Up to 1,200 Geared Turbofan Airbus Jet Engines Recalled

The recall was caused by on impurities in powdered metal.

The RTX corporation revealed in an earnings call on July 25 that it was recalling up to 1,200 of its PW1100G Geared Turbofan Engines, built by subsidiary engine-maker Pratt & Whitney, for accelerated inspection.

The culprit—microscopic contaminants discovered in the powdered metal produced at a New York facility. The metal was used for engine’s stage 1 and 2 high-pressure turbine discs, manufactured at a factory in Columbus, Georgia between 2015 and 2021. The impurities expose the components to risk of accumulating micro-cracks in advance of their specified service lives.

The flaws were first detected in a broken disc on a Vietnamese A321ceo airliner using the older IAE V2500 turbofan—the product of a joint venture with Pratt & Whitney. However, in mid-July, Pratt & Whitney determined that they weren’t comfortable estimating the risk posed by the powdered metal to its latest-generation PW1100G engines, and that they merited an accelerated inspection schedule.

At present, RTX (formerly known as Raytheon) plans to inspect 200 of the oldest higher-priority engines by September. An estimated 1,000 more engines may require inspection in the year to follow—though the final number could end up below or above that, depending in part on the findings of the initial tranche of inspections.

Two PW1100G-JM engines are used in some of Airbus’s A320neo and A321neo jetliners, which closely rival the Boeing 737 for the crown of most prolific jetliners in service. The estimated 1,200 engines amount to 40% of the roughly 3,000 PW-1100Gs delivered.

Each inspection requires two months to dismantle the engine, replace the discs (if flawed), and reassemble them. Based on prior experience looking for flawed discs in 3,000 engines, Pratt & Whitney is optimistic that only around 1% of the discs will require immediate replacement.

That recall (or ‘shortened inspection intervals’ as the firm put its) still risks disrupting operations by carriers that operates PW1100G-equipped jetliners, as in-service aircraft are taken out of rotation early for inspection. However, the discovered flaws don’t pertain to or affect deliveries of new GTF engines (the plant corrected them in 2021) or production of new aircraft.

RTX’s executive Greg Hayes conceded during the call that the “disappointing” problem would be expensive to fix and would impact customers—though he insisted that it didn’t amount to an “existential problem” for either Pratt & Whitney or RTX.

Nonetheless, investor backlash led to a 10% drop in RTX share value after the recalls were announced, while Airbus took a 2.5% hit. RTX itself reduced its estimated 2023 cash flow by a half billion dollars to a net $4.3 billion.

The A320’s most numerous operator is India’s IndiGo, with 143 aircraft. Other major operators that received A320neos and A321neos are found in the U.S. (Delta, Jet Blue, Spirit, United, Hawiian), China (including Air China, Shenzhen and Sichuan Airlines), Hungary, Japan, Mexico, Turkey, and Vietnam. America Airline’s large A320 and A321 fleet, however, uses the rival CFM LEAP engine for propulsion.

The two predominant jetliners in production today are the Boeing 737MAX and Airbus A320neo series of single-aisle airliners. While the 737MAX is fitted with the LEAP engine developed by market leader CFM International (a French-American joint venture), the A320neo can be fitted with either LEAP turbofans or the Geared Turbofan (GTF) developed by Pratt & Whitney.

Both high-bypass turbofans were pegged as offering fuel efficiency improvements around 16%, which adds up to huge savings over older aircraft. Given that a typical jetliner might fly 3,000 hours annually, improving fuel efficiency and lowering operating costs are the name of the game in commercial jet travel. Carbon-emission reduction benchmarks and offsets seeking to slow down climate change further multiply the value of such efficiencies.

Though LEAP and GTF both incorporate many advanced technologies, such as new wear-resistant coatings, GTF is overall less conventional. They introduced a gearbox that allows the fan and the spool of the engine to turn at different, more optimal speeds.

GTF has its origins in research by Pratt & Whitney at NASA wind tunnel facilities that began in the 1990s. Pratt & Whitney began investing more seriously in the program in 2006, and had engine prototypes first flight tested by 2008. An A320neo-specific subvariant, the PW1100G, then took to the skies in 2013 and received FAA certification in December of 2014. This variant has a fan 2.05 meters in diameter, generates up to 17.5 tons of static thrust, and each one weighs 3.15 tons.

One early analysis estimated that GTF would exhibit lower operating costs due to having fewer components that would be exposed to less stress at lower temperatures—also making it preferable for airlines operating in hotter climates. GTF also is expected to reduce engine noise by up to 75%. On the downside, the gearbox does introduce some weight and complexity, though it doesn’t require any special lifetime maintenance other than periodic oil changes.

In practice, U.S. Department of Transportation figures from 2017-2020 show that the LEAP engines on A320neos require half as many repair and maintenance hours as the GTF, and have only half (or lower) the operating costs of the GTF, despite the GTF exhibiting lower fuel burn costs.

To be fair, these figures may reflect the identification and correction of teething issues that plagued the GFT engine family early on.

While many are partial to the PW1500G variant used on smaller Airbus A220-series airliners, the PW-1100Gs specific issues began with lengthy start times (7 minutes up from typical 2.5), attributed to asymmetric deformation of turbofan rotors due to thermal buildup. This was gradually addressed through modifications introduced between 2016 and 2017 in the form of revised fuel nozzles, inserted dampers, software upgrades, and a boron-nitride coating applied to rotor tips.

But, by 2018, engine vibrations emerged in PW1100Gs while climbing at high power, leading to Lufthansa grounding its A320nos for 8.5 months. Problems with a knife-edge seal used in the PW1100G’s compressor led Airbus to cease accepting deliveries of the engine until Pratt & Whitney replaced already delivered seals with a corrected design.

Indian carriers operating GTF turbofans in hot, heavily polluted environments experienced especially frequent problems that resulted in slow serviceability rates, with airline Go First even blaming the engines (both failure rate, and speed of replacement) for its bankruptcy. Pratt & Whitney argued that the airline’s mismanagement was to blame.

At present, Aviation Week reports that 11% (over one out of ten) airliners using GTF-series engines were either grounded or being flown only once per week, often due to delays— either caused by waiting on reception of spare parts from Pratt Whitney, or by waiting for slots to free up for engine overhauls at 13 (going on 19) facilities worldwide that support GTF maintenance.

Pratt & Whitney says that it plans to create a surplus of spare parts to help circumvent these major delays.

The costs of quality control

The silver lining of the frustrations posed by the latest recall is the willingness of the company to take on the costs of preemptively identifying risks—even if they expect to find flaws in only 1% of all engine discs.

Time will tell whether the diverse issues exhibited by the GTF family of turbofans can be fully ironed out to achieve the desired improvements to reliability and reductions in operating costs.

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