File photo of N773UA, the aircraft involved in the incident. Image courtesy of Aero Icarus.
United Airlines flight 1175 was forced to make a landing in Honolulu on February 13, 2018 when parts of the nacelle of the starboard PW4077 engine detached as the aircraft was preparing to descend into the Honolulu area. Judging from photos of the damaged aircraft, the entire engine cowling forward of the thrust reversers appears to have been blown off. In addition, many components of the engine appear to have been exposed. The incident caused the entire aircraft to shake as the aircraft descended towards Honolulu.
Approximately 35 minutes before arrival in Honolulu, passengers onboard the aircraft reported that the engine cowling "broke away," and the aircraft started shaking throughout the entire final descent. It is not clear whether an explosion ripped the nacelle from the engine. Passenger Erik Haddad (@erikhaddad), who was onboard the flight, tweeted a series of photos that appear to show extensive damage to the PW4077 engine's nacelle. Similarly, Maria Falaschi (@mfalaschi) also tweeted shocking photos of the damage done to the engine.
The Boeing 777-222, registered N773UA, is the fourth Boeing 777 series aircraft to roll off the production line. It has been fitted with the United 777 regional cabin, with 28 lie-flat seats in first class, and 336 economy seats laid out in a 3-4-3 configuration. At the time of the incident, the aircraft was approximately 23 years old.
The pilots sent out a distress call immediately after the accident, with one requesting Air Traffic Controls to "roll the fire trucks" upon arrival in Honolulu. According to an official statement from United Airlines, the aircraft landed safely at 12:38 PM, local time. Below is an excerpt of the statement:
United flight 1175 traveling to Honolulu from San Francisco landed safely after the pilots called for an emergency landing because of an issue with the #2 engine. Our pilots followed all necessary protocols to safely land the aircraft.
Thankfully, the aircraft was able to land without further incident, and once it parked at a gate, passengers were able to disembark normally. Additionally, fire trucks and EMS were on hand to assist if needed. The aircraft has been subsequently taken out of service, and I expect the FAA and NTSB to conduct a full investigation.
Although right now it is too early to speculate on what might have caused the engine to fail, photos by Instagram user @b_rice_k appear to show that two fan blades have detached, possibly leading to an uncontained engine failure. Similar incidents involving engine failure after fan blades detached have occurred recently in many widebody aircraft, but no similar incidents have occurred on Pratt & Whitney-powered 777s (although a Korean Air 777-300 powered by PW4090 engines did suffer an engine fire in 2016). The cowling thankfully did not cause damage to the wing after separating from the engine assembly, a relief because damage to the wing would have resulted in much lower chance of the aircraft landing safely.
Eerily, this incident reminds me of the Air France Flight 66 incident, in which the #4 Engine Alliance GP7270 engine of an Airbus A380 experienced an "uncontained engine failure" over the Atlantic Ocean, en route to Los Angeles. This engine was developed by both Pratt & Whitney and General Electric, and most likely shares some commonality with the PW4077 engine involved in the United incident. That engine had much of its nacelle, fan, and high pressure combustor ripped away during the incident, and the aircraft subsequently diverted to Goose Bay, Canada. Hopefully, the aircraft will be repaired in Honolulu soon, and the FAA and NTSB will be able to reach a definitive conclusion in the coming months.
Twitter user @MetraModeller posted this shocking image of N773UA after landing in Honolulu.