Investigators in India have identified that the separation of a high-pressure turbine (HPT) blade was behind the way in-flight failure of a CFM International Leap-1A engine aboard an IndiGo Airbus A321neo.
According to the final investigation report from the Directorate General of Civil Aviation (DGCA), CFM has already redesigned the Leap-1A’s first-stage HPT blade, which has “demonstrated improved durability during production testing” and will be retrofitted globally.
The IndiGo jet (VT-ILN) was operating flight 6E2789 from Delhi to Chennai on 10 June 2023 when the incident occurred. Around 6min after take-off as the aircraft was climbing the flightcrew heard a loud bang, then received stall and failure warnings for the No.1 engine.
The crew transmitted a ‘pan pan’ message and shut down the powerplant. They subsequently performed a single-engine landing at Delhi airport, 30min after departure.
There was no evidence of external fire or smoke from the aircraft. There were no injuries sustained by the 233 passengers and seven crew members.
Post-flight engine inspections found “metal particles” in the exhaust of the Leap-1A. Subsequent borescope inspections conducted by CFM revealed severe damage to the stage-one and -two HPT blades, and to the low-pressure turbine blades.
Damage included ”numerous fractures observed at the root area of several HPT stage 1 blades”, says the DGCA. Based on those findings, the investigation concludes that the HPT blade was released ”during high-power operation of the engine during climb”, causing further heavy damage to the high- and low-pressure sections.
That led to a “stall, rotor imbalance, high vibration, and [high-speed spool] rotor seizure”, says the report.
“Such a failure of stage one HPT blades is an industry issue on CFM Leap engines,” it adds.
CFM informed the investigators that the HPT blades were ”were not subjected to further investigation or metallurgical analysis” because it was ”well-acquainted with the signatures associated with blade liberation” from engines examined during previous shop visits.
The engine maker says there have been ”a total of three comparable incidents… all attributed to the root cause of [HPT blade] liberation”. That total includes the June 2023 event.
A service bulletin issued in September 2022 has “proven effective in mitigating such failures”, CFM told the inquiry. It is also ”nearing the final stages of releasing a newly designed” HPT blade, which will be retrofitted across the global fleet.
The DGCA also notes that the incident was the first in a string of Leap-1A engine issues experienced by the Indian low-cost carrier over the span of a year.
In October 2023, another A321neo flying from Udaipur to Mumbai had its No.1 engine fail while at 14,000ft, forcing a diversion to Ahmedabad.
Two further shutdowns – one uncommanded – happened in January and May this year, on an A320neo and A321neo, respectively.
The DGCA has requested IndiGo to carry out borescope inspections of existing blades on its Leap-1A engines until the new turbine blades have been installed across its fleet.
According to Cirium fleets data, the aircraft (MSN10151) was delivered to the airline in 2021. IndiGo has 90 A321neos in service, 79 of which are powered by CFM engines.
