Background
United Airlines flight 15, a Boeing 767-400ER (registration N59053), was operating a regularly scheduled passenger flight from Newark Liberty International Airport (EWR) to Honolulu International Airport (HNL) under 14 CFR Part 121. The flight carried 250 passengers and crew.
Sequence of Events
The flight was uneventful across the continental United States. Over the Pacific Ocean, dispatch sent an ACARS message advising of an area of possible embedded thunderstorms. Light to moderate turbulence persisted for most of the remaining flight, requiring the seat belt sign to remain on.
About one hour from HNL, the captain returned early from crew rest after noticing areas of moderate turbulence. Before entering the flight deck, he saw the flight attendants seated in their jumpseats and advised the lead flight attendant to discontinue final service and remain seated. Shortly after retaking the left seat, as the flight passed immediately south of a line of embedded thunderstorms, the captain requested a descent from FL360 to FL240. The crew reported instrument meteorological conditions with precipitation during the descent. The weather radar was on and the seat belt sign was illuminated.
The flight encountered severe turbulence for about 30 seconds while descending through FL254. Flight data recorder data showed vertical acceleration fluctuating between -0.17 g and +1.62 g, lateral acceleration between -0.09 g and +0.11 g, and roll between 5° left and 12° right.
Injuries and Response
At the time of the turbulence, flight attendants were securing galleys, preparing the cabin for landing, and distributing agriculture documents. Four flight attendants in the aft galley were thrown against the ceiling and back to the floor, injuring all four. The crew declared an emergency with air traffic control and arranged for medical personnel to meet the aircraft at HNL. After landing, the four flight attendants were transported to the hospital: one was diagnosed with a fractured arm (serious injury), and the other three were released with minor injuries. Additionally, a passenger reported their child had suffered a bloody nose; the child was treated but not transported to the hospital. The aircraft was not damaged.