Individually Owned: 151,845
Corporate Owned: 143,699
Seattle-Tacoma Intl Airport
Aircraft Accident/Incident Report
Seattle, Washington 98188
Monday, September 1, 1997 21:10 PDT
NTSB Narrative Summary Released at Completion of Accident
During the landing roll-out, the nose landing gear collapsed. Examination of the nose landing gear revealed the nose gear upper lock link, PN 3914464-503, had failed, and had separated into two pieces. The link, which was subject to recurring non-destructive testing every 5000 cycles (per AD 97-02-10), had an eddy current inspection by the operator, 1075 cycles before the accident. The link was one of a series manufactured from plate stock, rather than being forged. Due to this changed process, the lack of draft angle allowances on the machined parts reduced the load-carrying cross sectional area of the machined links to less than that of the forged links, resulting in a decrease in the overall strength. Metallurgical analysis revealed that about 10,000 major fatigue progression cycles had occurred within about .6 inches of the crack progression. Based on two major stress cycles per gear retraction/extension cycle, the crack length at 1075 cycles before the accident would have been greater than .25 inches. The inspection procedure and process provided by the airframe manufacturer did not specify removal of the upper lock link from the aircraft before recurring non-destructive tests (NDT). During the investigation, NTSB investigators and FAA inspectors observed that access to the upper lock link for NDT was limited when the part remained installed on the airplane.
NTSB Probable Cause Narrative
fatigue failure of the nose landing gear upper lock link, due in part to reduced strength after the manufacturing process was changed from forged to machined plate stock; and inadequate non-destructive inspection process for testing the link.
Event Information
| Type of Event | Accident |
| Event Date | 9/1/1997 |
| Event Day of the Week | Monday |
| Time of Event | 2110 |
| Event Time Zone | Pacific Daylight Time |
| Event City | SEATTLE |
| Event State | WASHINGTON |
| Event Country | -- |
| Zipcode of the event site | 98188 |
| Event Date Year | 1997 |
| Event Date Month | 9 |
| MidAir Collision Indicator | No |
| On Ground Collision occurred ? | No |
| Event Location Latitude | |
| Event Location Longitude | |
| Event Location Airport | SEATTLE-TACOMA INTL |
| Event Location Nearest Airport ID | KSEA |
| Indicates whether the acc/inc occurred off or on an airport | On Airport |
| Distance from airport in statute miles | -- |
| Degrees magnetic from airport | -- |
| Airport Elevation | 420 |
| Weather Briefing Completeness | Unknown |
| Investigator's weather source | Pilot |
| Time of the weather observation | 0 |
| Direction of event from weather observation facility (degrees) | 0 |
| Weather Observation Facility ID | |
| Elevation of weather observation facility | 0 |
| Distance of event from weather observation facility (units?) | 0 |
| Time Zone of the weather observation | |
| Lighting Conditions | Night/Dark |
| Lowest Ceiling Height | 3800 |
| Lowest Non-Ceiling Height | 0 |
| Sky/Lowest/Cloud Conditions | Clear |
| Sky Condition for Lowest Ceiling | Broken |
| Visibility Runway Visual Range (Feet) | 0 |
| Visibility Runway Visual Value (Statute Miles) | 0 |
| Visibility (Statute Miles) | 10 |
| Air Temperature at event time (in degrees celsius) | 19 |
| Dew Point at event time (in degress fahrenheit) | 13 |
| Wind Direction (degrees magnetic) | 220 |
| Variable Wind Indicator | Unknown |
| Wind Speed (knots) | 6 |
| Wind Velocity Indicator | Unknown |
| Wind Gust Indicator | Not Gusting |
| Wind Gust (knots) | 0 |
| Altimeter Setting at event time (in. Hg) | 30 |
| Density Altitude (feet) | -- |
| Intensity of Precipitation | Unknown |
| METAR weather report | -- |
| Event Highest Injury | Minor |
| On Ground, Fatal Injuries | 0 |
| On Ground, Minor Injuries | 0 |
| On Ground, Serious Injuries | 0 |
| Injury Total Fatal | -- |
| Injury Total Minor | 19 |
| Injury Total None | 97 |
| Injury Total Serious | -- |
| Injury Total All | 19 |
| Investigating Agency | NTSB |
| NTSB Docket Number (internal use) | 1465 |
| NTSB Notification Source | -- |
| NTSB Notification Date | Sep 1 1997 12:00AM |
| NTSB Notification Time | 2155 |
| Fiche Number and/or location -used to find docket information | IMAGE |
| Date of most recent change to record | Dec 8 2000 12:34PM |
| User who most recently changed record | dbo |
| Basic weather conditions | Visual Meteorological Cond |
| FAA District Office | -- |
Aircraft Involved |
|
|---|---|
Aircraft #1 |
|
| Aircraft Registration Number | N951AS |
| NTSB Number | SEA97FA202 |
| Missing Aircraft Indicator | N |
| Federal Aviation Reg. Part | Part 121: Air Carrier |
| Type of Flight Plan filed | IFR |
| Flight plan Was Activated? | -- |
| Damage | Substantial |
| Aircraft Fire | None |
| Aircraft Explosion | None |
| Aircraft Manufacturer's Full Name | McDonnell Douglas |
| Aircraft Model | DC-9-82 (MD-82) |
| Aircraft Series Identifier | DC-9-82 (M |
| Aircraft Serial Number | 49111 |
| Certified Max Gross Weight | 149500 |
| Aircraft Category | Airplane |
| Aircraft Registration Class | U.S. Registered/U.S. Soil |
| Aircraft is a homebuilt? | No |
| Flight Crew Seats | -- |
| Cabin Crew Seats | -- |
| Passenger Seats | -- |
| Total number of seats on the aircraft | 138 |
| Number of Engines | 2 |
| Fixed gear or retractable gear | Retractable |
| Aircraft, Type of Last Inspection | AAIP |
| Date of Last Inspection | Aug 30 1997 12:00AM |
| Airframe hours since last inspection | -- |
| Airframe Hours | 45378 |
| ELT Installed | Unknown |
| ELT Activated | Unknown |
| ELT Aided Location of Event Site | Unknown |
| ELT Type | -- |
| Aircraft Owner Name | INTEGRATED AIRCRAFT SERVICES |
| Aircraft Owner Street Address | 10 UNION SQUARE EAST |
| Aircraft Owner City | NEW YORK |
| Aircraft Owner State | NY |
| Aircraft Owner Country | |
| Aircraft Owner Zipcode | 10003 |
| Operator is an individual? | -- |
| Operator Name | ALASKA AIRLINES |
| Operator Same as Owner? | No |
| Operator Is Doing Business As | -- |
| Operator Address Same as Owner? | No |
| Operator Street Address | BOX 68900 |
| Operator City | SEATTLE |
| Operator State | WA |
| Operator Country | |
| Operator Zip code | 98168 |
| Operator Code | ASAA |
| Owner has at least one certificate | Yes - certificate holder |
| Other Operator of large aircraft? | No |
| Certified for Part 133 or 137 Operation | Unknown |
| Operator Certificate Number | -- |
| Indicates whether an air carrier operation was scheduled or not | Scheduled |
| Indicates Domestic or International Flight | Domestic |
| Operator carrying Pax/Cargo/Mail | Passenger Only |
| Type of Flying (Per_Bus / Primary) | Unknown |
| Second Pilot on Board | Yes |
| Departure Point Same as Event | No |
| Departure Airport Code | KLAX |
| Departure City | LOS ANGELES |
| Departure State | CA |
| Departure Country | |
| Departure Time | 1821 |
| Departure Time Zone | PDT |
| Destination Same as Local Flt | crash at destination city |
| Destination Airport Code | KSEA |
| Destination City | |
| Destination State | |
| Destination Country | |
| Specific Phase of Flight | Landing |
| Report sent to ICAO? | -- |
| Evacuation occurred | -- |
| Date of most recent change to record | Dec 20 2002 12:42PM |
| User who most recently changed record | dbo |
| Since inspection or accident | -- |
| Event Location Runway Number and Location | 16L |
| Runway Length | 11900 |
| Runway Width | 150 |
| Sight Seeing flight | No |
| Air Medical Flight | No |
| Medical Flight | -- |