# NTSB CHI02FA148: Douglas DC-9-31, N8986E, Minneapolis, MN, June 4, 2002 - Type: NTSB accident investigation - Classification: Accident · No injuries · Field investigation · Final report - Date: June 3, 2002, 19:28 local (Jun 4, 2002, 00:28 UTC) - Place: Minneapolis, MN - Coordinates: 44.880554, -93.216941 - Nearby events: https://openairdocs.org/map.md?lat=44.8806&lon=-93.2169&mi=10 - Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 70 uninjured - Status: Completed, report November 25, 2003 - Report: Approved by Office Director - Parties: Air Line Pilots Association, Aircraft Mechanics Fraternal Association, Boeing, Federal Aviation Administration, Northwest Airlines - NTSB case key (mKey): 54836 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CHI02FA148 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/54836/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=54836 - Page: https://openairdocs.org/ntsb/CHI02FA148 ## Probable cause The failure of the right main landing gear due to fatigue. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Gear collapsed, landing - roll - landing gear,main gear strut - failure,total (cause) - landing gear,main gear strut - fatigue (cause) ## Analysis During landing rollout the right main landing gear (RMLG) collasped. The captain reported a normal landing was completed by the first officer and when he took over control of the airplane "the aircraft dropped sharply to the right and we began skidding down the runway with a continous warning horn. I continued braking and the aircraft came to a stop on centerline with a significant right lean." According to the NTSB Materials Laboratory Factual Report, the outer cylinder of the RMLG was fractured through the transition area above the fused section, with the fracture located approximately 19 inches from the upper end of the cylinder. The factual report noted the fracture initiation point "lies in the parting plane for the cylinder forging. The dark spot [fracture initiation point] was orientated transverse to the gear about 28 7/8 inches from the lower end of the cylinder." According to the factual report, multiple inclusions and intergranular cracks were uncovered within the examined fracture sample. The inclusions were mostly oxides of aluminum and calcium and some inclusions contained small sulfides of iron and manganese. The report noted there were fracture features that were consistent with overstress separation "emanating from the dark spot [fracture initiation point] with mostly ductile dimple formations and some cleavage like features." ## Factual narrative HISTORY OF FLIGHT On June 3, 2002, at 1928 central daylight time (cdt), a Douglas DC-9-31, N8986E, owned and operated by Northwest Airlines, sustained substantial damage when the right main landing gear (RMLG) collapsed during landing rollout on runway 12L (8,200 feet by 150 feet, concrete) at the Minneapolis-St. Paul International Airport (MSP), Minneapolis, Minnesota. The flight was being operated under the provisions of 14 CFR Part 121 as Northwest Airlines flight 877. Visual meteorological conditions prevailed at the time of the accident. The captain, first officer (FO), 2 flight attendants, and 66 passengers reported no injuries. The flight departed Louisville International Airport (SDF), Louisville, Kentucky, at 1836 eastern daylight time and was on an active instrument flight rules (IFR) flight plan. According to the captain's written statement, the FO was the flying pilot during the accident flight. The captain reported that the instrument landing system (ILS) runway 12L approach was flown on autopilot until approximately 1,000 feet above ground level (agl) when the airplane was below the overcast cloud layer. The remainder of the approach was hand-flown by the FO and the aircraft touched-down approximately 1,000 feet from the end of the runway. The captain reported, "The touchdown was smooth and on centerline. Both mains [main landing gear] touched the runway at the same time." The captain stated that the FO applied reverse thrust after the nose landing gear made contact with the ground. The captain reported that he took over control of the aircraft at approximately 60 knots and, "Immediately after my initial brake application the aircraft dropped sharply to the right and we began skidding down the runway with a continuous warning horn. I continued braking and the aircraft came to a stop on centerline with a significant right lean." According to the FO's written statement, "All aspects of the approach were normal and I disconnected the autopilot at 1,000[feet] msl [above mean sea level] when I reported seeing the runway and calling 'landing'. The final portion of the approach was normal and the touchdown was a smooth roll on with both mains touching down together." The FO reported, "I began normal braking below 100 knots and received a normal 80 knots callout from the captain at which time I began reducing the thrust reversing and at the 60 knot call completely stowed the reversers. As this was being done the captain told me he was joining me on the brakes and that he had control of the aircraft at which time I told him he had control of the aircraft. As this change was occurring I felt the brakes give an initial release followed by a hard tilt to the right with a continuous warning horn and I instinctively rode the controls with the captain until the aircraft came to a complete stop on centerline after about a 1,500 foot slide." PERSONNEL INFORMATION The captain was the holder of an airline transport pilot certificate with an airplane multi-engine land rating. The captain was type rated for the Douglas DC-9 aircraft. The captain's last medical examination was conducted on May 15, 2002, and he was issued a first-class medical certificate with no limitations or restrictions. According to company records, the captain had a total flight time of 8,043 hours, of which 884 hours were in the DC-9. The captain was reported to have flown 177 hours in the last 90 days and 8.0 hours in the last 24 hours. The captain's last currency checkride was satisfactorily completed in a Douglas DC-9 aircraft on January 01, 2002. The FO was the holder of an airline transport pilot certificate with an airplane multi-engine land rating. The FO was not type rated for the Douglas DC-9 aircraft. The FO's last medical examination was conducted on July 24, 2001, and he was issued a first-class medical certificate with no limitations or restrictions. According to company records, the FO had a total flight time of 1,844 hours, of which 1,844 hours were in the DC-9. The FO was reported to have flown 227 hours in the last 90 days and 8.0 hours in the last 24 hours. The FO's last proficiency check was satisfactorily completed in a Douglas DC-9 simulator on July 28, 2001. AIRCRAFT INFORMATION The aircraft was a Douglas DC-9-31, serial number 47402. The Douglas DC-9-31 is a low-wing monoplane of all-metal semi-monocoque construction. The DC-9-31 has fully cantilevered wings, a T-tail empennage, and is powered by two Pratt & Whitney JT8D-7B engines, each producing 14,000 lbs of thrust. The accident airplane was configured to accommodate a maximum of 100 passengers and an 8-person flightcrew. The Douglas DC-9-31 has a certified maximum takeoff weight of 108,000 lbs and a maximum zero fuel weight of 87,000 lbs. The accident airplane was maintained by compliance with a Federal Aviation Administration (FAA) approved continuous airworthiness program and accumulated a total time of 75,241.57 hours at the time of the accident. METEOROLOGICAL INFORMATION A weather observation station located at MSP recorded the weather approximately 11 minutes after the accident as: Observation Time: 1939 cdt Wind: 090 degrees magnetic at 9 knots Visibility: 9 statute miles Sky Condition: 1,200 feet agl overcast Temperature: 13 degrees Celsius Dew Point: 11 degrees Celsius Pressure: 29.89 inches of mercury FLIGHT RECORDERS The solid state flight data recorder (FDR), Fairchild model F1000, serial number 01787, was removed from the accident aircraft and sent to the National Transportation Safety Board's (NTSB) laboratory in Washington, D.C., for readout and evaluation. No anomalies were noted during the touchdown and rollout until the RMLG collapsed. Landing vertical g-force peaked at 1.176, a value that is within the acceptable limits for the aircraft. Landing lateral acceleration peaked at 0.056 g, a value that is within the acceptable limits for the aircraft. The NTSB FDR Factual Report is included with the docket material associated with this investigation. WRECKAGE AND IMPACT INFORMATION The aircraft came to rest 5,220 feet from the runway 12L threshold and 10 feet right of the runway centerline. The outer-cylinder of the right main landing gear strut had fractured into two sections approximately 2 inches above the designed-fuse section of the strut assembly. The lower portion of the right main landing gear (including the wheels, brakes, and hub assembly) was impacted up into the right inboard flap assembly. The outboard 1/2 of the right wing had scraping damage through the lower wing skin and into the main spar and surrounding wing structure. SURVIVAL ASPECTS The captain reported that he decided that an evacuation of the aircraft was not necessary after being notified by the control tower that there was no fire and/or smoke observed coming from the airplane. Airport crash/rescue confirmed there was no fire and/or smoke coming from the airplane and instructed the captain to shutdown both engines and the auxiliary power unit (APU). The passengers and flightcrew departed the airplane via a portable stairway located at the forward galley left-side entrance. The passengers were transported from the accident site in buses provided by Northwest Airlines. According to airport crash/rescue records, all passengers and flightcrew personnel were clear of the airplane at 2010 cdt. The flightcrew and 66 passengers reported no injuries as result of the accident and/or post-accident activities. TESTS AND RESEARCH The right main landing gear strut assembly was disassembled at a Northwest Airlines maintenance facility. The fractured outer-cylinder was sent to the NTSB Materials Laboratory Division in Washington, D.C., for examination. According to the NTSB Materials Laboratory Factual Report, the outer cylinder (part number 5925371-502) of the RMLG was fractured through the transition area above t ## Aircraft - Registration: [N8986E](https://openairdocs.org/deregistered/N8986E-2014-09-02), registration cancelled 2014-09-02, S/N 47402, built 1969 (OpenAirDocs) - Reported make and model: Douglas DC-9-31 - Registry model: [Douglas DC-9-31](https://openairdocs.org/model/douglas-dc-9-31) (registry code 3022065) (OpenAirDocs) - Registry engine: [Pratt & Whitney JT8D series](https://openairdocs.org/engine/pratt-whitney-jt8d-series) (registry code 52053, turbo-jet) (OpenAirDocs) - Category: Airplane - Serial number: 47402 - Airframe hours: 75241.57 - Engines: Pratt & Whitney JT8D-7B 14000 lbs thrust turbo fan - Damage: Substantial damage - Flight: Part 121 - Registered owner: Northwest Airlines, Inc. - Airworthiness certificate: Standard, Transport - Departed: SDF, Louisville, KY - Destination: MSP, Minneapolis, MN - Flight plan: IFR - Airport: MSP, Minneapolis/St. Paul Intl, runway 12, 8,200 × 150 ft, concrete ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 46; injuries: none; airline transport; airplane ratings: multi-engine land; instrument ratings: airplane; medical: class 1, valid medical--no waivers/lim.; last flight review January 1, 2002; seat: left; flight hours: 8,043 total, 884 in this make and model, 177 in the last 90 days, 8 in the last 24 hours - Co-pilot; age 38; injuries: none; airline transport; airplane ratings: multi-engine land; instrument ratings: airplane; medical: class 1, valid medical--no waivers/lim.; last flight review July 28, 2001; seat: right; flight hours: 1,844 total, 1,844 in this make and model, 227 in the last 90 days, 8 in the last 24 hours ## Weather - Conditions: Visual (VMC), Dusk - Wind: 90° at 9 knots - Visibility: 9 statute miles - Lowest ceiling: 1,200 ft overcast - Temperature: 55 °F, dew point 52 °F - Altimeter: 29.88 inHg - Observed at: MSP ## 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 20020603024629A](https://openairdocs.org/incident/20020603024629A), Jun 3, 2002: Doug DC931, Minneapolis, MN, Substantial damage. (-23) Northwest airlines flight 877 from louisville KY (sdf) to Minneapolis MN (msp) experienced normal flight until the landing roll out. The co-pilot was… ## Docket (18 files) The files NTSB released with the investigation on October 17, 2003, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=54836. 7.8 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 681 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40442565&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF - Materials Laboratory 15 - Factual Report 02-066 (item 2, .PDF, 10 photos, 3.8 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40163242&FileExtension=.PDF&FileName=Materials%20Laboratory%2015%20-%20Factual%20Report%2002-066-Master.PDF - Materials Laboratory 15 - Factual Report 03-070 (item 3, .PDF, 14 photos, 1.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40187158&FileExtension=.PDF&FileName=Materials%20Laboratory%2015%20-%20Factual%20Report%2003-070-Master.PDF - Flight Data Recorder 10 - Factual Report of Group Chairman (item 4, .PDF, 11 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40169549&FileExtension=.PDF&FileName=Flight%20Data%20Recorder%2010%20-%20Factual%20Report%20of%20Group%20Chairman-Master.PDF - Flight Data Recorder 10 - Attachment 1 (item 5, .PDF, 6 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40169550&FileExtension=.PDF&FileName=Flight%20Data%20Recorder%2010%20-%20Attachment%201-Master.PDF - Flight Data Recorder 10 - Attachment 2 (item 6, .PDF, 102 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40169551&FileExtension=.PDF&FileName=Flight%20Data%20Recorder%2010%20-%20Attachment%202-Master.PDF - Flight Data Recorder 10 - Attachment 3 (item 7, .CSV, 16 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40169552&FileExtension=.csv&FileName=Flight%20Data%20Recorder%2010%20-%20Attachment%203-Master.csv - Main Landing Gear Diagram 1 (item 8, .PDF, 35 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40198568&FileExtension=.PDF&FileName=Main%20Landing%20Gear%20Diagram%201-Master.PDF - Main Landing Gear Diagram 2 (item 9, .PDF, 54 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40198569&FileExtension=.PDF&FileName=Main%20Landing%20Gear%20Diagram%202-Master.PDF - Main Landing Gear Diagram 3 (item 10, .PDF, 44 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40198570&FileExtension=.PDF&FileName=Main%20Landing%20Gear%20Diagram%203-Master.PDF - Statement of Party Representatives to NTSB Investigation (item 11, .PDF, 343 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40442566&FileExtension=.PDF&FileName=Statement%20of%20Party%20Representatives%20to%20NTSB%20Investigation-Redacted.PDF - Release of Aircraft Wreckage, NTSB Form 6120.15 (item 12, .PDF, 107 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40442567&FileExtension=.PDF&FileName=Release%20of%20Aircraft%20Wreckage,%20NTSB%20Form%206120.15-Redacted.PDF - Photo 1. Main Wreckage Overview (item 13, .PDF, 191 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40198575&FileExtension=.PDF&FileName=Photo%201.%20%20Main%20Wreckage%20Overview-Master.PDF - Photo 2. Main Wreckage Overview (item 14, .PDF, 185 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40198576&FileExtension=.PDF&FileName=Photo%202.%20%20Main%20Wreckage%20Overview-Master.PDF - Photo 3. Fracture Overview (item 15, .PDF, 227 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40198578&FileExtension=.PDF&FileName=Photo%203.%20%20Fracture%20Overview-Master.PDF - Photo 4. Fracture Overview (item 16, .PDF, 220 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40198579&FileExtension=.PDF&FileName=Photo%204.%20%20Fracture%20Overview-Master.PDF - Photo 5. Fracture Overview (item 17, .PDF, 217 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40198580&FileExtension=.PDF&FileName=Photo%205.%20%20Fracture%20Overview-Master.PDF - Photo 6. Fracture Overview (item 18, .PDF, 217 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40198581&FileExtension=.PDF&FileName=Photo%206.%20%20Fracture%20Overview-Master.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.