# NTSB FTW98IA019: Boeing 757-222, N581UA, Seattle, WA, October 16, 1997 - Type: NTSB incident investigation - Classification: Incident · No injuries · Incident investigation · Final report - Date: October 16, 1997, 08:30 local (15:30 UTC) - Place: Seattle, WA - Coordinates: 47.440917, -122.310592 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=47.4409&lon=-122.3106&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 196 uninjured - Status: Completed, report May 4, 1998 - Report: Approved by Office Director - Safety recommendations: Yes - NTSB case key (mKey): 20436 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=FTW98IA019 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/20436/pdf - Page: https://openairdocs.org/ntsb/FTW98IA019 ## Probable cause Maintenance personnel's failure to properly secure the left off-wing slide door after routine slide replacement, allowing an inflight separation of the slide. Factors were inadequate training of maintenance personnel and inadequate written instructions by the airplane manufacturer. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Airframe/component/system failure/malfunction, climb - to cruise - door,emergency exit - not secured (cause) - maintenance,replacement - improper, company maintenance personnel (cause) - inadequate training, company maintenance personnel (contributing factor) - instructions,written/verbal - inadequate, manufacturer (contributing factor) - misc eqpt/furnishings,slides - separation ## Analysis As the airplane was rotated for liftoff from Seattle, the captain noticed that the EICAS (engine indication and crew alerting system) 'EMERGENCY DOOR' light had illuminated. According to the Airplane Fight Manual, if pressurization is normal (and it was), the crew need not take further action. During the descent for landing, a flight attendant said she heard a loud noise from the left side of the airplane. The airplane landed uneventfully at Denver. Inspection disclosed the left off-wing slide had separated from the airplane, causing minor damage to the access door, flap, and fuselage skin. The slide had been routinely replaced the previous evening by a mechanic using a flashlight and referencing the airplane maintenance manuals. After installing the slide, the mechanic closed the panel and placed the actuator handle in the horizontal position (as per instructions placarded on the maintenance access door). He said he had never received any training for installing the off-wing slide. There have been four similar incidents since the airplane entered commercial service, prompting the manufacturer to issue Service Bulletin (S.B.) 757-25-0182. ## Factual narrative HISTORY OF FLIGHT On October 16, 1997, between 0830 Pacific daylight time and 1127 mountain daylight time, a Boeing 757-222, N581UA, owned and operated by United Airlines, Inc., sustained minor damage when the left off-wing evacuation slide separated from the airplane during its flight from Seattle, Washington, to Denver, Colorado. There were no injuries to the airline transport-rated captain, airline transport-rated first officer, 6 flight attendants, and 188 passengers. Visual meteorological conditions prevailed, and an IFR flight plan had been filed. The airplane was being operated as Flight 724 in scheduled domestic passenger service under Title 14 CFR Part 121 when the incident occurred. The flight departed Seattle at 0830. The first officer was flying the airplane. As the airplane was rotated for liftoff, the captain noticed that the EICAS (engine indication and crew alerting system) "EMERGENCY DOOR" light had illuminated. According to United's Boeing 757/767 Flight Manual, if pressurization is normal --- and it was --- the crew need not take further action. During the descent for landing, a flight attendant said she heard a loud noise from the left side of the airplane. The airplane landed uneventfully at Denver at 1127. DAMAGE TO AIRCRAFT Postincident inspection disclosed the left off-wing slide had separated from the airplane. The slide was never recovered. There was a 1-1/2 inch tear in the left inboard flap near the trailing edge, a 1-inch tear in the evacuation slide access door, a 9-inch horizontal tear in the honeycomb fillet panel, and a 20-inch tear in the fuselage skin between F.S. (fuselage station) 1420 and 1440. Repair costs were estimated at $75,000. AIRCRAFT INFORMATION According to United Airlines, there had been a routine replacement of the left off-wing evacuation slide on the evening before the incident. One of two mechanics involved in replacing the slide was interviewed on November 4, 1997. The mechanic, a 12-year veteran with United, said this was the second time he had replaced the off-wing slide, the first time occurring some 10 years before. The replacement was made during the hours of darkness, using a flashlight and referencing Boeing 757 Maintenance Manuals 25-65-00 and 25-65-01. After installing the slide, he closed the panel and, following the instructions placarded on the maintenance access door, placed the actuator handle in the horizontal position. He said he had never received any training for installing the off-wing slide. ADDITIONAL INFORMATION In a meeting with Boeing officials that same day, it was revealed that since the airplane entered service in November 1984, there had been four other incidents similar to that involving N581UA. The first incident also involved United Airlines and occurred on June 8, 1993, in Los Angeles California. The incident was investigated by NTSB's Southwest Regional Office (see LAX 93-I-A245). The second incident occurred on September 23, 1995, at Newark, New Jersey, and involved Continental Airlines. On rotation for liftoff, the EICAS illuminated. The flight continued to Houston, Texas. After landing, it was discovered that the right overwing slide had deployed and was hanging off the right wing. The third incident occurred on November 15, 1995, during a test flight at Everett, Washington. The airplane involved was scheduled to be delivered to Northwest Airlines. The last incident occurred on June 24, 1997, at Dallas-Fort Worth, Texas, and involved American Airlines. The Emergency Doors EICAS light illuminated shortly after takeoff. The airplane returned and landed uneventfully. American Airlines officials said the slide had hung in the slipstream for approximately 10 seconds before separating, causing a discernible airframe vibration. As a result of these incidents, Boeing issued Service Bulletin (S.B.) 757-25-0182, dated October 10, 1996, and revised it on June 12, 1997. It calls for the replacement of the lockbase retainer and the bearing for the door latch tube, and relocating the door sensor to a forward position on the slide compartment door to enable a more positive indication that the slide compartment door is latched. ## Aircraft - Registration: N581UA (not matched to a registry record) - Reported make and model: Boeing 757-222 - Category: Airplane - Serial number: 26701 - Airframe hours: 15521 - Engines: P&W PW-2037(M) 38200 lbs thrust turbo fan - Damage: Minor damage - Flight: Part 121 - Registered owner: United Airlines, Inc. - Airworthiness certificate: Standard, Transport - Last inspection: Continuous airworthiness, September 19, 1997, 258 hours before - Departed: SEA, WA - Destination: DEN, DENVER, CO - Flight plan: IFR ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 56; flight engineer, airline transport, commercial; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 1, valid medical--no waivers/lim.; seat: left; flight hours: 20,997 total, 4,346 in this make and model ## Weather - Conditions: Visual (VMC), Day - Visibility: 6 statute miles - Lowest ceiling: none - Temperature: 52 °F, dew point 52 °F - Altimeter: 30.00 inHg - Observed at: SEA ## 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 19971016040099I](https://openairdocs.org/incident/19971016040099I), Oct 16, 1997: Boeing 757222, Seattle, WA, Minor damage. Eicas left wing slide. Landing noted slide pack missing. Aft fuselage puncture. 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.