Title: NTSB Identifies Miscommunication as Cause of United Boeing 777's Plunge Over Pacific
The National Transportation Safety Board (NTSB) has determined that a miscommunication between the pilots of a United Boeing 777 led to the aircraft descending to under 800 feet over the Pacific Ocean shortly after departing Kahului, Hawaii, on December 18, 2022. The NTSB investigation found that the error resulted in the mishandling of the aircraft's vertical flightpath, airspeed, and pitch.
United Flight 1722, en route to San Francisco with 281 passengers and crew, encountered heavy rain and instrument meteorological conditions (IMC) after takeoff from Kahului. The aircraft descended rapidly from 2100 feet to approximately 748 feet above the water before the crew managed to recover the plane. Fortunately, no injuries or damage occurred, and the flight continued as planned.
The incident unfolded as the captain and first officer agreed on a takeoff with flaps 20 and reduced thrust. During taxi, ground control alerted the crew to low-level windshear advisories, prompting the crew to revise their takeoff plan to use full thrust. While hand-flying the departure with autothrottles engaged, turbulence and wind shear caused the 777's airspeed to fluctuate during climb-out.
As the aircraft accelerated, the captain called for flaps five, but a miscommunication led the first officer to set flaps 15 instead. The captain then noticed an unexpected shift in the maximum operating speed indicator and manually reduced power to avoid overspeed. Subsequently, the captain once again called for flaps five, and the first officer set the correct configuration.
This sequence of events resulted in a decreasing pitch attitude and increasing airspeed, leading to the sudden descent from low altitude. The ground proximity warning system activated, prompting the captain to initiate a controlled flight into terrain (CFIT) recovery by applying full power.
The NTSB concluded that "the flight crew's failure to manage the airplane's vertical flightpath, airspeed, and pitch attitude following a miscommunication about the captain's desired flap setting during the initial climb" was the primary cause of the incident. Both pilots voluntarily reported the event to the NTSB. In response, United has made modifications to its operations training and issued a flightpath awareness notice to its pilots.
