N52492Cessna 172P · 1980

On November 19, 2017, about 1500 Pacific standard time, a Cessna 172P airplane, N52492, was substantially damaged when it was involved in 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.

During the accident flight, the pilot was seated in the front left seat and the pilot-rated passenger was seated in the front right seat. A passenger was seated in the row 2 left seat, behind the pilot. The front seat occupants had agreed that the pilot would fly the airplane while the pilot-rated passenger made radio calls and verified checklist items. They computed the airplane's weight and balance, takeoff distance and roll with full fuel tanks. After a preflight inspection, they taxied the airplane to the airport run-up area. The pilot ran the engine up to 1,800 rpm and observed a 50 rpm drop when she selected the right and left magnetos individually, during which time she observed a difference of 75 rpm between the magnetos. The pilot reported that she followed the airplane checklist for each procedure, then selected both fuel tanks and departed after she received a clearance from air traffic control. She did not deploy the flaps during the accident flight. The instrument indications were in the green as the airplane lifted off the runway 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 and then quiet, but it didn't stop functioning. According to the pilot, she attempted to maintain an airspeed above 44 knots, which was the airplane's stall speed. Immediately, the pilot-rated passenger stated that they needed to land and announced "MAYDAY, MAYDAY" to air traffic control. The pilot performed a wide turn and allowed the airplane to descend slightly. She eventually observed a green field and then the airport perimeter, but estimated that the airplane would not reach the airport. During the airplane's final movements, the nose suddenly dropped as the airplane descended towards the ground. The pilot retarded the mixture control to idle/cutoff and changed the fuel selector to the OFF position just before impact. Later, the pilot noted that she was unable to maintain altitude before she entered the wide turn. She further remarked that she had engaged the noise canceling function of her headset for the accident flight and that the engine sounded normal during the takeoff roll.

The pilot-rated passenger's statement was consistent with the pilot's. He added that the airplane stopped climbing just after it departed the runway surface. The pilot-rated passenger observed a tree located beyond the departure end of the runway and across a road that he uses as a landmark during flights. They were approaching the tree and both observed the airplane wasn't climbing, so they decided to level off and troubleshoot the anomaly. He observed the pilot struggle to maintain control of the airplane for the rest of the flight.

A smartphone recording captured the airplane's initial climb and subsequent movements. The recording showed the airplane maintain a low altitude and then enter a shallow left turn in a slight nose high attitude, shortly after its departure from the runway. During this time, the propeller appeared to be rotating. At the end of its 180° turn, the airplane's bank angle progressed into a steep turn as the airplane descended rapidly and the propeller's rotation reduced significantly. In its final movements, the airplane's pitch attitude decreased and the airplane's wings leveled out before the airplane disappeared behind trees. The airplane's flaps were observed in the retracted position just before it disappeared and impacted the ground.

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The airplane was powered by a Lycoming O-320-D2J, air cooled, 160 horsepower engine. Maintenance records indicated that the airplane's 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. At the time the engine had accrued a total of 2,151.5 flight hours since its most recent engine overhaul, which was accomplished 2,173 flight hours prior to the accident. According to the airplane's tachometer, at the time of the accident, the engine had accrued 1,779 hours total time in service and 22 flight hours since the airplane's most recent inspection.

The logbook records showed that the no. 3 cylinder had been replaced 171 hours prior to the accident. Additionally, the flight school owner and maintenance director reported that his maintenance team applied PRC to the no. 2 cylinder to stop a "nuisance oil leak", which required them to remove and re-install the no. 2 cylinder. The flight school owner further reported that they had a planned to replace the engine after the accident flight.

Magneto Check

According to the "Magneto Check" excerpt from the pilot's operating handbook (POH), the engine rpm drop observed should not exceed 125 rpm on either magneto or show greater than a 50 rpm differential between magnetos. The excerpt states that if there is a doubt concerning operation of the ignition system, the rpm checks should be performed at higher engine speeds to confirm if there is a deficiency.

Emergency Procedure - Loss of Power

The Emergency Procedure section of the POH contains the procedural steps below for executing an emergency landing without engine power.

Airspeed – 65 KIAS (flaps up); 60 KIAS (flaps down)

Mixture – Idle Cut-off

Fuel Selector Valve – OFF

Ignition Switch – OFF

Wing flaps – As Required (30° recommended)

Master Switch – OFF

Doors – Unlatched prior to touchdown

Touchdown – Slightly tail low

Brakes – Apply heavily

Engine Failure

The Emergency Procedure section of the POH also includes a discussion about engine failures.

Prompt lowering of the nose to maintain airspeed and establish a glide attitude is the first response to an engine failure after takeoff. In most cases, the landing should be planned straight ahead with only small changes in direction to avoid obstructions. Altitude and airspeed are seldom sufficient to execute a 180° gliding turn necessary to return to the runway.

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The airplane was powered by a Lycoming O-320-D2J, air cooled, 160 horsepower engine. Maintenance records indicated that the airplane's 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. At the time the engine had accrued a total of 2,151.5 flight hours since its most recent engine overhaul, which was accomplished 2,173 flight hours prior to the accident. According to the airplane's tachometer, at the time of the accident, the engine had accrued 1,779 hours total time in service and 22 flight hours since the airplane's most recent inspection.

The logbook records showed that the no. 3 cylinder had been replaced 171 hours prior to the accident. Additionally, the flight school owner and maintenance director reported that his maintenance team applied PRC to the no. 2 cylinder to stop a "nuisance oil leak", which required them to remove and re-install the no. 2 cylinder. The flight school owner further reported that they had a planned to replace the engine after the accident flight.

Magneto Check

According to the "Magneto Check" excerpt from the pilot's operating handbook (POH), the engine rpm drop observed should not exceed 125 rpm on either magneto or show greater than a 50 rpm differential between magnetos. The excerpt states that if there is a doubt concerning operation of the ignition system, the rpm checks should be performed at higher engine speeds to confirm if there is a deficiency.

Emergency Procedure - Loss of Power

The Emergency Procedure section of the POH contains the procedural steps below for executing an emergency landing without engine power.

Airspeed – 65 KIAS (flaps up); 60 KIAS (flaps down)

Mixture – Idle Cut-off

Fuel Selector Valve – OFF

Ignition Switch – OFF

Wing flaps – As Required (30° recommended)

Master Switch – OFF

Doors – Unlatched prior to touchdown

Touchdown – Slightly tail low

Brakes – Apply heavily

Engine Failure

The Emergency Procedure section of the POH also includes a discussion about engine failures.

Prompt lowering of the nose to maintain airspeed and establish a glide attitude is the first response to an engine failure after takeoff. In most cases, the landing should be planned straight ahead with only small changes in direction to avoid obstructions. Altitude and airspeed are seldom sufficient to execute a 180° gliding turn necessary to return to the runway.

The airplane impacted a trailer and several small trees before it collided with the front of a residence and came to rest in the front yard. All three landing gear had collapsed or separated from the fuselage, which was resting flush against the ground. The outboard portion of the left wing was separated and the right wing was partially separated about mid-span. The empennage displayed some buckling at the aft fuselage.

Aircraft Examination

Flight control continuity was traced from the cockpit to the elevator, rudder, and ailerons. The left aileron cable and through cable were both fractured in tensile overload at the aileron-flap junction. The wing flap actuator was not extended, consistent with a flap retracted position.

Continuity of the mixture and throttle controls were confirmed from the cockpit to their respective arms on the fuel control unit; however, damage to the throttle and mixture control inhibited their full range of movement. The stall warning horn did not display any anomalies.

Several ounces of fuel that resembled 100 low lead aviation grade gasoline were drained through the fuel strainer, which did not present any contamination or debris. Fuel line continuity was confirmed from the door posts to the fuel selector valve, which moved normally through each of its detents.

The top spark plugs were removed and thumb compression and suction was obtained for all four cylinders and in the proper firing order. Mechanical continuity was established throughout the rotating group, valve train and accessory section as the engine was manually rotated at the propeller. For this particular engine, the intake valves of opposing cylinders share a common camlobe. The engine was rotated once more with the rocker covers removed, which showed inhibited movement for the intake valves to cylinder nos. 3 and 4, as they did not extend to their full travel positions. A subsequent examination after the engine was disassembled revealed that the camshaft lobe supporting the intake valves to these cylinders was severely worn with extensive pitting, a condition that is known to develop over time. Additionally, the lifters for both intake valves were spalled. Additionally, the camshaft lobe that supports the intake valves for cylinder nos. 1 and 2 exhibited some wear and the lifters were spalled. The combustion chambers remained mechanically undamaged, and there was no evidence of foreign object ingestion or detonation.

The engine spark plugs were gray in appearance, consistent with normal wear when compared to the Champion Aerospace Aviation Service Manual. Both magnetos remained attached to the engine accessory case and all 8 ignition harness leads displayed normal wear and exhibited spark when the propeller was rotated by hand.

The propeller remained attached to the propeller flange and the engine. One blade exhibited chordwise scratches, blade tip curling and the blade tip was separated. The other blade displayed a gouge and bending at the tip, which had separated.

Carburetor Examination

The carburetor, which had separated from the engine case, was examined by the manufacturer with oversight from a representative of the Federal Aviation Administration. A flow test was not performed due to the physical damage the unit incurred during the impact. Further, the unit could not be evaluated for operational anomalies due to the damage on the casting, throttle, venturi, and mounting features. The examination revealed no evidence of debris or contamination in the needle valve seat or accelerator pump check valve. The needle valve was intact, the main jet was clean and undamaged and the float met the manufacturer's clearance specifications.

Lycoming Service Bulletin 301B

The engine manufacturer issued a mandatory service bulletin on February 18, 1977, to serve as a standard for all valve maintenance procedures. According to section (1)(b) of the bulletin, the engine rocker box covers should be removed and the engine subsequently rotated every 400 hours to verify that each cylinder displays normal valve lift.

The engine logbook records did not contain any record of compliance with Lycoming Service bulletin 301B nor did it provide any indication that the camshaft had been inspected in the engine's previous 400 hours of service.

Lycoming Service Instruction 1009AZ

According to Lycoming Engines Service Instruction SI1009AZ "Recommended Time Between Overhaul Schedule" this particular engine model should be overhauled at 2,000 hour intervals or before the twelfth year, whichever occurs first.

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