F­35C Joint Strike Fighter Additive Manufacturing Tailhook Redesign 4/24/16 Submitted to Lockheed Martin Representative Team EDSGN 100, Section: 23 Group 4: Kiran Judd, James Harris, Madeline Woody, and Zach Ceneviva Abstract: The objective for the project was to design, prototype, and manufacture an effective ​ redesign of the Lockheed Martin F­35C tailhook, utilizing additive manufacturing. The F­35C tailhook, like many other subtractive manufactured parts, suffers from a waste of excess material and limitations when creating advanced designs. The main question relating to the current process is how does one eliminate the total amount of material used, while still retaining the original strength? For this reason, when designing the prototype material reduction, affordability, accessibility in the field, effectiveness, and durability were treated with the utmost importance with respect to design criteria. After the printing of the prototype, it was necessary to test the design criteria in order to see if the efficiency and reliability met the desired goals for the tailhook. The tailhook prototype did not pass all of the set criteria for its design, but performed especially well when compared to the set criteria for the durability. Although the initial prototype performed well during the durability test, it did not perform as well as hoped within the material reduction, affordability, and effectiveness categories. These areas proved to be lacking, leading to corrections which would later lead to the improved second prototype, created by the team. Following the improvements implemented within the second prototype, an effective, durable tailhook was created utilizing additive manufacturing processes. Table of Contents Introduction Pg. 2­4 Methods Pg. 5­6 Results and Discussion I Pg. 7­9 Results and Discussion II Pg. 10­13 Conclusion Pg. 14 References Pg. 15 Appendix Pg. 16­17 1 Introduction: The Goal of this project was to redesign the F­35C Joint Strike Fighter tailhook while improving the capabilities of the legacy design, through reduced weight, reduced part count, faster assembly, and improved performance. The subsequent design process aimed to solve the current deficiencies found within the F­35C tailhook subtractive manufacturing process. For this reason, the design produced intended to solve Lockheed Martin’s problem, while providing the United States Navy and Marine Corps an ability to manufacture tailhooks aboard aircraft carriers. The F­35 Lightning II is a 5th Generation fighter, combining advanced stealth with fighter speed and agility, fully fused sensor information, network­enabled operations and advanced sustainment [1]. There are three variants of the F­35 that will replace the current legacy fighters for the U.S. Air Force, the U.S. Navy, the U.S. Marine Corps. The Joint Strike Fighter developmental program was signed into action on November 16, 1996, selecting Lockheed Martin and Boeing as competing companies for the JSF concept demonstration phase [2]. On October 26, 2001, the Lockheed Martin X­35 design beat out the Boeing X­32, wining the Joint Strike Fighter contract. Although both aircraft designs were found to meet or exceed the given requirements, it was decided that the X­35 would have less risk and more growth potential over the X­32 [2]. The United States plans to acquire around 2,500 aircraft, intending to provide the bulk of the manned tactical airpower for U.S. Air Force, Navy and the Marine Corps over the coming decades. Deliveries of the F­35 Joint Strike Fighter for the U.S. military are scheduled to be completed in 2037, having a projected service life of about 50 years [2]. The first production F­35 rolled off of the assembly line in Fort Worth, Texas, in February of 2006, proceeding to make its first flight in December of the same year. Over the next few years, flight and ground test articles of all three variants rolled off the production line and began collecting test points. In 2012, the F­35 program ramped up with 30 aircraft deliveries and an increase in testing ​ operations across the United States [2]. It was during this time that the program reached several milestones in weapons separation testing, angle of attack testing, aerial refueling training, and surpassed more than 5,000 flight hours with more than 2,100 recorded flights in that year [2]. Figure 1: The chart shows the three variants for the ​ F­35. The standard F­35A, vertical take­off STOVL F­35B, and carrier based F­35C are depicted with their respective service branches. [3] 2 As testing continued on the F­35, problems began to arise within the carrier based, or C­variant of the fighter. The F­35C variant has larger wings and more robust landing gear than ​ the other variants, making it suitable for catapult launches and fly­in arrestments aboard naval aircraft carriers [4]. Its wingtips also fold to allow for more room on the carrier’s deck while deployed. Landing testing had began to show that the design of the tailhook, the device meant to capture the arresting wire on the deck of an aircraft carrier, had various shortcomings. It was later found that the placement on the aircraft’s fuselage was causing the tailhook to bounce and thereby miss the arresting wire while landing. After two years of redesigning, Lockheed Martin produced a new, improved version of the original tailhook, aiming to improve upon the inabilities of catching the arresting wire seen on the early model [4]. Although Lockheed Martin designed an improved variant of the tailhook, critics still argue that it does not operate to complete standards. The manufacturing process used to create the tailhooks is also described as being a complicated, wasteful process due to the usage of subtractive manufacturing methods [4]. For this reason, the design team chose to redesign the tailhook utilizing additive manufacturing in order to reduce material used, reduce weight, and improve the manufacturing process. Before the design and prototype phase, it was necessary to select a set of design principles and criteria in order to properly follow the 8­step design process. After careful consideration for the needs of the Lockheed Martin, the mission of the F­35C tailhook, and the producibility of the tailhook, a set of criteria was created. The five main criterion for the tailhook redesign are presented in Table 1. Table 1: Design Criteria and Set Requirements ​ Design Criteria Specifications For Requirements Material Reduction Must use at least 10% less material Affordability Must be 15% cheaper when mass produced (2,500 planes) Accessibility in the Field Ability to be 3­D printed aboard US aircraft carriers Effectiveness Must consistently hook onto arresting wire Durability Must withstand 250N force 3 These design criteria were created using a brainstorming process, that allowed each group member to contribute ideas that would be most effective when solving the problem. The material reduction requirement was created to facilitate a design that Lockheed Martin and the United States Military could use to reduce the amount of material required. Affordability was the least important criteria due to the fact that the costs for production of the tailhook would be minimal compared to the current cost of $159 million per plane. Accessibility in the field was an important criteria, because the ability to 3­D print a tailhook while being deployed aboard an aircraft carrier would provide major advantages in repair time and logistical support. Effectiveness and durability criteria were created in order to address the shortcomings of previous tailhook models, while increasing the strength of the arresting gear. The durability of 250N was scaled down from 20,000N based off of the size of the prototype, the material of the prototype, the print method of the prototype, and the size of the prototype. All of these factors differ greatly from how the actual part would be printed. 4 Methods: After the creation of design criteria that were described in the introduction, multiple solutions were considered for the tailhook prototype. It was later narrowed down to four main designs. The four designs consisted of a solid steel, solid titanium, lattice structure steel, and lattice structure titanium redesign all utilizing additive manufacturing. Each of these design concepts had specialized strong suits in differing areas, which allowed for a large variety of design options to choose from. The design concepts and their specialties are displayed within Table 2. Table 2: Prototype Design Concepts and Design Specialties ​ Prototype Concept Design Specialty/Benefits Solid Titanium Extremely strong, lightweight Solid Steel Relatively cheap, strong Lattice Structure Titanium Extremely strong, lightweight, less material Lattice Structure Steel Relatively cheap, strong, less material After the the solution requirements were defined, they had to be weighted in order of importance, allowing them to be applied to the prototype concepts, thus quantifying their effectiveness. The criteria were then weighted as decimals on a scale from 0 to 1, with the most important criteria taking the majority of the weight. Material reduction was weighted the highest, due to the fact that Lockheed Martin wants to improve the manufacturing process through additive manufacturing. There would be no level of improvement if more material was utilized, because it would increase both costs and weight. Effectiveness and durability were both the second most highly weighted, because it was extremely important to make the tailhook catch on the arresting wire properly. This allows for a confidence in the design’s ability to withstand the forces while landing and its ability to catch properly. Accessible in the field was given the second to lowest weight, since this is not an imperative goal for Lockheed Martin. Affordability was given a smaller weighting than the rest of the criteria because it is not as explicitly important to the overall mission of improvement.