We’ve all heard the recent news about the grounding of several Airbus A320neo family jets in the Philippines and elsewhere around the globe. Reports attribute these disruptions to a shortage of components for their Geared Turbofan (GTF) engines. Considering these are newer models leveraging the latest technology, you’d naturally expect them to be more reliable than their predecessors using conventional turbofan engines. However, that is not always the case.
So what makes these GTF engines, adopted in modern jet airliners like the Airbus A320neos, so distinct and yet more prone to maintenance? Let’s peel back the layers of GTF technology and understand its strengths, its pitfalls, and the reasons behind the maintenance challenges.
Understanding GTF Engines and Their Role in Modern Aviation
Airbus A320neo and Boeing 737 MAX are among the most advanced commercial jetliners. However, the A320neos are unique in offering the PW1100G-JM GTF engines as one of their options. The Boeing 737 MAX uses solely the CFM LEAP-1B. The A320neo is also offered with the CFM LEAP-1A, similar to that on the Boeing 737 MAX. Other planes that use GTF engines are the A220 (PW1500) and the Embraer E195-E2 (PW1900).
In the Philippines, both Philippine Airlines and Cebu Pacific opt for PW1100G GTF engines for their A321neos and A320neos. The AirAsia group’s A320neos and A321neos, on the other hand, are powered by CFM LEAP-1A engines.
Breaking Down the Mechanism of GTF Engines
A geared turbofan is a specialized type of turbofan aircraft engine, equipped with a planetary gearbox situated between the low-pressure compressor/turbine and the fan. This strategic placement allows each component to spin at its optimal speed. The primary advantages of this design include substantial reductions in fuel consumption and operating noise. However, these benefits come with a trade-off – increased weight and complexity.
A traditional turbofan engine consists of a single “low-pressure” or LP shaft connecting the fan, the low-pressure compressor, and the low-pressure turbine. This design necessitates a cap on the maximum speed for the larger radius fan, which limits the rotation speed of the LP shaft, and consequently, the LP compressor and turbine. In high bypass ratios, this calls for additional compressor and turbine stages to maintain optimal efficiency levels.
In contrast, a geared turbofan employs a planetary reduction gearbox between the fan and the LP shaft. This design allows the LP shaft to operate at higher rotation speeds, cutting down the need for additional stages in the LP turbine and the LP compressor. The resulting improvements in efficiency and weight reduction, however, are slightly offset by the weight of the gearbox and the heat produced within it. Furthermore, there are considerations regarding manufacturing cost and reliability.
GTF engines’ ability to run at lower fan speeds enables higher bypass ratios, leading to reduced fuel consumption and significantly less noise. The BAe 146, equipped with geared turbofans, remains one of the quietest commercial aircraft.
The Challenges Faced by GTF Engines
Despite their superior technology and benefits, GTF engines, such as the PW1100G, have been plagued by issues ranging from oil leaks and inflight shutdowns to higher maintenance cycles. Compared to the robust CFM56 conventional turbofan engines, which require maintenance only after 20,000 cycles, the PW1100G necessitates maintenance every 6,000 cycles.
However, Pratt & Whitney is consistently working towards enhancing the durability and reliability of their GTF engines. Notable progress includes the introduction of the latest- configuration Block D hardware, currently deployed in sixty percent of the fleet and projected to cover over ninety percent within the next two to three years. Block D enhancements comprise improved hot section durability, new erosion coatings, and the extension of rotating part lives.
Significant strides have also been made in reducing engine removal rates on the PW1100G-JM for the A320neo family, thanks to a new oil seal design. Similar updates, categorized as Block D.1, are expected to be available in 2024 for the PW1500G and PW1900G engines serving the Airbus A220 and Embraer E2-series.
First love never dies. I fell in love with airplanes and aviation when I was a kid. My dream was to become a pilot, but destiny led me to another path: to be an aviation digital media content creator and a small business owner. My passion for aviation inspires me to bring you quality content through my website and social accounts. Aviation is indeed in my blood and blog!
