# NTSB LAX98LA036: Cessna 172RG, N9451D, San Diego, CA, November 12, 1997 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: November 12, 1997, 11:30 local (19:30 UTC) - Place: San Diego, CA - Coordinates: 32.799163, -117.130386 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=32.7992&lon=-117.1304&mi=10 - Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed, report January 28, 2000 - Report: Approved by Office Director - NTSB case key (mKey): 29996 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=LAX98LA036 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/29996/pdf - Page: https://openairdocs.org/ntsb/LAX98LA036 ## Probable cause Overload of the main gear actuator piston and the subsequent collapse of the landing gear. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Gear collapsed, landing - roll - landing gear,main gear attachment - overload (contributing factor) ## Analysis The pilot and his instructor visually checked that the landing gear was down. On the landing roll the aircraft started to vibrate, and then rotated to the left. The instructor pilot shut down the engine and the right landing gear collapsed. The main gear actuator piston for the left main landing gear was found broken. A determination as to when the actuator piston was broken could not be made due to the extent of the damage. An examination of the aircraft logbook revealed that the main landing gear actuator piston had accumulated 1,530.2 hours since installation. The aircraft was examined on-scene with no further anomalies noted. An examination found beach marks on the fracture surface characteristic of a fatigue crack growth. The examination revealed that the fracture outside of the fatigue region was the result of a single event overload and not due to the fatigue crack. ## Factual narrative On November 12, 1997, at 1130 hours Pacific standard time, a Cessna 172RG, N9451D, had a left main gear collapse on landing and came to rest off runway 28L at Montgomery Field, San Diego, California. The aircraft, operated by American Flyers, sustained substantial damage. The commercial rated flight instructor pilot and private pilot were not injured. Visual meteorological conditions existed for the local instructional flight and no flight plan was filed. The private pilot reported that he had been cleared for a straight-in landing on runway 28L by the control tower. He and the instructor visually checked that the landing gear was down for the short field landing. After landing, the aircraft started to vibrate and rotated to the left. The instructor pilot shut down the engine, and then right landing gear collapsed. The aircraft came to rest approximately 40 feet left of runway 28L. The pilot reported that, "at no time before, during or after touchdown was a gear warning horn heard from the overhead speaker." A Federal Aviation Administration (FAA) inspector from the San Diego, California, Flight Standards District Office examined the aircraft on-scene and found that the left main gear actuator piston was broken. An examination of the aircraft logbook by the Safety Board revealed that the main gear actuator piston had been replaced in November 1994. It had accumulated 1,530.2 hours since installation. Metallurgical and fractographic examinations were conducted under FAA supervision on the main landing gear actuator piston at the Cessna Aircraft Company facilities in Wichita, Kansas. The metallurgical examination revealed that the actuator piston was within manufactured specifications. During the visual examination it was noted that beach marks were present on the fracture surface that is characteristic of a fatigue crack growth. However, no other cracks were found in the actuator piston. The fractographic examination determined that the fracture outside of the fatigue region was the result of a single event overload and not due to the fatigue crack growth beach mark (see attached report). ## Aircraft - Registration: [N9451D](https://openairdocs.org/deregistered/N9451D-1999-09-08), registration cancelled 1999-09-08, S/N 172RG1167 (OpenAirDocs) - Reported make and model: Cessna 172RG - Registry model: [Cessna 172RG](https://openairdocs.org/model/cessna-172rg) (registry code 2072438) (OpenAirDocs) - Category: Airplane - Serial number: 172RG1167 - Airframe hours: 11826 - Engines: Lycoming O-360-FIAG 180 horsepower reciprocating - Damage: Substantial damage - Flight: Instructional, Part 91 - Operator: American Flyers - Registered owner: Ate Of Texas Inc. - Airworthiness certificate: Standard, Normal - Last inspection: 100 hour, October 6, 1997, 79 hours before - Departed: MYF - Destination: MYF - Airport: MYF, Montgomery Field, runway 28L, 3,399 × 60 ft, asphalt ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 31; flight instructor, commercial; airplane ratings: single-engine land; instrument ratings: airplane; medical: class 2, valid medical--no waivers/lim.; seat: left; flight hours: 382 total, 54 in this make and model, 295 as pilot in command, 157 in the last 90 days, 69 in the last 30 days, 2 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 290° at 10 knots - Visibility: 40 statute miles - Lowest ceiling: 20,000 ft overcast - Temperature: 68 °F, dew point 46 °F - Altimeter: 29.00 inHg - Observed at: MYF ## 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 19971112039969A](https://openairdocs.org/incident/19971112039969A), Nov 12, 1997: Cessna 172RG, San Diego, CA, Substantial damage. Left main gear collapsed landing. (.4)the pilot and his instructor visually checked that the landing gear was down. On the landing roll the aircraft started to… ## Other investigations on N9451D (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 LAX99LA134](https://openairdocs.org/ntsb/LAX99LA134), Mar 29, 1999: Cessna 172RG (N9451D), Moorpark, CA, substantial damage. Probable cause: The failure and separation of the number two cylinder for undetermined reasons. A factor was the soft terrain at the forced landing site. 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.