Accident Overview
On February 19, 2022, about 1328 mountain standard time, an experimental, amateur-built Vans RV-7A airplane, registration N787NV, was destroyed when it was involved in an accident near White Hills, Arizona. The pilot, who was the sole occupant, was fatally injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.
Flight Data
According to recorded automatic dependent surveillance-broadcast (ADS-B) data and onboard data from a Dynon SkyView D1000 panel-mounted display, the airplane departed from Boulder City Municipal Airport (BVU), Boulder City, Nevada, about 1315. It climbed to about 5,500 ft mean sea level (msl) and traveled east for about 7 minutes, making several wide 90-degree turns. After crossing US Highway 93, the airplane turned right and tracked above the highway. A few seconds later, the data indicated a maneuver consistent with an aileron roll, followed by a rapid descent of about 1,000 ft before regaining its prior altitude and track. About 2 minutes later, near Triangle Airpark (AZ50) in White Hills, the data showed a slight right turn and a maneuver consistent with a split-S, after which the airplane descended rapidly to the left over the accident site.
Detailed data from the Dynon display showed that about 3 minutes before the last recorded point, the airplane was wings-level at about 5,575 ft msl, airspeed about 137 KIAS (150 KTAS). A left roll maneuver began, rolling more than 360° in about 10 seconds with a loss of about 1,000 ft. The throttle was not reduced during the maneuver. The airplane then climbed to its initial course. About 11.5 seconds before the last data point, at wings-level, 5,609 ft msl, 138 KIAS (150 KTAS), with a slight nose-up pitch of 1.8° and a vertical climb rate of 215 ft/min, a right roll maneuver began. The airplane rolled right to a maximum recorded angle of about 166°, and pitch decreased continuously to about 62° nose-down. Descent rate increased to 9,587 fpm in 7 seconds, then 9,999 fpm for the final 4.5 seconds. The throttle was not reduced. The last recorded data point showed the airplane at about 3,199 ft msl, airspeed about 248 KIAS (262 KTAS), magnetic heading about 307°, nose-down pitch about 61.7°, right roll about 133.1°, and vertical acceleration about 4.1 g.
Video Evidence
Security video near the accident site captured the airplane in a steep nose-down descent before impacting the ground near hangars at AZ50. Multiple objects were seen falling to the ground south of the accident site. Another video near the impact crater showed the airplane moments before impact; the left horizontal stabilizer and elevator, and the vertical stabilizer and rudder, were not attached. A portion of the right horizontal stabilizer and elevator remained attached. The left wing tip and canopy were also detached.
Pilot and Aircraft Information
The pilot held an airline transport pilot certificate with several transport category aircraft type ratings and single-engine and multiengine-land endorsements. No evidence of acrobatic training was found. The pilot was the owner/builder of the accident airplane, completed in 2019. The airplane's Pilot Operating Handbook (POH) section titled Aerobatic Information indicated a weight limitation of 1,600 pounds for aerobatics and recommended entry speeds for various maneuvers including Aileron Rolls (104-165 knots), Split-S (87-96 knots), etc. The calculated weight at the time of the left roll maneuver was 1,663.4 pounds and at the split-S maneuver was 1,661.6 pounds, exceeding the maximum aerobatic weight.
Wreckage Examination
The debris field was about 1,500 ft long on a heading of about 345°, along the north side of the highway and airport property. The vertical stabilizer and attached upper rudder sections were found farthest from the impact crater. The left horizontal stabilizer, left elevator, left wingtip fairing, and sliding canopy were near the middle of the debris field. The main wreckage near the impact crater had extensive impact damage.
Postaccident examination of the engine revealed no preimpact anomalies that would have precluded normal operation. Examination of the airframe revealed damage consistent with an in-flight rudder flutter event.
Additional Information
The investigation reviewed several in-flight breakup events involving various Van's airplane models with similar damage characteristics. These events fell into two groups: maneuvering events or weather encounters. In most maneuvering events, data showed aerobatic maneuvers preceding loss of control, increased airspeed, and in-flight breakup. The maximum permissible airspeed (VNE) for the RV-7/7A is defined as 200 knots (230 mph). Clarifying information was added to the Construction Manual in December 2023 specifying that the red line marking for VNE is for both indicated and true airspeeds.
Flutter is an aeroelastic phenomenon where an airplane’s natural structural vibration couples with aerodynamic forces to produce rapid oscillation. Flutter can become dynamically unstable if damping is inadequate or speed increases, leading to destructive forces. Airspeed, structural stiffness, and mass distribution govern flutter. The airplane manufacturer performed flutter testing on the prototype to establish VNE; the RV-7 was tested to 220 knots true airspeed (1.1VNE). A ground vibration test for the RV-7 showed that the first flutter mode is a fuselage side bending mode coupled with a rudder flutter mode, with damping dependent on true airspeed. Test results indicated the model was free from flutter within the design envelope.