NTSB Says Miscommunication Led To United Airlines' Boeing 777 Dive Near Maui
Summary
- Miscommunication between pilots led to a United Airlines Boeing 777 losing altitude after departing from Maui.
- The widebody jet plunged in altitude shortly after takeoff, but the crew was able to recover before any harm was done.
- The mistake resulted in the failure to manage the aircraft’s vertical flight path, airspeed, and pitch attitude.
The National Transportation Safety Board (NTSB) confirmed on Thursday that “miscommunication” was the cause of what led to a United Airlines Boeing 777 losing altitude after departing from Maui. The incident happened in December without any injuries or damage to the aircraft.
The aircraft had come within 800 feet of the ocean but was able to recover and continue with the remainder of its climb. As a result, United has reportedly updated some of the training for its pilots.
Details of the incident
On December 18, 2022, UAL1722 traveled from Kahului Airport (OGG) to San Francisco International Airport. The flight was operated by N212UA, a 777-200, and departed while OGG was experiencing heavy rain conditions. In a statement, the NTSB said the aircraft lost altitude shortly after takeoff.
“United flight 1722 lost altitude about 1 minute after departure while in instrument meteorological conditions, which included heavy rain. The airplane descended from 2,100 ft to about 748 ft above the water before the crew recovered from the descent. No injuries were reported, and the airplane was not damaged.”
Photo: Santi Rodriguez/Shutterstock
According to the NTSB, the captain and first officer agreed on takeoff procedures with flaps set to 20 degrees and reduced thrust, per performance calculations. When the plane was taxiing, ground air traffic control (ATC) informed the pilots that low-level wind shear advisories were in effect, which prompted the captain to choose to switch to a maximum thrust departure. The captain reportedly hand-flew the aircraft while autothrottle was engaged, contributing to a normal rotation and initial climb.
As the widebody aircraft increased altitude, its airspeed fluctuated due to turbulence and wind shear. Once reaching acceleration altitude, the captain slightly reduced the plane’s pitch and called for the flap setting to be decreased to five degrees, the NTSB reported. However, the first officer reportedly thought the captain announced the flaps to be set at 15 degrees and did so without contacting the departure ATC to discuss the weather conditions.
Gaining speed but losing altitude
Once this happened, the captain noticed that the aircraft’s maximum operating speed indicator shifted to a lower value than expected, and the airspeed started to accelerate rapidly, according to the NTSB. To avoid going overspeed, the captain manually reduced the engine thrust, which overrode the auto throttle engagement. The captain also noticed the flaps indicator showed 15 degrees and called again for the flaps to be set at five degrees – which the first officer then adjusted.
“The first officer recalled that the captain asked for flaps 1 soon after he had called for flaps 5, and when the first officer set the flaps to 1°, he then noticed the airspeed had increased further, and the control column moved forward,” the NTSB said.
At that time, the plane’s pitch attitude was decreasing, which made it gain speed. The move reportedly caused the aircraft to nose-dive dramatically for around 10 seconds. According to CNN, passengers on the flight said there were several screams during the terrifying event.
“Pull up, pull up”
Both pilots told the NTSB that they heard the initial warnings from the ground proximity warning system (GPWS), and the first officer recalled announcing, “Pull up, pull up.” The captain then pulled back on the controls to lift the aircraft, reducing power to decrease speed. Then, the captain applied full power to initiate the CFIT (controlled flight into terrain) recovery.
“After noting a positive rate of climb, the captain lowered the nose to resume a normal profile, ensured that the flaps and speed brakes were fully retracted, and engaged the autopilot. The remainder of the flight was uneventful,” the Board explained.
Photo: NTSB
In the NTSB’s final report, “miscommunication” was deemed a probable cause.
“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.”
Addressing the incident, United has since modified one of its operations training modules and reportedly issued an awareness campaign at its training center regarding flight path management. The Chicago-based carrier also said that both pilots continue to fly today.
“There’s nothing more important than the safety of our crew and customers, which is why we’re drawing on the lessons learned from this flight to inform the training of all United pilots. Our pilots voluntarily reported this event and United fully cooperated with the independent investigation so that insights could be used to enhance the safety of the entire industry. Both pilots received additional training and continue to fly for United today.”
Since the incident did not reportedly meet the requirements of federal regulations, the NTSB was not immediately notified. Two months after the incident, when the Board learned of the event, an investigation ensued.
Source: CNN
