If you wish to contribute or participate in the discussions about articles you are invited to join SKYbrary as a registered user

 Actions

B733, en-route, Santa Barbara CA USA, 1999

From SKYbrary Wiki

Summary
On 2 September 1999, a United Airlines Boeing Boeing 737-300 in the cruise at FL240, experienced severe turbulence due to an encounter with the wake vortex from a preceding MD11 on a similar track which had climbed through the level of the B737 with minimum lateral separation, 1.5 minutes earlier.
Event Details
When September 1999
Actual or Potential
Event Type
Wake Vortex Turbulence
Day/Night Day
Flight Conditions VMC
Flight Details
Aircraft BOEING 737-300
Operator United Airlines
Domicile United States
Type of Flight Public Transport (Passenger)
Origin Los Angeles
Intended Destination San Francisco International Airport
Take off Commenced Yes
Flight Airborne Yes
Flight Completed Yes
Flight Phase Cruise
ENR
Location En-Route
Origin Los Angeles
Destination San Francisco International Airport
Location
Approx. near Santa Barbara, CA
Loading map...
WAKE
Tag(s) ICAO Standard Wake Separation prevailed,
In trail event
CS
Tag(s) Turbulence Injury - Cabin Crew
Turbulence Injury - Pax with Seat Belts off"Turbulence Injury - Pax with Seat Belts off" is not in the list (Disruptive Pax, Turbulence Injury - Cabin Crew, Cabin Stowage - Pax Items, Toilet compartment fire, Cabin furnishings fire, Evacuation slides deployed, Pax oxygen mask drop, Unauthorised PED use, IFE fire, Cabin air contamination, ...) of allowed values for the "CS" property.
Outcome
Damage or injury Yes
Aircraft damage Minor
Injuries Few occupants
Causal Factor Group(s)
Group(s) Aircraft Operation
Safety Recommendation(s)
Group(s) None Made
Investigation Type
Type Independent

Description

On 2 September 1999, a United Airlines Boeing Boeing 737-300 in the cruise at FL240, experienced severe turbulence due to an encounter with the wake vortex from a preceding MCDONNELL DOUGLAS MD-11 on a similar track which had climbed through the level of the B737 with minimum lateral separation, 1.5 minutes earlier.

Synopsis

This is an extract from the official report into the accident published by the National Transportation Safety Board (NTSB).

"The flight had just leveled off at FL240 with the autopilot still engaged. The seat belt sign had been off for about 5 minutes, and the cabin crew was in the process of preparing a beverage service. The airplane was crossing a VORTAC when the flight encountered turbulence the crew categorized as 'severe,' with a rapid right roll and pitch excursion. The captain disconnected the autopilot and attempted to counter the excursions with control inputs. As a result of the aircraft motions, 1 flight attendant sustained serious injuries, and another flight attendant and 13 passengers sustained minor injuries. The airplane sustained minor damage, limited primarily to ceiling tiles and seats. A review of the meteorological data showed no evidence of any atmospheric phenomena in the area. A simulation study comparing the known airplane response to control inputs versus the motion of the airplane as recorded on the DFDR data showed that the flight controls alone did not cause the recorded motion of the airplane. Radar data established that the flight was in trail of a MD-11 by 11.5 nm21,298 m
21.298 km
69,875.328 ft
and 97 seconds when the upset occurred. The MD-11 had climbed through the flight's cruise altitude and was 600 feet above the flight at the time of the encounter. Wake vortex studies by NASA have documented vortex descent rates between 270 and 440 feet per minute."

Related Articles

WAKE

Further Reading

For further information see the NTSB Report (LAX99LA291)