History of Flight
On November 19, 2017, about 1500 Pacific standard time, a Cessna 172P airplane, N52492, was substantially damaged during an accident in San Jose, California. The private pilot sustained minor injuries, and the two passengers were seriously injured. The airplane was operated by Squadron 2 Flight Club as a Title 14 Code of Federal Regulations Part 91 personal flight.
The pilot occupied the front left seat, a pilot-rated passenger sat in the front right seat, and a passenger was in the left rear seat. The front seat occupants agreed that the pilot would fly while the pilot-rated passenger handled radio calls and verified checklist items. They computed weight and balance, takeoff distance, and roll with full fuel tanks. After a preflight inspection, they taxied to the run-up area. The pilot ran the engine to 1,800 rpm and observed a 50 rpm drop when selecting each magneto individually, with a 75 rpm difference between magnetos. The pilot followed the airplane checklist, selected both fuel tanks, and departed after receiving air traffic control clearance. Flaps were not deployed during the accident flight. Instrument indications were in the green as the airplane lifted off at 55 knots.
During the initial climb to about 50 ft indicated altitude, the pilot observed a decreasing climb rate and airspeed with a simultaneous drop in rpm. The airplane stopped climbing, and the engine harmonic became rough then quiet, but it did not stop functioning. The pilot attempted to maintain airspeed above 44 knots, the stall speed. The pilot-rated passenger declared a mayday to air traffic control. The pilot performed a wide turn, allowing the airplane to descend slightly. She observed a green field and then the airport perimeter but estimated the airplane would not reach the airport. During final movements, the nose dropped suddenly. The pilot retarded the mixture to idle/cutoff and changed the fuel selector to OFF just before impact. The pilot noted she was unable to maintain altitude before the turn and remarked that she had engaged the noise canceling function of her headset and the engine sounded normal during the takeoff roll.
The pilot-rated passenger's statement was consistent. He added that the airplane stopped climbing just after departing the runway surface. He observed a tree beyond the departure end of the runway, used as a landmark, and they both saw the airplane was not climbing, so they decided to level off and troubleshoot. He observed the pilot struggling to maintain control for the rest of the flight.
A smartphone recording showed the airplane maintaining low altitude, then entering a shallow left turn in a slight nose-high attitude shortly after departure. The propeller appeared rotating. At the end of a 180° turn, the bank angle steepened as the airplane descended rapidly, and the propeller rotation reduced significantly. In final movements, pitch attitude decreased, wings leveled, and the airplane disappeared behind trees. Flaps were observed retracted before impact.
Aircraft Information
The airplane was powered by a Lycoming O-320-D2J, air cooled, 160 horsepower engine. Maintenance records indicated the most recent 100-hour engine inspection was completed on November 4, 2017, at a total time of 14,748.3 flight hours and a tachometer time of 1,756.4 hours. The engine had accrued 2,151.5 flight hours since its most recent overhaul. According to the tachometer, at the accident, the engine had 1,779 hours total time in service and 22 flight hours since the last inspection. Logbook records showed the no. 3 cylinder had been replaced 171 hours prior. The flight school owner reported that his maintenance team applied PRC to the no. 2 cylinder to stop a "nuisance oil leak," which required removal and re-installation. He also reported a planned engine replacement after the accident flight.
The pilot's operating handbook (POH) magneto check excerpt indicated that rpm drop should not exceed 125 rpm on either magneto or show a differential greater than 50 rpm. It stated that if there is doubt concerning ignition system operation, checks should be performed at higher engine speeds to confirm deficiency. The emergency procedure for loss of power included establishing glide airspeed (65 KIAS flaps up, 60 KIAS flaps down), mixture idle cut-off, fuel selector off, ignition off, wing flaps as required (30° recommended), master switch off, doors unlatched, touchdown slightly tail low, and brakes applied heavily. The POH also stated that prompt lowering of the nose to maintain airspeed is the first response to an engine failure after takeoff, and that altitude and airspeed are seldom sufficient for a 180° gliding turn to return to the runway.
Wreckage and Impact
The airplane impacted a trailer and several small trees before colliding with the front of a residence and coming to rest in the front yard. All three landing gear collapsed or separated. The fuselage was flush against the ground. The outboard portion of the left wing separated, and the right wing was partially separated about mid-span. The empennage displayed buckling at the aft fuselage.
Flight control continuity was traced from the cockpit to the elevator, rudder, and ailerons. The left aileron cable and through cable were fractured in tensile overload at the aileron-flap junction. The wing flap actuator was not extended, consistent with a retracted position. Continuity of mixture and throttle controls was confirmed, but damage inhibited full range. The stall warning horn showed no anomalies. Several ounces of fuel resembling 100 low lead aviation gasoline were drained through the strainer, with no contamination or debris. Fuel line continuity was confirmed from door posts to the fuel selector valve, which moved normally through detents.
Top spark plugs were removed, and thumb compression and suction were obtained for all cylinders in proper firing order. Mechanical continuity was established throughout the rotating group, valve train, and accessory section as the engine was manually rotated. With rocker covers removed, intake valves for cylinders no. 3 and 4 showed inhibited movement, not extending to full travel. After engine disassembly, the camshaft lobe supporting these intake valves was severely worn with extensive pitting. The lifters for both intake valves were spalled. The camshaft lobe for cylinders no. 1 and 2 exhibited some wear, and their lifters were spalled. Combustion chambers were mechanically undamaged, with no evidence of foreign object ingestion or detonation. Spark plugs were gray, consistent with normal wear. Both magnetos remained attached and exhibited spark when the propeller was rotated. All ignition harness leads showed normal wear.
The propeller remained attached to the flange and engine. One blade had chordwise scratches, tip curling, and tip separation. The other blade had a gouge and bending at the tip, which had separated.
The carburetor separated from the engine case and was examined by the manufacturer with FAA oversight. A flow test could not be performed due to impact damage. The unit could not be evaluated for operational anomalies due to damage to the casting, throttle, venturi, and mounting features. No debris or contamination was found in the needle valve seat or accelerator pump check valve. The needle valve was intact, the main jet clean and undamaged, and the float met manufacturer specifications.
Additional Information
Lycoming Service Bulletin 301B, issued February 18, 1977, mandated valve maintenance procedures. Section (1)(b) required removal of rocker box covers and rotation every 400 hours to verify normal valve lift. The engine logbook contained no record of compliance with this bulletin nor any indication that the camshaft had been inspected in the previous 400 hours of service. Lycoming Service Instruction 1009AZ recommended overhaul of the engine model at 2,000-hour intervals or before the twelfth year, whichever occurs first.