# NTSB SEA98LA158: Cessna 182, N6437A, Yellowpine, ID, August 7, 1998 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: August 7, 1998, 09:15 local (15:15 UTC) - Place: Yellowpine, ID - Coordinates: 45.019142, -115.520545 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=45.0191&lon=-115.5205&mi=10 - Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 3 uninjured - Status: Completed, report January 11, 2000 - Report: Approved by Office Director - NTSB case key (mKey): 43714 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=SEA98LA158 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/43714/pdf - Page: https://openairdocs.org/ntsb/SEA98LA158 ## Probable cause Right main landing gear spring strut fatigue, improper maintenance, and subsequent separation of the strut end. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Airframe/component/system failure/malfunction, landing - roll - landing gear,main gear strut - fatigue (cause) - maintenance - improper, other maintenance personnel (cause) - landing gear,main gear strut - separation (cause) ## Analysis Upon landing the pilot heard a bang and the right wing dropped. The airplane incurred substantial damage during a ground loop maneuver, following the separation of the right main wheel and lower strut end immediately after touchdown. Post-crash examination revealed that the lower end of the right main landing gear spring strut had broken off. Examination of the fracture surfaces revealed features characteristic of fatigue cracking in multiple locations. The fatigue cracks originated at the surface of the holes, at the edge between the wall of the hole and flat face of the leg. Separation of the spring strut was caused by fatigue cracks that originated from the surface of the two upper holes. No chamfer was found at the surfaces of the two upper holes. The surface of these holes contained for the most part a corner edge that is a stress raiser and, in turn, this stress raiser sensitized the hole to cracking. The two upper holes most likely were drilled oversize to remove anomalies such as corrosion or fretting damage. The diameter of the oversize holes was sufficient to have removed evidence of the chamfer. There was no airframe log information available which identified any maintenance on the spring strut. ## Factual narrative On August 7, 1998, approximately 0915 mountain daylight time, a tailwheel equipped Cessna 182, N6437A, registered to and being flown by a private pilot, incurred substantial damage during a ground loop maneuver, following the separation of the right main wheel and lower strut end immediately after touchdown at the Johnson Creek airstrip, Yellowpine, Idaho. The pilot and two passengers were uninjured. Visual meteorological conditions prevailed and no flight plan had been filed. The flight, which was personal, was to have been operated under 14CFR91, and originated from McCall, Idaho, approximately 0830. The pilot reported that after arriving in the Yellowpine area he executed "a normal approach for landing - - - touched down & rolled approx[imately] twenty or 50 feet when [he] heard a bang and the right wing dropped but did not come in contact with the runway." Post-crash examination revealed that the lower end of the right main landing gear spring strut had broken off. The break was observed to pass through the two bolt holes at the top side of the strut end which attaches the wheel and brake assembly to the strut (refer to photograph 1). The lower end of the strut was found still attached by the two upper and two lower bolts to the wheel and brake assembly (refer to photograph 2). The lower end of the spring strut was removed from the wheel assembly and examined at the Safety Board's Office of Research and Engineering, Materials Lab. Bench binocular microscope examination of the fracture revealed thumbnail features characteristic of fatigue cracking that stemmed from three separate locations. The fatigue cracks originated at the surface of the holes, at the edge between the wall of the hole and flat face of the leg. According to a representative from Cessna, a 45-degree chamfer is specified for the surface of the 4 holes. The edge of one of the holes that was intersected by a fatigue crack origin appeared to be slightly round. The edges of the holes that were intersected by the remaining two fatigue origins exhibited a right angle corner, and contained no chamfer. The fatigue cracks propagated away from the edge of the hole. The largest fatigue region propagated as much as 0.05 inch. Shear lips were noted on the edge of the fractures in areas outside of fatigue regions, and the fractures outside the fatigue regions contained features typical of overstress. The corners between the upper holes and the face of the leg opposite from the fatigue initiation sites did not contain a chamfer. The corners of the two lower holes contained a chamfer on both faces. The same representative from Cessna indicated that the diameter of the upper holes should be 0.316 +/- 0.01 inch, whereas, the diameter of the lower two holes should be larger (0.377 +/- 0.01 inch). Although the fracture intersected the upper two holes, these two upper holes contained at least a half portion of a circumference that could be measured. The diameter of all four holes measured approximately 0.38 inch. These measurements indicated that the diameters of the upper holes were larger than specified and that the diameters of the lower holes were within specification limits (refer to attached Materials Laboratory Factual Report). There was no airframe log information available which identified any maintenance on the spring strut. ## Aircraft - Registration: [N6437A](https://openairdocs.org/aircraft/N6437A), registered now, S/N 33237, built 1956 (OpenAirDocs) - Reported make and model: Cessna 182 - Registry model: [Cessna 182](https://openairdocs.org/model/cessna-182) (registry code 2072702) (OpenAirDocs) - Registry engine: [Continental O-470 series](https://openairdocs.org/engine/continental-o-470-series) (registry code 17026, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 33237 - Airframe hours: 2022 - Engines: Continental O-520-F-T5 240 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Operator: Terway, William, E. - Registered owner: Terway, William, E. - Airworthiness certificate: Standard, Normal - Last inspection: Annual, August 1, 1997, 40 hours before - Departed: MYL, MCCALL, ID - Destination: 3U2 - Airport: 3U2, Johnson Creek, runway 17, 3,400 × 150 ft, grass/turf ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 54; private; airplane ratings: single-engine land; medical: class 2, valid medical--w/ waivers/lim; seat: left; flight hours: 855 total, 85 in this make and model, 779 as pilot in command, 19 in the last 90 days, 11 in the last 30 days, 4 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: calm - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 68 °F, dew point 48 °F - Altimeter: 30.00 inHg - Observed at: MYL, 26 nm away ## 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 19980807020159A](https://openairdocs.org/incident/19980807020159A), Aug 7, 1998: Cessna 182, Yellow Pine, ID, Substantial damage. Acft right main gear collapsed on landing. (.23)N6437A was landing on runway 17 when the right wheel was observed to separate from the landing gear whereby it… 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.