the ground in a near-wings-level attitude. During the impact sequence, the airplane contacted trees, causing the wings to separate and resulting in substantial damage to the wings and fuselage.
Post-Accident Examination
Examination revealed that the flight control system was intact except for damage from the impact. The airplane had manual trim for yaw and roll and electric pitch trim. The rudder trim tab was neutral, and the horizontal stabilizer leading edge was near the maximum nose-up trim marking. Aileron trim could not be assessed due to wing damage. The engines rotated freely with no preimpact anomalies detected. The yaw damper system, which was optional, was found inoperative: the servo clutch would not engage, and the yaw damper computer was not receiving signals from its internal accelerometer, causing a constant neutral output. Other avionics components exhibited some out-of-specification parameters but would not have caused a complete automatic flight control failure.
ADS-B Data Analysis
The flight originated from New Orleans Lakefront Airport (NEW) at 1204, climbing to approximately 20,000 feet. Descent toward UES began about 1440. Performance study of ADS-B data showed that at 1458:15, the airplane was at 2,160 feet and 192 knots, turning inbound on the localizer. By 1459:00, it slowed below 160 knots, the crew-reported minimum speed for icing conditions (ice protection was on, no visible ice). At 1459:07, descent along the glideslope began. At 1459:14, it passed through 130 knots, the selected approach speed. The airplane continued descending in a level attitude, reaching 102 knots at 1459:28. At that point, it descended below the glideslope and began a slight right turn. Initially descending at 1,500 ft/min, the airspeed continued to drop. By 1459:34, airspeed fell below 100 knots with a 27° right bank. Descent rate then increased to over 4,000 ft/min, airspeed rose, and groundspeed remained 80-90 knots. The airplane then rolled sharply left. The sudden roll and altitude loss after reaching low airspeed were consistent with an aerodynamic stall. At 1459:46, altitude was 1,260 feet (about 400 feet AGL), with final data points showing reduced descent rate and near-level wings, matching the impact attitude.