# NTSB LAX90LA066: Mooney M20B, N74520, Santa Ana, CA, January 7, 1990

- Type: NTSB accident investigation
- Classification: Accident · Minor injuries · Limited investigation · Final report
- Date: January 6, 1990, 17:02 local (Jan 7, 1990, 01:02 UTC)
- Place: Santa Ana, CA
- Location: 33.6757° N, 117.8682° W: Placed by OpenAirDocs at JOHN WAYNE/ORANGE COUNTY (SNA), within about a mile (OpenAirDocs)
- Nearby events: https://openairdocs.org/map.md?lat=33.6757&lon=-117.8682&mi=10
- Phase of flight: [Approach](https://openairdocs.org/ntsb-phases/500) (OpenAirDocs' grouping)
- Highest injury: Minor injuries
- Injuries: 1 minor
- Status: Completed, report October 2, 1992
- Report: Approved by Office Director
- NTSB case key (mKey): 26717
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=LAX90LA066
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/26717/pdf
- Page: https://openairdocs.org/ntsb/LAX90LA066

## Probable cause

THE FAILURE OF BOLTS RETAINING THE IDLER SHAFT ALLOWING THE CAM SHIFT TIMING TO CHANGE AND BY ITS FAILURE TO DRIVE THE LEFT MAGNETO.

## Sequence of events

In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf).

- Loss of engine power(total) - mech failure/malf, approach - vfr pattern - final approach
  - engine assembly,timing gear - disengaged (cause)
  - ignition system,magneto - disconnected (cause)
  - maintenance - inadequate, other maintenance personnel (cause)

## Analysis

THE ENGINE ON A MOONEY M20B FAILED WHILE ON SHORT FINAL APPROACH. EXAMINATION REVEALED THAT THE BOLTS RETAINING THE IDLER SHAFT HAD SHEARED ALLOWING A CHANGE IN THE INTERNAL TIMING AND FAILURE TO DRIVE THE LEFT MAGNETO. BOTH BOLT HEADS, THE LOCKPLATE, AND THE COTTER KEYS WERE FOUND IN THE OIL SUMP. THE IGNITION SPRINGS ON THE ELECTRICAL HARNESS HAD EVIDENCE OF ARCING.

## Aircraft

- Registration: [N74520](https://openairdocs.org/deregistered/N74520-1995-04-04), registration cancelled 1995-04-04, S/N 1907 (OpenAirDocs)
- Reported make and model: MOONEY M20B
- Registry model: [Mooney M20B](https://openairdocs.org/model/mooney-m20b) (registry code 5870206) (OpenAirDocs)
- Category: Airplane
- Serial number: 1907
- Engines: LYCOMING O-360-A1D 180 horsepower reciprocating
- Damage: Substantial damage
- Flight: Personal, Part 91
- Operator: Robley D. Mc Cants
- Departed: SNA
- Destination: SNA
- Airport: SNA, John Wayne, runway 19, 5,700 × 150 ft, macadam

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 40; private; airplane ratings: single-engine land; medical: class 3, valid medical--w/ waivers/lim; flight hours: 557 total, 86 in this make and model

## Weather

- Conditions: Visual (VMC), Day
- Wind: 190° at 5 knots
- Visibility: 5 statute miles
- Lowest ceiling: none
- Temperature: -0 °F, dew point -0 °F

## FAA reports on this event (1)

The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs).

- [Accident 19900106000199A](https://openairdocs.org/incident/19900106000199A), Jan 6, 1990: Mooney M20B, Santa Ana, CA, Substantial damage. Lost power on final. Hit light pole in parking lot. Idler gear shaft bolts sheared. Ignition harness springs arcing

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.

---
OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.