Throughout the aviation industry, jet engine vibration is an everyday concern. Maintenance, repair, and overhaul (MRO) crews worldwide are tasked with monitoring engine vibration to ensure flight safety and efficient service.
Overall gas turbine engine vibration, however, is the summation of contributions from various moving parts within the engine. To correlate vibration magnitude with specific engine components, maintenance engineers rely on vibration analysis and trim balancing tools.
Vibration analysis detects discrepancies in rotational machine dynamics while trim balancing is used to reduce vibration amplitudes of gas turbine shafts. Together, they help engineers ascertain and correct individual sources of vibration within an engine.
Vibration analysis, balancing
A modern turbine engine will typically contain two or three concentric shafts with compressors, fans, and turbines. These shafts – referred to as spools – are aerodynamically coupled, so each spool turns at a rate variable to its fellow spool. Consequently, each spool contains a speed pickup or tachometer so rotational velocity and the spool rotational angle can be known.
In addition, vibration sensors are affixed to one or more positions on the engine case, measuring the magnitude of physical shaking. These built-in tachometer and vibration sensors are intended to provide a means for measuring speed and vibration as the engine operates. Reliable signal detection, however, is no trivial task as the signals are extremely noisy. Complicating matters further, different engines feature different signal types.
The PBS-4100 turbine vibration analyzer/balancing system gives users the ability to check the engine’s vibration amplitude and balance that engine if necessary. It does this with a series of on-board digitizers designed to measure each spool’s rotational speed and magnitude of vibration. Embedded logic assesses each engine spool’s 12 o’clock position to understand where an imbalance might be located.
A series of configurable tracking filters correlates vibration to the spools. These specialized computer algorithms measure the rotational speed of a given spool and then filter the vibration content outside a narrow band of interest. The narrow band of interest is the characteristic frequency of vibration around each spool’s rotational speed.
By using the tracking filter for each speed, the contribution of vibration of each spool can be separated. As vibration varies with engine speed, measurement data is stored and presented in vibration-versus-speed trend plots.
In testing an engine, the operator will execute a vibration survey on the turbine engine – a slow cycling of engine speed from idle to maximum, then back down to idle again. As this occurs, the vibration analyzer will measure the vibration contribution from each of the spools and chart its findings on a series of plots. The overall vibration is also plotted.
The operator is warned if pre-defined limits of vibration are exceeded. By the end of the survey, the vibration profile is summarized for comparison against original equipment manufacturer (OEM) recommendations. If the vibration of any given spool exceeds an allowable limit, it is possible to add offset weights to bring the spool into balance, similar to the addition of lead weights by an auto mechanic onto an imbalanced tire.
Because the vibration magnitude and the angular position are known on the spool, a solution may be calculated with a variety of techniques using the algorithms within the vibration analyzer. Such a solution would add one or more precisely defined weights onto designated locations/angular positions on the spool.
For some aircraft engine MRO situations, vibration data and balancing are not necessary; only the tachometer signal conditioning function is needed. Therefore, a signal conditioning unit fills the bill. The TSC-4800A uses the same tachometer conditioning technology in the PBS-4100, and can accommodate all types of engine speed signals.
With the signal conditioning unit, users can test engines with a long-tooth or short-tooth embedded N1 signal; engines with older high-voltage tachometer generators; or engines with offset tooth design.The signal conditioning unit can be configured to condition as many as three individual speed signals. Channels A, B, and C can be assigned to a different engine speed signal, and each channel can be individually controlled and programmed to condition different speed signals. Because many engines have primary and secondary speed signals, the signal conditioning unit also offers multiple input sources for each channel.
Early analysis of turbine vibration can identify problems quickly, saving the time and cost of engine removal. Implementing such troubleshooting techniques, however, can prove difficult. Mechanical constraints under the engine cowls and the complex design of aircraft wiring harnesses can make the installation of accelerometers, charge amplifiers, and cables a time consuming and error-prone task.
A portable vibration analysis and engine trim balance instrument, such as MTI’s PBS-4100+, connects directly to the engine’s built-in sensors to read necessary signals. Coupled with aircraft-specific accessory kits, the unit simplifies jet engine balancing and vibration testing.
As with the larger test cell version, the portable instrument employs a series of on-board digitizers and configurable tracking filters. With these, the operator executes a vibration survey on the turbine engine. The survey is a slow cycling of engine speed from idle to maximum, then back down to idle again. As this occurs, the unit measures the vibration from each spool and plots its findings, including overall vibration.
3D printing has enabled aerospace companies to create complex components previously impossible with traditional techniques. This fosters innovation while reducing costs and turnaround times in a complex, highly-regulated environment.
Due to the typically short runs of parts, the aerospace industry is a prime candidate to benefit from 3D printing. It gives companies the flexibility to print specific aerospace parts for applications in the hundreds or thousands without costly tooling changes. Beyond part production, 3D printing improves manufacturing capabilities for tools that are needed to create those parts. It can also facilitate lightweighting efforts for aerospace structures, increasing fuel savings and reducing environmental impact.
Starting the process
How does this process get started? The approach at Materialise begins with an information sharing session between our team and the aerospace team, identifying all the applications and operations where 3D printing could offer an advantage compared to traditional manufacturing.
From there, engineers get involved to see what parts can appropriately be 3D-printed. What follows is a cost analysis to ensure that the parts identified for 3D printing will be produced more cost effectively. The more complex a part is, the more expensive traditional manufacturing becomes.
The next step is going to the aerospace organization’s factory to walk the lines to identify pain points and where 3D printing can further assist. Often, we find parts and processes such as jig and drill fixtures that can benefit from 3D printing customization.
Materialise is focused on determining the strength and functional requirements to meet the needs of the highly-regulated aerospace industry. From there, we identify parts, design them with lightweight structures, and run them through 3D printing software to optimize and prepare the files for printing. Unique to 3D printing, mesh/lattice structures allow parts to have the same strength and function with less material, reducing overall weight.
In one example of lightweighting through 3D printing, Materialise obtained EN9100 and EASA 21G certification to deliver airworthy additive manufactured end-use parts at the end of 2015. Then we partnered with Airbus, manufacturing plastic parts for the A350 XWB which consumes 25% less fuel, due in part to 3D printed parts. Through software solutions, such as Streamics production management solution, companies can benefit from certified production workflows that are traceable and repeatable.
Another notable collaboration is with 328 Group. The organization handles the maintenance, modification, and refurbishment of its fleet of Do328 commuter airliners. In preparation to re-launch serial production of this aircraft, 328 Group works with Materialise to make plastic spare parts lighter, faster, and less expensively.
While 3D printing has entered the aerospace industry focusing on smaller-scale parts, it is possible that entire aerospace frames could be 3D printed in the future. We are already seeing this in smaller craft and drones, such as the SoleonAgro. Intended for biological pest control in agriculture, it was developed using 3D printing for rapid prototyping, testing, and design verification to reduce the cost of product development. Once designs were finalized, the company turned to Materialise to optimize files with lightweight lattice structures and prepare them for printing. This process gives Soleon the flexibility to design drones to fit various customer needs, from pest control to photography.
As the industry continues to see the value of 3D printing for aerospace, we also expect companies to begin developing on-site 3D printing operations, which would reduce supply chain, shipping, and storage costs for parts. On-site printing capabilities could also offer real-time design, processing, trial, and implementation of customized parts.
The software and processes for 3D printing with metal are also rapidly evolving, which will have a great impact on aerospace manufacturing processes. New software, such as our e-Stage for Metal, can produce and customize drill and jig fixture parts. Design requirements for these parts change rapidly, and 3D printing allows for faster, easier design changes to reduce the need for expensive trial and error when creating tools to help companies keep up with the pace of the industry.
The next 5 to 10 years will be an exciting time to watch this collaboration of aerospace and 3D printing grow stronger. We can’t wait to see where the industry is headed.
Companies continuously face tough decisions when it comes to investing in enterprise resource planning (ERP) or product lifecycle management (PLM) solutions. In practical terms, PLM enables product engineering and innovation. Funding these enterprise initiatives and their continuous delivery activities is often challenging due to conflicting expectations and priorities from multiple stakeholders. Successfully implementing enterprise change requires merging multiple requirements and negotiating expectation tradeoffs.
Typically, PLM investments deliver greater financial and strategic impacts than ERP investments, and PLM investments deliver competitive advantages in a way that ERP cannot.
Prioritizing technology investments can have a dramatic impact on return on investment (ROI). Prioritizing PLM investments can lead to a more effective ERP engine. The reverse might lead to lean ERP operations with unreliable, incomplete, or inaccurate PLM data – a garbage in, garbage out scenario which can spiral into deployment or support issues.
Asking who pays for PLM often relates to asking who benefits and how to fund it. However, causality between these questions is not always clear as PLM is sometimes seen as a necessary evil to deliver production-ready data to the wider enterprise.
PLM investment decisions should go beyond dollar-for-dollar return, as the platform is essential to an enterprise in its entirety.
For instance, PLM is an enabling platform engineers must use to complete their work. Few clearly recognize or appreciate that it should help them work more effectively and become better at what they do.
While rooted in engineering for product creation – historically product data management (PDM) – most PLM value relates to cross-business functions and integration. Product creation (engineering PDM) and product data usage (wider enterprise PLM) have complementary, albeit sometimes conflicting, requirements.
Engineering teams can perceive enterprise PLM as a burden that constrains day-to-day creativity with non-value-added activities.
Benefit realization (such as productivity and knowledge sharing) is not tracked properly; PLM initiatives end-up being managed by incidents, while success is measured based on the ability to close technical issues rather than end-to-end business improvement.
For most cross-functional initiatives, the enterprise should fund the PLM foundation and spread the investment across the relevant functions or user programs. The cost of PLM spreads across three main categories:
Implementation investment (build): Technology and supplier selection, implementation, and preparation of the solution (people-process-technology readiness) includes setting up the infrastructure; building the selected tools and technologies through configuration; customizing, testing the solution, and validating the new processes; preparing data migration and interface procedures and tools; preparing the transition; aligning human elements.
Deployment investment (execute): Interface with the business, training end users, running the transition, facilitating business adoption, performing legacy data extraction, and deploying relevant interfaces on the selected infrastructure (including the cloud).
Support investment (maintain): Capture knowledge and capitalize on PLM implementation, prepare day-to-day usage continuous improvements, and maintain evolution roadmaps.
PLM implementation investments require robust business case creation supported by experienced implementation practitioners. The implementation budget should be owned and managed by the enterprise (across functions) and considered as a sunk cost to deliver the foundation of an enabling platform across the entire value chain.
Adoption challenges, incentives
Some organizations might decide to distribute deployment and support running costs across impacted business functions. This needs to be done carefully to avoid associated challenges. For example, asking project teams or functional teams to pay for on-demand PLM usage with cross-charging models might be perceived as a usage tax that could discourage the business from using the solution.
Teams might work outside of PLM and only use the solution to release or publish data. Or, by limiting access to a few PLM users to check data in and out for the rest of the team, users could create hidden factories outside the enterprise platform – leading to data duplication, uncontrolled processes and data, and other inefficiencies. This, in turn, will affect concurrent engineering and collaboration effectiveness, data reuse, early error identification, quality, and adherence to process.
To show PLM as on-going deployment and to support cost distribution, link usage to continuous business benefit realization and incentivize value enablement. Don’t simply consider quantitative measures which relate to business consumption or usage cost.
PLM as a service
Cloud solutions can lower barriers to PLM technology adoption if users consider service models as more than just cost models. Enterprises should consider PLM-as-a-service for what – and where – benefits are realized so that the appropriate users can access the right data at the right time, from the right source, at the right location, for the right purpose, and at the right price. Evaluate cloud PLM across business processes, partners, technology resources, performance requirements, security needs, enterprise application interoperability, and infrastructure. It is only effective if it helps meet business goals.
Teaming up with supply chain partners early and conducting small-stage automated fiber placement (AFP) trials can pay big dividends as aerospace manufacturers increase their use of lightweight composites.
Formatted composite processed through various types of AFP equipment
A best practice is for the fabricator, material manufacturer, automation equipment supplier, and material formatter to come together early in a four-way collaboration. Together, they can adjust materials, formats, and lay-up processes to achieve strategic breakthroughs long before final decisions and investments have been made for commercial-scale processes.
Ideally, product development will entail a series of small-scale trials with all production partners. Each trial might involve runs at the material supplier’s facility, followed by runs at the precision formatter’s, and finally runs at the machine designer’s plant. As the partner that interacts with the material suppler and automation designer, the precision formatter is well positioned to coordinate these rounds of trials. In many cases, an entire cycle can be completed in less than two months.
Four key early trial benefits stand out.
1. Shorter production lead times – Trials take time, but they shorten the total timeline to market and allow the parties to identify problems and address issues early. Encountering these issues later often leads to costly delays and changes and might even mandate complete redesigns of production processes or equipment.
2. Faster lay-up rates – The rate at which composite materials are applied is critical. Fast material lay-down rates yield greater manufacturing throughout. Early trials allow material formatting and automation processes to be calibrated for the fastest possible lay-up process.
3. Fewer stoppages and changeovers – Continuous operation is just as important as speed. By including precision formatting as part of the product development process, expensive and time-consuming unplanned shutdowns can be minimized.
For example, spool format and sizing are key factors in changeovers. Spool design should be based on part size, production schedule, and out-time constraints for the specific application. If it takes 100ft of composite slit tape to fabricate a part, and six parts are produced per day, spools should carry at least 600ft of slit tape. Otherwise, there will be a need for changeover during a day’s production, causing unnecessary delays. Moreover, if the spool size is wrong for an application, a material management issue can arise with remnant spools or expensive material wasted due to out-time. It seems simple, but even this fundamental type of planning impacts the material manufacturer and the automation equipment supplier.
Poor tape quality can also cause downtime. Tapes that have not been properly formatted can have uneven, hairy edges or stringers that can get caught, shutting down the AFP machine. Resolving spool sizing and tape quality issues before production can avert unnecessary stoppages and changeovers.
4. Increased material yield – Material yield usually depends on parent roll specifications versus the formatted tape’s width and length, the manufactured part’s size and shape, and the type of splices acceptable in the finished part; it also involves tradeoffs, such as the choice between wide or narrow composite tape. Wider tape allows more material to be laid down with each machine pass, but there could also be more waste from saw-tooth edges. Narrower tape might improve yield, but at the cost of more production time. Creating optimum slit width(s) and number of tapes per laydown are vital in meeting production throughput and costing goals. Combining multiple sizes can also improve throughput without compromising yield.
Resolving these issues during product development conserves composite materials, improves the buy-to-fly ratio, and cuts production costs. Conducting early trials allows supply-chain partners to identify and work through challenges and take advantage of opportunities to use new materials, formats, and fabrication methods.
Trial results typically lead to further fine-tuning of the part- fabrication operation so production can begin with the materials, processes, and automation fully validated and ready to roll.
About the authors: Michael Quarrey is Web Industries Inc.’s vice president of operations for aerospace. He can be reached at firstname.lastname@example.org. Ashley Graeber is Web Industries’ aerospace sales director. He can be reached at email@example.com.
Aerospace Manufacturing and Design welcomes all aircraft enthusiasts to join the fun and NAME THAT PLANE! Each issue, a new aircraft will be featured. Given a photo and a clue box, readers are encouraged to guess what plane is being described and submit their answers to www.AerospaceManufacturingAndDesign.com/Form/NameThatPlane.
March 2018 answer: Lockheed P-38 Lightning
MARCH 2018 winner
Mark Williams, Senior Process Engineer, Spirit AeroSystems Inc., Kinston, North Carolina
How long have you been in the aerospace business? For 38 years. I started as a design engineer on the F-16 Fighting Falcon.
How did you become interested in aircraft? My interest started as a teenager, flying with my dad in a Piper 140 on his business trips. I got my pilot’s license at age 16.
What is your favorite aircraft (and why)? My favorite is the Lockheed P-38 Lightning. It was the first model airplane I built as a boy.
Brain McCoy Materials Engineer Manager SKF Aeroengine North America Falconer, New York
Lee Sorrell Senior Program Manager Areté Associates Arlington, Virginia