# NTSB SEA00LA120: Cessna U206B, N3488L, Yellow Pine, ID, July 2, 2000 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: July 2, 2000, 12:00 local (18:00 UTC) - Place: Yellow Pine, ID - Coordinates: 45.020523, -115.520957 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=45.0205&lon=-115.5210&mi=10 - Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 4 uninjured - Status: Completed, report June 14, 2001 - Report: Approved by Office Director - NTSB case key (mKey): 49587 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=SEA00LA120 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/49587/pdf - Page: https://openairdocs.org/ntsb/SEA00LA120 ## Probable cause The locknut was not secured and backed off the bolt. An improper maintenance installation was a factor. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Airframe/component/system failure/malfunction, landing - roll - maintenance,installation - improper, other maintenance personnel (contributing factor) - miscellaneous,bolt/nut/fastener/clamp/spring - not secured (cause) - Nose over, landing - roll ## Analysis The pilot reported that he set-up for a soft field landing on a grass airstrip. The airplane touched down on the main landing gear, and immediately after the nose wheel touched down, grass and dirt started to come over the windshield and the airplane rapidly decelerated, subsequently nosing over. After the accident, it was noted that the nose wheel had separated from the nose wheel fork. The axle bolt, both buckets, and a locknut were found on the grass airstrip along the aircraft's ground track. Inspection of the parts and a review of the maintenance records disclosed evidence that the nose gear and tire installation were for a Piper PA32. The accident aircraft was a Cessna U206B. Although the two installations are similar, the Piper installation used an axle bolt that is secured with a lock nut (on the aircraft at the time of the accident). The Cessna installation used an axle bolt that is drilled for a castle nut and cotter key installation. An inspection of the nut and bolt threads was conducted at the NTSB Materials Lab. The specialist reported that the threads on both the bolt and nut showed no evidence of excessive loading or stripping damage. Due to the lack of damage to the axle bolt and nut, it appeared that the bolt was not locked down at the last maintenance inspection and backed off. ## Factual narrative On July 2, 2000, about 1200 mountain daylight time, a Cessna U206B, N3488L, registered to and operated by the pilot as a 14 CFR Part 91 personal flight, nosed over during the landing roll at Johnson Creek, Yellow Pine, Idaho. Visual meteorological conditions prevailed at the time and no flight plan was filed. The airplane was substantially damaged and the commercial pilot and his three passengers were not injured. The flight had departed from McCall, Idaho, about 20 minutes prior to the accident. During a telephone interview and subsequent written statement, the pilot reported that he flew the normal traffic pattern for the soft field landing technique on runway 17. The airplane touched down on the main landing gear, and immediately after the nose wheel touched down, grass and dirt started to come over the windshield and the airplane rapidly decelerated, subsequently nosing over. A deputy from the Valley County Sheriff's Department responded to the accident site and diagramed the location of where parts were found on the airstrip that separated from the aircraft. The deputy also noted ground disturbances leading up to the inverted aircraft. (see attached Sheriff's report) The deputy noted finding a 3/8-inch nylon nut, an axle bolt with end cups, and the nose wheel fork on the airstrip north of the main wreckage. The nose wheel also separated from the nose wheel yoke, however, the deputy did not make note of its location. Maintenance records indicate that on February 27, 1991, a PA32 nose fork, s/n 594, was installed in accordance with Cessna Service and Parts Manual. A receipt indicated that the "PA32-206L Nose Fork, serial number 594" was purchased from Airglas Engineering Company, Anchorage, AK, by AeroWest Inc., of Troutdale, Oregon, on September 18, 1990. This installation was accomplished prior to the current owner's purchase of the aircraft. The most recent annual inspection accomplished under the current pilot's ownership was completed on July 8, 1999. On September 15, 1999, a logbook entry indicated that a new nose wheel tire and tube were installed approximately 98 hours prior to the accident by the same mechanic who signed off the July 1999, annual inspection. (see Maintenance Information attachment) The Cessna Accessory Kit nose wheel and main wheel conversion applicable to this aircraft, (see Cessna Gear and Tire Installation attachment) indicated that an AN5-55 axel bolt (5 5/8 inches long, and 5/16 inch in diameter) be used with an AN310-5 castle nut and cotter pin. The parts that were recovered at the accident site indicate that the aircraft was equipped with an axel bolt that was not drilled for a castle nut and cotter key configuration. A representative for the Cessna Aircraft Company reported that there is no Cessna approved axle bolt installation without the cotter key configuration. The NTSB Investigator-in-charge contacted a representative from Piper Aircraft to request parts information for the applicable nose gear strut assembly on a Piper PA-32. The parts catalog (see Piper Nose Gear Strut Assembly attachment) indicated use of an AN6-76A axle bolt and secured with an MS20365-624C Nut. Measurements taken of the axle bolt recovered at the accident site indicated that the bolt was 7 3/4 inches long, and 3/8 inch in diameter. These dimensions match the specifications for an AN6-76A bolt. The bolt and nut were sent to the National Transportation Safety Board Materials Laboratory in Washington DC, for further inspection of the locking tightness of the nut. The specialist reported that, "The thread on both the bolt and nut showed no evidence of excessive loading or stripping. Detailed examination of the threads from the bolt revealed the presence of minor wear on the pressure flanks of all the threads, with the exception of one or two threads adjacent to the unthreaded bolt shank. Wear was also noted on the non-pressure flanks of about half of the threads (those closer to the end of the bolt.)" The specialist further stated that, "Detailed examination of the threads of the lock nut revealed the presence of minor wear on the pressure flanks along the entire length of the nut, indicating that the nut had been threaded completely onto a bolt at some time." "Wear was also noted on the non-pressure flanks in the deformed area associated with the locking cuts." ## Aircraft - Registration: [N3488L](https://openairdocs.org/deregistered/N3488L-2012-09-10), registration cancelled 2012-09-10, S/N U206-0788 (OpenAirDocs) - Reported make and model: Cessna U206B - Registry model: [Cessna U206B](https://openairdocs.org/model/cessna-u206b) (registry code 2073322) (OpenAirDocs) - Category: Airplane - Serial number: U206-0788 - Airframe hours: 4878 - Engines: Continental IO-520-F 300 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Registered owner: Neil M. Salmi - Airworthiness certificate: Standard, Normal - Last inspection: Annual, July 8, 1999, 100 hours before - Departed: MYL, MCCALL, ID - Airport: 3U2, Johnson Creek, runway 17, 3,400 × 150 ft, grass/turf ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 53; commercial, flight instructor; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 3, valid medical--w/ waivers/lim; seat: left; flight hours: 5,788 total, 500 in this make and model, 5,710 as pilot in command, 15 in the last 90 days, 15 in the last 30 days ## Weather - Conditions: Visual (VMC), Day - Wind: 290° at 7 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 64 °F, dew point 45 °F - Altimeter: 29.00 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 20000702007809A](https://openairdocs.org/incident/20000702007809A), Jul 2, 2000: Cessna U206B, Yellow Pine, ID, No damage. (-23) During landing rollout, the aircraft experienced separation of nosewheel when it contacted the ground. The aircraft flipped over onto it's back before… ## Other investigations on N3488L (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 WPR11CA034](https://openairdocs.org/ntsb/WPR11CA034), Nov 2, 2010: Cessna U206B (N3488L), Cascade, ID, substantial damage. Probable cause: The pilot's failure to maintain clearance from terrain during a turn onto the final approach leg of the traffic pattern. 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.