# NTSB FTW00LA107: Cessna 172N, N75958, Maud, OK, March 24, 2000 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: March 24, 2000, 16:15 local (22:15 UTC) - Place: Maud, OK - Coordinates: 35.130268, -96.769752 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=35.1303&lon=-96.7698&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed, report July 17, 2001 - Report: Approved by Office Director - NTSB case key (mKey): 51127 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=FTW00LA107 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/51127/pdf - Page: https://openairdocs.org/ntsb/FTW00LA107 ## Probable cause the loss of engine power while maneuvering as a result of the separation of the exhaust rocker arm retaining stud due to fatigue, which resulted in a precautionary landing. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Loss of engine power(partial) - mech failure/malf, maneuvering - miscellaneous,bolt/nut/fastener/clamp/spring - fatigue (cause) - miscellaneous,bolt/nut/fastener/clamp/spring - separation (cause) - On ground/water collision with object, emergency descent/landing - precautionary landing - performed, pilot in command(cfi) - object - fence ## Analysis The flight instructor and private pilot receiving instruction were practicing basic maneuvers, during an instrument training flight, when the airplane began to 'vibrate violently.' They retarded the throttle, checked the magnetos, and then performed a precautionary landing to an open field. During the landing roll, the right horizontal stabilizer impacted a fence. An FAA inspector reported that the #3 exhaust rocker arm retaining stud separated. A section of stud was found lodged beneath the intake rocker arm, and the remaining portion of the stud remained seated in the cylinder head assembly. Metallurgical examination revealed that the stud failed due to fatigue that originated at the thread root from multiple origins. ## Factual narrative On March 24, 2000, at 1615 central standard time, a Cessna 172N airplane, N75958, was substantially damaged during a precautionary landing near Maud, Oklahoma. The airplane was registered to and operated by Airman Flight School, Inc., of Norman, Oklahoma. The flight instructor (CFI) and private pilot receiving instruction were not injured. Visual meteorological conditions prevailed and no flight plan was filed for the 14 Code of Federal Regulations Part 91 instructional flight. The local flight originated from the University of Oklahoma Westheimer Airport, Norman, Oklahoma, at 1540. According to the CFI and private pilot, the flight departed on an "instrument training flight," during which the student was "practicing basic attitudes." They reported that during the flight the "airplane started to vibrate violently." They retarded the throttle and checked the magnetos; however, the vibration intensified. Subsequently, a precautionary landing was executed to an open field, where the airplane impacted a fence during the landing roll. According to an FAA inspector, who examined the airplane, the right horizontal stabilizer was bent upward and the propeller blades were damaged. He examined the Lycoming O-320-H2AD engine and determined that the #3 cylinder's exhaust rocker arm retaining stud had separated. A portion of the separated stud was found lodged beneath the intake rocker arm, and the remaining portion of the stud remained seated in the cylinder head assembly. The cylinder head assembly and the separated portion of the exhaust rocker arm retaining stud were sent to the Textron Lycoming Materials Laboratory, Williamsport, Pennsylvania, for further examination. Macroscopic examination of the stud fracture surface revealed the presence of beach marks and ratchet marks on the fracture surface indicating that the stud failed in fatigue, which originated at the thread root from multiple origins. A hardness test reveled that the stud met the manufacturer's specifications and there were no additional defects noted with the stud's material. The airplane and engine underwent their most recent annual and 100-hour inspections, respectively, on February 8, 2000, at which time they had accumulated a total of 7,010.7 hours and 1,350.2 hours since overhaul, respectively. ## Aircraft - Registration: [N75958](https://openairdocs.org/deregistered/N75958-2012-12-12), registration cancelled 2012-12-12, S/N 17268069, built 1976 (OpenAirDocs) - Reported make and model: Cessna 172N - Registry model: [Cessna 172N](https://openairdocs.org/model/cessna-172n) (registry code 2072434) (OpenAirDocs) - Registry engine: [Lycoming 0-320 series](https://openairdocs.org/engine/lycoming-0-320-series) (registry code 41508, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 17268069 - Airframe hours: 7011 - Engines: Lycoming O-320-H2AD 180 horsepower reciprocating - Damage: Substantial damage - Flight: Instructional, Part 91 - Registered owner: Airman Flight School Inc. - Airworthiness certificate: Standard, Normal - Last inspection: Annual, February 8, 2000, 60 hours before - Departed: OUN, NORMAN, OK ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; flight instructor; airplane ratings: single-engine land; instrument ratings: airplane; medical: class 1, valid medical--no waivers/lim.; seat: right; flight hours: 423 total, 28 in this make and model, 198 in the last 90 days ## Weather - Conditions: Visual (VMC), Day - Wind: 230° at 11 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 165 °F ## Other investigations on N75958 (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 DEN83LA151](https://openairdocs.org/ntsb/DEN83LA151), Jun 17, 1983: Cessna 172 (N75958), Ellicott, CO, substantial damage 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.