# NTSB SEA04TA147: WSK PZL Mielec M-18A, N495WP, Burns, OR, July 26, 2004 - Type: NTSB accident investigation - Classification: Accident · No injuries · Final report - Date: July 26, 2004, 13:26 local (20:26 UTC) - Place: Burns, OR - Coordinates: 43.852779, -119.181663 - Nearby events: https://openairdocs.org/map.md?lat=43.8528&lon=-119.1817&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report October 28, 2004 - Report: Approved by Office Director - Parties: FAA FSDO - NTSB case key (mKey): 59810 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=SEA04TA147 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/59810/pdf - Page: https://openairdocs.org/ntsb/SEA04TA147 ## Probable cause The improper installation of the throttle linkage clevis to the throttle control arm by unknown maintenance personnel. Contributing factors were the nylon lock nut separating from its' bolt, which permitted the throttle cable to disconnect from the throttle control arm, and the fence post. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Airframe/component/system failure/malfunction, maneuvering - aerial application - maintenance,installation - improper, other maintenance personnel (cause) - throttle/power lever,cable - disconnected (contributing factor) - Loss of engine power(partial) - mech failure/malf, climb - to cruise - Forced landing, emergency descent/landing - On ground/water collision with object, landing - roll - object - fence post (contributing factor) ## Analysis The pilot was attempting to climb following a fire retardant drop. When he moved the throttle forward, the engine did not respond. The airplane started loosing altitude, and the pilot performed a forced landing to an open plateau. During the landing, the throttle would not retard all the way. In order to land the airplane, the pilot turned the fuel selector to the off position. During the landing roll, the left wing impacted a fence pole bending ribs and wrinkling the aileron. Post accident examination revealed that the bolt normally connecting the throttle linkage clevis to the throttle arm was missing. The investigating team examined a sister aircraft from the same provider. They found that a nylon lock nut had been installed on the clevis bolt, and it was loose enough to be removed without the aid of any tools. The industry standard, found in FAA Advisory Circular AC43.13-1B, chapter 7, section 4, paragraph 7-64, states that nylon locking nuts should not be used with rotating components or assemblies. It further states that nylon and/or fiber nuts are highly susceptible to wear from repetitive use and from high heat applications. ## Factual narrative On July 26, 2004, at 1326 Pacific daylight time, a WSK PZL Mielec M-18A [Dromader], N495WP, was substantially damaged when it struck a fence post during a forced landing attempt near Burns, Oregon. The commercial pilot was not injured. Western Pilot Service Inc., Maricopa, Arizona, was operating the aircraft for the United States Department of Agriculture, United States Forest Service. Visual meteorological conditions prevailed for the fire retardant application flight that originated approximately 20 minutes before the accident. A company VFR flight plan was on file. The pilot reported that he was attempting to climb following a retardant drop. When he moved the throttle forward, the engine did not respond. He said the airplane started loosing altitude, and pumping the throttle had no effect. The pilot saw a plateau just southwest of the fire, and he performed a forced landing to it. During the landing, the throttle would not retard all the way. In order to land the airplane where he wanted to, he turned the fuel selector to the off position. During the landing roll, the left wing impacted a fence pole bending ribs and wrinkling the aileron. Post accident examination revealed that the bolt normally connecting the throttle linkage clevis to the throttle arm was missing. The investigating team examined a sister aircraft from the same provider. They found that a nylon lock nut had been installed on the clevis bolt, and it was loose enough to be removed without the aid of any tools. The industry standard, found in FAA Advisory Circular AC43.13-1B, chapter 7, section 4, paragraph 7-64 states that nylon locking nuts should not be used with rotating components or assemblies. It further states that nylon and/or fiber nuts are highly susceptible to wear from repetitive use and from high heat applications. ## Aircraft - Registration: [N495WP](https://openairdocs.org/deregistered/N495WP-2011-04-27), registration cancelled 2011-04-27, S/N 1Z02026, built 1989 (OpenAirDocs) - Reported make and model: WSK PZL Mielec M-18A - Registry model: [WSK PZL Mielec M-18A](https://openairdocs.org/model/wsk-pzl-mielec-m-18a) (registry code 9810103) (OpenAirDocs) - Registry engine: [Pezetel ASZ-621R-M18](https://openairdocs.org/engine/pezetel-asz-621r-m18) (registry code 49800, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 1Z0206 - Airframe hours: 3659 - Engines: Pezetel ASZ621RM18 985 horsepower reciprocating - Damage: Substantial damage - Flight: Aerial application, Part 137 - Operator: United States Forest Service - Registered owner: Western Pilot Service Inc. - Airworthiness certificate: Special, Restricted (Special) - Last inspection: 100 hour, June 22, 2004, 32 hours before - Departed: BNO, Burns, OR - Flight plan: Company VFR ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 59; injuries: none; commercial; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 2, valid medical--w/ waivers/lim; last flight review January 10, 2004; seat: single; flight hours: 5,047 total, 2,373 in this make and model, 4,999 as pilot in command, 66 in the last 90 days, 33 in the last 30 days, 2 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 0° at 4 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 88 °F, dew point 37 °F - Altimeter: 30.06 inHg - Observed at: BNO, 28 nm away 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.