# NTSB MIA99IA249: Douglas DC-9-31, N993Z, Nashville, TN, September 9, 1999 - Type: NTSB incident investigation - Classification: Incident · Minor injuries · Incident investigation · Final report - Date: September 9, 1999, 11:38 local (16:38 UTC) - Place: Nashville, TN - Coordinates: 36.109184, -86.660255 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=36.1092&lon=-86.6603&mi=10 - Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping) - Highest injury: Minor injuries - Injuries: 3 minor, 43 uninjured - Status: Completed, report May 9, 2001 - Report: Approved by Office Director - NTSB case key (mKey): 47349 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=MIA99IA249 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/47349/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=47349 - Page: https://openairdocs.org/ntsb/MIA99IA249 ## Probable cause A preexisting crack on the left main landing gear outer cylinder housing and the first officer's failure to maintain the proper rate of descent resulting in a hard landing on touchdown, and subsequent total failure and separation of the left main landing gear on landing rollout. Contributing to the accident was the pilot-in-commands improper supervision of the first officer during the approach phase of the landing. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Hard landing, landing - flare/touchdown - landing gear - failure,total - proper descent rate - not maintained, other crewmember (cause) - landing gear - fractured (cause) - supervision - improper, pilot in command (contributing factor) - landing gear - separation ## Analysis The first officer failed to maintain the proper rate of descent (sink rate) resulting in a hard landing on touch down, and separation of the left main landing gear during landing rollout. The pilot-in-command stated he knew the first officer was not going to make a good landing. He did not take any corrective action other than informing the first officer initially to increase power. Examination of the left main landing gear assembly revealed a preexisting crack in the outer cylinder housing. ## Factual narrative HISTORY OF FLIGHT On September 9, 1999, at about 1138 central daylight time, a Douglas DC-9-31, N993Z, TWA Flight 600, registered to First Security Bank, North American Trustee, operated as a 14 CFR Part 121 domestic passenger flight, experienced a separation of the left main landing gear during touchdown and landing rollout at Nashville International Airport, Nashville, Tennessee. Visual meteorological conditions prevailed and an IFR flight plan was filed. The airplane sustained minor damage. The airline transport rated pilot-in-command (PIC), first officer (FO), 3 flight attendants and 38 passengers reported no injuries. Three passengers were transported and released from a local area hospital with minor injuries. The flight originated from St. Louis, Missouri, 54 minutes before the incident. The FO stated he was flying the airplane and was vectored to the downwind and cleared for a visual approach to runway 02 left. He turned final and his sink rate was between 600 to 800 feet. They were in the landing configuration, normal profile, flaps 40, VREF 116, and there was not much of a crosswind correction used for the wind angle, nor did they encounter any wind shear on the approach or receive any advisories. The airplane touched down hard on the right main landing gear, which surprised him and the PIC. The PIC immediately got on the flight controls with him as the airplane bounced. He asked the PIC if they were going to land or make a go-around. He received no response and continued with the landing. On the second impact he felt a vibration, and it became evident that they had a directional control problem. He initially thought they had a landing gear strut or tire failure. The left wing started to settle and made contact with the ground. The PIC informed the tower to roll the equipment, and pulled the left start fuel lever to the off position. He pulled the right start fuel lever to the off position, and the airplane came to a stop. The crash rescue fire (CRF) vehicles arrived, and the PIC communicated with them and the tower. They completed the evacuation checklist, and briefed the flight attendants and passengers. After some communication with the CRF personnel an evacuation was made down the evacuation emergency slide at the L-1 door. The PIC stated right before touchdown, he knew the FO was not going to make a good landing. He stated he did not add any power during the event, and he could not recall if the spoilers deployed on the first touchdown. The airplane touched down hard, but he did not expect a hard landing of that magnitude. He stated in a subsequent statement, "Everything was stabilized on final approximately 4 miles out. Aircraft was a little fast on final. The F/O throttled back to compensate and at about 500' I called bug+12 sink 800. On short final the speed decayed a bit more and some sink developed. The F/O added power and I urged him to add more." He immediately got on the flight controls and remained on the controls until the airplane came to a stop. On the second touchdown, he felt a wobble on the left side. The airplane started a left roll, and he experienced directional control problems. He used right brake to keep the airplane on centerline. As soon as the airplane stopped, he started coordinating with CRF and tower personnel. The CRF arrived without delay. They ran the evacuation checklist, and he briefed the flight attendants and passengers. A short time later after coordination with the CRF personnel, he commanded an evacuation out the L-1 door. All flight attendants stated the airplane experienced a hard landing. All personnel completed an emergency evacuation out the L-1 door in an orderly fashion. No problems were encountered with the emergency equipment. Witnesses who observed the incident stated the airplane touched down in the touchdown zone. The airplane touched down hard, ballooned or bounced into the air between 50 to 100 feet, and the left main landing gear separated from the airplane. The airplane continued down the runway and came to a stop. Review of recorded transmissions between TWA 600, Nashville Approach Arrival East (ARE), and Nashville Tower Local Control (LC1), revealed TWA 600 informed ARE at 1625:06 (1138:06), "nashville twa six hundred out of uh twelve four for uh one zero thousand with hotel." TWA 600 was cleared to land at 1635:02. At 1638:06, Northwest Airlines flight 1746 informed the tower that TWA had just lost its gear. The FO of Northwest 1746 wrote in a statement to the NTSB, "While taxing out to runway 02L for takeoff I witnessed the "hard Landing" of a TWA DC-9-30. I observed the aircraft as it approached about 1 mile from the runway until it touched down. The approach looked very stable until the very short final, IM guessing it was at somewhere between 100 to 75 feet agl., (IM not certain of the specific altitude) when the sink rate of the aircraft really began to increase. You could tell from just watching this sink rate that it was going to hit hard. It appeared that whoever was flying the aircraft was trying to arrest this high sink rate with "pitch" only and not power. I never saw the exhaust of smoke that one sometimes sees when power is being applied to a jet engine!...Needless to say we observed an extremely hard touchdown of the main gears. The aircraft subsequently went airborne again from the initial touchdown. When it did I observed the "flutter" of the attached gear door of the left main landing gear. The gear itself (the left main gear) then separated from the aircraft when the airplane was at the apex of the bounce! Seeing that we both saw the gear separate from the aircraft the captain I was flying with picked up the mike on tower frequency and told them that "TWA just lost his left main gear." PERSONNEL INFORMATION The PIC was hired by TWA on April 22, 1988, and was qualified as a captain in the DC-9 on March 6, 1999. He holds an airline transport pilot certificate with ratings and limitations for airplane multiengine land, airplane single engine land, glider aero tow, flight instructor, airplane single engine, and instrument airplane issued on January 26, 1999. In addition, he holds a flight engineer certificate with rating for turbojet powered issued on October 14, 1988. He was issued a first class medical certificate on July 7, 1999. All pertinent aviation regulations, 14 CFR Part 121, airman competency and proficiency checks, had been recorded as conducted for the PIC. The FO was hired by TWA on February 18, 1999, and was qualified as a DC-9 FO on May 4, 1999. He holds an airline transport pilot certificate with ratings and limitations for airplane multiengine land, airplane single engine land, flight instructor airplane single engine land, and instrument airplane issued on March 22, 1999. In addition, he holds an aircraft dispatcher certificate, mechanic certificate with rating for airframe, and an advanced ground instructor certificate issued on March 22, 1999. He was issued a first class medical certificate on January 22, 1999. All pertinent aviation regulations, 14 CFR Part 121, airman competency and proficiency checks had been recorded as conducted for the FO. The L-1 flight attendant was hired by TWA on May 3, 1977, and was qualified as a flight attendant on June 1, 1977. The R-1 flight attendant was hired by TWA on February 2, 1978, and was qualified as a flight attendant on March 29, 1978. The C-1 flight attendant was hired by TWA on February 26, 1978, and qualified as a flight attendant on March 29, 1978. All pertinent aviation regulations, 14 CFR Part 121, airman competency and proficiency checks had been recorded as conducted for all three flight attendants. AIRCRAFT INFORMATION The airplane is a Douglas model DC-9-31, serial No. 47082, registration No. N993Z, manufactured in 1967. The airplane is registered to First Security Bank NA Owner Trustee, Salt Lake City, Utah, and is operated by Trans Wor ## Aircraft - Registration: [N993Z](https://openairdocs.org/deregistered/N993Z-2001-08-28), registration cancelled 2001-08-28, S/N 47082 (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) - Category: Airplane - Serial number: 47082 - Airframe hours: 11838 - Engines: P&W JT8D-9A 14500 lbs thrust turbo fan - Damage: Minor damage - Flight: Part 121 - Operator: Trans World Airlines Inc. - Registered owner: 1st Security Bank Na Trustee - Airworthiness certificate: Standard, Transport - Last inspection: Continuous airworthiness, December 7, 1998, 1,874 hours before - Departed: STL, ST. LOUIS, MO - Destination: BNA - Flight plan: IFR - Airport: BNA, Nashville International, runway 2L, 7,702 × 150 ft, concrete ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 39; flight instructor, airline transport, private, commercial; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 1, valid medical--no waivers/lim.; seat: left; toxicology performed; flight hours: 13,332 total, 5,022 in this make and model, 5,319 as pilot in command, 138 in the last 90 days, 73 in the last 30 days, 8 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 30° at 10 knots - Visibility: 10 statute miles - Lowest ceiling: 9,000 ft broken - Temperature: 82 °F, dew point 52 °F - Altimeter: 29.00 inHg - Observed at: BNA ## FAA reports on this event (1) The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs). - [Incident 19990909029049I](https://openairdocs.org/incident/19990909029049I), Sep 9, 1999: Doug DC931, Nashville, TN, Minor damage. (.19) On September 9, 1999, at about 1138 central daylight time, a Douglas DC-9-31, N993Z, twa flight 600, registered to first security bank, north American… ## Docket (18 files) The files NTSB released with the investigation on November 20, 2000, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=47349. 10.1 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 1.7 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40471597&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Master.PDF - Supplement E - Second Pilot Information (item 2, .PDF, 150 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40471598&FileExtension=.PDF&FileName=Supplement%20E%20-%20Second%20Pilot%20Information-Master.PDF - Supplement S - Aircraft Occupant and Injured Ground Personnel (item 3, .PDF, 61 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40129894&FileExtension=.PDF&FileName=Supplement%20S%20-%20Aircraft%20Occupant%20and%20Injured%20Ground%20Personnel-Master.PDF - Witness Statements (item 4, .PDF, 293 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40471599&FileExtension=.PDF&FileName=Witness%20Statements-Master.PDF - FAA ATCT Statements (item 5, .PDF, 416 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40471600&FileExtension=.PDF&FileName=FAA%20ATCT%20Statements-Master.PDF - Transcript of Radio Communications (item 6, .PDF, 305 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40471601&FileExtension=.PDF&FileName=Transcript%20of%20Radio%20Communications-Master.PDF - Weather Reports and Records (item 7, .PDF, 412 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40129898&FileExtension=.PDF&FileName=Weather%20Reports%20and%20Records-Master.PDF - Flight Data Recorder 10 - Factual Report of Group Chairman (item 8, .PDF, 1.9 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40471602&FileExtension=.PDF&FileName=Flight%20Data%20Recorder%2010%20-%20Factual%20Report%20of%20Group%20Chairman-Master.PDF - Cockpit Voice Recorder 12 - Factual Report of Group Chairman (item 9, .PDF, 417 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40471603&FileExtension=.PDF&FileName=Cockpit%20Voice%20Recorder%2012%20-%20Factual%20Report%20of%20Group%20Chairman-Master.PDF - Airworthiness Group Chairman's Factual Report (item 10, .PDF, 1.0 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40471604&FileExtension=.PDF&FileName=Airworthiness%20Group%20Chairman%27s%20Factual%20Report-Master.PDF - Materials Laboratory 15 - Factual Report of Group Chairman (item 11, .PDF, 822 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40471605&FileExtension=.PDF&FileName=Materials%20Laboratory%2015%20-%20Factual%20Report%20of%20Group%20Chairman-Master.PDF - FAA Accident/Incident Report (item 12, .PDF, 279 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40471606&FileExtension=.PDF&FileName=FAA%20Accident%2FIncident%20Report-Master.PDF - Nashville Airport Authority Aircraft Emergency Incident Report (item 13, .PDF, 670 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40471607&FileExtension=.PDF&FileName=Nashville%20Airport%20Authority%20Aircraft%20Emergency%20Incident%20Report-Master.PDF - TWA Information Concerning Drug and Alcohol Testing (item 14, .PDF, 157 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40471608&FileExtension=.PDF&FileName=TWA%20Information%20Concerning%20Drug%20and%20Alcohol%20Testing-Master.PDF - Toxicological Report (item 15, .PDF, 407 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40471609&FileExtension=.PDF&FileName=Toxicological%20Report-Master.PDF - Statement of Party Representatives to NTSB Investigation (item 16, .PDF, 341 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40471610&FileExtension=.PDF&FileName=Statement%20of%20Party%20Representatives%20to%20NTSB%20Investigation-Master.PDF - Release of Aircraft Wreckage, NTSB Form 6120.15 (item 17, .PDF, 524 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40471611&FileExtension=.PDF&FileName=Release%20of%20Aircraft%20Wreckage,%20NTSB%20Form%206120.15-Master.PDF - Reports from Parties to the Investigation (ALPA comments and recommendations received by NTSB IIC on June 11, 2001) (item 18, .PDF, 190 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40471612&FileExtension=.PDF&FileName=Reports%20from%20Parties%20to%20the%20Investigation%20(ALPA%20comments%20and%20recommendations%20received%20by%20NTSB%20IIC%20on%20June%2011,%202001)-Master.PDF From the NTSB's public API. 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