The T-50 Golden Eagle fires its engine. Ground crew dressed in matching gray jumpsuits hustle around the airplane, preparing it for flight. They pull the chocks and make a few more checks. The engine revs and the airplane moves forward. Engineers, support, and production personnel gathered at Korea Aerospace Industries facilities in Sachon, South Korea, applaud the orange, white, and gold aircraft thundering past. Heat waves generated by the August sun ripple off the pavement as the jet proceeds over a small bridge to the main runway at the Sachon air base. The runway—normally shared by the 3rd Air Wing of the Republic of Korea Air Force, which trains fighter pilots in Sachon, KAI, and several Korean commercial airliners—is devoid of air traffic. Today, other air traffic is put on hold as the T-50 prepares for its maiden flight.

After a few final checks, the General Electric F404 engine roars to full military power. The T-50 accelerates down the runway, lifts into the air, and joins two ROKAF F-16D chase aircraft. The T-50, with chase aircraft close by, climbs out of sight and to 7,000 feet for preliminary handling tests. Lt. Col. Gwang Je Cho, test pilot for the flight, takes the two-seat advanced jet trainer to 15,000 feet where he conducts more tests, including engine transients. The aircraft reaches a maximum speed of 245 knots and a maximum angle of attack of thirteen degrees. Thirty-nine minutes after taking off, the T-50 lands safely back at Sachon.

Cho steps down from cockpit, smiles, and signals thumbs up. He radiates the restraint of a test pilot: “This was a very enjoyable flight,” he says. “If future flights are as successful as this one, we should have a great advanced jet trainer.

Concept To Reality

No Sun Park, the director and plant manager for the KAI Sachon plant, exudes a little more enthusiasm as he reminds visitors of the significance of the first flight. “That flight marked the transition from concept to reality for the T-50,” he says. “We are now seeing the fruit of years of labor. We believe this airplane has a great future.”

Korea’s military establishment and government view the T-50 program as a critical step in modernizing their air force and nurturing an indigenous aerospace industry. The program originated in the early 1990s when South Korea’s Defense Development Agency and Samsung began studying designs for an aircraft that could function as both an advanced jet trainer and a fighter lead-in trainer, or LIFT. The trainers would replace several aircraft in ROKAF inventory.

The T-50 supersonic advanced jet trainer is the latest product of a relatively new, but highly successful, aviation industry in South Korea. That industry dates back to the late 1970s when Korean Air Lines began performing depot-level maintenance on USAF aircraft based in the Pacific. Daewoo, Hyundai, and Samsung established similar capabilities soon afterwards. KAL began assembling F-5Es for the ROKAF in the 1980s. Korean industry consistently received high marks for its workmanship and quality. It subsequently won contracts to produce a wide range of components and subassemblies for other aerospace companies, including Lockheed Martin. South Korea began developing its first aircraft, the Daewoo KT-1 Woong-Bee, in 1988. This turboprop trainer first flew in 1991, entered service with the ROKAF in 2000, and, as of late 2002, has accumulated more than 10,000 flying hours. In the meantime, Samsung became the prime contractor for the Korean Fighter Program, which involved the production of more than 100 F-16s for the ROKAF. The last of these F-16s are now rolling off the KAI assembly line at Sachon.

“While the T-50 is not the first aerospace project Korean industry has undertaken,” explains Park, “it is certainly the most challenging. Designing and developing a modern supersonic aircraft is an enormous task. It requires the efforts of hundreds of engineers and other technical personnel from companies around the world.” Those companies include General Electric, BAE Systems, Smith Industries, Martin Baker, BF Goodrich, General Dynamics, Moog, Honeywell, Litton, Raytheon, and Rockwell. Lockheed Martin, the primary subcontractor on the program, is responsible for the wing, digital flight control system, and the design of the avionics system. The company also provides substantial technical assistance to KAI.

Designing The T-50

The T-50 design balances the conflicting characteristics of performance, cost, reliability, and maintainability. The final shape of the aircraft is the product of the first phase of the program, the preliminary design phase. Engineers conducted configuration trade studies, wind tunnel testing, and design optimization in this initial stage. Predicted operational use sized the structure based upon the required service life of the airframe. Engineers then created specifications for major subsystems and components. Suppliers for these systems were selected based upon the best combination of cost and performance. Additional trade studies determined cost benefits for potential manufacturing methods and assembly sequences.

A detail design phase followed preliminary design. In this second phase of the program, which began in the summer of 1999, engineers generated the drawings needed to build parts, tools, assemblies, and installations. “The challenges of this second phase of the program were staggering,” notes Park. “We had to produce detailed plans for more than 12,000 parts, assemblies, and installation—all in twenty months. Our KAI design teams successfully met the drawing release schedule. The number of drawing changes required because of interference or altered requirements was also very low compared with similar programs.”

Advanced computer-aided design and manufacturing was a key factor in the success of the program. “We took advantage of all of the computerized tools available,” says Park. “We did not have to build a metal mockup for anything. This airplane was a 100 percent computerized mockup from the start. We also used concurrent engineering. For example, as the structural engineers designed the bulkheads, the manufacturing engineers designed the tools needed to manufacture the bulkheads. We made changes early in the design to improve how the airframe would be manufactured. The center fuselage began as a three-piece assembly, like the F-16. For manufacturing reasons, we changed it to a two-piece assembly. The change saved weight and simplified the manufacturing process. We could make this change because we worked with a digital design process to design the airplane and its manufacturing process at the same time.”

A critical design review marked the completion of the detail design. The review verified that the design was mature and that the airplane’s predicted performance would meet all of the requirements established by the ROKAF. Final assembly for the first full-scale development aircraft began in January 2001 when the forward, center, and aft fuselages along with the tails were mated together for the first time. KAI is building six FSD aircraft—four flying prototypes and two structural test vehicles. Structural testing began on the test vehicles in January 2002. The first (flying) T-50 rolled off the KAI production line in mid September 2001. KAI conducted an official rollout ceremony at Sachon six weeks later.

Designed For Training

From above, the T-50 looks much like a two-seat F-16. A bubble canopy, blended wing/fuselage, and the general planform shape are similar. With a length of forty-three feet and a wingspan of thirty feet, the T-50 is about four feet shorter than an F-16. The control surfaces and tails are larger relative to the T-50’s smaller size. The extra area improves handling characteristics at lower speeds and makes the aircraft easier to land. Other distinguishing characteristics include a canopy bow that provides additional birdstrike protection; a narrower, more streamlined nose that corresponds to smaller radar requirements; and larger landing gears that absorb forces produced by higher sink rates (the vertical speed at which the airplane lands).

The most distinctive features of the T-50 are its twin side-mounted inlets that direct air to a single General Electric F404-GE-102 engine—the same basic engine used in the F-18 Hornet. The afterburning engine produces 17,700 pounds of thrust, giving the aircraft an excellent thrust-to-weight ratio. The maximum takeoff gross weight is 29,800 pounds, and the maximum speed is Mach 1.5. The service ceiling is 48,500 feet. The design load factor is eight g’s; the trainer airframe is designed for a 10,000-hour service life (8,300 hours for the lead-in fighter trainer version).

The T-50 has an onboard oxygen generating system, which simplifies maintenance tasks and reduces the amount of necessary ground equipment. A triple-redundant electrical system increases safety. Relaxed static stability and fly-by-wire digital flight controls offer superior aerodynamic performance and handling qualities. Modern cockpit features include hands-on throttle and sidestick mechanization, electronic flight instruments, head-up display, up-front controls, two five- by five-inch color multifunction displays, integrated advanced avionics systems and sensors, GPS/INS navigation, in-flight recording and post-mission debriefing capability, and a Martin Baker zero-zero ejection seat. The seatback angle is seventeen degrees, which is similar to the seat angles of the F-35 and the F/A-22.

“The T-50 is going to be a great trainer,” says Cho, who flew a variety of fighters and trainers before becoming the chief test pilot for the T-50. “The aircraft was designed for low-speed approach landings. The larger tail, flaperons, and rudder make the aircraft easier to control at lower speeds. In addition, the control surfaces move at fast rates, which further improves handling characteristics. By design, the aircraft lands better than most fighters. The angle of approach is lower than that of an F-16, so the pilot has a better forward view on landing. The raised aft seat gives instructor pilots a much better view in front of the airplane as well. The flight control sidesticks in the front and rear seats move together, so instructor pilots can feel student pilot inputs.”

The aircraft is designed to have the performance needed to support the lead-in fighter training missions. The LIFT version of the aircraft features a Lockheed Martin APG-67 multimode fire control radar, a modified General Dynamics M61 20mm internal gun, a weapons management system, and seven hardpoints for carrying a variety of air-to-air and air-to-ground weapons. (The standard T-50 has no radar or internal gun.)

Structural Testing

The T-50 structural ground test program, which began in January 2002, includes ground vibration tests, full-scale static test, and full-scale durability test as well as several other component tests. The ground vibration tests measure the dynamic frequency characteristics of the airframe structure and validate years of complex analysis. The full-scale static tests demonstrate that the structure can withstand the design loads with no detrimental deformation at limit load or rupture at ultimate load (1.5 times the limit load). The full-scale durability tests demonstrate the airframe structure will not fail from fatigue cracking for twice the predicted service life of the most severe predicted usage for the LIFT version, which is more than 8,300 equivalent flying hours. Durability testing for the second lifespan of the aircraft is scheduled to be completed in mid 2004. Vibration and static testing will be completed in fall 2003.

Flight Testing

ROKAF and KAI formed a combined test force to plan, manage, and conduct the flight test program, which is scheduled to last through September 2005 when the production phase of the program begins. “KAI is using a US model to conduct flight tests,” notes T.H. Ha, deputy chief of the T-50 Combined Test Force and the flight test director for KAI. “We based our flight test plan on the F-16 and then modified the plan to fit our needs.”

The first T-50 aircraft will be used mostly to expand the envelope and to evaluate handling qualities. The second aircraft will be used for stability and control testing. The third aircraft, the first T-50 LIFT version, will be used to evaluate avionics systems. The fourth aircraft (another T-50 LIFT version) will be used to test the radar, various weapons, and other loadings. The flight test program first establishes an operational flight envelope. Afterwards, T-50 subsystems and capabilities, such as the radar and external weapons carriage, go through development and integration testing. Detailed test plans undergo extensive KAI and ROKAF review for technical and safety considerations. The results of the flight tests are analyzed by KAI and ROKAF and incorporated into the recommendations each party makes for the final certification of the T-50 for operational use.

“This flight test program was set up to start more slowly than it would have started in the United States,” notes Tom Ryan, a Lockheed Martin senior technical manager in Korea. Flight testing a jet aircraft is something relatively new for Korean industry personnel, so they have a steeper learning curve. “New relationships have to be established between KAI and ROKAF in a combined test force environment,” he continues. “Relationships between the military aviation and the aerospace industry are already in place in the United States. The T-50 flight test program is being conducted on a base where the 3rd Air Wing carries out a training role. The ROKAF generates a lot of training sorties. Commercial air traffic has eight flights in and out of Sachon every day on top of that. So scheduling is an issue. Weather is a factor here as well.”

Ryan is one member of a team of Lockheed Martin employees working on the T-50 program at Sachon. “We perform two specific functions for the program here,” says Craig Lawrence, a flight test engineer on the program. “One is technology transfer. We’re here to assist KAI engineers to plan and conduct the flight test program. Our other function is to help the program run efficiently. We’re here to help them maintain the schedule.”

The technical assistance from Lockheed Martin has been invaluable. “My relationship with Tom Ryan and with other engineers from Lockheed Martin has helped me to be successful,” says Ha, who was in charge of KF-16 acceptance flight testing before transitioning to the T-50 program. The team effort is paying off. “The airplane is showing good performance and flying as expected. The problems we’ve experienced are typical early development problems. And that’s why we do flight testing. Not all design issues are visible with computer modeling and wind tunnel testing. We’re finding problems and fixing them before we go into production.”

As the flight test program progresses, the developmental test flights will incorporate more and more operational testing. “This testing, planned and managed by the ROKAF, will determine that the T-50 satisfies the operational requirements for a primary jet trainer and an advanced fighter lead-in trainer,” explains Col. Hee-Woo Lee, the director for T-50 development at the ROKAF System Program Office at Sachon. “Aside from test flights, the ROKAF will also assess the suitability of the T-50 integrated logistics support capabilities. In other words, we’re evaluating how the airplane will be maintained. These evaluations cover technical publications as well.”

“We’re testing an advanced jet trainer, the T-50, and an advanced fighter lead-in trainer version of the T-50, the T-50 LIFT,” explains Lawrence. The first T-50 flew for the first time on 20 August 2002. The second T-50 flew on 8 November. The two T-50 LIFT prototypes are scheduled to fly in late summer 2003. “The T-50 LIFT has a fire control radar and a 20mm internal gun,” Lawrence continues. “We will conduct weapon separation tests on the T-50 LIFT. About sixty percent of the flight test program is geared toward the fighter lead-in role. We could finish the testing for the advanced trainer version in eighteen months. Adding a radar, gun, weapons, and all of the related avionics significantly increases the size, scope, and complexity of the flight test program.”

Four test pilots are currently active on the T-50 Program with more to be added in 2003. All of them are recruited from the ROKAF. “Pilots volunteer for the assignment,” explains Cho, who has been on the T-50 program since 1999. “Because of the T-50’s importance to ROKAF and to South Korea, we are honored to be chosen to fly for the program.”

KAI is planning to hire two test pilots by mid 2003. “These pilots will most likely be ex-ROKAF pilots,” says Ha, who will be involved in the selection. “Experience and a good relationship with the ROKAF are important criteria for selecting a company test pilot. ROKAF rotates test pilots through this program. Cho, for example, leaves this year. He takes with him most of the flight test experience and the historical information associated with the flying. Dedicated KAI test pilots will provide continuity and corporate knowledge for the program. Eventually, the company test pilots will become the senior test pilots on the program and will convey their knowledge to ROKAF test pilots new to the program.”

More Than An Airplane

The ROKAF, like many air forces around the world, uses a wide variety of aircraft to train its fighter pilots. In Korea, students progress from the prop-driven Cessna T-41 Mescalero, to the subsonic jet-powered Cessna T-37 Tweet, and then to the supersonic Northrop T-38 Talon and the subsonic Hawk Mk 67. They then proceed to the F-5 before finally entering operational conversion training, which takes place at the operational units. Most of these training aircraft are very old.

“The ROKAF plans to replace all of these aircraft with two trainers—the KT-1 and the T-50,” says Park. “The T-50 takes students from advanced jet training to actual operational type training missions in a single type of airframe. Reducing the number of aircraft used in our training fleet makes obvious sense because it lowers logistics and support costs. However, the training system associated with the T-50 can decrease training costs even further.”

Lockheed Martin Aeronautics Company is analyzing the training requirements for different nations around the world to see how a T-50 syllabus can fit into their training programs and to see how much time and manpower a T-50-based training system can save. “You have to look at how much an air force spends to graduate a pilot from a flight academy and award him or her first wings,” says Park. “The T-50 addresses training costs systematically. A pilot can’t make as smooth a transition from a T-38 or a Hawk to an advanced fighter like the F-16. The T-50, with its modern cockpit and supersonic performance, is much closer to an advanced fighter like the F-16 or the Joint Strike Fighter. The T-50 familiarizes students with the weapons system and reduces the conversion time to the actual fighters. For a typical conversion course for the F-16, for example, our training system can save as much as thirty-five flight hours of flight time per student. The F-16 units can, in turn, use that extra thirty-five hours more effectively, say for tactical training.

“The T-50 should be viewed as a training system,” Park continues. “The system includes cockpit trainers, maintenance trainers, computer-based training, simulators, a training management system, and a ground training scoring system, to name just a few of the components. We even have training systems associated with the portable maintenance aid we use to identify and fix aircraft problems on the T-50.”

As more and more air forces look to commercial approaches for their training requirements, the T-50 stands out as one of the most viable and concrete alternatives. “Air forces around the world want a total package for training,” says Park. “They don’t want manufacturers to give them an airplane and then have to turn around and develop a training syllabus and training system themselves. They want a complete package. While the airplane is the most visible portion, customers will be just as impressed by the entire training system.”

The initial ROKAF procurement for the T-50 is approximately 100 aircraft, with a potential of another 200 to replace the ROKAF F-5s. KAI and Lockheed Martin project potential sales of as many as 600 aircraft worldwide. “We think the T-50 will become one of the world’s premiere training systems,” concludes Park. “That was one of the objectives we had for the airplane when we designed it. The first flight last summer was just one step on the path to success.”

Eric Hehs is the editor of Code One.