# NTSB CEN12LA077: Cessna 152, N6436P, Princeton, MN, November 22, 2011 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: November 22, 2011, 10:55 local (16:55 UTC) - Place: Princeton, MN - Coordinates: 45.559722, -93.608055 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=45.5597&lon=-93.6081&mi=10 - Phase of flight: [Approach](https://openairdocs.org/ntsb-phases/500) (OpenAirDocs' grouping) - Defining event: [Approach-VFR pattern base: Loss of engine power (partial)](https://openairdocs.org/ntsb-events/342) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report May 15, 2012 - Report: Approved by Office Director - NTSB office: Central Region - Parties: FAA Minneapolis FSDO - NTSB case key (mKey): 82372 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN12LA077 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/82372/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=82372 - Page: https://openairdocs.org/ntsb/CEN12LA077 ## Probable cause The inadequate installation of the threaded insert in the No. 2 cylinder spark plug hole by maintenance personnel, which resulted in a loss of engine power during initial climb. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Engine (reciprocating): recip eng cyl section](https://openairdocs.org/ntsb-findings/01058530): Aircraft › Aircraft power plant · Incorrect service/maintenance (probable cause); cases with it: [Cessna 152, 5 cases](https://openairdocs.org/ntsb-findings/01058530/cases.md?model=2071835), [All aircraft, 373 cases](https://openairdocs.org/ntsb-findings/01058530/cases.md) - [Ignition system: spark plugs/igniters](https://openairdocs.org/ntsb-findings/01057421): Aircraft › Aircraft power plant · Incorrect service/maintenance (probable cause); cases with it: [Cessna 152, 3 cases](https://openairdocs.org/ntsb-findings/01057421/cases.md?model=2071835), [All aircraft, 38 cases](https://openairdocs.org/ntsb-findings/01057421/cases.md) - [Maintenance: installation](https://openairdocs.org/ntsb-findings/02062035): Personnel issues › Task performance · Maintenance personnel (probable cause); cases with it: [Cessna 152, 4 cases](https://openairdocs.org/ntsb-findings/02062035/cases.md?model=2071835), [All aircraft, 371 cases](https://openairdocs.org/ntsb-findings/02062035/cases.md) - [Terrain: rough terrain](https://openairdocs.org/ntsb-findings/03021015): Environmental issues › Physical environment · Contributed to outcome; cases with it: [Cessna 152, 6 cases](https://openairdocs.org/ntsb-findings/03021015/cases.md?model=2071835), [All aircraft, 442 cases](https://openairdocs.org/ntsb-findings/03021015/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Approach-VFR pattern base: Loss of engine power (partial)](https://openairdocs.org/ntsb-events/342) (defining event); cases with it: [Cessna 152, 21 cases](https://openairdocs.org/ntsb-events/342/sequence.md?model=2071835), [All aircraft, 1,858 cases](https://openairdocs.org/ntsb-events/342/sequence.md) - [Landing-landing roll: Nose over/nose down](https://openairdocs.org/ntsb-events/096); cases with it: [Cessna 152, 37 cases](https://openairdocs.org/ntsb-events/096/sequence.md?model=2071835), [All aircraft, 2,287 cases](https://openairdocs.org/ntsb-events/096/sequence.md) ## Analysis The student pilot conducted two takeoffs and landings without incident. During initial climb after the third takeoff, he heard a loud “pop,” and the airplane started to vibrate severely and lose engine power. He executed a forced landing to a nearby field. The airplane landed hard and nosed over during the landing roll. The examination of the airplane revealed that the lower spark plug from the No. 2 cylinder and its associated threaded insert were missing. The threads in the top portion of the spark plug hole were stripped, and only the bottom three threads remained. No other engine anomalies were observed. The engine maintenance logbook indicated that, 7 days prior to the accident, the Nos. 1 and 2 cylinders had new threaded inserts installed in the lower spark plug holes. ## Factual narrative On November 22, 2011, at 1055 central standard time, a Cessna C-152, N6436P, sustained substantial damage during a forced landing to a field after a partial loss of power near the Princeton Municipal Airport (PNM), Princeton, Minnesota. The student pilot, the sole occupant, was not injured. The airplane was registered to Ascend Aviation LLC and was being operated by the student pilot as an instructional flight under the provisions of the 14 Code of Regulations Part 91. Visual meteorological conditions prevailed at the time of the accident. No flight plan was filed for the local training flight. The student pilot reported that he and his instructor had completed an hour of dual instruction in the airplane just prior to the accident flight. After the dual instruction flight was completed, he departed on his solo instruction flight and conducted two takeoffs and landings without incident. During initial climb after the third takeoff at about 300 – 400 feet above the ground, he heard a loud “pop,” and the airplane started to vibrate severely and lose engine power. He executed a forced landing to a nearby field. The airplane landed hard and nosed over during the landing roll. A Federal Aviation Administration airworthiness inspector examined the airplane. The examination revealed that the lower spark plug of the number two cylinder and its associated threaded insert were missing. The threads in the top portion of the spark plug hole were stripped and only the bottom three threads remained. No other engine anomalies were observed. The inspection of the airplane’s engine maintenance logbook indicated that on November 15, 2011, the number one and number two cylinders had threaded inserts installed in the lower spark plug holes. ## Aircraft - Registration: [N6436P](https://openairdocs.org/aircraft/N6436P), registered now, S/N 15285013, built 1981 (OpenAirDocs) - Reported make and model: CESSNA 152 - Registry model: [Cessna 152](https://openairdocs.org/model/cessna-152) (registry code 2071835) (OpenAirDocs) - Registry engine: [Lycoming 0-235 series](https://openairdocs.org/engine/lycoming-0-235-series) (registry code 41505, 4 cycle) (OpenAirDocs) - Category: Airplane - Serial number: 15285013 - Airframe hours: 15700 - Engines: LYCOMING 0-235 SERIES 115 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Operator: Ascend Aviation LLC - Registered owner: Ascend Aviation LLC - Airworthiness certificate: Standard, Normal - Last inspection: 100 hour, September 5, 2011 - Departed: PNM, Princeton, MN - Destination: PNM, Princeton, MN - Airport: PNM, Princeton Municipal Airport ## Flight crew As NTSB recorded them. NTSB leaves out names. - Student pilot; age 33; injuries: none; student; medical: class 3; seat: left; flight hours: 14 total, 14 in this make and model, 1 as pilot in command, 14 in the last 90 days, 11 in the last 30 days, 1 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 120° at 4 knots - Visibility: 7 statute miles - Lowest ceiling: 2,300 ft broken - Temperature: 36 °F, dew point 30 °F - Altimeter: 30.10 inHg - Observed at: PNM ## 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 20111122027059A](https://openairdocs.org/incident/20111122027059A), Nov 22, 2011: Cessna 152, Princeton, MN, Substantial damage. The aircraft was being operated by a student pilot as an instructional flight on his second solo. This was the third takeoff of the solo event. At about 350… ## Other investigations on N6436P (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 MKC89LA101](https://openairdocs.org/ntsb/MKC89LA101), May 2, 1989: Cessna 152 (N6436P), Buffalo, MN, substantial damage. Probable cause: THE PILOT'S FAILURE TO MAINTAIN DIRECTIONAL CONTROL. FACTORS RELATED TO THE ACCIDENT WERE: THE CROSSWIND, THE PILOT'S IMPROPER COMPENSATION FOR WIND CONDITIONS, HIS IMPROPER USE OF THE THROTTLE, AND… ## Docket (7 files) The files NTSB released with the investigation on April 9, 2012, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=82372. 3.8 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 1.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40365562&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF - Maintenance Logbook Entries (item 2, .PDF, 1.7 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40365566&FileExtension=.PDF&FileName=Maintenance%20Logbook%20Entries-Redacted.PDF - Record of Conversation - 1 (item 3, .PDF, 51 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40365589&FileExtension=.PDF&FileName=Record%20of%20Conversation%20-%201-Master.PDF - Photo 1: Aircraft nosed over in a field. (item 4, .PDF, 363 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40365583&FileExtension=.PDF&FileName=Photo%201%3A%20Aircraft%20nosed%20over%20in%20a%20field.-Master.PDF - Photo 2: View of three spark plugs. (item 5, .PDF, 198 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40365585&FileExtension=.PDF&FileName=Photo%202%3A%20View%20of%20three%20spark%20plugs.-Master.PDF - Photo 3: View of the spark plug hole. (item 6, .PDF, 247 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40365587&FileExtension=.PDF&FileName=Photo%203%3A%20View%20of%20the%20spark%20plug%20hole.-Master.PDF - Photo 4: A second view of the sparkplug hole. (item 7, .PDF, 234 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40365594&FileExtension=.PDF&FileName=Photo%204%3A%20A%20second%20view%20of%20the%20sparkplug%20hole.%20-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. --- 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.