On May 31, 2020, at 1757 Pacific daylight time, an experimental Cub Crafters CCK-1865, N303KP, was substantially damaged when it was involved in an accident near Valley Center, California. The pilot sustained fatal injuries and the passenger was seriously injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.
On the day of the accident, the pilot’s family was having a gathering at his hangar. The pilot took family members on four 20-minute flights. The accident flight, the fifth flight of the day, the pilot planned to take his niece to circle over her friend’s house. She was seated in the rear seat, and he secured her seat belt.
The airplane departed from Lake Wohlford Resort Airport, Escondido, California, about 1735 and flew northwest. Track data were consistent with the airplane maneuvering around a building briefly before heading east. (see figure 1.)
Figure 1: Flight Path
At 1752, the airplane began to circle around the accident site. The calculated calibrated airspeed slowed to between 40 and 50 kts as the airplane completed a series of left and right turns between 100 ft to 300 ft above ground level (agl). Starting at 1756, the airplane completed a 180° right turn and climbed 100 ft while the calibrated airspeed dropped to near 35 kts. About 1756:30, the airspeed was above 45 kts and the airplane began a left turn. The airplane completed a full 360° turn and was continuing to turn and descend with a bank angle greater than 40° left-wing-down. The last recorded data point was at 1757:13 and was located about 100 ft from the accident site. (see figure 2.)
Figure 2: Flight Path Around Accident Site
Several witnesses on the ground recorded video of the airplane maneuvering. Just before impact, the airplane pitched up in a nose-high attitude. About 5 seconds later, the airplane rolled left along its longitudinal axis with the left wing dropping down toward the ground. The airplane then dropped nose-low, pointing directly toward the ground. (see figure 3.)
Figure 3: Excerpts of the Video Prior to Impact
The airplane manufacturer provided estimated power-off stall speed versus bank angle information. The airplane’s wings-level, no flaps, power-off stall speed was reported to be 42 kts calibrated airspeed. During the final minutes of the flight, the airplane’s calibrated airspeed was between 40 and 50 kts while circling.
Using the relationship between bank angle and stall speed for the clean, no-flaps configuration, the stall speed was calculated. (see figure 4.) The power-on speed increases the stall margin several kts as compared to the reported power-off stall speeds. After 1757, the airplane’s turn tightened, increasing the bank angle, as the airplane’s speed continued to decrease. The airplane at this point was less than 200 ft above the terrain. It impacted the ground shortly after.
Figure 4: Altitude (msl), Calibrated Airspeed, and Bank Angle Compared to Power-off Stall Speed
A sound spectrum analysis revealed that when the airplane was at about 1,850 ft msl the engine was operating at the recommended speed between around 1,800-2,000 rpm. Engine monitor data revealed that the cylinder head temperatures and exhaust gas temperatures all remained within normal ranges until the end of the data. The last recorded point showed an airspeed of 28 kts and a vertical speed in excess of -300 ft per minute.
The Federal Aviation Administration (FAA) inspectors who responded to the accident site stated that they confirmed flight control continuity. Conditions at Accident Site: Visual (VMC) Condition of Light: Day Observation Facility, Elevation: KCRQ,328 ft msl Distance from Accident Site: 16 Nautical Miles Observation Time: 17:59 Local Direction from Accident Site: 235° Lowest Cloud Condition: Clear Visibility 10 miles Lowest Ceiling: None Visibility (RVR):
Wind Speed/Gusts: 4 knots / Turbulence Type Forecast/Actual: None / None Wind Direction: 190° Turbulence Severity Forecast/Actual: N/A / N/A Altimeter Setting: 29.7 inches Hg Temperature/Dew Point: 24°C / 14°C Precipitation and Obscuration: No Obscuration; No Precipitation Departure Point: Escondido, CA (8CL1) Type of Flight Plan Filed: None