History of Flight
On December 8, 2021, at about 1013 mountain standard time, a Vans RV-4 airplane, registration N456MC, sustained substantial damage in an accident near Walsenburg, Colorado. The pilot sustained fatal injuries. The flight was conducted as a personal flight under Title 14 Code of Federal Regulations Part 91.
Two other pilots participating in the flight reported that the accident flight was a three-airplane formation flight practicing position changes and low-level maneuvering. The group departed Meadow Lake Airport (FLY) in Colorado Springs, Colorado, and flew south with the accident airplane as the lead. About 30 minutes after takeoff, the airplanes passed south of Pueblo, Colorado, and began descending toward the Cucharas Reservoir, northeast of Walsenburg. The formation was in a right-echelon route formation and prepared to transition to a trail formation for low-level work within a river canyon.
Approximately 1 mile north of the reservoir, the accident pilot directed the other pilots to "go trail" and initiated a left turn and descent toward a river canyon extending north of the reservoir. The pilots reported entering a descent and encountering strong surface winds and turbulence above the canyon rim. The accident airplane descended below the canyon rim and continued to near the canyon bottom. One pilot noted a strong south-southwest wind (210° at 35 mph) a couple thousand feet above the surface and remained above the rim to assess turbulence. During the third turn, less than a minute inside the canyon, the other pilots observed the accident airplane's left wing contact the canyon edge at high speed. The airplane fragmented and came to rest in the canyon. After the accident, the pilots circled the area, contacted air traffic control to report the location, and returned to FLY.
Automatic dependent surveillance-broadcast (ADS-B) data reviewed during the investigation showed flight tracks consistent with witness reports. The accident airplane's data ended about 1 mile west of the accident site.
Meteorological Information
Several pilot reports (PIREPs) indicated light-to-moderate turbulence over the area before the accident, with at least four urgent reports of moderate-to-severe turbulence after the accident. The National Weather Service Graphic Turbulence Guidance provided eddy dissipation rates between 20 and 45 over southern Colorado near the accident site, consistent with moderate-to-severe turbulence.
Huerfano County Sheriff’s personnel, who responded shortly after receiving a report of a missing airplane, noted that winds above the canyon rim differed in intensity and direction from those within the canyon. Winds inside the canyon were strong and variable depending on terrain features.
Wreckage and Impact Information
Postaccident examination of the accident site showed the left wing and wing tip at the initial impact area. The forward fuselage impacted rocky terrain, and the airplane fragmented into multiple sections. The engine, fractured composite propeller blades, and main landing gear separated and came to rest between the initial impact and the main wreckage. The main wreckage consisted of the cockpit/cabin, empennage, and inboard sections of both wings.
Flight control continuity was established from the cockpit to all flight control surface connections. The engine/propeller control assembly was separated inside the cockpit; the throttle and mixture control levers were found in the full forward positions. The composite propeller blades were sheared off at the propeller hub.
Postaccident examination revealed no evidence of any preimpact mechanical malfunctions or failures that would have precluded normal operations. A fragmented Dynon SV-D1000 Skyview Display unit was sent to the NTSB recorders laboratory for data extraction, but the display was missing and the nonvolatile memory (NVM) was damaged, preventing data recovery.
Medical and Pathological Information
The El Paso County Coroner's Office performed an autopsy on the pilot's remains. The autopsy report listed the cause of death as "multiple blunt force injuries" and the manner of death as accident. Severe coronary artery disease was identified, with the left anterior descending and right coronary arteries exhibiting focal eccentric stenosis of about 75%. The right coronary artery showed evidence of recanalization. Toxicology testing found salicylic acid (a metabolite of aspirin) in the pilot's blood and liver; no ethanol was detected.