Individually Owned: 150,657
Corporate Owned: 137,281
Aircraft Accident/Incident Report
Des Moines, Iowa 50301
Thursday, February 20, 1997 6:45 CST
NTSB Narrative Summary Released at Completion of Accident
There was an electrical fire during cruise flight at FL310. The flight crew extinguished the flames by turning off both generators and the battery switch. The flight diverted to Des Moines, Iowa, where it landed without further incident. Inspection of the airplane revealed the cross tie relay along with four other relays and their associated wiring in the left main equipment rack near the left forward cabin door were charred. Investigation revealed the fire was a result of a phase-to-phase short in the cross tie relay arc box. The short resulted from relay contact wear products (metal dust) migrating through the arc box. The relay manufacturer recommended a 7,000 hour time between overhaul (TBO) for this relay when it is used as a cross tie relay. The aircraft manufacturer recommended a 7,000 hour TBO regardless of how the relay is used. The operator used a 14,000 hour TBO, based on an FAA approved TBO reliability program for the relay installed in a vertical or horizontal orientation. The failed relay had a total of 7,775.26 hours since overhaul.
NTSB Probable Cause Narrative
the cross tie relay shorted resulting in a fire in the left main electrical equipment rack.
Event Information
| Type of Event | Incident |
| Event Date | 2/20/1997 |
| Event Day of the Week | Thursday |
| Time of Event | 645 |
| Event Time Zone | Central Standard Time |
| Event City | DES MOINES |
| Event State | IOWA |
| Event Country | -- |
| Zipcode of the event site | 50301 |
| Event Date Year | 1997 |
| Event Date Month | 2 |
| MidAir Collision Indicator | No |
| On Ground Collision occurred ? | No |
| Event Location Latitude | |
| Event Location Longitude | |
| Event Location Airport | |
| Event Location Nearest Airport ID | |
| Indicates whether the acc/inc occurred off or on an airport | Off Airport/Airstrip |
| Distance from airport in statute miles | -- |
| Degrees magnetic from airport | -- |
| Airport Elevation | -- |
| Weather Briefing Completeness | Unknown |
| Investigator's weather source | Weather Observation Facility |
| Time of the weather observation | 654 Central Daylight Time |
| Direction of event from weather observation facility (degrees) | 0 |
| Weather Observation Facility ID | DSM |
| Elevation of weather observation facility | 957 |
| Distance of event from weather observation facility (units?) | 0 |
| Time Zone of the weather observation | CDT |
| Lighting Conditions | Dawn |
| Lowest Ceiling Height | 1100 |
| Lowest Non-Ceiling Height | 0 |
| Sky/Lowest/Cloud Conditions | Unknown |
| Sky Condition for Lowest Ceiling | Overcast |
| Visibility Runway Visual Range (Feet) | 0 |
| Visibility Runway Visual Value (Statute Miles) | 0 |
| Visibility (Statute Miles) | 7 |
| Air Temperature at event time (in degrees celsius) | -16 |
| Dew Point at event time (in degress fahrenheit) | -18 |
| Wind Direction (degrees magnetic) | 140 |
| Variable Wind Indicator | Unknown |
| Wind Speed (knots) | 7 |
| Wind Velocity Indicator | Unknown |
| Wind Gust Indicator | Unknown |
| Wind Gust (knots) | 0 |
| Altimeter Setting at event time (in. Hg) | 29 |
| Density Altitude (feet) | -- |
| Intensity of Precipitation | Unknown |
| METAR weather report | -- |
| Event Highest Injury | None |
| On Ground, Fatal Injuries | 0 |
| On Ground, Minor Injuries | 0 |
| On Ground, Serious Injuries | 0 |
| Injury Total Fatal | -- |
| Injury Total Minor | -- |
| Injury Total None | 36 |
| Injury Total Serious | -- |
| Injury Total All | -- |
| Investigating Agency | NTSB |
| NTSB Docket Number (internal use) | 5043 |
| NTSB Notification Source | -- |
| NTSB Notification Date | Feb 20 1997 12:00AM |
| NTSB Notification Time | 745 |
| Fiche Number and/or location -used to find docket information | IMAGE |
| Date of most recent change to record | Dec 8 2000 12:07PM |
| User who most recently changed record | dbo |
| Basic weather conditions | Visual Meteorological Cond |
| FAA District Office | -- |
Aircraft Involved |
|
|---|---|
Aircraft #1 |
|
| Aircraft Registration Number | N93S |
| NTSB Number | CHI97IA072 |
| Missing Aircraft Indicator | N |
| Federal Aviation Reg. Part | Part 121: Air Carrier |
| Type of Flight Plan filed | IFR |
| Flight plan Was Activated? | -- |
| Damage | Minor |
| Aircraft Fire | In-flight |
| Aircraft Explosion | None |
| Aircraft Manufacturer's Full Name | McDonnell Douglas |
| Aircraft Model | DC-9-15 |
| Aircraft Series Identifier | DC-9-15 |
| Aircraft Serial Number | 47078 |
| Certified Max Gross Weight | 90700 |
| 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 | 83 |
| Number of Engines | 2 |
| Fixed gear or retractable gear | Retractable |
| Aircraft, Type of Last Inspection | Continuous Airworthiness |
| Date of Last Inspection | -- |
| Airframe hours since last inspection | -- |
| Airframe Hours | 5454 |
| ELT Installed | No |
| ELT Activated | Unknown |
| ELT Aided Location of Event Site | Unknown |
| ELT Type | -- |
| Aircraft Owner Name | NORTHWEST AIRLINES |
| Aircraft Owner Street Address | 5101 NORTHWEST DRIVE |
| Aircraft Owner City | ST. PAUL |
| Aircraft Owner State | MN |
| Aircraft Owner Country | |
| Aircraft Owner Zipcode | 55111 |
| Operator is an individual? | -- |
| Operator Name | |
| Operator Same as Owner? | Yes |
| Operator Is Doing Business As | -- |
| Operator Address Same as Owner? | Yes |
| Operator Street Address | |
| Operator City | |
| Operator State | |
| Operator Country | |
| Operator Zip code | |
| Operator Code | NWAA |
| 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 | MSP |
| Departure City | MINNEAPOLIS |
| Departure State | MN |
| Departure Country | |
| Departure Time | 600 |
| Departure Time Zone | CDT |
| Destination Same as Local Flt | -- |
| Destination Airport Code | MCI |
| Destination City | KANSAS CITY |
| Destination State | MN |
| Destination Country | |
| Specific Phase of Flight | Cruise |
| Report sent to ICAO? | -- |
| Evacuation occurred | -- |
| Date of most recent change to record | Jan 2 2001 10:30AM |
| User who most recently changed record | dbo |
| Since inspection or accident | -- |
| Event Location Runway Number and Location | 0 |
| Runway Length | -- |
| Runway Width | -- |
| Sight Seeing flight | No |
| Air Medical Flight | No |
| Medical Flight | -- |