# NTSB ERA09LA399: Cessna 172N, N4773G, Rochester, MA, July 12, 2009

- Type: NTSB accident investigation
- Classification: Accident · No injuries · Limited investigation · Final report
- Date: July 12, 2009, 12:45 local (16:45 UTC)
- Place: Rochester, MA
- Coordinates: 41.721668, -70.801391 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=41.7217&lon=-70.8014&mi=10
- Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping)
- Defining event: [Enroute-cruise: Powerplant sys/comp malf/fail](https://openairdocs.org/ntsb-events/340)
- Highest injury: No injuries
- Injuries: 4 uninjured
- Status: Completed, report April 19, 2010
- Report: Approved by Office Director
- NTSB office: Eastern Region Aviation
- Parties: FAA/FSDO
- NTSB case key (mKey): 74256
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ERA09LA399
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/74256/pdf
- NTSB docket: https://data.ntsb.gov/Docket?ProjectID=74256
- Page: https://openairdocs.org/ntsb/ERA09LA399

## Probable cause

An engine vibration as reported by the pilot, for undetermined reasons.

## Findings

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

- [Not determined](https://openairdocs.org/ntsb-findings/05000000): Not determined › Not determined · Unknown/Not determined (probable cause); cases with it: [Cessna 172N, 24 cases](https://openairdocs.org/ntsb-findings/05000000/cases.md?model=2072434), [All aircraft, 2,247 cases](https://openairdocs.org/ntsb-findings/05000000/cases.md)
- [Runway/land/takeoff/taxi surface](https://openairdocs.org/ntsb-findings/03023000): Environmental issues › Physical environment · Not specified; cases with it: [Cessna 172N, 4 cases](https://openairdocs.org/ntsb-findings/03023000/cases.md?model=2072434), [All aircraft, 253 cases](https://openairdocs.org/ntsb-findings/03023000/cases.md)

## Sequence of events

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

- [Enroute-cruise: Powerplant sys/comp malf/fail](https://openairdocs.org/ntsb-events/340) (defining event); cases with it: [Cessna 172N, 11 cases](https://openairdocs.org/ntsb-events/340/sequence.md?model=2072434), [All aircraft, 820 cases](https://openairdocs.org/ntsb-events/340/sequence.md)
- [Emergency descent: Off-field or emergency landing](https://openairdocs.org/ntsb-events/440); cases with it: [Cessna 172N, 31 cases](https://openairdocs.org/ntsb-events/440/sequence.md?model=2072434), [All aircraft, 3,365 cases](https://openairdocs.org/ntsb-events/440/sequence.md)

## Analysis

The pilot reported that the airplane was in cruise flight when the engine developed sporadic engine vibrations. Manipulation of the carburetor heat and mixture controls did not remedy the situation and the engine subsequently developed a severe vibration. The pilot then elected to reduce engine power and perform a precautionary landing to a field. The airplane touched down in a cranberry bog, and sustained substantial firewall and airframe damage. Examination of the wreckage did not reveal any mechanical malfunctions. It was noted that the No. 2 cylinder lower spark plug was fouled and that the compression on the No. 4 cylinder was lower than that of cylinders 1, 2 and 3; however, the reason for the severe engine vibration could not be determined. The airplane had been operated for approximately 74 hours since its most recent 100 hour inspection, which was performed about two months prior to the accident.

## Factual narrative

On July 12, 2009, about 1245 eastern daylight time, a Cessna 172N, N4773G, was substantially damaged during a precautionary landing in Rochester, Massachusetts. The certificated private pilot and three passengers were not injured. Visual meteorological conditions prevailed and no flight plan had been filed for the flight that departed Boire Airport (ASH), Nashua, New Hampshire, about 1140, destined for Martha's Vineyard Airport (MVY), Vineyard Haven, Massachusetts. The personal flight was conducted under Title 14 Code of Federal Regulations Part 91. The pilot reported that the airplane had descended to a cruise altitude of 1,500 feet when he began to feel "sporadic engine vibrations." The carburetor heat was still in the "on" position from the recent descent, and the pilot turned the carburetor heat to the "off" position, and enriched the fuel mixture. The vibration increased when engine power was added and was becoming worse. The pilot elected to reduce engine power and perform a precautionary landing to a field. The airplane subsequently touched down in a cranberry bog, and sustained substantial firewall and airframe damage. Examination of the wreckage by a Federal Aviation Administration (FAA) inspector did not reveal any mechanical malfunctions. The inspector noted that the No. 2 cylinder lower spark plug was fouled and that the compression on the No. 4 cylinder was lower than that of cylinders 1, 2 and 3; however, the reason for the severe engine vibration reported by the pilot could not be determined. According to maintenance records, the airplane had accumulated 5,311 total flight hours and had been operated for approximately 74 hours since its most recent inspection, a 100 hour inspection, which was performed on May 12, 2009. The engine had accumulated 3,668 total hours and 1,430 hours since major overhaul. It had accumulated 74 flight hours since inspection on May 12, 2009. The pilot reported 61 hours of total flight experience; all accumulated in the same make and model as the accident airplane. A weather observation taken at 1253, at the New Bedford Regional Airport (EWB), located about 8 miles southwest of the accident site, reported: clam winds; visibility 10 statute miles; ceiling 2,300 feet broken; temperature 24 degrees Celsius (C), dew point 18 degrees C; altimeter 29.87 inches of mercury.

## Aircraft

- Registration: [N4773G](https://openairdocs.org/deregistered/N4773G-2014-03-24), registration cancelled 2014-03-24, S/N 17273342 (OpenAirDocs)
- Reported make and model: CESSNA 172N
- Registry model: [Cessna 172N](https://openairdocs.org/model/cessna-172n) (registry code 2072434) (OpenAirDocs)
- Category: Airplane
- Serial number: 17273342
- Airframe hours: 5385
- Engines: Lycoming O-320-H2AD 160 horsepower reciprocating
- Damage: Substantial damage
- Flight: Personal, Part 91
- Operator: New England Flight Operations LLC
- Registered owner: New England Flight Operations LLC
- Airworthiness certificate: Standard, Normal
- Last inspection: 100 hour, May 12, 2009, 75 hours before
- Departed: ASH, Nashua, NH
- Destination: MVY, Vineyard Haven, MA

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 28; injuries: none; private; airplane ratings: single-engine land; medical: class 3, without waivers/limitations; last flight review December 13, 2008; seat: left; flight hours: 61 total, 61 in this make and model, 17 as pilot in command, 4 in the last 90 days, 1 in the last 30 days, 0 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Visibility: 10 statute miles
- Lowest ceiling: 2,300 ft broken
- Temperature: 75 °F, dew point 64 °F
- Altimeter: 29.87 inHg
- Observed at: EWB, 8 nm away

## Docket (3 files)

The files NTSB released with the investigation on February 23, 2010, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=74256. 675 KB in all.

- Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 430 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40324007&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF
- Witness Statements (item 2, .PDF, 167 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40324047&FileExtension=.PDF&FileName=Witness%20Statements-Redacted.PDF
- FAA Inspector Statement (item 3, .PDF, 78 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40324031&FileExtension=.PDF&FileName=FAA%20Inspector%20Statement-Redacted.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.

---
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.