Individually Owned: 150,657
Corporate Owned: 137,281
Aircraft Accident/Incident Report
Janesville, Wisconsin 53545
Monday, March 1, 2004 14:22 CST
NTSB Narrative Summary Released at Completion of Accident
A flight attendant suffered a broken ankle and tibia when the airplane encountered turbulence during descent. The captain reported the seat belt sign was turned on as they descended through 18,000 feet. He reported they encountered about 15 seconds of moderate turbulence as they passed through 16,000 feet. He reported there were no weather returns in the area and they were back in smooth air after the encounter. The first officer reported that he informed the flight attendants to take their seats as soon as they began to encounter the turbulence. He reported he was getting ready to call the flight attendants after the turbulence to make sure they were alright, when the cockpit received a call from the back stating that one of the flight attendants injured her ankle. The first officer reported that they requested paramedics meet the flight upon landing. The injured flight attendant reported she was in the aft galley when they encountered the turbulence. She stated she tried to get in the jumpseat, but was unable to because of the turbulence. The injured flight attendant stated she heard another flight attendant tell a passenger who was in the aft galley to sit on the floor, so she decided to do the same. She stated that as she was sitting down, the "plane dropped" and she fell. Once the turbulence subsided, the other flight attendant and a passenger helped her off the floor and into a seat. None of the flight attendants recalled having any advance warning of the turbulence. Rapidly building convective activity was evident along the upper Mississippi Valley at the time of the accident. Convective tops averaging FL250 in the area were moving north-northeast at 60 knots. Severe Weather Advisory 15S, valid from 1731 universal coordinated time (UTC) to 2301 UTC, covered the route of flight from the Mississippi River to ORD. The severe thunderstorm watch included a forecast for hail, surface wind gusts to 60 knots, maximum cloud tops to FL450, and a storm motion vector to 240 degrees at 35 knots. Convective Sigmet 25C was valid until 2255UTC. The Sigmet called for an area of embedded thunderstorms moving from 190 degrees at 20 knots. The thunderstorms had tops to FL300. Data from the digital flight data recorder shows the airplane experienced vertical acceleration fluctuations from a minimum of 0.437 g's, to a maximum of 1.994 g's, and back to 0.576 g's in less then 3 seconds.
NTSB Probable Cause Narrative
The unexpected encounter with convective turbulence.
Event Information
| Type of Event | Accident |
| Event Date | 3/1/2004 |
| Event Day of the Week | Monday |
| Time of Event | 1422 |
| Event Time Zone | Central Standard Time |
| Event City | Janesville |
| Event State | WISCONSIN |
| Event Country | -- |
| Zipcode of the event site | 53545 |
| Event Date Year | 2004 |
| Event Date Month | 3 |
| MidAir Collision Indicator | No |
| On Ground Collision occurred ? | No |
| Event Location Latitude | 423710N |
| Event Location Longitude | 0890225W |
| 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 | Full |
| Investigator's weather source | Weather Observation Facility |
| Time of the weather observation | 1445 Central Standard Time |
| Direction of event from weather observation facility (degrees) | 90 |
| Weather Observation Facility ID | JVL |
| Elevation of weather observation facility | 808 |
| Distance of event from weather observation facility (units?) | 20 |
| Time Zone of the weather observation | CST |
| Lighting Conditions | Day |
| Lowest Ceiling Height | 6500 |
| Lowest Non-Ceiling Height | 3200 |
| 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) | 13 |
| Dew Point at event time (in degress fahrenheit) | 7 |
| Wind Direction (degrees magnetic) | 200 |
| Variable Wind Indicator | Wind direction could be determined |
| Wind Speed (knots) | 6 |
| Wind Velocity Indicator | -- |
| Wind Gust Indicator | Not Gusting |
| Wind Gust (knots) | -- |
| Altimeter Setting at event time (in. Hg) | 29.5 |
| Density Altitude (feet) | -- |
| Intensity of Precipitation | -- |
| METAR weather report | -- |
| Event Highest Injury | Serious |
| On Ground, Fatal Injuries | -- |
| On Ground, Minor Injuries | -- |
| On Ground, Serious Injuries | -- |
| Injury Total Fatal | -- |
| Injury Total Minor | -- |
| Injury Total None | 175 |
| Injury Total Serious | 1 |
| Injury Total All | 1 |
| Investigating Agency | NTSB |
| NTSB Docket Number (internal use) | 17690 |
| NTSB Notification Source | United Airlines |
| NTSB Notification Date | Mar 4 2004 12:00AM |
| NTSB Notification Time | 1205 |
| Fiche Number and/or location -used to find docket information | DMS |
| Date of most recent change to record | Jun 8 2005 12:51PM |
| User who most recently changed record | NTSB\JOHB |
| Basic weather conditions | Visual Meteorological Cond |
| FAA District Office | Shiller Park, IL ORD FSDO |
Aircraft Involved |
|
|---|---|
Aircraft #1 |
|
| Aircraft Registration Number | N516UA |
| NTSB Number | CHI04LA084 |
| Missing Aircraft Indicator | -- |
| Federal Aviation Reg. Part | Part 121: Air Carrier |
| Type of Flight Plan filed | IFR |
| Flight plan Was Activated? | No |
| Damage | None |
| Aircraft Fire | None |
| Aircraft Explosion | None |
| Aircraft Manufacturer's Full Name | Boeing |
| Aircraft Model | 757-200 |
| Aircraft Series Identifier | -- |
| Aircraft Serial Number | 24860 |
| Certified Max Gross Weight | 240000 |
| 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 | 192 |
| Number of Engines | 2 |
| Fixed gear or retractable gear | Retractable |
| Aircraft, Type of Last Inspection | Continuous Airworthiness |
| Date of Last Inspection | Nov 15 2002 12:00AM |
| Airframe hours since last inspection | 3699 |
| Airframe Hours | 45092 |
| ELT Installed | No |
| ELT Activated | Unknown |
| ELT Aided Location of Event Site | Unknown |
| ELT Type | -- |
| Aircraft Owner Name | United Airlines, 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? | Yes |
| Operator Street Address | -- |
| Operator City | -- |
| Operator State | -- |
| Operator Country | -- |
| 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 | PDX |
| Departure City | Portland |
| Departure State | OR |
| Departure Country | USA |
| Departure Time | 915 |
| Departure Time Zone | PST |
| Destination Same as Local Flt | -- |
| Destination Airport Code | ORD |
| Destination City | Chicago |
| Destination State | IL |
| Destination Country | USA |
| Specific Phase of Flight | Descent - normal |
| Report sent to ICAO? | No |
| Evacuation occurred | No |
| Date of most recent change to record | Mar 30 2005 1:03PM |
| User who most recently changed record | SULP |
| Since inspection or accident | -- |
| Event Location Runway Number and Location | NA |
| Runway Length | -- |
| Runway Width | -- |
| Sight Seeing flight | No |
| Air Medical Flight | No |
| Medical Flight | -- |