Individually Owned: 150,657
Corporate Owned: 137,281
Chicago O'hare International Airport
Aircraft Accident/Incident Report
Chicago, Illinois 60601
Friday, December 28, 2001 14:31 CST
NTSB Narrative Summary Released at Completion of Accident
The Boeing 737 airplane encountered wake turbulence during cruise descent. The captain reported the aircraft was descending from 10,000 feet mean sea level (msl) when he noticed a "subtle vibration" that was followed by the airplane entering an uncommanded roll to the right. The captain reported that he disconnected the autopilot system at approximately 20 degrees right roll, and he regained control of the aircraft using manual control inputs of left rudder and left aileron. The captain stated that he had "complete usage of the rudder" during the recovery. The flightcrew declared an emergency and made an uneventful landing. Aircraft radar track data indicated the incident airplane (UAL Flt 1260) was following a Boeing 777, operated by American Airlines as flight 154 (AAL Flt 154). Both aircraft were en route to Chicago O'Hare International Airport and were flying the same arrival procedure. Both airplanes were maintaining a lateral separation of approximately 8.3 nm or about 97 seconds. AAL Flt 154 began its descent 12.56 nm from KRENA intersection, and 23 seconds later UAL Flt 1260 began its descent 6.23 nm from the intersection. During the uncommanded roll and subsequent recovery, all rudder control surface movements correlated with the position of the rudder pedals. No flight control anomalies were found during the post-incident examination and verification flight test.
NTSB Probable Cause Narrative
The wake turbulence encounter.
Event Information
| Type of Event | Incident |
| Event Date | 12/28/2001 |
| Event Day of the Week | Friday |
| Time of Event | 1431 |
| Event Time Zone | Central Standard Time |
| Event City | Chicago |
| Event State | ILLINOIS |
| Event Country | -- |
| Zipcode of the event site | 60601 |
| Event Date Year | 2001 |
| Event Date Month | 12 |
| MidAir Collision Indicator | No |
| On Ground Collision occurred ? | No |
| Event Location Latitude | 415847N |
| Event Location Longitude | 0875416W |
| Event Location Airport | Chicago O'Hare International |
| Event Location Nearest Airport ID | ORD |
| 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 | 668 |
| Weather Briefing Completeness | Unknown |
| Investigator's weather source | Weather Observation Facility |
| Time of the weather observation | 1456 Central Standard Time |
| Direction of event from weather observation facility (degrees) | 0 |
| Weather Observation Facility ID | KORD |
| 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 | 5000 |
| Lowest Non-Ceiling Height | 4200 |
| Sky/Lowest/Cloud Conditions | Scattered |
| Sky Condition for Lowest Ceiling | Broken |
| Visibility Runway Visual Range (Feet) | -- |
| Visibility Runway Visual Value (Statute Miles) | -- |
| Visibility (Statute Miles) | 10 |
| Air Temperature at event time (in degrees celsius) | -5 |
| Dew Point at event time (in degress fahrenheit) | -13 |
| Wind Direction (degrees magnetic) | 290 |
| Variable Wind Indicator | Wind direction could be determined |
| Wind Speed (knots) | 14 |
| Wind Velocity Indicator | -- |
| Wind Gust Indicator | Not Gusting |
| Wind Gust (knots) | -- |
| Altimeter Setting at event time (in. Hg) | 29.64 |
| Density Altitude (feet) | -1217 |
| Intensity of Precipitation | -- |
| METAR weather report | METAR KORD 282056Z 29014KT 10SM SCT042 BKN050 M05/ |
| Event Highest Injury | None |
| On Ground, Fatal Injuries | -- |
| On Ground, Minor Injuries | -- |
| On Ground, Serious Injuries | -- |
| Injury Total Fatal | -- |
| Injury Total Minor | -- |
| Injury Total None | 104 |
| Injury Total Serious | -- |
| Injury Total All | -- |
| Investigating Agency | NTSB |
| NTSB Docket Number (internal use) | 15064 |
| NTSB Notification Source | FAA |
| NTSB Notification Date | Dec 28 2001 12:00AM |
| NTSB Notification Time | 1506 |
| Fiche Number and/or location -used to find docket information | DMS |
| Date of most recent change to record | Mar 30 2004 8:14AM |
| User who most recently changed record | NTSB\MONR |
| Basic weather conditions | Visual Meteorological Cond |
| FAA District Office | FAA, O'Hare FSDO |
Aircraft Involved |
|
|---|---|
Aircraft #1 |
|
| Aircraft Registration Number | N941UA |
| NTSB Number | CHI02IA058 |
| Missing Aircraft Indicator | -- |
| Federal Aviation Reg. Part | Part 121: Air Carrier |
| Type of Flight Plan filed | IFR |
| Flight plan Was Activated? | Yes |
| Damage | None |
| Aircraft Fire | None |
| Aircraft Explosion | None |
| Aircraft Manufacturer's Full Name | Boeing |
| Aircraft Model | 737-522 |
| Aircraft Series Identifier | -- |
| Aircraft Serial Number | 26676 |
| Certified Max Gross Weight | 123500 |
| 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 | 111 |
| Number of Engines | 2 |
| Fixed gear or retractable gear | Retractable |
| Aircraft, Type of Last Inspection | Continuous Airworthiness |
| Date of Last Inspection | Jan 11 2001 12:00AM |
| Airframe hours since last inspection | 2602 |
| Airframe Hours | 27409 |
| ELT Installed | No |
| ELT Activated | No |
| ELT Aided Location of Event Site | No |
| ELT Type | -- |
| Aircraft Owner Name | United Air Lines, Inc. |
| Aircraft Owner Street Address | P.O. Box 66100 |
| Aircraft Owner City | Chicago |
| Aircraft Owner State | IL |
| Aircraft Owner Country | USA |
| Aircraft Owner Zipcode | 60666 |
| Operator is an individual? | No |
| Operator Name | -- |
| Operator Same as Owner? | Yes |
| Operator Is Doing Business As | -- |
| Operator Address Same as Owner? | No |
| Operator Street Address | -- |
| Operator City | -- |
| Operator State | IL |
| Operator Country | USA |
| Operator Zip code | -- |
| Operator Code | UALA |
| Owner has at least one certificate | -- |
| Other Operator of large aircraft? | -- |
| Certified for Part 133 or 137 Operation | -- |
| 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) | -- |
| Second Pilot on Board | Yes |
| Departure Point Same as Event | No |
| Departure Airport Code | CID |
| Departure City | Cedar Rapids |
| Departure State | IA |
| Departure Country | USA |
| Departure Time | 1357 |
| Departure Time Zone | CST |
| Destination Same as Local Flt | crash at destination city |
| Destination Airport Code | ORD |
| Destination City | Chicago |
| Destination State | IL |
| Destination Country | USA |
| Specific Phase of Flight | Cruise |
| Report sent to ICAO? | No |
| Evacuation occurred | No |
| Date of most recent change to record | Feb 19 2004 1:49PM |
| User who most recently changed record | SULP |
| Since inspection or accident | Time of Accident |
| Event Location Runway Number and Location | NA |
| Runway Length | -- |
| Runway Width | -- |
| Sight Seeing flight | No |
| Air Medical Flight | No |
| Medical Flight | -- |