United B789 near Singapore on May 14th 2024, uncontained engine failure
Last Update: September 4, 2025 / 16:31:23 GMT/Zulu time
Incident Facts
Date of incident
May 14, 2024
Classification
Incident
Airline
United
Flight number
UA-28
Departure
Singapore, Singapore
Destination
San Francisco, United States
Aircraft Registration
N27957
Aircraft Type
Boeing 787-9 Dreamliner
ICAO Type Designator
B789
The FAA reported: "AIRCRAFT DEPARTED, SHORTLY AFTER REPORTED A #1 LEFT ENGINE FAILURE AND RETURNED TO AIRPORT, POST FLIGHT INSPECTION REVEALED A HOLE IN THE LEFT ENGINE COWLING AND ENGINE CASE, SINGAPORE."
The airline reported the aircraft returned to resolve an engine issue.
On Jun 26th 2024 the NTSB released their preliminary report stating:
On May 14, 2024, at 1430 UTC, a Boeing 787-9, registration N27957, operated as United Airlines flight 28, experienced an uncontained No. 1 (left) engine failure shortly after takeoff from Singapore Changi Airport. The flight crew secured the No. 1 engine, declared an emergency, and executed an air return to SIN where they made an uneventful single engine landing. There were no injuries reported. The airplane was operated as a Title 14 Code of Federal Regulations Part 121 flight from Singapore Changi Airport (SIN) to San Francisco International Airport (SFO), San Francisco, California.
According to the flight crew, after just reached a cruise altitude of FL310 when they heard a pop and felt the aircraft shutter, followed by a No. 1 engine fire warning indication. A visual inspection of the No. 1 engine was performed after landing at SIN. Damage was observed to the No. 1 engine nacelle and there was a hole in the engine case at approximately the 10 o’clock position.
The data recorders will be downloaded at the NTSB Headquarters in Washington, DC. The No. 1 engine will be retained for teardown examination.
Due to the failure of the No. 1 engine taking place in international waters outside the territory of a State, the NTSB is leading the investigation as the State of Registry in accordance with ICAO Annex 13 guidelines. Additional parties to the investigation include the Federal Aviation Administration (FAA), Boeing, United Airlines, and GE Aerospace.
On Sep 4th 2025 the NTSB released their final report concluding the probable causes of the incident were:
The uncontained left engine failure was caused by the failure and liberation of the HPT stage 1 aft blade retainer as a result of a fatigue crack in the upper collet radius that originated from a surface connected cluster of Oxide/Carbonitride/Nitride/Carbide (OCNC) particles.
Contributing to the failure of the HPT stage 1 aft blade retainer was an unknown material behavior unique to OCNC clusters in Rene 65 material that are surface connected in highly stressed material that may result in a localized reduction of material fatigue life capability.
The NTSB analysed:
The No. 1 (left) engine high pressure turbine (HPT) stage 1 aft blade retainer developed a fatigue crack that initiated and propagated through thickness and circumferentially until final overload failure that was not contained by the turbine case.
Fractography of the HPT stage 1 aft blade retainer revealed the crack initiated in the upper collet radius at a single point of origin which corresponded to a surface connected material anomaly that measured 0.005 inches by 0.015 inches by 0.0005 inches. The fracture surface contained an area of intergranular fracture morphology with visible beach marks, consistent with hold-time fatigue growth and the remaining fracture surface was consistent with overload fracture.
Further examination of the material anomaly was determined to be a cluster of particles enriched with Titanium, Aluminum, Zirconium, Magnesium, and Oxygen, which is consistent with Oxide/Carbonitride/Nitride/Carbide (OCNC) particles. Analysis of the HPT stage 1 aft blade retainer material found all dimensional and material characteristics to be conforming to GE Aerospace drawings and material specifications. The presence of OCNC particles and clusters of particles is inherent to Rene 65 material with quantity and size distributions accounted for within GE’s philosophy for material life limit calculations.
The calculated stress conditions for the GEnx HPT stage 1 aft blade retainer collet feature were found to be uniquely high when compared to the stress conditions of other rotating hardware. This higher stress environment was determined to be the result of the assembly interference fits between the HPT stage 1 disk, the HPT stage 1 aft blade retainer, and the HPT mid seal in combination with the engine’s operational loads.
Aircraft Registration Data
Incident Facts
Date of incident
May 14, 2024
Classification
Incident
Airline
United
Flight number
UA-28
Departure
Singapore, Singapore
Destination
San Francisco, United States
Aircraft Registration
N27957
Aircraft Type
Boeing 787-9 Dreamliner
ICAO Type Designator
B789
This article is published under license from Avherald.com. © of text by Avherald.com.
Article source
You can read 2 more free articles without a subscription.
Subscribe now and continue reading without any limits!
Read unlimited articles and receive our daily update briefing. Gain better insights into what is happening in commercial aviation safety.
Send tip
Support AeroInside by sending a small tip amount.
Related articles
Fleet type match
United B789 at Houston on Apr 16th 2022, gear did not come up
A United Boeing 787-9, registration N27957 performing flight UA-5 from Houston Intercontinental,TX (USA) to London Heathrow,EN (UK), was climbing out…
Fleet type match
United B789 at London on Apr 14th 2022, indicator light needed maintenance
A United Boeing 787-9, registration N27957 performing flight UA-26 from London Heathrow,EN (UK) to Denver,CO (USA), was climbing out of Heathrow's…
Fleet type match
United B764 at Newark on May 3rd 2026, too low on final, struck light pole and truck
A United Boeing 767-400, registration N77066 performing flight UA-169 from Venice (Italy) to Newark,NJ (USA) with 218 passengers and 13 crew,…
Fleet type match
United B763 near London on May 5th 2026, PED caught fire
A United Boeing 767-300, registration N675UA performing flight UA-135 from Zurich (Switzerland) to Newark,NJ (USA), was enroute at FL340 about 110nm…
Fleet type match
United A21N at Denver and Washington on May 2nd 2026, blown tyre on departure
A United Airbus A321-200N, registration N34547 performing flight UA-347 from Denver,CO to Washington Dulles,DC (USA), departed Denver's runway 08,…
Fleet type match
United B752 near Newark on Apr 30th 2026, pitot heater not working
A United Boeing 757-200, registration N14120 performing flight UA-270 from Newark,NJ (USA) to Shannon (Ireland) with 176 people on board, was…
United B739 near Chicago on Apr 30th 2026, odour in cabin
A United Boeing 737-900, registration N61882 performing flight UA-1631 from Newark,NJ to Las Vegas,NV (USA), was enroute at FL320 about 150nm north…
Newest articles
PSA CRJ9 at Kansas City on May 15th 2026, smoke in cabin
A PSA Airlines Canadair CRJ-900 on behalf of American Airlines, registration N616NN performing flight AA-5318 from Washington National,DC to Kansas…
Croatia BCS3 at Split on May 16th 2026, rejected takeoff due to runway excursion
A Croatia Airlines Bombardier C-Series CS-300, registration 9A-CAN performing flight OU-412 from Split (Croatia) to Frankfurt/Main (Germany) with 130…
Subscribe today
Are you researching aviation incidents? Get access to AeroInside Insights, unlimited read access and receive the daily newsletter.
Pick your plan and subscribePartner
ELITE Simulation Solutions is a leading global provider of Flight Simulation Training Devices, IFR training software as well as flight controls and related services. Find out more.
SafetyScan Pro provides streamlined access to thousands of aviation accident reports. Tailored for your safety management efforts. Book your demo today
AeroInside Blog
Popular aircraft
Airbus A320Boeing 737-800
Boeing 737-800 MAX
Popular airlines
American AirlinesUnited
Delta
Air Canada
Lufthansa
British Airways