Due to their long service life, aircraft engines evolve over the years to take account of such factors as reliability and maintainability, as well as, more recently sustainability. Ian Harbison found out what some of the major OEMs are up to.
Frank Preli, vice president, propulsion and material technologies at Pratt & Whitney says the company is committed to continually advancing the efficiency of aircraft propulsion systems, whether through revolutionary step changes in performance like with the GTF engine family, or through more incremental upgrades.
In the last 12 months, it has announced two new engine upgrade programs– the GTF Advantage and PW127XT.
Designed for Airbus A320neo Family aircraft, the GTF Advantage engine enables a further 1% improvement in fuel efficiency and reduced CO2 emissions, in addition to the 16% step change originally achieved by the GTF at entry into service in 2016. At the same time, the GTF Advantage provides operators with 1,000lb greater thrust. However, it will actually run cooler than the current 33,000lb thrust models, offering greater durability.
The power increase gives a takeoff thrust improvement of 4% at sea level, providing longer range and higher payload, making it particularly suitable for A321XLR aircraft, while, for hot and high operations, there is an increase of up to 8% takeoff thrust at higher altitudes. GTF Advantage will be intermixable and interchangeable with the current GTF engine to ensure maximum operational flexibility.
In early October, Airbus started development flight tests of the GTF Advantage engine on an A320neo aircraft. The program will involve testing in a variety of environments, including hot and cold weather and operation from high-altitude airports. This is an extension of ongoing product development by Pratt & Whitney and Airbus over the last eighteen months. Engine certification will continue through the first half of 2023, including flights currently underway on a Boeing 747SP flying test bed at Pratt & Whitney in Mirabel, Québec, Canada, as well as extensive endurance testing to ensure product maturity at entry into service. The company has also started FAR33 certification testing. The engine has completed more than 2,400 hours and 7,800 cycles of testing, including a successful test on 100% sustainable aviation fuel (SAF).
The latest GTF engines for the A320neo family are demonstrating dispatch reliability rates consistent with mature rates on the V2500 engine for the A320ceo family but, says Preli, the company is still making improvements to extend time on wing, with the upgrades that have been incorporated in the current engine demonstrating positive results. All these upgrades will carry over to GTF Advantage.
The Pratt & Whitney Canada PW127XT turboprop has been developed for ATR 42/72 aircraft and received Transport Canada certification in August. compared to the PW127M, time on wing has been extended by 40% by increasing the period required between engine overhauls and hot section inspections to 20,000 hours, while, with only two scheduled engine events over 10 years (based on typical mission lengths and 2,000 annual flying hours), maintenance costs should be reduced by 20%. It also provides a 3% improvement in fuel efficiency compared to the previous generation engine and will be capable of running on 100% sustainable aviation fuel (SAF).
Preli comments that this will further increase the environmental performance and operating economics of regional turboprop aircraft, which can be up to 40% more efficient than regional jets on equivalent routes.
In June, it was announced that another variant of the engine, the PW127XT-S had been selected by Deutsche Aircraft to power its D328eco regional turboprop. The two companies will also cooperate on enabling the PW127XT-S engine to run on 100% SAF, including hydrogen-based Power-to-Liquid (PtL) fuel.”
For GE, it is focused on three aspects:
• Engine hardware upgrades: Improved and validated designs that can be introduced on legacy platforms
• Services technology: Ways to clean, inspect and repair engines to improve efficiency, reduce turnaround time and extend service time
• Analytics and fleet stability: Analytics Based Maintenance used to predict optimal time for preventative maintenance
An example of an engine hardware upgrade is the HPT durability upgrade program for CF34-8 engines that was launched in 2019. Under this program, GE provides customers with upgraded parts that can be incorporated into the engine during its next overhaul. These parts are listed in a series of Service Bulletins that GE issued and include components in the fan, compressor, combustor and HPT modules. The set maintenance offer is providing up to $30 per cycle lower engine life cost of maintenance.
On the GE90-115B, the company has invested in component improvements, from the front composite fan blades to HPT nozzles, blades and shrouds. Today, according to FDM data, the average engine cycles from EIS to first shop visit on a newly-built GE90 engine has increased from around 2,000 in 2007) to more than 4,000 today.
In 2021, the GEnx engine completed more than 3,000 cycles of dust ingestion testing in a simulated severe environment using a specialized dust ingestion rig. The endurance tests validated several hardware improvements, including an improved combustor deflector and redesigned high pressure turbine stage 1 blade. The endurance testing mimicked the dust GEnx engines encounter flying in some of the most severe operating environments in the world. In partnership with GE Research, dust was reversed engineered to replicate specific field conditions.
GE completed similar testing in 2021 on the FAA-certified GE9X engine, which will enter service on the Boeing 777X.
These tests were partly aimed at helping customers in the Middle East, where sand ingestion is a recurring problem, as was development of another services technology: 360 Foam Wash. With more cleaning capability than the water wash method, the 360 Foam Wash cart injects a proprietary foam detergent into target areas within the engine that reduces the build-up of deposits, lowers exhaust gas temperatures and improves engine compressor efficiency, increasing time on wing. It is completely self-contained, so can be used inside hangars.
The system was first introduced in 2017as a development program and tested on engines in the field and in service with customers. but a major step forward came in 2021 with its launch in partnership with Etihad Airways, which has included it in its Boeing 787 Greenliner Programme. After training their staff, airlines can obtain technical licenses from GE for GE90, GEnx and CF34 models, as well as Engine Alliance GP7200 engines.
Etihad obtained licenses for GE90 and GEnx-1B engines on its Boeing 777 and 787 fleets and was quickly followed in the region by. Emirates, Qatar Airways, Royal Jordanian Airlines and Saudi Arabian Airlines.
GE estimates using 360 Foam Wash on a GEnx engine operating in the Middle East can produce fuel savings of 15,900 gallons of fuel, based on 650 cycles a year, with each cycle lasting six hours. For a GE90, the savings are 35,500 gallons of fuel per year, based on 700 cycles a year, with each cycle lasting 6.5 hours. Of course, there an associated reduction in CO2 emissions.
Outside the Middle East, Air India received a technical license for GEnx-1B aircraft engines on its fleet of 27 Boeing 787s and expects to save approximately 230,000 gallons and a reduction of more than 2,200 tonnes of CO2 in 2022.
The latest customer, getting its technical license in January this year, is Japan Airlines, which is the first to use the system on the CF34, in this case the CF34-8E powering Embraer 170 aircraft operated by Japan Airlines and its subsidiary, J-Air. Expected annual savings are up to 82,000 liters of fuel and up to 285 tonnes of CO2 carbon emissions by replacing some water washes.
Returning to hardware upgrades, again with hot and harsh flying environments in mind, the Thermal Barrier Coating (TBC) Shield is a tool that can be used on-wing to re-apply thermal coatings in the GEnx combustor, increasing engine durability and reducing maintenance requirements. The application is carried out by a small robotic arm that enters the igniter port on the combustor.
On the CF6 engine, GE is performing metal additive component repairs. One example is the repair of high-pressure compressor (HPC) blades that run at high speeds with tight clearances, producing regular erosion. Repairing these blade tips used to require a long process of cutting, welding and grinding to create the proper shape but the company has established an automated additive manufacturing process to repair the HPC blade tips, saving time and costs associated with labor and machining. Image-analysis software maps the shape of a used blade and creates customized instructions for a Concept Laser M2 machine to build a new tip with precise alignment and profile. The 3D-printed part is near-net shape and can be finished with minimal additional processing. Beyond much faster turn-around times, the technology reduces the scrap.
For analytics and fleet stability, GE uses data received to monitor on-wing aircraft engines and help diagnose operational disruptions before they happen. For example, GE Aviation employees in both Cincinnati and Shanghai perform 24/7 data analysis, seeking to identify trends such as oil usage, vibrations and gas temperature. Once a trend is spotted, they are capable of alerting the airline customer and identifying potential engine issues with recommended maintenance actions.
The company’s engine health monitoring service includes self-serve access to GE’s customer web portals, where customers can find technical updates, and analysis of key engine performance trends and more. Customer Notification Reports (CNRs) issued to GE Aviation customers identify potential engine issues with recommended maintenance actions. Additionally, customers can receive 24/7 global support for AOG situations.