# NTSB SEA99LA063: Lake LA-4, N152WB, Coeur D'Alene, ID, May 15, 1999 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: May 15, 1999, 12:30 local (19:30 UTC) - Place: Coeur D'Alene, ID - Coordinates: 47.779365, -116.710456 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=47.7794&lon=-116.7105&mi=10 - Phase of flight: [Unknown](https://openairdocs.org/ntsb-phases/990) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed, report November 30, 2000 - Report: Approved by Office Director - NTSB case key (mKey): 46443 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=SEA99LA063 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/46443/pdf - Page: https://openairdocs.org/ntsb/SEA99LA063 ## Probable cause The fatigue failure of a repair weld on one of the engine pylon mount straps and the resultant reduction in directional control. Factors include an inadequate repair of the strap, variable wind speeds and sudden wind shifts. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Airframe/component/system failure/malfunction, unknown - fuselage - fatigue (cause) - fuselage - failure,partial (cause) - maintenance,major repair - improper, unknown (contributing factor) - Loss of control - on ground/water, landing - flare/touchdown - directional control - diminished (cause) - weather condition - variable wind (contributing factor) - weather condition - sudden windshift (contributing factor) ## Analysis While landing in variable, shifting winds, both the dual student and the instructor had trouble maintaining directional control of the aircraft. After touchdown, the aircraft started turning toward the right side of the runway, and the instructor could not get it to straighten out using maximum left brake and full left rudder. He therefore added power to get airflow over the rudder to increase its efficiency, but the aircraft continued to turn sharper, eventually departing the right side of the runway and impacting the segmented circle at the base of the wind sock. It was later discovered that an improper repair weld on one of the engine pylon mounting straps had failed from fatigue, allowing the engine pylon to twist out of alignment with the longitudinal axis of the aircraft. ## Factual narrative On May 15, 1999, approximately 1230 Pacific daylight time, a Lake LA-4, N152WB, impacted the metal segmented circle at the base of the wind sock during a landing attempt on runway 19 at Coeur D'Alene, Idaho. The certified flight instructor (CFI) and his student, who holds a private pilot license, were not injured, but the aircraft, which was owned by the CFI, sustained substantial damage. The 14 CFR Part 91 instructional flight, which originated at Coeur D'Alene about three hours earlier, was being operated in visual meteorological conditions. No flight plan had been filed, and there was no report of an ELT activation. According to the instructor pilot, the student allowed the aircraft to get high on approach while attempting to land in variable, quickly shifting winds. The instructor told the student to steepen the approach and to center the nose of the aircraft on the runway centerline, which he monetarily did. Just prior to the flare, the instructor noticed that the wind sock was "blowing from side to side," and he again "...instructed rudder correction." Then according to the instructor, during the flare, the nose of the aircraft "...veered sharply to the right and the nose pitched up." The student was unable to bring the aircraft back into correct alignment with the runway during the touchdown, and he allowed the aircraft to land hard while "...sideways on the runway." The instructor then took over just after the aircraft touched down, but it "...jerked sharply to the right and off the runway." The instructor was unable to get the aircraft realigned with the runway using full left rudder and left brake, so he added a burst of power because he thought the increased airflow over the rudder would cause it to be more effective. The addition of power did not help in the instructor's attempt to turn the aircraft back to the left, and instead, the rate of turn to the right increased as the aircraft departed the runway and impacted the segmented circle. While the aircraft was being disassembled after the accident, the left side engine pylon mount upper strap was found to have failed through a weld that appeared to be part of a previous repair. A portion of the strap, to include the weld line, was sent to the NTSB materials laboratory for analysis. During that analysis, it was determined that there were crack arrest position marks along portions of the weld that were consistent with propagation of a fatigue crack. It was further determined that when the repair weld was made, it had inadequate penetration, minimal fusion, and numerous voids. Also, the strap, which was made of low-alloy steel, was welded using a stainless steel electrode. A review of the log books did not reveal when the repair had been made, nor whether Service Letter #43, which calls for inspecting the straps for cracks every 100 hours, had been complied with. It was also noted that with the strap fractured, the engine mounting pylon would twist when a cylinder was grasped by hand and forward pressure was applied. ## Aircraft - Registration: [N152WB](https://openairdocs.org/deregistered/N152WB-2017-05-23), registration cancelled 2017-05-23, S/N 268, built 1964 (OpenAirDocs) - Reported make and model: Lake LA-4 - Registry model: [Lake LA-4](https://openairdocs.org/model/lake-la-4) (registry code 5110302) (OpenAirDocs) - Registry engine: [Lycoming O&VO-360 series](https://openairdocs.org/engine/lycoming-o-vo-360-series) (registry code 41514, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 268 - Airframe hours: 1367 - Engines: Lycoming O-360-A1A 180 horsepower reciprocating - Damage: Substantial damage - Flight: Instructional, Part 91 - Operator: Mike D. Kincaid - Registered owner: Checklist Training Systems - Airworthiness certificate: Standard, Normal - Last inspection: Annual, August 11, 1998, 48 hours before - Departed: COE - Airport: COE, Coeur D'Alene, runway 19, 5,400 × 75 ft, asphalt ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 49; flight instructor, commercial; airplane ratings: single-engine land, single-engine sea; instrument ratings: airplane; medical: class 2, valid medical--w/ waivers/lim; seat: right; flight hours: 4,286 total, 52 in this make and model, 75 in the last 90 days, 23 in the last 30 days, 3 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: variable at 10 knots - Visibility: 10 statute miles - Lowest ceiling: 3,500 ft broken - Temperature: 55 °F, dew point 34 °F - Altimeter: 30.00 inHg ## 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 19990515005169A](https://openairdocs.org/incident/19990515005169A), May 15, 1999: Conaer LA4, Coeur D Alene, ID, Substantial damage. Pilot was practicing touch and go landings when the acft crash-landed near rwy 1/19, other circumstances are unknown. (-23) flight instructor michael kincaid… 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.