What happened
On March 14, 2017, at approximately 18:35 local time, a U-28A, registration 0724, crashed approximately one-quarter mile south of Clovis Municipal Airport in New Mexico. The aircraft was being operated by the 318th Special Operations Squadron, part of the 27th Special Operations Wing based at Cannon Air Force Base.
The flight originated from Cannon Air Force Base at 15:12 local time, initially traveling to Lubbock, Texas, for tactical training. After completing training in Lubbock airspace, the crew proceeded toward Clovis Municipal Airport. Upon arrival at the airport, the crew entered the traffic pattern at 18:06 local time to perform several approaches and landings, including a practice turnback Emergency Landing Pattern (ELP).
During the execution of the practice turnback maneuver, the aircraft experienced an excessive descent rate and nose-down attitude. In an attempt to correct the flight path and align with the runway centerline, the crew applied back-pressure on the yoke and increased the bank angle. This maneuver caused the airspeed to drop below the stall speed for the zero-degree flap configuration, leading to a loss of controlled flight. Despite attempts to increase power, the aircraft could not recover before impacting the ground. The impact resulted in the destruction of the aircraft and three fatalities.
Findings
Investigations into the accident identified several contributing factors related to the aircraft's configuration and flight dynamics during the maneuver:
- The use of zero-degree flaps during the practice turnback ELP necessitated a higher nose-down attitude and a faster descent rate to maintain a safe angle of attack compared to a 15-degree flap approach.
- The stall speed for the aircraft was significantly higher at zero-degree flaps, specifically by 15 to 25 knots, during the bank angles utilized by the crew.
- The crew was unable to achieve the necessary bank angle in time to align with the extended runway centerline, creating an overshoot condition.
- The application of back-pressure on the yoke to arrest the descent caused the airspeed to fall below the stall speed for the current flap setting, triggering the aerodynamic stall.