Cessna 177RG N2085Q accident near Lake Havasu City, Arizona

Probable cause

A partial loss of engine power during the airplane's initial climb due to wear of internal engine components, which prevented the engine from developing full-rated power and resulted in a loss of altitude.

NTSB analysis

The airplane was departing at a slow groundspeed, and the engine sounded as if it was producing partial power. The airplane did not ascend as expected and veered to the right of the centerline. The airplane then pitched up to a nose-high attitude and made an aggressive left bank, consistent with pilot attempting to make 180° turn to the runway while making a radio transmission that he did not complete. The airplane’s wingspan turned nearly perpendicular to the horizon and then stalled with the left wing dropping toward terrain. The airplane subsequently impacted terrain, and a postcrash fire ensued.

The terrain ahead of the accident site was uninhabited and populated with low brush. If the pilot had considered landing there instead of making a 180° turn, the outcome of this accident might have been different.

A postaccident examination revealed that two piston rings were fractured and that the pistons showed evidence of excessive wear and heat. The extensive wear on the piston ring surfaces indicated that they had fractured before the accident and were continuing to wear during the accident flight when the pistons actuated inside the cylinders. Fracture and wear of the rings likely resulted in blow-by of combustion gases past the cylinder and oil leakage into the combustion chamber. The lifter surfaces were spalled, the cam lobes were worn, and one of the lifter bodies was cracked, all consistent with excessive wear. The fractured rings, a lack of sealing, and blow-by would all have contributed to partial engine power and led to an airplane stall and a loss of altitude.

Three days before the accident, the pilot had sent samples of the engine oil for analysis and did not receive the results before the accident. The oil sample exhibited elevated aluminum, chromium, iron, silicon, and nickel levels. A previous oil sample report had stated that the amounts of aluminum, chromium, and iron would indicate piston, ring, and steel wear. All were indications of the excessive wear of the engine components and broken piston rings, which likely would result in blowby and contribute to the partial loss of power.

Text from the NTSB. Open the NTSB docket for WPR21FA340 for the full record.