CEN21LA067

The pilot and passenger were concluding a cross-country flight and were flying in the traffic pattern at their intended destination when the airplane pitched nose down and descended rapidly into mountainous terrain during the turn from the base leg to final approach. There were multiple witnesses who reported seeing the airplane enter a steep left turn toward the airport followed by a nose-down descent toward terrain. One witness reported that the airplane completed 3 or 4 spins while it descended nose down in a vertical descent and that the sound of the engine was “quite loud.” Airport security camera footage showed the airplane in a left-wing down, nose down, descending turn into terrain east of the airport. According to automatic dependent surveillance-broadcast (ADS-B) data, shortly after the airplane entered the left turn from the base leg to final approach, the airplane decelerated to 50 knots calibrated airspeed (KCAS) and the descent rate increased from 600 to 3,850 ft/min. According to the airplane kit manufacturer, the airplane’s wings-level aerodynamic stall speed at a maximum gross weight was 47 KCAS. The airplane maneuvering in the traffic pattern would require turns and, as such, there was a corresponding increase to aerodynamic stall speed during the turns. Additionally, the airplane’s left-wing-down roll was increasing when the airplane entered the rapid descent. Postaccident examination revealed no evidence of a preexisting mechanical malfunction or failure that would have precluded normal operation of the airplane. Based on the surveillance video footage, witness accounts, and the recorded ADS-B data, it is likely the pilot did not maintain adequate airspeed during the left turn from the base leg to final approach, which resulted in the airplane exceeding its critical angle of attack and inadvertently entering an aerodynamic stall/spin at a low altitude over mountainous terrain. Toxicology testing detected morphine in the pilot’s urine but not in his blood. The detection of acetaminophen suggests that the pilot had taken codeine with acetaminophen for mild to moderate pain relief. Since no morphine was present in the blood, no impairing effects would be expected. Thus, the effect of the pilot’s use of morphine or opiate pain reliever was not a factor in this accident.

The airplane’s maintenance logbooks were not located during the investigation. According to the airplane kit manufacturer, the airplane had a useable fuel capacity of 32 gallons distributed evenly between two wing fuel tanks. According to a fuel purchase receipt, before departing on the flight from TEX to DRO, the pilot dispensed 23.87 gallons of 100 low-lead aviation fuel using the self-serve fuel pump at TEX. According to Federal Aviation Administration airport documentation, the traffic pattern altitude for runway 27 at TEX was 10,484 ft msl, about 1,414 ft above the runway 27 threshold elevation. On November 26, 2020, about 1259 mountain standard time, a Vans RV4 airplane, N87LW, was substantially damaged when it was involved in an accident near Telluride, Colorado. The pilot and passenger were fatally injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. According to the airport manager for the Telluride Regional Airport (TEX), the pilot told an employee with the fixed base operator (FBO) at the airport that he intended to fly from TEX to Durango-La Plata County Airport (DRO), Durango, Colorado, to retrieve a passenger and then return to TEX. According to automatic dependent surveillance-broadcast (ADS-B) data, at 1125, the airplane departed TEX on runway 27 and flew direct to DRO and landed on runway 3 at 1150. At 1229, the airplane departed DRO on runway 3 and proceeded north back toward TEX, as shown in figure 1. About 1256:39, the airplane turned onto a left downwind for runway 27 at TEX. A FBO employee at TEX reported that she was monitoring the airport’s UNICOM frequency when the pilot transmitted that he was on the downwind leg for runway 27. The FBO employee told the pilot to park in the hangar after landing and the pilot replied “cool.” Further review of the recorded ADS-B data indicated that the airplane entered the traffic pattern while descending through 10,000 ft mean sea level (msl) and flew the downwind leg about 1 statute mile (sm) south of the runway 27 centerline, as shown in figure 2 and figure 3. The airplane continued to descend about 250 feet per minute (ft/min) during the downwind leg. The airplane entered the traffic pattern at 100 knots calibrated airspeed (KCAS) and decelerated during the downwind and base legs. Figure 1 – ADS-B Track Data for Flight Figure 2 – ADS-B Track Data for Airplane in Traffic Pattern Figure 3 – Altitude, Speed, and Vertical Speed About 1258:12, the airplane entered a left turn toward the base leg for runway 27 and continued to descend and decelerate. About 1258:58, the airplane entered a left turn from the base leg toward a 0.5 sm-final-approach-course to runway 27. During the final 4 seconds of recorded ADS-B data, the airplane decelerated to 50 KCAS and the descent rate increased from 600 ft/min to 3,850 ft/min, as shown in figure 4. The airplane’s calculated roll angle was left-wing down and varied between 23° and 88° during the final 4seconds of data, as shown in figure 5. According to the airplane kit manufacturer, the airplane’s wings-level aerodynamic stall speed at a maximum gross weight of 1,500 lbs was 47 KCAS. Figure 4 – Altitude, Speed, and Vertical Speed Figure 5 – Ground Track Angle, Roll Angle, and Flight Path Angle According to the FBO employee monitoring the airport’s UNICOM frequency, at exact time unknown, there was a brief transmission where the pilot exclaimed “oh [expletive].” The FBO employee noted that the airplane disappeared from the FBO’s flight tracking system a few minutes after the pilot’s final transmission and that a representative with the United States Air Force Search and Rescue called the airport inquiring about an emergency locator transmitter signal that had been detected. Airport security camera footage showed the airplane in a left-wing down, nose down, descending turn into mountainous terrain east of the airport. There was no video evidence of a postimpact fire or explosion. There were multiple witnesses who reported seeing the airplane enter a steep left turn toward the airport followed by a nose-down descent toward terrain. One witness reported that the airplane completed 3 or 4 spins while it descended nose down in a vertical descent and that the sound of the engine was “quite loud.” According to the autopsy authorized by the San Miguel County Coroner’s Office, Telluride, Colorado, the pilot’s cause of death was multiple traumatic injuries, and the manner of death was an accident. No significant natural disease was identified during the autopsy. Toxicological testing, completed by the Federal Aviation Administration Forensic Sciences Laboratory, detected the opiate narcotic morphine in the pilot’s urine at 34 nanograms per milliliter (ng/mL) but not in his cavity blood. The non-impairing pain reliever acetaminophen, commonly marketed as Tylenol, was detected in his cavity blood and urine. Morphine is prescribed for pain relief but may be present as a metabolite of the pain reliever codeine. The plasma half-life of codeine is around 3 hours and the half-life of morphine is around 4 hours. Both morphine and codeine are impairing medications and patients should not drive or operate dangerous machinery until they know how they react to the medication. Codeine is often prescribed in combination with acetaminophen. The pilot’s flight logbook was not located during the investigation. The airplane impacted mountainous terrain about 0.5 sm east-southeast of the runway 27 threshold at TEX. The elevation of the accident site was about 8,877 ft msl. The airplane impacted nose-down into steep terrain. All major airframe structural components and flight control surfaces were present at the accident site, as shown in figure 6. The wreckage was recovered to a secure facility where it was examined. The postaccident examination did not reveal any evidence of a preexisting mechanical malfunction or failure that would have prevented normal operation. Allphysical damage to the airframe, engine, and propeller was consistent with ground impact. Figure 6 – Main Wreckage at the Accident Site