The flight crew on a United Airlines Boeing 777 in Kahului, Hawaii failed to manage the vertical flightpath, airspeed and pitch attitude of the aircraft after miscommunication in the cockpit led to the plane dropping from 2,100 feet to 748 feet above the water. The NTSB found out about the event two months after it occurred and chose to open an investigation, releasing the final report this week.
On Dec. 18, 2022 United Flight 1722 lost altitude just one minute after departure while in instrument meteorological conditions, including heavy rain. The plane dropped 1,352 feet before recovering from the drop and no injuries or damage were reported. The captain was the pilot flying at the time, reporting to the NTSB that he and the first officer had planned for a flaps-20 takeoff with a reduced-thrust setting based on performance calculations. The crew was advised during taxi that low-level wind shear advisories were in effect and based on this information, the captain chose a flaps-20 maximum thrust takeoff instead.
During takeoff, the captain hand-flew with the auto throttles engaged. The rotation and initial climb were normal during takeoff but as the plane continued to climb the crew reported airspeed fluctuations when encountering turbulence. The 777 reached the acceleration altitude and the captain reduce the pitch attitude and called for the flap setting to be reduced to flaps 5. The first officer told the NTSB he thought the captain had said flaps 15. The first officer selected flaps 15 before contacting the departure controller and discussing the weather.
The captain reported noticing the maximum operating speed indicator moved to a lower value than he expected and the airspeed had begun to accelerate quickly. He reduced the engine thrust manually and overrode the auto throttle servos to avoid a flap overspeed and then he began to diagnose a flap condition. He saw the indicator show 15 degrees and again called for a flaps 5 then confirmed that the first officer had moved the flap handle to the 5-degree position.
The first officer told the NTSB he was aware the captain was having trouble with airspeed control and asked the captain about it. He began to wonder if his own, right-side instrumentation was in error but he received no response from the captain. At this time, both the captain and first officer noticed the plane's pitch attitude was decreasing and the airspeed was increasing. The first officer told the NTSB the captain asked for flaps 1 shortly after calling for flaps 5 and when he set the flaps to 1-degree he noticed the airspeed increased and the control column moved forward.
Both of the pilots heard the warnings from the ground proximity warning system and the first officer called out "pull up pull up" alongside the warnings. The captain pulled aft on the control column and reduced power to reduce the airspeed, after which applying full power to start the fully controlled flight into terrain recovery. The first officer told the NTSB that as the captain was performing the recovery, the GPWS alerted again as the descent started the reverse trend. According to available data, the GPWS alerted again at about 748 feet above the water.
Once he note a positive rate of climb, the captain lowered the nose to resume a normal profile and ensured the flaps and speed brakes were fully retracted, then he engaged the autopilot. The crew continued with the flight without any additional complications.
The crew did not notify the NTSB as the event did not meet the requirements of Title 49 Code of Federal Regulations Part 830.5. The NTSB found out two months later, opting to open an investigation. By the time the investigation began, both the flight data recorder and cockpit voice durations had been exceeded. The NTSB used flight crew statements and other available records to conduct the investigation.
As a result of the event, United Airlines changed an operation training manual to address this problem and an awareness campaign about flight path management at their training center.