History of Flight
On July 29, 2017, about 1420 Pacific daylight time, a Cessna 172N airplane, N5381J, was substantially damaged after it collided with mountainous terrain shortly after departure from Big Bear City Airport (L35), Big Bear, California. The commercial pilot and passenger were fatally injured. The airplane was registered to and operated by Midfield Aviation under Title 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed, and no flight plan was filed for the personal flight, which departed about 1415 and was destined for Apple Valley Airport (APV), Apple Valley, California.
According to airport personnel, the pilot and his girlfriend arrived at L35 in the accident airplane the day before the accident. After deplaning, the pilot proposed to his girlfriend on the airport ramp. The following day, an airport surveillance camera captured the airplane depart runway 08 normally and begin a climb. A witness located near the departure end of the runway reported that the airplane came into view about 100 ft above ground level, did not gain altitude, and entered a nose-high attitude described as "hanging on the prop." The engine sounded smooth and continuous. As it reached a park adjacent to the departure end of the runway, it turned to the crosswind leg momentarily before turning 90° to a tight downwind leg. The turns appeared coordinated, but the airplane maintained a nose-high pitch attitude. It then sank slowly, and the wings began to rock before it disappeared behind trees. Another witness near the crosswind leg observed the airplane fly low southward, begin a right turn, and disappear over a hill; the engine sound was continuous.
Personnel Information
The pilot, age 30, held a commercial pilot certificate with ratings for airplane single- and multi-engine land and instrument airplane, and rotorcraft-helicopter and instrument helicopter. His most recent FAA first-class medical certificate was issued on April 12, 2017, with no limitations. At the time of the exam, he reported 225 total hours of flight experience, with 0 hours in the previous 6 months. According to his personal logbook, current as of July 10, 2017, he had accumulated a total of 225 total hours. Most of his single-engine time was in a Diamond DA-40. He had completed three flights and accrued 13 hours in the accident airplane make and model. He also flew the UH-60 Black Hawk, but that experience was not in his logbook. His logbook showed a previous flight to L35 in a Cessna 172 on May 10, 2017, his only prior flight to that high-altitude airport.
On May 1, 2017, the pilot received a checkout in a Cessna 172 owned by the same flight school. The instructor reported that the local flight included slow flight, steep turns, and fuel/air mixture control leaning procedures, since the pilot was less experienced with reciprocating engines. The school's standard practice was to review mixture leaning due to APV's elevation about 3,000 ft msl and typical warm temperatures.
Aircraft Information
The airplane, manufactured in 1980, was powered by a Lycoming O-320-H2AD, 160-horsepower, air-cooled, reciprocating engine. Logbooks showed it had accrued about 54 flight hours since its most recent 100-hour inspection on July 2, 2017, at 4,252.6 total time in service. At the accident, the engine had about 643 total hours since its most recent overhaul on October 23, 2015. Total time in service was 4,306.4 hours.
Engine records showed the engine was removed and reinstalled in 2016 due to "camlobe and no. 3 cylinder." The logbook did not detail the discrepancies. The No. 3 cylinder was replaced during the most recent 100-hour inspection.
A fuel receipt from an airport fueler showed the pilot purchased 5.14 gallons of 100LL aviation gasoline at 1406 on the accident day. No fuel contamination or engine anomalies were reported by other customers that day.
Meteorological Information
The 1615 recorded weather at L35 included wind from 090° at 7 knots, 10 statute miles visibility, scattered clouds at 8,500 ft, temperature 25°C (77°F), dew point 5°C (41°F), and altimeter 30.33 inches of mercury. An NTSB weather study showed a density altitude of 9,138.9 ft msl about the accident time. Pressure altitude was 6,362.2 ft.
Wreckage and Impact Information
The airplane came to rest in a wooded area about 0.5 nautical miles south of L35. The initial impact point was identified by a tree scar near the top of a 45-ft-tall tree and the left wingtip. Another scar was found on a tree about 20 ft forward. The right elevator remained attached to its horizontal stabilizer and was located 20 ft forward of the second tree. The main wreckage, oriented on an 085° heading with multiple broken tree branches, was positioned at a 40° nose-down angle about 40 ft past the initial impact point heading of 227°. It comprised the engine, fuselage, wings, and empennage.
The right wing was displaced forward a few degrees with a depression at the leading edge near the wing root and a cluster of dents near the outboard leading edge. The left aileron exhibited buckling and compression; the flap had compression wrinkles. Tree impact signatures were throughout the right wing. Multiple dents and compression wrinkles were on the upper and lower right wing skins. The left wing separated from the wing root with an approximate 10-inch depression at the outboard leading edge, aft bending at the outboard leading edge, and aft compression at the inboard leading edge.
The fuselage was intact except that the engine had separated from the firewall. The vertical stabilizer, rudder, and left horizontal stabilizer were secured to the empennage, which remained attached to the aft fuselage. The right horizontal stabilizer separated at the root and displayed a depression consistent with tree impact.
Control cables were traced from the cockpit to their respective surfaces. The flap indicator and handle indicated flaps extended 10°, but the jackscrew showed no threads, consistent with flaps retracted. The throttle was broken; the mixture control knob was in the full rich position.
Both wing fuel tanks were breached and contained an odor of 100 low lead aviation gasoline. Fuel line continuity was confirmed from wing lines to the engine through the fuel selector valve, which rotated normally. The fuel gascolator bowl contained traces of foreign debris.
Rotational continuity was established throughout the engine and valve train by manually rotating the crankshaft. Thumb compression and suction were obtained for all four cylinders. Cylinder combustion chambers and barrels appeared normal; bores, valve heads, and piston faces showed normal operation and combustion signatures. Cylinder overhead components exhibited normal operation and lubrication signatures. Top and bottom spark plugs showed normal wear. The oil filter and sump contained no metallic particles.
The carburetor throttle and mixture linkages were attached. Trace fuel was observed in the float valve chamber. Internal components, including needle valve floats, appeared normal. The single-drive dual magneto rotated normally but did not seat during each turn; spark was observed at all eight ignition harness leads when actuated manually.
The two-blade ground-adjustable propeller was attached; both blades had chordwise scratches, one with forward bending and the other with tip curling.
Additional Information
The FAA Pamphlet FAA-P-8740-2, Density Altitude, outlines hazards: reduced air density adversely affects aerodynamic performance and decreases engine horsepower output, increasing takeoff distance and reducing climb rate. At density altitude above 5,000 feet, leaning normally-aspirated engines for maximum power is essential to avoid excessively rich mixture. According to the FAA Airplane Flying Handbook, under high density altitude, an airplane may become airborne at insufficient airspeed but be unable to climb out of ground effect and may not clear obstructions. The FAA Pilot's Operating Handbook states that due to reduced drag in ground effect, an aircraft may seem capable of takeoff below recommended speed; rising out of ground effect with speed deficiency can result in marginal climb performance, especially in high density altitude.
Medical and Pathological Information
The Sheriff-Coroner conducted an autopsy on the pilot. Cause of death was listed as "multiple blunt force injuries, seconds." The autopsy noted an enlarged heart with 70% narrowing of the left anterior descending and right coronary arteries and 40% narrowing of the left circumflex artery. A blood sample detected 21 mg/dL ethanol in chest blood, 10 mg/dL in vitreous fluid, and a blood alcohol concentration of 0.021 g/100mL. No drugs of abuse were indicated. The FAA's toxicology testing detected 27 mg/dL ethanol in urine, 18 mg/dL in cavity blood, and propanol in urine and cavity blood. It is likely that some or all of the ethanol was from sources other than ingestion.
Tests and Research
Weight and balance computations used occupant weights of 199 lbs (pilot) and 177 lbs (passenger), baggage of 66 lbs, empty weight 1,473 lbs, and two fuel weights: 120 lbs (half) and 240 lbs (full). Gross weight with half fuel was 1,969 lbs; with full fuel, 2,089 lbs. Maximum gross weight per POH was 2,300 lbs.
Takeoff distance from POH performance chart: at 30°C and 1,900 lbs gross weight, ground roll 980 ft; at 2,100 lbs, 1,245 ft. The POH maximum rate of climb table showed at 6,000 ft pressure altitude and 20°C, climb rate about 440 fpm at max gross weight.
Surveillance video analysis by NTSB vehicle performance division estimated shortly after rotation: airspeed about 60 kts, rate of climb about 780 fpm, pitch angle about 8.5°. Subsequently, when about 90 ft above the runway, values declined: after 10 seconds, airspeed about 49 kts, rate of climb about 340 fpm, pitch angle about 5°.