Individually Owned: 150,657
Corporate Owned: 137,281
Eppley Airfield Airport
Aircraft Accident/Incident Report
Omaha, Nebraska 68110
Wednesday, March 15, 2006 16:14 CST
NTSB Narrative Summary Released at Completion of Accident
The air carrier flight encountered turbulence associated with mountain wave activity during cruise at flight level 390 (FL390). One flight attendant located in the aft galley sustained serious injuries. The passengers and remaining crew were not injured. The aircraft was not damaged. The captain reported that the airplane was established in cruise at FL390 with smooth air conditions. She stated that the turbulence encounter began with a "slight buffet" and "rapidly increasing" airspeed. She attempted to maintain cruise airspeed by decreasing engine power and climbing to a higher altitude. She noted that as she initiated the climb, the aircraft experienced moderate turbulence. She reported that as the airplane reached FL400, the airspeed began a "rapid decrease" and she initiated a descent back to FL390. The flight subsequently descended to FL350 before the conditions smoothed out. She noted that the turbulence was encountered "suddenly and without warning." The flight data recorder indicated that the airspeed increased from 236 knots to 273 knots during the encounter. A vertical acceleration spike of 1.81 g's, followed by 0.61 g's, was recorded 64 seconds after the initial increase in airspeed. The weather forecast provided to the crew listed a risk of moderate turbulence between 20,000 and 38,000 feet. While ATC communications were describing light turbulence and moderate chop at lower altitudes, no reports from ATC, company dispatch, or other aircraft were received regarding mountain wave activity or turbulence at 39,000 feet.
NTSB Probable Cause Narrative
An inadvertent encounter with unforecast mountain wave turbulence during cruise flight. A contributing factor was the mountain wave (terrain induced) turbulence.
Event Information
| Type of Event | Accident |
| Event Date | 3/15/2006 |
| Event Day of the Week | Wednesday |
| Time of Event | 1614 |
| Event Time Zone | Central Standard Time |
| Event City | Omaha |
| Event State | NEBRASKA |
| Event Country | -- |
| Zipcode of the event site | 68110 |
| Event Date Year | 2006 |
| Event Date Month | 3 |
| MidAir Collision Indicator | No |
| On Ground Collision occurred ? | No |
| Event Location Latitude | 411811N |
| Event Location Longitude | 0955339W |
| Event Location Airport | Eppley Airfield |
| Event Location Nearest Airport ID | OMA |
| 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 | -- |
| Investigator's weather source | Weather Observation Facility |
| Time of the weather observation | 1553 Mountain Standard Time |
| Direction of event from weather observation facility (degrees) | -- |
| Weather Observation Facility ID | CYS |
| Elevation of weather observation facility | 6156 |
| Distance of event from weather observation facility (units?) | -- |
| Time Zone of the weather observation | MST |
| Lighting Conditions | Day |
| Lowest Ceiling Height | -- |
| Lowest Non-Ceiling Height | -- |
| Sky/Lowest/Cloud Conditions | Clear |
| Sky Condition for Lowest Ceiling | None |
| Visibility Runway Visual Range (Feet) | -- |
| Visibility Runway Visual Value (Statute Miles) | -- |
| Visibility (Statute Miles) | 10 |
| Air Temperature at event time (in degrees celsius) | 4 |
| Dew Point at event time (in degress fahrenheit) | -8 |
| Wind Direction (degrees magnetic) | 280 |
| Variable Wind Indicator | Wind direction could be determined |
| Wind Speed (knots) | 24 |
| Wind Velocity Indicator | -- |
| Wind Gust Indicator | Gusting |
| Wind Gust (knots) | 36 |
| Altimeter Setting at event time (in. Hg) | 29.73 |
| Density Altitude (feet) | -- |
| Intensity of Precipitation | -- |
| METAR weather report | METAR KCYS 152153Z 28024G36KT 10SM CLR 04/M08 A297 |
| 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 | 97 |
| Injury Total Serious | 1 |
| Injury Total All | 1 |
| Investigating Agency | NTSB |
| NTSB Docket Number (internal use) | 21351 |
| NTSB Notification Source | FAA |
| NTSB Notification Date | Mar 15 2006 12:00AM |
| NTSB Notification Time | -- |
| Fiche Number and/or location -used to find docket information | DMS |
| Date of most recent change to record | Apr 25 2007 2:54PM |
| User who most recently changed record | NTSB\lema |
| Basic weather conditions | Visual Meteorological Cond |
| FAA District Office | FAA-Casper FSFO |
Aircraft Involved |
|
|---|---|
Aircraft #1 |
|
| Aircraft Registration Number | N518UA |
| NTSB Number | CHI06LA099 |
| 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 | 757-222 |
| Aircraft Series Identifier | -- |
| Aircraft Serial Number | 24871 |
| Certified Max Gross Weight | 229800 |
| Aircraft Category | Airplane |
| Aircraft Registration Class | -- |
| Aircraft is a homebuilt? | No |
| Flight Crew Seats | -- |
| Cabin Crew Seats | -- |
| Passenger Seats | -- |
| Total number of seats on the aircraft | 119 |
| Number of Engines | 2 |
| Fixed gear or retractable gear | Retractable |
| Aircraft, Type of Last Inspection | Continuous Airworthiness |
| Date of Last Inspection | Jun 1 2005 12:00AM |
| Airframe hours since last inspection | -- |
| Airframe Hours | 51779 |
| 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 | -- |
| 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 | SFO |
| Departure City | San Francisco |
| Departure State | CA |
| Departure Country | USA |
| Departure Time | 1221 |
| Departure Time Zone | PST |
| Destination Same as Local Flt | -- |
| Destination Airport Code | JFK |
| Destination City | New York |
| Destination State | NY |
| Destination Country | USA |
| Specific Phase of Flight | Cruise |
| Report sent to ICAO? | -- |
| Evacuation occurred | -- |
| Date of most recent change to record | Mar 7 2007 2:45PM |
| 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 | -- |