Individually Owned: 150,657
Corporate Owned: 137,281
O'hare International Airport
Aircraft Accident/Incident Report
Chicago, Illinois 60666
Monday, May 1, 1995 11:20 CDT
NTSB Narrative Summary Released at Completion of Accident
The flightcrew reported that during the application of takeoff power, when the throttles were in approximately the vertical position, the numbers 1 and 3 engines were indicating approximately 70% N1. The number 2 engine was indicating about 48% N1 and not accelerating. They heard a 'crack' and aborted the takeoff. Examination of the engine revealed that the low pressure turbine (LPT) stage one disk had separated from the LPT rotor at the stage one to two flange joint. Seven intact toroid bolts and sets of associated hardware were recovered. No evidence of fatigue cracking or corrosion (pitting) was noted on any of the bolt pieces recovered from the engine. The shank of one of the toroid bolts exhibited significant damage. The lug arm, used for safetying the bolt, exhibited relatively minor damage. Examination of several of the lug arms revealed 'noticeable wear patterns' and 'crack arrest positions indicative of fatigue cracking.' Statements by UAL maintenance personnel indicate failures of the toroid bolt safeties are occasionally discovered when the engines are disassembled for major overhaul.
NTSB Probable Cause Narrative
failure of the safety wire and/or safety wire lug arm on one of the stage one to two disk flange bolts due to an inadequate safetying method.
Event Information
| Type of Event | Incident |
| Event Date | 5/1/1995 |
| Event Day of the Week | Monday |
| Time of Event | 1120 |
| Event Time Zone | Central Daylight Time |
| Event City | CHICAGO |
| Event State | ILLINOIS |
| Event Country | -- |
| Zipcode of the event site | 60666 |
| Event Date Year | 1995 |
| Event Date Month | 5 |
| MidAir Collision Indicator | No |
| On Ground Collision occurred ? | No |
| Event Location Latitude | |
| Event Location Longitude | |
| Event Location Airport | O'HARE INTERNATIONAL |
| Event Location Nearest Airport ID | ORD |
| 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 | 668 |
| Weather Briefing Completeness | Full |
| Investigator's weather source | Weather Observation Facility |
| Time of the weather observation | 1015 Central Standard Time |
| Direction of event from weather observation facility (degrees) | 0 |
| Weather Observation Facility ID | ORD |
| Elevation of weather observation facility | 668 |
| Distance of event from weather observation facility (units?) | 0 |
| Time Zone of the weather observation | CST |
| Lighting Conditions | Day |
| Lowest Ceiling Height | 0 |
| Lowest Non-Ceiling Height | 4000 |
| Sky/Lowest/Cloud Conditions | Scattered |
| Sky Condition for Lowest Ceiling | None |
| Visibility Runway Visual Range (Feet) | 0 |
| Visibility Runway Visual Value (Statute Miles) | 0 |
| Visibility (Statute Miles) | 15 |
| Air Temperature at event time (in degrees celsius) | 11 |
| Dew Point at event time (in degress fahrenheit) | 3 |
| Wind Direction (degrees magnetic) | 70 |
| Variable Wind Indicator | Unknown |
| Wind Speed (knots) | 15 |
| Wind Velocity Indicator | Unknown |
| Wind Gust Indicator | Unknown |
| Wind Gust (knots) | 24 |
| Altimeter Setting at event time (in. Hg) | 30 |
| Density Altitude (feet) | 700 |
| 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 | 192 |
| Injury Total Serious | -- |
| Injury Total All | -- |
| Investigating Agency | NTSB |
| NTSB Docket Number (internal use) | 5033 |
| NTSB Notification Source | -- |
| NTSB Notification Date | May 1 1995 12:00AM |
| NTSB Notification Time | 1215 |
| Fiche Number and/or location -used to find docket information | IMAGE |
| Date of most recent change to record | Dec 7 2000 4:15PM |
| User who most recently changed record | dbo |
| Basic weather conditions | Visual Meteorological Cond |
| FAA District Office | -- |
Aircraft Involved |
|
|---|---|
Aircraft #1 |
|
| Aircraft Registration Number | N1811U |
| NTSB Number | CHI95IA142 |
| 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 | None |
| Aircraft Explosion | None |
| Aircraft Manufacturer's Full Name | MCDONNELL DOUGLAS |
| Aircraft Model | DC10-10 |
| Aircraft Series Identifier | DC10-10 |
| Aircraft Serial Number | 46610 |
| Certified Max Gross Weight | 433000 |
| 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 | 302 |
| Number of Engines | 3 |
| Fixed gear or retractable gear | Retractable |
| Aircraft, Type of Last Inspection | Continuous Airworthiness |
| Date of Last Inspection | Jul 23 1994 12:00AM |
| Airframe hours since last inspection | 1903 |
| Airframe Hours | 63749 |
| ELT Installed | Yes |
| ELT Activated | No |
| ELT Aided Location of Event Site | Unknown |
| ELT Type | -- |
| Aircraft Owner Name | UNITED AIRLINES |
| Aircraft Owner Street Address | P. O. BOX 66100 |
| Aircraft Owner City | CHICAGO |
| Aircraft Owner State | IL |
| Aircraft Owner Country | |
| Aircraft Owner Zipcode | 60666 |
| 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 | UALA |
| 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 | Yes |
| Departure Airport Code | ORD |
| Departure City | |
| Departure State | IL |
| Departure Country | |
| Departure Time | 1120 |
| Departure Time Zone | CST |
| Destination Same as Local Flt | -- |
| Destination Airport Code | IAD |
| Destination City | WASHINGTON |
| Destination State | DC |
| Destination Country | |
| Specific Phase of Flight | Takeoff |
| 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 | 9L |
| Runway Length | 7967 |
| Runway Width | 150 |
| Sight Seeing flight | No |
| Air Medical Flight | No |
| Medical Flight | -- |