# NTSB CEN12TA122: Cessna 172P, N54872, Conroe, TX, January 4, 2012

- Type: NTSB accident investigation
- Classification: Accident · No injuries · Final report
- Date: January 3, 2012, 21:45 local (Jan 4, 2012, 03:45 UTC)
- Place: Conroe, TX
- Coordinates: 30.30861, -95.449996
- Nearby events: https://openairdocs.org/map.md?lat=30.3086&lon=-95.4500&mi=10
- Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping)
- Defining event: [Landing: Collision during takeoff/land](https://openairdocs.org/ntsb-events/490)
- Highest injury: No injuries
- Injuries: 1 uninjured
- Status: Completed, report April 20, 2012
- Report: Approved by Office Director
- NTSB office: Central Region
- Parties: FAA FLIGHT STANDARDS DISTRICT OFFICE
- NTSB case key (mKey): 82616
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN12TA122
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/82616/pdf
- NTSB docket: https://data.ntsb.gov/Docket?ProjectID=82616
- Page: https://openairdocs.org/ntsb/CEN12TA122

## Probable cause

Failure of the rear crankshaft gear dowel pin due to improper installation, which resulted in a total loss of engine power.

## Findings

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

- [Engine (reciprocating): recip eng rear section](https://openairdocs.org/ntsb-findings/01058540): Aircraft › Aircraft power plant · Failure (probable cause); cases with it: [Cessna 172P, 1 case](https://openairdocs.org/ntsb-findings/01058540/cases.md?model=2072436), [All aircraft, 42 cases](https://openairdocs.org/ntsb-findings/01058540/cases.md)
- [Action: incomplete action](https://openairdocs.org/ntsb-findings/02041040): Personnel issues › Action/decision · Maintenance personnel (probable cause); cases with it: [Cessna 172P, 1 case](https://openairdocs.org/ntsb-findings/02041040/cases.md?model=2072436), [All aircraft, 105 cases](https://openairdocs.org/ntsb-findings/02041040/cases.md)
- [Object/animal/substance: wire](https://openairdocs.org/ntsb-findings/03022032): Environmental issues › Physical environment · Contributed to outcome; cases with it: [Cessna 172P, 1 case](https://openairdocs.org/ntsb-findings/03022032/cases.md?model=2072436), [All aircraft, 588 cases](https://openairdocs.org/ntsb-findings/03022032/cases.md)
- [Object/animal/substance: pole](https://openairdocs.org/ntsb-findings/03022010): Environmental issues › Physical environment · Contributed to outcome; cases with it: [Cessna 172P, 4 cases](https://openairdocs.org/ntsb-findings/03022010/cases.md?model=2072436), [All aircraft, 142 cases](https://openairdocs.org/ntsb-findings/03022010/cases.md)

## Sequence of events

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

- [Enroute-climb to cruise: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341); cases with it: [Cessna 172P, 14 cases](https://openairdocs.org/ntsb-events/341/sequence.md?model=2072436), [All aircraft, 3,820 cases](https://openairdocs.org/ntsb-events/341/sequence.md)
- [Emergency descent: Off-field or emergency landing](https://openairdocs.org/ntsb-events/440); cases with it: [Cessna 172P, 22 cases](https://openairdocs.org/ntsb-events/440/sequence.md?model=2072436), [All aircraft, 3,365 cases](https://openairdocs.org/ntsb-events/440/sequence.md)
- [Landing: Collision during takeoff/land](https://openairdocs.org/ntsb-events/490) (defining event); cases with it: [Cessna 172P, 7 cases](https://openairdocs.org/ntsb-events/490/sequence.md?model=2072436), [All aircraft, 1,309 cases](https://openairdocs.org/ntsb-events/490/sequence.md)

## Analysis

The airplane was at 1,600 feet mean sea level with the engine power set at 2,300 rpm. When the airplane was about 6 miles from the airport, the pilot heard a loud “boom” and the engine lost all power. The pilot did not have sufficient altitude to glide to the airport, so he landed the airplane on a street. When the airplane was on final approach to land, it collided with power lines. The pilot was able to land the airplane, but was forced to swerve to the right to avoid oncoming traffic. The right wing struck a utility pole, which resulted in substantial damage. A postaccident engine examination revealed that when the crankshaft was turned, there was no movement of the intake or exhaust valves or magneto gears. The rear crank gear bolt was loose and the gear dowel pin was sheared, which would cause the camshaft and rear accessory gears to stop turning. Metallurgical examination revealed beach markings at the aft end of the crankshaft approximately in plane with the aft face of the crankshaft where it mated to the crankshaft gear. There was fretting damage on the crankshaft gear, wear on the dowel pins, and wear on the lock washer, indicative of movement as a result of insufficient clamping force from the attachment bolt at the time of installation. The engine had accrued 752 hours since it was overhauled in August 2007.

## Factual narrative

On January 3, 2012, about 2145 central standards time, the pilot of a Cessna 172P, N54872, made a forced landing on a street in Conroe, Texas, after the engine lost power. The pilot, the sole occupant on board, was not injured. The public use airplane was substantially damaged. The airplane was registered to and operated by the Civil Air Patrol (CAP), Maxwell AFB, Alabama, as CAP flight 4272. Dark night visual meteorological conditions (VMC) prevailed at the time of the accident, and a company flight plan had been filed. The flight originated from the West Houston Airport (KIWS), Houston, Texas, approximately 2120, and was en route to Lone Star Executive Airport (KCXO), Conroe, Texas. According to the pilot’s statement, engine power was set at 2300 rpm (revolutions per minute) and the airplane was at 1,600 feet msl (mean sea level). When the airplane was about 6 miles from the destination airport, the pilot heard a loud “boom” and the engine lost all power. The pilot did not have sufficient altitude to glide to the airport and landed on Highway 105 and North 6th Street in Conroe, Texas. When the airplane was on final approach, it collided with power lines. The pilot was able to land the airplane, but was forced to swerve to the right to avoid oncoming traffic. The airplane struck a curb and spun around. The right wing struck a utility pole, resulting in substantial damage. On January 24, the engine was disassembled and examined under the direction of a Federal Aviation Administration (FAA) inspector at the facilities of Fritz Aviation in Fredericksburg, Texas. CAP records indicate the engine had accrued 752 hours since it was overhauled in August 2007. When the crankshaft was turned, no movement of the intake or exhaust valves or magneto gears was observed. Upon removal of the rear accessory case, it was discovered that the rear crank gear bolt was loose and the gear dowel pin (part number STD 1065) was sheared. According to the FAA inspector, there was a line on the dowel pin, similar to a pre-existing crack. According to the attending mechanic’s report, the sheared dowel pin would cause the camshaft and rear accessory gears to stop turning. The crankshaft gear, attachment bolt, and crankshaft dowel pin were submitted to the National Transportation Safety Board’s Materials Laboratory for examination. According their report, the dowel pin was fractured from the aft end of the crankshaft approximately in plane with the aft face of the crankshaft where it mated to the crankshaft gear. Magnified optical examination of the dowel pin fracture revealed a relatively flat transverse fracture with beach markings indicative of fatigue progression initiating at two locations on opposing sides on the outer diameter of the dowel pin. The fatigue region emanating from the origin area (primary origin area) was substantially larger than that emanating from the upper side. The cylinder faces of the dowel pin appeared relatively smooth and reflective consistentwith wear of the original surfaces. The wear was present around most of the dowel pin periphery. The dowel pin’s diameter was reduced an estimated 0.005 inch by wear adjacent to the fatigue origin leaving a visible step. The crankshaft gear exhibited fretting damage on the forward face consistent with relative motion at the gear-to-crankshaft interface. The lock washer on the aft side of the crankshaft gear showed wear damage corresponding to contact with the underside of the attachment bolt head.

## Aircraft

- Registration: [N54872](https://openairdocs.org/deregistered/N54872-2016-06-30), registration cancelled 2016-06-30, S/N 17275074 (OpenAirDocs)
- Reported make and model: CESSNA 172P
- Registry model: [Cessna 172P](https://openairdocs.org/model/cessna-172p) (registry code 2072436) (OpenAirDocs)
- Registry engine: [Lycoming 0-320 series](https://openairdocs.org/engine/lycoming-0-320-series) (registry code 41508, reciprocating) (OpenAirDocs)
- Category: Airplane
- Serial number: 17275074
- Airframe hours: 4757
- Engines: Lycoming O-360-A4M 180 horsepower reciprocating
- Damage: Substantial damage
- Flight: Public aircraft - federal, Public use
- Operator: Civil Air Patrol, Inc.
- Registered owner: Civil Air Patrol, Inc.
- Airworthiness certificate: Standard, Normal
- Last inspection: Annual, June 28, 2011, 89 hours before
- Departed: KIWS, HOUSTON, TX
- Destination: KCXO, Conroe, TX
- Flight plan: Company VFR

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 22; injuries: none; private; airplane ratings: single-engine land; medical: class 2, without waivers/limitations; seat: left; flight hours: 108 total, 83 in this make and model, 66 as pilot in command, 39 in the last 90 days, 11 in the last 30 days, 1 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Night/dark
- Wind: calm
- Visibility: 10 statute miles
- Lowest ceiling: none
- Temperature: 32 °F, dew point 27 °F
- Altimeter: 30.61 inHg
- Observed at: KCXO

## 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 20120103000539A](https://openairdocs.org/incident/20120103000539A), Jan 3, 2012: Cessna 172P, Conroe, TX, Substantial damage. Aircraft departed kiws @ 2120 local time northeast bound, navigated the david wayne hooks airport airspace. Flight continued on with plans to land at kcxo @…

## Docket (14 files)

The files NTSB released with the investigation on March 8, 2012, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=82616. 24.4 MB in all.

- NTSB Form 6120, Pilot-Operator Aircraft Accident Report (item 1, .PDF, 3.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40362561&FileExtension=.PDF&FileName=NTSB%20Form%206120,%20Pilot-Operator%20Aircraft%20Accident%20Report-Redacted.PDF
- Materials Laboratory 15 - Factual Report 12-025 (item 2, .PDF, 1.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40363944&FileExtension=.PDF&FileName=Materials%20Laboratory%2015%20-%20Factual%20Report%2012-025-Master.PDF
- Pilot's Statement (item 3, .PDF, 192 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40362550&FileExtension=.PDF&FileName=Pilot%27s%20Statement-Master.PDF
- FAA Inspector's Statement (item 4, .PDF, 109 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40362552&FileExtension=.PDF&FileName=FAA%20Inspector%27s%20Statement-Redacted.PDF
- Mechanic's Statement (item 5, .PDF, 78 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40362551&FileExtension=.PDF&FileName=Mechanic%27s%20Statement-Redacted.PDF
- Map of Accident Location (item 6, .PDF, 135 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40363953&FileExtension=.PDF&FileName=Map%20of%20Accident%20Location-Master.PDF
- Weather Reports and Records (item 7, .PDF, 73 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40363954&FileExtension=.PDF&FileName=Weather%20Reports%20and%20Records-Master.PDF
- Statement of Party Representatives to NTSB Investigation (item 8, .PDF, 353 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40362566&FileExtension=.PDF&FileName=Statement%20of%20Party%20Representatives%20to%20NTSB%20Investigation-Redacted.PDF
- Photo 1 - N54872 at the accident site (item 9, .PDF, 4.0 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40364090&FileExtension=.PDF&FileName=Photo%201%20-%20N54872%20at%20the%20accident%20site-Master.PDF
- Photo 2 - Damaged powerline pole with embedded paint chips and smears (item 10, .PDF, 2.0 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40364091&FileExtension=.PDF&FileName=Photo%202%20-%20Damaged%20powerline%20pole%20with%20embedded%20paint%20chips%20and%20smears-Master.PDF
- Photo 3 - Power lines wrapped around propeller (item 11, .PDF, 3.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40364092&FileExtension=.PDF&FileName=Photo%203%20-%20Power%20lines%20wrapped%20around%20propeller-Master.PDF
- Photo 4 - Right wing damage (fuel being drained) (item 12, .PDF, 2.7 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40364093&FileExtension=.PDF&FileName=Photo%204%20-%20Right%20wing%20damage%20(fuel%20being%20drained)-Master.PDF
- Photo 5 - Loose rear crankshaft gear bolt (item 13, .PDF, 1.7 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40364095&FileExtension=.PDF&FileName=Photo%205%20-%20Loose%20rear%20crankshaft%20gear%20bolt-Master.PDF
- Photo 6 - Sheared gear dowel pin (item 14, .PDF, 5.3 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40364096&FileExtension=.PDF&FileName=Photo%206%20-%20Sheared%20gear%20dowel%20pin-Master.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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