# NTSB FTW99LA170: Wsk Pzl Mielec M-18A, N7075D, Basile, LA, June 18, 1999 - Type: NTSB accident investigation - Classification: Accident · Minor injuries · Limited investigation · Final report - Date: June 18, 1999, 07:50 local (12:50 UTC) - Place: Basile, LA - Coordinates: 30.47961, -92.599777 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=30.4796&lon=-92.5998&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Highest injury: Minor injuries - Injuries: 1 minor - Status: Completed, report April 6, 2001 - Report: Approved by Office Director - NTSB case key (mKey): 46585 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=FTW99LA170 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/46585/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=46585 - Page: https://openairdocs.org/ntsb/FTW99LA170 ## Probable cause The separation of the right wing forward spar lower attachment fitting due to a fatigue fracture, which emanated from corrosion as a result of maintenance not being performed. ## 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 - wing,wing attachment fitting - fatigue (cause) - wing,wing attachment fitting - fractured (cause) - wing,wing attachment fitting - corroded - maintenance - not performed, other maintenance personnel (cause) - In flight collision with terrain/water, descent - uncontrolled - aircraft control - not possible, pilot in command - terrain condition - ground ## Analysis The pilot was applying a chemical to a field. After completing a pass, as he applied aft elevator for a straight-ahead pull-up, a loud 'boom' was heard, and the outboard section of the right wing separated. The airplane became 'uncontrollable' and impacted in an uncultivated field. Metallurgical examination revealed that the separation of the right wing forward spar lower attachment fitting was the result of fatigue cracking in the bracket lugs. The fatigue cracking initiated from areas of severe corrosion damage in the lugs. Evidence of extensive corrosion pitting was found in brackets from all other examined front spar attachment fittings, particularly on the internal surfaces of the lugs. The Service Manual and applicable service bulletins call for fluorescent penetrant or magnetic particle inspection of wing attachment fittings during the 3,000-hour inspection for extension of the airframe life to 6,000-hours. Although the aircraft records show that during the last annual inspection, which was completed approximately 596.5 hours prior to the accident, at an airframe time of 4,245.5 hours, all time life items were complied with, the metallurgical examination disclosed no trace of dye penetrant residue on any of the examined components. ## Factual narrative On June 18, 1999, at 0750 central daylight time, a Wsk Pzl Mielec M-18A agricultural airplane, N7075D, registered to and operated by Basile Flying Service, Inc., of Basile, Louisiana, was substantially damaged while maneuvering near Basile, Louisiana. The commercial pilot, sole occupant of the airplane, sustained minor injuries. Visual meteorological conditions prevailed, and a flight plan was not filed for the 14 Code of Federal Regulations Part 137 aerial application flight. The local flight originated from the Basile Flying Service airstrip, at 0740. The pilot reported that he was applying chemical to a field. After completing a west-east pass, as he applied aft elevator for a straight-ahead pull-up, a loud "boom" was heard, and the outboard section of the right wing separated from the fuselage. The airplane became "uncontrollable" and impacted in an uncultivated field. Examination of the aircraft revealed that the right wing forward spar lower attachment fitting had failed. The right wing upper and lower attachment fittings along with the left wing lower attachment fitting (for comparison) were sent to the NTSB Materials Laboratory in Washington, D.C. for examination. Examination of the separated bracket lugs from the right wing forward spar lower attachment fitting with the aid of a low power binocular microscope revealed that the fractures in the lower ligaments of the lugs, were flat, darkly discolored, and contained ratchet marks and crack arrest positions indicative of fatigue propagation. Rough irregular features on the fracture faces on the upper ligaments of the lugs, and the extent of plastic deformation associated with both of these fractures were typical of final overstress separations. Evidence of corrosion damage was noted in the bore of both lugs on the internal face of each lug, and on the fracture faces in the fatigue fracture regions. On the forward lug, severe pitting corrosion was noted on the bore surface along the back face of the lug; also noted were secondary cracks in the corrosion-damaged area of the bore. The most severe corrosion in the aft lug was noted in the area of the fatigue fracture origin. The split bushing from the right wing forward spar lower attachment fitting had evidence of corrosion damage, secondary rotational scoring, fretting, and galling on the exterior surface. Mating of surface features on the bore of the forward and aft lugs with the features on the exterior surface of the bushing disclosed that areas of fatigue origins in the lugs coincided with a band of severe pitting corrosion in the bushing. Examination of the right wing forward spar upper attachment fitting revealed severe pitting corrosion damage on the back (internal) face of the forward lug and moderate corrosion on the front (internal) face of the aft lug. No cracking was found in the bracket lugs of this fitting. The fracture features and the extent of plastic deformation in all other separated components, including the right wing rear spar attachment fitting and the spacer, were consistent with overstress separations. The left wing front spar lower attachment fitting was disassembled. Examination of the disassembled components with the aid of a binocular microscope revealed areas of extensive pitting corrosion on the exterior surface of the split bushing and on the bore and internal faces of both the forward and aft lugs in the bushing. The examination also revealed a crack in the forward lug. A review of the aircraft's maintenance records indicated that an annual inspection was completed on March 1, 1999, at 4,245.5 hours total time, approximately 596.5 hours prior to the accident. The records showed that during this inspection, the right wing aft spar attachment fitting was replaced. No work related to any of the other wing attachment fittings was reported. The Service Manual for the PZL M18 series airplanes and subsequent service bulletins, No. K/02.142/91 and No. E/02.152/94, call for a 3,000-hour inspection for extension of the airframe service life to 6,000 hours. According to these bulletins, all wing attachment fittings shall be examined by fluorescent penetrant or magnetic particle techniques during this inspection. The aircraft records indicated that during the March 1, 1999, annual inspection, all 6,000-hour time life items were complied with, including the special inspection requirements for the wing attachment fittings. Examination at the NTSB Materials Laboratory of the upper and lower front spar attachment fittings for the right wing, as well as the lower attachment fitting for the left wing front spar showed that the bore surfaces of all lugs and corresponding surfaces of all bushings contained only patches of dried up lubrication grease. No evidence of sufficient lubrication was noted in any of the joints. Examination also revealed no evidence of fluorescent penetrant dye stain on the surface of any bracket or the mating fracture faces on the bracket lugs from the right wing forward spar lower fitting. ## Aircraft - Registration: [N7075D](https://openairdocs.org/deregistered/N7075D-2001-04-05), registration cancelled 2001-04-05, S/N 1Z024-13 (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) - Category: Airplane - Serial number: 1Z024-13 - Airframe hours: 4842 - Engines: Pzl-Kalisz ASZ-621R-M18 967 horsepower reciprocating - Damage: Substantial damage - Flight: Aerial application, Part 137 - Registered owner: Basile Flying Service, Inc. - Airworthiness certificate: Special, Restricted (Special) - Last inspection: Annual, March 1, 1999, 597 hours before - Departed: NONE ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 45; flight instructor, commercial; airplane ratings: single-engine sea, single-engine land, multi-engine land; instrument ratings: airplane; medical: class 2, valid medical--w/ waivers/lim; seat: center; flight hours: 19,302 total, 4,840 in this make and model, 18,222 as pilot in command, 560 in the last 90 days, 200 in the last 30 days, 8 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 360° at 2 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 81 °F ## 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 19990618007349A](https://openairdocs.org/incident/19990618007349A), Jun 18, 1999: Wsk M18A, Basile, LA, Substantial damage. Acft was pulling up after completing a spray run during an aerial application operation when the right wing separatd from the acft, other circumstances are… ## Docket (21 files) The files NTSB released with the investigation on February 8, 2001, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=46585. 8.3 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1/2 (item 1, .PDF, 424 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40405843&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1%2F2-Redacted.PDF - Pilot/Operator Aircraft Accident Report, Photo 1 (item 2, .PDF, 40 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40131920&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20Photo%201-Master.PDF - Pilot/Operator Aircraft Accident Report, Photo 2 (item 3, .PDF, 38 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40131921&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20Photo%202-Master.PDF - Pilot/Operator Aircraft Accident Report, Photo 3 (item 4, .PDF, 42 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40131922&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20Photo%203-Master.PDF - Materials Laboratory Factual Report (item 5, .PDF, 281 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40405844&FileExtension=.PDF&FileName=Materials%20Laboratory%20Factual%20Report-Redacted.PDF - Materials Laboratory Factual Report, Figure 1 (item 6, .PDF, 47 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40131924&FileExtension=.PDF&FileName=Materials%20Laboratory%20Factual%20Report,%20Figure%201-Master.PDF - Materials Laboratory Factual Report, Figure 2 (item 7, .PDF, 35 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40131925&FileExtension=.PDF&FileName=Materials%20Laboratory%20Factual%20Report,%20Figure%202-Master.PDF - Materials Laboratory Factual Report, Figure 3 (item 8, .PDF, 49 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40131926&FileExtension=.PDF&FileName=Materials%20Laboratory%20Factual%20Report,%20Figure%203-Master.PDF - Materials Laboratory Factual Report, Figure 4 (item 9, .PDF, 45 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40131927&FileExtension=.PDF&FileName=Materials%20Laboratory%20Factual%20Report,%20Figure%204-Master.PDF - Materials Laboratory Factual Report, Figure 5 (item 10, .PDF, 42 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40131928&FileExtension=.PDF&FileName=Materials%20Laboratory%20Factual%20Report,%20Figure%205-Master.PDF - Materials Laboratory Factual Report, Figure 6 (item 11, .PDF, 33 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40131929&FileExtension=.PDF&FileName=Materials%20Laboratory%20Factual%20Report,%20Figure%206-Master.PDF - Materials Laboratory Factual Report, Figure 7 (item 12, .PDF, 39 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40131930&FileExtension=.PDF&FileName=Materials%20Laboratory%20Factual%20Report,%20Figure%207-Master.PDF - Materials Laboratory Factual Report, Figure 8 (item 13, .PDF, 40 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40131931&FileExtension=.PDF&FileName=Materials%20Laboratory%20Factual%20Report,%20Figure%208-Master.PDF - Materials Laboratory Factual Report, Figure 9 (item 14, .PDF, 42 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40131932&FileExtension=.PDF&FileName=Materials%20Laboratory%20Factual%20Report,%20Figure%209-Master.PDF - Type Certificate Data Sheet No. A47EU (item 15, .PDF, 392 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40131933&FileExtension=.PDF&FileName=Type%20Certificate%20Data%20Sheet%20No.%20A47EU-Master.PDF - Aircraft Maintenance Records (item 16, .PDF, 1.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40405845&FileExtension=.PDF&FileName=Aircraft%20Maintenance%20Records-Redacted.PDF - Service Bulletin for the PZL M-18 Airplanes (item 17, .PDF, 1.5 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40131935&FileExtension=.PDF&FileName=Service%20Bulletin%20for%20the%20PZL%20M-18%20Airplanes-Master.PDF - Excerpts of the Service Manual for the PZL M18 Airplanes (item 18, .PDF, 2.6 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40131936&FileExtension=.PDF&FileName=Excerpts%20of%20the%20Service%20Manual%20for%20the%20PZL%20M18%20Airplanes-Master.PDF - View of Wing Attachment From Parts Manual (item 19, .PDF, 807 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40131937&FileExtension=.PDF&FileName=View%20of%20Wing%20Attachment%20From%20Parts%20Manual-Master.PDF - Statement of Party Representatives to NTSB Investigation (item 20, .PDF, 438 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40405846&FileExtension=.PDF&FileName=Statement%20of%20Party%20Representatives%20to%20NTSB%20Investigation-Redacted.PDF - Release of Aircraft Wreckage, NTSB Form 6120.15 (item 21, .PDF, 135 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40405847&FileExtension=.PDF&FileName=Release%20of%20Aircraft%20Wreckage,%20NTSB%20Form%206120.15-Redacted.PDF 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.