# NTSB DEN00IA023: Boeing 767-232, N111DN, Salt Lake City, UT, December 6, 1999 - Type: NTSB incident investigation - Classification: Incident · No injuries · Incident investigation · Final report - Date: December 6, 1999, 16:55 local (23:55 UTC) - Place: Salt Lake City, UT - Location: 40.7608° N, 111.8910° W: Placed by OpenAirDocs: center of Salt Lake City, UT, within about 6 miles (OpenAirDocs) - Nearby events: https://openairdocs.org/map.md?lat=40.7608&lon=-111.8910&mi=10 - Phase of flight: [Initial climb](https://openairdocs.org/ntsb-phases/350) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 85 uninjured - Status: Completed, report August 13, 2001 - Report: Approved by Office Director - NTSB case key (mKey): 47887 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=DEN00IA023 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/47887/pdf - Page: https://openairdocs.org/ntsb/DEN00IA023 ## Probable cause Total failure of the main landing gear retract actuator due to stress corrosion caused by the use of a faulty sealant by company maintenance personnel that allowed moisture to enter the joint. A factor was the use of an improper fillet seal. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Airframe/component/system failure/malfunction, takeoff - initial climb - landing gear,normal retraction/extension assembly - stress corrosion (cause) - maintenance,overhaul - improper, company maintenance personnel (cause) - material inadequate,improper, company maintenance personnel (contributing factor) - landing gear,normal retraction/extension assembly - failure,total (cause) ## Analysis The crew heard a loud noise and felt a vibration when the landing gear was retracted after takeoff. An emergency was declared, and the flight returned to Salt Lake City. When the landing gear was lowered, the nose and right main landing gear DOWN AND LOCKED lights illuminated, but a GEAR UNSAFE light illuminated for the left main landing gear. Following a low pass over the airport, maintenance personnel advised the landing gear appeared to be down and locked. An uneventful landing was made. Maintenance personnel informed the crew that the landing gear actuator had sheared and could not be pinned for towing. The part was later removed and examined. Stress corrosion cracking had occurred through 75% of the piston, followed by ductile separation. The corrosion had formed when a faulty fillet seal around the base of the rod end allowed moisture to enter the joint. The retract actuator was an original part, but it was determined that it had previously been reworked. ## Factual narrative On December 6, 1999, at 1655 mountain standard time, a Boeing 767-232, N111DN, operated by Delta Air Lines, Inc., as flight 990, scheduled domestic passenger service from Salt Lake City, Utah, to Dallas-Fort Worth, Texas, sustained minor damage when the main landing gear retraction arm failed during initial climb immediately following takeoff from Salt Lake City International Airport, Salt Lake City, Utah. There were no injuries to the airline transport certificated captain and first officer, a first officer riding in the jump seat, 6 flight attendants, and 76 passengers. Visual meteorological conditions prevailed, and an IFR flight plan had been filed for the regularly scheduled domestic passenger flight being conducted under Title 14 CFR Part 121. The flight was originating at the time of the incident. The following is based on written statements submitted by the captain, check captain, and a deadheading first officer. The captain had just received his Boeing 767 type rating, and this was his first initial operating experience (IOE) flight. The crew heard a loud noise and felt a vibration when the landing gear was retracted after takeoff. An emergency was declared, and the flight returned to Salt Lake City. When the landing gear was lowered, the nose and right main landing gear DOWN AND LOCKED lights illuminated, but a GEAR UNSAFE light illuminated for the left main landing gear. Following a low pass over the airport, maintenance personnel advised the landing gear appeared to be down and locked. An uneventful landing was made at 1705, and the airplane was stopped on the runway. Maintenance personnel informed the crew that the landing gear actuator had sheared and could not be pinned for towing. Passengers were deplaned via mobile stairs and bused to the terminal. It was discovered the main landing gear retract actuator (p/n 273T1104-3) had failed. The part was shipped to the Boeing Airplane Company's metallurgical laboratory where, under FAA direction, it was examined. According to the Boeing report, stress corrosion cracking had occurred through 75% of the piston, followed by ductile separation. The corrosion had formed when a faulty fillet seal around the base of the rod end allowed moisture to enter the joint. The retract actuator was an original part, but it was determined that it had previously been reworked. ## Aircraft - Registration: N111DN (not matched to a registry record) - Reported make and model: Boeing 767-232 - Category: Airplane - Serial number: 22223 - Airframe hours: 51977 - Engines: GE CF6-80A2 48000 lbs thrust turbo fan - Damage: Minor damage - Flight: Part 121 - Registered owner: Delta Air Lines, Inc. - Airworthiness certificate: Standard, Transport - Last inspection: Continuous airworthiness, December 4, 1999 - Departed: SLC - Destination: DFW, DALLAS-FT WORTH, TX - Flight plan: IFR ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 53; airline transport; airplane ratings: multi-engine land; instrument ratings: airplane; medical: class 1, valid medical--no waivers/lim.; seat: left; flight hours: 15,000 total, 1 in this make and model, 120 in the last 90 days ## Weather - Conditions: Visual (VMC), Day - Wind: 290° at 4 knots - Visibility: 8 statute miles - Lowest ceiling: 7,000 ft broken - Temperature: 36 °F, dew point 27 °F - Altimeter: 30.00 inHg - Observed at: SLC ## 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 19991206035119I](https://openairdocs.org/incident/19991206035119I), Dec 6, 1999: Boeing 767232, Salt Lake City, UT. (-23) Delta airlines B-767 N111DN departed Salt Lake City International Airport on December 6, 1999, and returned to the airport due to a landing gear problem.… 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.