CESSNA 177RG near Crestview, FL — 2023-04-14

Probable cause

The total loss of engine power due to the loosening and separation of the No. 1 connecting rod cap nuts in flight, resulting in catastrophic internal engine damage. Contributing to the accident was the pilot/owner’s failure to comply with the engine manufacturer’s service instruction on engine overhaul intervals.

Contributing factors

Contributing to the accident was the pilot/owner’s failure to comply with the engine manufacturer’s service instruction on engine overhaul intervals.

NTSB narrative

The pilot reported that, during a flight in visual conditions, he heard a “boom” from the propeller hub. The propeller immediately began to oscillate and shudder violently, accompanied by severe engine vibration and oil loss. He shut the engine down and executed a forced landing to a field that resulted in structural damage to the airplane. The pilot sustained serious injuries. A teardown examination of the engine after recovery of the wreckage revealed that the No. 1 connecting rod cap separated from the rod during flight, resulting in catastrophic engine damage. Damage to the rod cap bolts and nuts was consistent with the nuts loosening and backing out over time. There was no evidence of heat distress on the affected parts. A review of the aircraft maintenance logbooks revealed that the last overhaul of the engine was performed more than 30 years before the accident. A service instruction issued by the engine manufacturer instructs all engine models to be overhauled within twelve calendar years of the date they first entered service or of the last overhaul.

Analysis

Primary failure mode

Mechanical failure

First missed decision gate

Pilot could have opted for a go-around instead of continuing the approach.

NTSB coding

• Loss of engine power (total) · Approach-IFR initial approach
• Maintenance

Evidence available

• Photos
• 11 docket documents

Docket documents11

• PILOT/OPERATOR AIRCRAFT ACCIDENT REPORT, NTSB FORM 6120.1form
• STATEMENT OF PARTY REPRESENTATIVES TO NTSB INVESTIGATIONform
• INSPECTOR'S STATEMENTinterview
• ENGINE OVERHAUL AND LAST ANNUAL INSPECTIONother
• LYCOMING SERVICE INSTRUCTION 10009BEother
• INVESTIGATION PHOTOGRAPHSphotos
• ELECTRONIC DEVICES - SPECIALIST'S FACTUAL - ATTACHMENT 1 - TABULAR DATAreport
• ELECTRONIC DEVICES - SPECIALIST'S FACTUAL - ATTACHMENT 2 - TABULAR DATAreport
• ELECTRONIC DEVICES - SPECIALIST'S FACTUAL REPORTreport
• MEMORANDUM - WRECKAGE EXAMINATIONwreckage
• WRECKAGE RELEASE AND EVIDENCE CONTROLwreckage