# NTSB CEN22FA064: Vans RV-4, N456MC, Walsenburg, CO, December 8, 2021 - Type: NTSB accident investigation - Classification: Accident · Fatal · Class 3 · Field · Final report - Date: December 8, 2021, 10:13 local (17:13 UTC) - Place: Walsenburg, CO · Cucharas River canyon - Coordinates: 37.792822, -104.57616 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=37.7928&lon=-104.5762&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Defining event: [Maneuvering-low-alt flying: Loss of control in flight](https://openairdocs.org/ntsb-events/240) - Highest injury: Fatal - Injuries: 1 fatal - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Central Region - Parties: FAA FSDO - NTSB case key (mKey): 104374 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN22FA064 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/104374/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=104374 - Page: https://openairdocs.org/ntsb/CEN22FA064 ## Probable cause The pilot’s failure to maintain clearance from terrain while intentionally maneuvering in a canyon at low altitude. Contributing to the accident was the pilot’s decision to enter a canyon environment at a low altitude, and the sudden change in wind conditions within the canyon. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Info processing/decision: decision making/judgment](https://openairdocs.org/ntsb-findings/02041520): Personnel issues › Action/decision · Pilot (probable cause); cases with it: [Michael V Cranford VANS RV-4, 1 case](https://openairdocs.org/ntsb-findings/02041520/cases.md?model=05638VM), [All aircraft, 3,098 cases](https://openairdocs.org/ntsb-findings/02041520/cases.md) - [Use of equip/info: aircraft control](https://openairdocs.org/ntsb-findings/02063040): Personnel issues › Task performance · Pilot (probable cause); cases with it: [Michael V Cranford VANS RV-4, 1 case](https://openairdocs.org/ntsb-findings/02063040/cases.md?model=05638VM), [All aircraft, 9,295 cases](https://openairdocs.org/ntsb-findings/02063040/cases.md) - [Performance/control parameters: altitude](https://openairdocs.org/ntsb-findings/01062012): Aircraft › Aircraft oper/perf/capability · Not attained/maintained (probable cause); cases with it: [Michael V Cranford VANS RV-4, 1 case](https://openairdocs.org/ntsb-findings/01062012/cases.md?model=05638VM), [All aircraft, 1,310 cases](https://openairdocs.org/ntsb-findings/01062012/cases.md) - [Wind: sudden wind shift](https://openairdocs.org/ntsb-findings/03034010): Environmental issues › Conditions/weather/phenomena · Effect on operation (probable cause); cases with it: [Michael V Cranford VANS RV-4, 1 case](https://openairdocs.org/ntsb-findings/03034010/cases.md?model=05638VM), [All aircraft, 114 cases](https://openairdocs.org/ntsb-findings/03034010/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Maneuvering-low-alt flying: Loss of control in flight](https://openairdocs.org/ntsb-events/240) (defining event); cases with it: [Michael V Cranford VANS RV-4, 1 case](https://openairdocs.org/ntsb-events/240/sequence.md?model=05638VM), [All aircraft, 5,002 cases](https://openairdocs.org/ntsb-events/240/sequence.md) - [Maneuvering-low-alt flying: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Michael V Cranford VANS RV-4, 1 case](https://openairdocs.org/ntsb-events/470/sequence.md?model=05638VM), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md) ## Analysis The accident occurred during a three-airplane formation flight to practice position changes and low-level maneuvering. About 30 minutes after takeoff, the pilots began a descent toward a reservoir, with the accident airplane as the lead. The airplanes were in a right-echelon route formation and were prepared to go to a trail formation for low-level maneuvering in the river canyon. About 1 mile north of the reservoir, the accident pilot directed the two other pilots to “go trail,” and he executed a left turn and descent toward a river canyon that extended north of the reservoir. The pilots reported they entered a descent and encountered strong surface winds and turbulence above the canyon rim. The accident pilot’s airplane descended below the canyon rim and continued the descent to near the bottom of the canyon. One pilot reported there was a strong south-southwest wind (210° at 35 mph) a couple thousand feet above the surface, so he remained above the canyon rim to assess potential turbulence. During the third turn and less than a minute inside the canyon, the pilots observed the accident airplane’s left wing contact the edge of the canyon at high speed. The airplane fragmented and came to a stop in the canyon. Postaccident examination of the airplane revealed no evidence of any preimpact mechanical malfunctions or failures that would have precluded normal operations. Local authorities who responded to the accident location reported intense and variable winds within the canyon that were different than the winds they encountered above the canyon rim. Available weather information indicated that conditions in the vicinity of the accident site were favorable for the presence of moderate-to-severe turbulence. The circumstances of the accident are consistent with the pilot’s loss of control due to high-speed, variable wind conditions while maneuvering at low altitude in a canyon. The autopsy revealed the pilot’s severe coronary artery disease put him at risk for an acute coronary event, which could acutely cause chest pain, shortness of breath, palpitations, or fainting. However, there is nothing about the operational information in this investigation to suggest such an event contributed to the circumstances of the accident. Therefore, it is unlikely his coronary artery disease contributed to this accident. ## Factual narrative The airplane logbooks and records were not located during the investigation. On December 8, 2021, about 1013 mountain standard time, a Vans RV-4 airplane, N456MC, sustained substantial damage when it was involved in an accident near Walsenburg, Colorado. The pilot sustained fatal injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. According to two other pilots involved in the flight, the accident flight was a three-airplane formation flight to practice position changes and low-level maneuvering. The three airplanes departed Meadow Lake Airport (FLY), Colorado Springs, Colorado, and headed south with the accident airplane as the lead airplane. About 30 minutes after takeoff, the airplanes flew south past Pueblo, Colorado, and began a descent toward the Cucharas Reservoir, northeast of Walsenburg. The airplanes were in a right-echelon route formation and were prepared to go to a trail formation for low-level maneuvering within the river canyon. About 1 mile north of the reservoir, the accident pilot directed the two other pilots to “go trail,” and he made a left turn and a descent toward a river canyon that extended north of the reservoir. The pilots reported they entered a descent and encountered strong surface winds and turbulence above the canyon rim. The accident pilot’s airplane descended below the canyon rim and continued the descent to near the bottom of the canyon. One pilot reported there was a strong south-southwest wind (210° at 35 mph) a couple thousand feet above the surface, so he remained above the canyon rim to assess potential turbulence. During the third turn and less than a minute inside the canyon, the pilots observed the accident airplane’s left wing contact the edge of the canyon at a high speed. The airplane fragmented and came to a stop in the canyon. After the accident, the pilots circled the area, contacted air traffic control to report the accident location, and then returned to FLY. A review of the automatic dependent surveillance-broadcast (ADS-B) data revealed the flight tracks for the three airplanes were consistent with the witness reports. The accident airplane’s data ended about 1 mile west of the accident site. The El Paso County Coroner’s Office, Colorado Springs, Colorado, 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 was an accident. In addition, severe coronary artery disease was identified; the left anterior descending and right coronary arteries exhibited focal eccentric stenosis of about 75%. The right coronary artery exhibited evidence of recanalization (meaning previously having greater occlusion and reopening to some degree). No other mention was made of other cardiac findings and no other significant disease was identified. Toxicology testing performed at the Federal Aviation Administration Forensic Sciences Laboratory found salicylic acid in thepilot’s blood and liver. Salicylic acid is a metabolite of aspirin, an over-the-counter analgesic that may be used to prevent heart attacks. No ethanol was detected. There were several pilot reports (PIREPs) of light-to-moderate turbulence over the area prior to 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 in the vicinity of the accident site consistent with moderate-to-severe turbulence. Huerfano County Sheriff’s personnel, who responded to the accident site shortly after receiving the report of a missing airplane, reported the winds above the canyon rim were different in intensity and direction than the winds encountered within the canyon. The winds within the canyon were strong and variable depending on the terrain features. Postaccident examination of the accident site revealed the left wing and wing tip were at the initial impact area. The airplane’s forward fuselage impacted rocky terrain, and the airplane fragmented into multiple sections. The engine, fractured composite propeller blades, and the main landing gear were 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 the left and right wings (see figure). Figure. Accident Site and Main Wreckage 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 of the airplane 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 National Transportation Safety Board recorders laboratory for data extraction. The unit sustained impact damage, and the display was missing from the device. The unit stored data in the nonvolatile memory (NVM); however, further examination of the device revealed that the NVM was damaged in the accident. The extent of damage precluded normal recovery procedures and additional attempts were unsuccessful in recovering usable data. ## Aircraft - Registration: [N456MC](https://openairdocs.org/deregistered/N456MC-2022-12-31), registration cancelled 2022-12-31, S/N 2005, built 2020 (OpenAirDocs) - Reported make and model: VANS RV-4 - Registry model: [Michael V Cranford VANS RV-4](https://openairdocs.org/model/michael-v-cranford-vans-rv-4) (registry code 05638VM) (OpenAirDocs) - Registry engine: [Lycoming IO-360 series](https://openairdocs.org/engine/lycoming-io-360-series) (registry code 41881, reciprocating) (OpenAirDocs) - Category: Airplane, amateur-built - Serial number: 2005 - Year built: 2020 - Engines: Lycoming IO-360 180 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Airworthiness certificate: Special, Experimental (Special) - Departed: FLY, Colorado Springs, CO - Equipment: Electronic primary flight display, Electronic multifunction display, ADS-B ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 70; injuries: fatal; commercial, airline transport; airplane ratings: single-engine land; instrument ratings: airplane; medical: basicmed, without waivers/limitations; seat: front; restraint: 4-point; toxicology performed; flight hours: 20,181 total, 23 in this make and model ## Weather - Conditions: Visual (VMC), Day - Wind: 280° at 13 knots, gusting 23 - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 52 °F, dew point 19 °F - Altimeter: 29.90 inHg - Turbulence: Moderate - Observed at: K4V1, 9.5 nm away ## FAA reports on this event (1) The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs). - [Accident 20211208020679A](https://openairdocs.org/incident/20211208020679A), Dec 8, 2021: Michael V Cranford VANS RV-4, Walsenburg, CO, Substantial damage, 1 fatal. On December 8, 2021, about 1013 mountain standard time, a vans RV-4 airplane, N456MC, sustained substantial damage when it was involved in an accident near… ## Docket (14 files) The files NTSB released with the investigation on June 7, 2022, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=104374. 99.3 MB in all. - Flight overview (item 1, PDF, 3 pages, 14.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13769061&FileExtension=pdf&FileName=Flight%20Track%20Overview-Rel.pdf - N456MC flight data (item 2, CSV, 25 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13769458&FileExtension=csv&FileName=N456MC%20OpsVue%20Data-Rel.csv - N223RL flight data (item 3, CSV, 37 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13769804&FileExtension=csv&FileName=N223RL%20OpsVue%20Data-Rel.csv - N642BG flight data (item 4, CSV, 25 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13769350&FileExtension=csv&FileName=N642BG%20OpsVue%20Data-Rel.csv - N223RL witness statement (item 5, PDF, 3 pages, 14.9 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13769606&FileExtension=pdf&FileName=Airplane%20Witness%20Statement%202-Rel.pdf - N642BG witness statement (item 6, PDF, 5 pages, 66.9 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13769596&FileExtension=pdf&FileName=Airplane%20Witness%20Statement_Redacted-Rel.pdf - Record of conversation - huerfano county sheriff personnel (item 7, PDF, 1 page, 144 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13769616&FileExtension=pdf&FileName=ROC%20Huerfano%20County%20Sheriff%20Personnel-Rel.pdf - Aircraft examination summary (item 8, PDF, 3 pages, 1.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13770015&FileExtension=pdf&FileName=Aircraft%20Examination%20Summary-Rel.pdf - Recorded flight data specialist's factual report (item 9, PDF, 2 pages, 574 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13725687&FileExtension=pdf&FileName=Recorded%20Flight%20Data%20Specialist%27s%20Factual%20Report-Rel.pdf - Weather summary (item 10, PDF, 1 page, 206 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13769814&FileExtension=pdf&FileName=Weather%20Summary-Rel.pdf - Toxicological report (item 11, PDF, 1 page, 378 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13770025&FileExtension=pdf&FileName=Tox_Redacted-Rel.pdf - Autopsy memo (item 12, PDF, 1 page, 210 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13769636&FileExtension=pdf&FileName=Autopsy%20Memo-Rel.pdf - Medical factual report (item 13, PDF, 2 pages, 123 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13707385&FileExtension=pdf&FileName=CEN22FA064_Medical%20Factual-Rel.pdf - Release of aircraft wreckage, NTSB form 6120.15 (item 14, PDF, 1 page, 180 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13770306&FileExtension=pdf&FileName=Signed%20Wreckage%20Release_Redacted-Rel.pdf From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.