# NTSB CEN23LA062: Mooney M20K, N231GZ, Addison, TX, December 13, 2022

- Type: NTSB accident investigation
- Classification: Accident · Serious injuries · Class 3 · Limited · Final report
- Date: December 12, 2022, 20:05 local (Dec 13, 2022, 02:05 UTC)
- Place: Addison, TX · Aircraft lost 2-mile north of the field, on final for runway 16
- Coordinates: 32.9685, -96.8364 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=32.9685&lon=-96.8364&mi=10
- Phase of flight: [Approach](https://openairdocs.org/ntsb-phases/500) (OpenAirDocs' grouping)
- Defining event: [Approach-IFR final approach: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341)
- Highest injury: Serious injuries
- Injuries: 2 serious
- Status: Completed
- Report: Approved by Office Director
- Investigation class: Class 3
- NTSB office: Central Region
- Parties: FAA / FSDO
- NTSB case key (mKey): 106448
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN23LA062
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/106448/pdf
- NTSB docket: https://data.ntsb.gov/Docket?ProjectID=106448
- Page: https://openairdocs.org/ntsb/CEN23LA062

## Probable cause

The fatigue failure of the engine’s camshaft gear teeth which resulted in a loss of all engine power. Contributing to the accident was the non-compliance with the engine manufacturer’s recommended service bulletin.

## Findings

NTSB's coded findings; those marked are part of the probable cause.

- [Engine (reciprocating): recip engine power section](https://openairdocs.org/ntsb-findings/01058520): Aircraft › Aircraft power plant · Failure (probable cause); cases with it: [Mooney M20K, 4 cases](https://openairdocs.org/ntsb-findings/01058520/cases.md?model=5870220), [All aircraft, 233 cases](https://openairdocs.org/ntsb-findings/01058520/cases.md)
- [Maintenance/inspections](https://openairdocs.org/ntsb-findings/01010500): Aircraft › Aircraft handling/service · Not serviced/maintained (probable cause); cases with it: [Mooney M20K, 1 case](https://openairdocs.org/ntsb-findings/01010500/cases.md?model=5870220), [All aircraft, 103 cases](https://openairdocs.org/ntsb-findings/01010500/cases.md)
- [Maintenance/inspections: scheduled maint checks](https://openairdocs.org/ntsb-findings/01010520): Aircraft › Aircraft handling/service · Not serviced/maintained (probable cause); cases with it: [Mooney M20K, 1 case](https://openairdocs.org/ntsb-findings/01010520/cases.md?model=5870220), [All aircraft, 76 cases](https://openairdocs.org/ntsb-findings/01010520/cases.md)

## Sequence of events

The events NTSB coded, in order, by phase of flight. The defining event best describes what happened.

- [Approach-IFR final approach: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341) (defining event); cases with it: [Mooney M20K, 15 cases](https://openairdocs.org/ntsb-events/341/sequence.md?model=5870220), [All aircraft, 3,820 cases](https://openairdocs.org/ntsb-events/341/sequence.md)
- [Approach-IFR final approach: Attempted remediation/recovery](https://openairdocs.org/ntsb-events/060); cases with it: [Mooney M20K, 2 cases](https://openairdocs.org/ntsb-events/060/sequence.md?model=5870220), [All aircraft, 1,422 cases](https://openairdocs.org/ntsb-events/060/sequence.md)
- [Landing: Off-field or emergency landing](https://openairdocs.org/ntsb-events/440); cases with it: [Mooney M20K, 14 cases](https://openairdocs.org/ntsb-events/440/sequence.md?model=5870220), [All aircraft, 3,365 cases](https://openairdocs.org/ntsb-events/440/sequence.md)
- [Landing: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Mooney M20K, 28 cases](https://openairdocs.org/ntsb-events/470/sequence.md?model=5870220), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md)
- [Post-impact: Fire/smoke (post-impact)](https://openairdocs.org/ntsb-events/170); cases with it: [Mooney M20K, 1 case](https://openairdocs.org/ntsb-events/170/sequence.md?model=5870220), [All aircraft, 354 cases](https://openairdocs.org/ntsb-events/170/sequence.md)

## Analysis

The airplane lost all engine power during a precision instrument approach for landing to the destination airport. After the pilot was unsuccessful in attempting to restart the engine, he performed an off-airport landing to a road, during which the airplane struck a pole and a postcrash fire ensued. There was substantial damage to the wings and fuselage. Postaccident examination revealed that about 12 of the camshaft gear teeth were fractured due to fatigue cracking. The airplane engine’s camshaft gear part numbers were affected by the engine manufacturer’s service bulletin (SB) for camshaft gear tooth fracture or cracks of the teeth. The SB called for the replacement of the camshaft gear with a newer model. The intent of the SB was to eliminate the possibility of camshaft gear tooth fracture, resulting in power loss or in-flight shutdown; compliance with the SB is not mandatory for Part 91 operations. Based upon the camshaft gear part numbers, the SB was not complied with but likely would have addressed the fatigue failure of the camshaft gear teeth. The maintenance records for the airplane were destroyed in the postimpact fire and could not be examined.

## Factual narrative

On December 12, 2022, about 2005 central standard time, a Mooney M20K, N231GZ, was substantially damaged when it was involved in an accident near Addison, Texas. The pilot and passenger were seriously injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The flight originated at the Abilene Regional Airport (ABI) in Abilene, Texas, and was enroute to Addison Airport (ADS) in Addison, Texas. The pilot reported being vectored for an instrument landing system approach to runway 16 at ADS when the engine lost all power and the propeller automatically feathered. He stated that, after an unsuccessful attempt to restart the engine, he aligned the airplane with a road for a forced landing. During the approach to the road, the airplane impacted a power pole, which resulted in substantial damage to the wings and fuselage. A postimpact fire ensued. During a postaccident examination, 12 of the camshaft gear teeth were found either broken or missing. Six of the gear teeth were found in the oil sump. The aircraft owner reported that the maintenance logbooks were in the airplane at the time of the accident and were burned, so a review of engine maintenance could not be performed. In 2005 Continental Motors issued critical service bulletin (SB) CSB05-8C; in 2018, that SB was superseded by CSB05-8D. The SB pertained to certain camshaft gear part numbers on certain engines, including the TSIO-520-NB17N and the camshaft gear (part number 655516) installed on the accident airplane. The SB stated that during the airplane’s next 100 hour or annual inspection, the camshaft gear should be replaced with the newer model, part number 656818, which increased the camshaft gear face circumference by .060 inches to prevent the possibility of camshaft gear tooth failure. At the time of the accident, the accident airplane still had the old camshaft gear installed. Although compliance with the SB is not mandatory for Part 91 operations, laboratory analysis confirmed that the gear teeth fractured due to fatigue cracks, which were consistent with the description from the SB.

## Aircraft

- Registration: [N231GZ](https://openairdocs.org/aircraft/N231GZ), registered now, S/N 25-0253 (OpenAirDocs)
- Reported make and model: MOONEY AIRCRAFT CORP. M20K
- Registry model: [Mooney M20K](https://openairdocs.org/model/mooney-m20k) (registry code 5870220) (OpenAirDocs)
- Registry engine: [Continental TSIO-360 series](https://openairdocs.org/engine/continental-tsio-360-series) (registry code 17019, reciprocating) (OpenAirDocs)
- Category: Airplane
- Serial number: 25-0253
- Year built: 1980
- Engines: Continental Motors TSIO-520-NB17N 310 horsepower reciprocating
- Damage: Substantial damage
- Fire: On-Ground
- Flight: Personal, Part 91
- Airworthiness certificate: Standard, Normal
- Departed: KABI, Abilene, TX
- Destination: KADS, Addison, TX
- Flight plan: IFR
- Airport: KADS, Addison Airport
- Equipment: Auto-pilot, Angle of attack indicator, ADS-B, Stall warning system, Satellite tracking device, Electronic primary flight display, Electronic multifunction display

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 60; injuries: serious; private; airplane ratings: single-engine land; instrument ratings: airplane; medical: class 3, with waivers/limitations; last flight review May 21, 2021; seat: left; restraint: lap only; flight hours: 2,400 total, 2,000 in this make and model

## Weather

- Conditions: Instrument (IMC), Night
- Wind: 120° at 13 knots, gusting 18
- Visibility: 2 statute miles
- Lowest ceiling: 400 ft overcast
- Temperature: 63 °F, dew point 59 °F
- Altimeter: 2984.00 inHg
- Turbulence: Unknown
- Observed at: KADS, 2 nm away
- METAR: SPECI KADS 130210Z 12013G18KT 2SM -RABR OVC004 17/15 A2984=

## 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 20221212022859A](https://openairdocs.org/incident/20221212022859A), Dec 12, 2022: Mooney Aircraft Corp. M20K, Carrollton, TX, Destroyed. On December 12, 2022 at approximately 1856 CST, [privacy data omitted], a Mooney M20K, departed abilene regional airport (abi) for a part 91 flight to Addison…

## Docket (6 files)

The files NTSB released with the investigation on April 18, 2024, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=106448. 20.2 MB in all.

- Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 10 pages, 4.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16715639&FileExtension=pdf&FileName=6120_Redacted-Rel.pdf
- Statement from pilot (item 2, PDF, 2 pages, 212 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16717646&FileExtension=pdf&FileName=Regarding%20maintenance%20logs_Redacted-Rel.pdf
- Engine exam summary (item 3, PDF, 5 pages, 139 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16717093&FileExtension=pdf&FileName=Examination%20Summary%20--%20CEN23LA062-Rel.pdf
- Service bulletin (item 4, PDF, 18 pages, 4.8 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16694967&FileExtension=pdf&FileName=Camshaft%20SB-Rel.pdf
- Photos (item 5, PDF, 6 pages, 769 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16693446&FileExtension=pdf&FileName=Photo%20Array-Rel.pdf
- Materials laboratory factual report (item 6, PDF, 22 pages, 27 photos, 10.0 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16666551&FileExtension=pdf&FileName=24-003%20-%20Materials%20Lab%20Factual%20Report%20(CEN23LA062)-Rel.pdf

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.

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