# Accident 19981021044259A: Mooney M20C, Denver, CO, October 21, 1998

- Type: FAA accident report (Accident/Incident Data System), as reported
- Date: October 21, 1998, 08:28 local time
- Place: Denver, CO
- Airport: Centennial Airport
- Damage: Substantial damage
- Phase of flight: Forced/Precautionary Landing
- Operating rules: General operating rules (Part 91)
- Location: 39.5800° N, 104.8590° W: From the FAA, an estimate near the named town, within about 3 miles
- Nearby events: https://openairdocs.org/map.md?lat=39.5800&lon=-104.8590&mi=10
- Aircraft: N6405U (not matched to a registry record)
- Reported make and model: MOONEY M20C
- Reported engine: LYC O360A1D
- Fatal injuries: 0
- Pilot flight hours: 1,018 total, 834 in this make and model, 43 in the last 90 days
- NTSB investigation: [NTSB DEN99LA015](https://openairdocs.org/ntsb/DEN99LA015) (OpenAirDocs)
- FAA source: FAA Aviation Safety Information Portal (https://asip.faa.gov/)
- Page: https://openairdocs.org/incident/19981021044259A

## Narrative

As the FAA filed it, in capitals; the FAA replaces private details with ^PRIVACY DATA OMITTED^.

(.4) DURING CLIMB FOLLOWING DEPARTURE, THE ENGINE LOST POWER. THE PILOT REPORTED THE EMERGENCY TO THE TOWER AND ATTEMPTED TO RETURN TO THE AIRPORT. DETERMINING THAT HE WOULD BE UNABLE TO MAKE IT BACK, HE MADE AN EMERGENCY LANDING IN A FIELD ONE AND A HALF MILES SOUTHEAST OF THE AIRPORT. POSTACCIDENT EXAMINATION OF THE ENGINE REVEALED THAT THE CAMSHAFT GEAR RETAINING BOLTS CONNECTING THE CAMSHAFT GEAR TO THE CAMSHAFT HAD LOST TORQUE.  AS A RESULT, THE LOBES FAILED TO OPEN THEIR RESPECTIVE VALVES, CREATING DISCONTINUITY TO THE GEAR TRAIN. THE TREAD ON EACH OF THE FOUR CAMSHAFT GEAR BOLTS EXHIBITED SHINY, WORN PATTERNS.  ACCORDING TO A TEXTRON LYCOMING ENGINEER, LOSS OF CAMSHAFT RETAINING BOLT TORQUE IS INDICATIVE OF THE BOLTS BEING IMPROPERLY TORQUED DURING THE ENGINE OVERHAUL. ACCORDING TO AIRCRAFT MAINTENANCE RECORDS, THE ENGINE WAS OVERHAULED ON MARCH 15, 1985, AND HAD ACCUMULATED 833 HOURS SINCE OVERHAUL.

## The NTSB's investigation of this event (1)

From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model.

- [NTSB DEN99LA015](https://openairdocs.org/ntsb/DEN99LA015), Oct 21, 1998: Mooney M20C (N6405U), Englewood, CO, substantial damage. Probable cause: The undertorquing of the camshaft gear retaining bolts during engine overhaul by maintenance personnel. A factor was the unsuitable terrain for a forced landing.

From the FAA Accident/Incident Data System. Reports are matched to registry aircraft by N-number and event date, checked against the reported make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. For accidents, the NTSB's own investigation is the fuller record.

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