History of Flight
On July 15, 2021, at 1154 Pacific daylight time, a Mooney M20J airplane, N4474H, was destroyed in an accident near Dinsmore Airport (D63), Dinsmore, California. The pilot, pilot-rated passenger, and two other passengers were fatally injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.
A witness located 0.25 miles east of the departure end of runway 9 observed the accident airplane circling twice before landing on runway 27. The witness reported the wind was from the west. The airplane traveled down the runway and stopped at the midpoint, where three people disembarked, one of whom walked around the airplane. All three then boarded, and the airplane taxied toward runway 9. The witness observed the airplane accelerate down the runway and rotate just short of the displaced runway threshold. The witness thought the airplane “barely cleared the fence” and that the rotation was not smooth because the pilot suddenly “jerked” the nose. The airplane subsequently impacted trees and then the ground about 1,600 ft from the departure end of runway 9.
Two security cameras located about 300 ft east of the departure end of runway 9 captured the accident airplane during the takeoff initial climb.
Aircraft Information
The airplane’s weight and balance records were not located. The Mooney M20J Pilot’s Operating Handbook contained a maximum performance takeoff distance chart. For a takeoff weight of 2,740 pounds, a flap setting of 15°, a leaned fuel/air mixture, a temperature of 10°C, and an altitude of 2,000 ft, the ground roll would be 1,022 ft, and 1,732 ft would be required for a 50-ft obstacle clearance. At 4,000 ft, the ground roll would be 1,309 ft, and 2,175 ft would be required for a 50-ft obstacle clearance. The calculated climb performance at gross weight and a density altitude of 2,500 ft would have been about 900 ft per minute with the landing gear retracted, maximum engine power, 0° flaps, and a rich fuel/air mixture.
Airport Information
Dinsmore Airport (D63) is located in Dinsmore, California. The airport has runways 9 and 27. The witness reported wind from the west at the time of the accident.
Wreckage and Impact Information
The wreckage was located on a magnetic heading of 126°. Examination revealed the airplane’s right wing impacted a tall redwood tree. Upon impact, the right wing separated and fell to the ground beneath the tree. The airplane came to rest inverted about 120 ft from the first point of impact on a magnetic heading of 170°.
Postaccident examination of the airplane revealed that the engine remained attached to the airframe by the engine mount. The engine sustained thermal and impact damage. The crankshaft rotated freely in both directions. Thumb compression was obtained on all four cylinders. The intake valve rocker arms of each cylinder moved about 40% less compared with the exhaust rocker arms.
Engine Examination
Disassembly of the engine found no evidence of heat distress on the crankshaft and its attached connecting rods. The main bearings exhibited significant wear. The main bearing saddles at each crankcase exhibited significant fretting signatures. The camshaft was intact. Each exhaust cam lobe exhibited an elliptical shape, and the corresponding tappet face remained undamaged and smooth. The intake cam lobes exhibited a worn and rounded shape, and the corresponding tappets were galled.
Engine Monitoring Data
An engine monitoring unit recovered from the wreckage provided data. About 3 minutes into the recording, engine speed increased to about 2,150 rpm and then increased moments later to about 2,700 rpm. Manifold pressure increased to 27 inches. The recording ended about 35 seconds later with an engine speed of 2,685 rpm and a manifold pressure of 27.3 inches. Other engine parameters appeared nominal.