The March sun rises over the Mojave Desert around six. The day’s first light accentuates silver metal hangars against the beige backdrop of Rogers Dry Lake. The hangars are the home of the F/A-22 Combined Test Force. Even at this early hour, the buildings on the north end of the flight line at the Air Force Flight Test Center at Edwards AFB, California, bustle with activity as technicians ready their Raptors for the morning flights. The first flight of the day was briefed an hour ago and the pilots are ready. Just after daybreak, twin Pratt & Whitney F119 engines disrupt the desert silence as they propel the world’s most advanced fighter to the runway for another flight.
Ten Raptors call Edwards AFB home this spring. Two of these, Raptors 02 and 03, are categorized as flight sciences aircraft. Four others—Raptors 04, 05, 06, and 07—are used primarily for avionics testing. Raptors 08 through 011 are assigned to the Air Force’s Operational Test and Evaluation Center’s Detachment 6, which is preparing for a yearlong operational evaluation formally called Dedicated Initial Operational Test and Evaluation, or DIOT&E for short.
Col. Joseph Lanni, the F/A-22 CTF commander, watches Raptors come and go from the second-floor window of his corner office in one of those large silver hangars. He is relatively new to the F/A-22, coming to the program in late 2002. After just ten hours of Raptor flight time, this Test Pilot School graduate with 4,000 flying hours in more than seventy aircraft has already come to some conclusions about his latest charge. “I am thoroughly convinced this airplane is going to revolutionize the way we fight,” he says. “The F/A-22 will fundamentally change the way we approach air-to-air engagements. Nothing will be able to touch us for decades to come.”
Lanni and others at the F/A-22 CTF are taking care of the business of transitioning the Raptor from developmental to operational status. That transition involves expanding the flight envelope, testing advanced avionics, and training DIOT&E personnel who will soon be evaluating the effectiveness of the Raptor.
Flight Sciences: Burning Down Test Points
With more than 900 and 800 flight hours respectively, Raptors 02 and 03 account for more than half of the total accumulated flight time on all F/A-22s built to date. The two airplanes have spent most of that time in some very demanding flight conditions.
“We have a flight envelope cleared on the clean aircraft up to nine g’s, sixty degrees AOA, and out to Mach 2,” Lanni explains. “We are now clearing the side and main weapon bays to those same extremes so we can launch missiles from the entire flight envelope. Almost all of the recent flight sciences testing has been conducted with open weapon bays.”
Clearing a flight envelope for a high-performance fighter is no easy task. Clearing the same envelope for a low-observable fighter with internal weapon bays significantly adds to the challenge. “Other aircraft don’t have to deal with opening doors with very thin diameter hinges at supersonic speeds,” Lanni continues. “Acoustics create vibrations that stress internal equipment, doors, and door hinges. Results from our work here lead to ensuring the aircraft released for operational use can withstand these stresses.”
“Open doors alter the aerodynamics of the airplane and affect how the aircraft handles,” adds George Law, the chief engineer for the flight sciences F/A-22s at Edwards. “Open bays also induce other loads on the aircraft as well as loads on the doors themselves. These loads vary according to speed and angle of attack. Air going through the weapon bay or any open cavity generates acoustic vibrations. The equipment has to survive.” Flight test engineers measure noise in the bay with microphones and vibrations with accelerometers. They measure loads on weapon bay door hinges with strain gauges. The flight sciences aircraft are filled with instrumentation.
The two flight sciences F/A-22s are flown primarily to expand the flight envelope. Raptor 02 is used to systematically explore the portion of the envelope dealing with high angles of attack. Raptor 03 is fully instrumented for flutter and loads testing. “The first time a test pilot goes to a new point, he performs pitch, roll, and yaw doublets to try to induce flutter,” Law explains. “We have completed all of our flutter testing above 10,000 feet on a clean aircraft with the weapon bay doors open out to 800 knots. We are now completing the flying quality and loads testing with the weapon bay doors open.”
Flying quality and loads testing is accomplished through a wide variety of both operational and specialized test maneuvers. Flutter and loads are measured objectively with strain gauges, accelerometers, and microphones. Handling qualities, on the other hand, are more subjective. Pilots rate flying qualities on the Cooper-Harper scale, which is a one to ten scale with one being the best in terms of the amount of pilot compensation required for a desired performance level. “Every pilot interacts with the controls differently,” notes Law. “Some test pilots are high gain. Others are low gain. We reduce the subjectivity by testing handling qualities with a variety of pilots.”
Dick Burton, the flight test manager for the flight sciences aircraft, describes the purpose of F/A-22 envelope expansion: “We use the flight sciences aircraft to make sure nothing in the flight envelope will jump out and bite another airplane. We closely monitor the airplane as we approach the edges of the flight envelope in small steps.”
Burton and Law are relatively new to the F/A-22 program. Code One readers might recognize them from articles on X-35 flight testing. They and several other former X-35 flight test personnel arrived at Edwards last July to accelerate F/A-22 envelope expansion. “We are here to increase the rate at which we burn down test points,” Burton explains. “I had no preconceptions about the status of the airplanes when I arrived. Still, I was pleasantly surprised. The airplanes are in great shape, so we’ve been focusing on generating flights.”
Burning down test points translates to scheduling ten to twelve flights per week and flying at least five. Three-hour missions are common. Two three-hour missions makes for a good day. The flight sciences aircraft have flown as much as eleven hours in one day. “The current testing requires longer flights,” Burton notes. “The points in the flight envelope we’re gathering data for these days are very hard to achieve. Once the airplanes are up and flying, we want to keep them airborne. Fortunately, we have the tanker support necessary to support longer flights at high speeds.”
“The airplane is usually airborne before eight in the morning and down before lunch,” says Law, explaining a typical day for the flight sciences F/A-22s at the CTF. “We then turn the jet for a two o’clock go. The second mission lasts until about five in the evening on a good day. Usually the plane comes back from the first mission with some issues we have to deal with. Flying at the edge of the envelope pushes this aircraft harder than any operational F/A-22 will ever be pushed. We ferret out problems, but that is the purpose of flight testing. Instrumentation comes loose, or we have to troubleshoot a maintenance code. Engineering and the crew work together to get the airplane ready for the afternoon mission. A night shift preps the jets for the next day. Everyone here works hard, and our current flight envelope reflects the success of their labor.”
Avionics Testing: Working Together
As the Raptors associated with flight sciences chip away at remaining test points to clear the flight envelope, the jets associated with avionics testing are getting all of the internal electronic systems to work together as a cohesive whole. “Like flight sciences, avionics testing has nothing left but the hard tests,” notes Lanni. “For example, some of these tests involve the datalink, low observables, radar, radar warning, and expendables. If just one system doesn’t work properly, we can’t sign off that test point and move on to the next one. I don’t think people understand the incredible complexity of some of these missions. All the systems involved and all the instrumentation have to work.”
As manager of F/A-22 avionics testing at the Raptor CTF, Terry Tomeny understands the complexity. Still, he can readily cite a list of recent successes. “We have tested most of the systems on the airplane,” he explains. “The radar is nearly fully tested and performing very well. The signature is better than expected. We have tested all of the modes of the electronic warfare system. We have started countermeasures testing. We have tested most of the modes of the communication and navigation system, which consists of radios, interrogator, tactical airborne navigation, and an instrument landing system. We have successfully fired four missiles for score—one AIM-9 Sidewinder and three AIM-120 AMRAAMs.”
Most of the avionics testing is being conducted on Raptors 05, 06, and 07. The aircraft are used for a combination of radar, electronic warfare, expendables, and missile shots. Raptor 07, which has full-up low-observable finishes, is used for LO testing as well. The avionics jets are occasionally used for flight sciences tests since electrical and heat loads associated with avionics have to be tested at extremes of the flight envelope. (Raptors 02 and 03 do not have a full complement of F/A-22 avionics.) The F/A-22 CTF plans to borrow Raptors from the DIOT&E for avionics tests requiring multiple LO-treated aircraft.
Avionics testing faces two major challenges: software stability and missile shots. “We are struggling with some stability problems,” Tomeny says. “The problems are similar to a home computer freezing when a program is launched. The computer has to be restarted. When our software works, it works very well. When the software related to a particular system freezes, we have to deal with restarts for that system. We’re getting the bugs out of the system so it starts correctly and works for the entire flight. These problems are encountered in every development program. We discover most of them in the lab and in the flying test bed. But other problems still crop up when we load software on the airplane. That, unfortunately, is the nature of software development.”
Avionics testing must also complete at least twelve more live missile shots to complete this phase of the F/A-22 program. “All are aggressive shots performed at high speeds, high-g loads, high angles of attack, or combinations of these more severe conditions,” Tomeny notes. “The program deleted many shots, relying instead on ground tests and modeling and simulation to reduce the risk of these edge-of-the-envelope missile launches.” This combination of ground and flight tests reduces the program schedule by lowering the total number of live launches to be executed during the flight test program.
Missile shots, especially AIM-120 shots, are time consuming and expensive. The CTF can’t plan a missile shot today and go out and perform it tomorrow. Each test requires one or more engineering runs to practice the mission profile. An F-16 acts as a target during these simulated runs. Data from these runs is thoroughly analyzed before the test team conducts the actual test. Range time has to be scheduled. The weather has to meet certain requirements. The team conducts a final dress rehearsal against the actual target before every shot. These rehearsals can be run during the same sortie as the actual test shot, but complex profiles may require a second flight. The average AIM-120 test, from engineering to the actual shot, can take a month.
The more complex missile tests involve firing multiple AMRAAMs against multiple targets. Two tests involve simultaneous AIM-120 launches from two Raptors. Another involves a ripple launch in which three missiles are fired in quick succession. The final test, called the graduation shot, involves firing four AIM-120s from one F/A-22 against four targets.
DIOT&E: Evaluating Effectiveness
As envelope expansion and avionics testing burn down developmental test points, another group at the F/A-22 CTF prepares to set fire to a few test points of its own. This collection of pilots and maintainers has been selected from the ranks of Air Combat Command. They form Detachment 6, and they are at Edwards to make a formal assessment of the F/A-22’s capabilities. The final report generated from DIOT&E testing goes to the Secretary of Defense and will form the basis for his decision to begin high-rate production for the F/A-22.
“The goal of this operational testing is to tell the warfighters how well the Raptor performs,” says Lt. Col. Art McGettrick, AFOTEC Det 6 deputy for operations. “We have to tell them what works well, what doesn’t work well, and what we don’t know about the airplane.”
DIOT&E pilots learn to fly the Raptor in a fourteen-flight syllabus preceded by twenty-nine hours of simulator time. The formal test plan begins after another dozen or so preparation flights. “We take tactics Air Combat Command has developed for the F/A-22 in the simulators and employ them in the actual aircraft,” McGettrick continues. “We’re getting an early look at how the airplane performs in an operational environment.”
The air-to-air portion of DIOT&E involves everything from flying one Raptor in basic air combat maneuvers against one adversary to employing multiple Raptors with B-2s and other assets in large-scale strike packages against sophisticated ground defenses.
“The Air Force Chief of Staff has asked us to work a Global Strike Force concept of operations into the test,” McGettrick explains. “The concept shapes how the United States will fight future wars. That is, we kick down the door with stealth assets. Once the door is down, we flow in legacy aircraft. We are going to practice that initial strike with the Raptors. We will take an F/A-22 with a B-2 and simulate going downtown in a hostile environment against a very high threat laydown of both air-to-air and surface-to-air threats. We have to prove that we can take down the threats, hit the ground targets, and come back out.
“DIOT&E consists of more than determining how fast the airplane can fly and how many bad guys it can shoot down,” McGettrick continues. “We are evaluating maintenance, reliability, deployability, and survivability. DIOT&E maintainers have been turning the wrenches and fixing the jets with the developmental test airplanes for some time. We have to use our pilots and maintainers exclusively once DIOT&E formally begins. We will use our own pilots, our own maintainers, and our jets out there on the ramp. By law, we can’t use contractor help during our evaluation unless the assistance is specifically approved by Air Combat Command. Everything in the evaluation must be operationally representative.”
Milestones: 3,000 Hours And Counting
No one broke out cupcakes, punch, and party hats when the F/A-22s at Edwards surpassed 3,000 flight hours in late February. The test team was too busy to celebrate. “We’ve made a huge amount of progress in the last year,” Lanni says, “but we rarely take the time to sit back and reflect on our success. We were having trouble getting jets airborne twelve months ago. We were dealing with engine problems and fuel leaks. Now the jets are flying great. We’ve done a supersonic AIM-120 launch and a supersonic AIM-9 launch. We completed the high angle-of-attack portion of the envelope expansion; we can fly from plus to minus sixty degrees angle of attack. The speed and altitude portion of the envelope were completed before that. We have completed almost all of the 800-knot flutter points. We have accomplished a lot.”
“We are turning a corner,” adds Burton. “We are getting the Raptor into the hands of operational pilots. They, more than anyone else, are going to sell the F/A-22. If they don’t like what they’re flying, the program will suffer. But every pilot who flies the Raptor talks about how great it is. Operational test pilots tend to be perfectionists by trade. The airplane impresses them. It is that good.”
Eric Hehs is the editor of Code One.
