F-22 Raptor Design Evolution, Part 2

By Eric Hehs Posted 16 October 1998

Secretary Aldridge’s Halloween announcement meant that Lockheed and Northrop had each won $691 million contracts to proceed to the demonstration/ validation phase of the Advanced Tactical Fighter program. The newly formed teams now led by the two winning companies would build two flying prototypes each one with Pratt & Whitney engines and the other with General Electric engines. Each team would also build ground-based avionics prototypes and a flying laboratory to demonstrate the avionics. The dem/val phase would determine which team would enter the next phase of the program and, ultimately, which team would build production versions of the ATF.

After the dem/val award announcement, the Advanced Tactical Fighter program returned to its stealthy status. Very little information about the project appeared in public until the prototypes were unveiled almost four years later in August 1990. Though concealed in quiet secrecy, work during the intervening four years was anything but quiet for those involved, as the ATF competition intensified.

Show and Tell

The dem/val award was announced on a Friday afternoon. The next Monday morning, representatives from Lockheed, Boeing, and General Dynamics met for the first time as a team at Lockheed facilities in Burbank, California. About 100 engineers and managers crowded into a large high-security conference room in Building 360, where representatives from each of the three companies were allotted two hours to present their proposed ATF concept. Lockheed went first. Boeing presented after lunch and was followed by General Dynamics late in the afternoon.

The all-day show-and-tell was unprecedented for everyone in attendance. Never before had they shared everything they knew about a program with an audience considered to be the competition only a week before. Though the three companies had a teaming agreement, they had not exchanged information. Doing so was not possible given the security clearances involved and the short time between the agreement signing and the contract award. Everyone saw everything at once.

"That Monday was the most fascinating day I ever spent in the aircraft business," remembers Randy Kent, the ATF program director for General Dynamics from 1985 to 1991. "Typically, we never know what other teams have done for months, if ever, after a contract is awarded. For ATF, however, each company made the same presentation at Burbank it made to the Air Force. We all put our models, layouts, and drawings on the table. Everyone received detailed views of what everyone else had done to that point in the program. The experience was amazing."

"The diversity of the proposals was surprising," adds Gerry Murff, the chief engineer for General Dynamics. "The depth and capabilities were impressive. Lockheed’s strength with its signature capability became apparent. Lockheed engineers knew how to design aircraft using a fixed set of angles, and they understood all of the supporting detail design technology. Their operations analysis showed why stealth was relevant. These factors were decisive to their win. They had an appreciation for the handling qualities required for the ATF, which led to their four-tail design. They also had a plan a very good plan."

The importance of that plan was reinforced in another, equally astonishing meeting that happened the day after the initial team meeting when Rick Abell, the Air Force’s lead technical evaluator, briefed the three companies on how their dem/val proposals were evaluated. Abell used the same evaluation charts the F-22 system program office had used when selecting the two winners. He went through about seventy strengths and about thirty weaknesses for each of the three proposals.

"This was the only time in my career that I saw an official government evaluation of what we and two of our strongest competitors had submitted for a competition," remembers Sherm Mullin, the program director and team leader for Lockheed. "And the evaluation came from an authoritative person, not through rumor. The system engineering volume of the proposals weighed very heavily in the selection. Advocating a point design, a single answer, hurt most of the proposals. Air Force officials made it clear in late 1986 that they wanted to see trade studies. They wanted every requirement challenged. They entertained alternate approaches to almost anything."

Lockheed’s plan was in fact a key to its win. "Everybody met the requirements in our evaluation of the proposals for the dem/val phase," explains Abell, who became the Air Force’s chief engineer for the ATF program. "The biggest single important point in our evaluation was risk reduction for the production configuration, what we called the preferred system concept. We weren’t looking at what the prototype would do or what the avionics would do or how they would perform. We wanted a program that was laid out to reduce the risk and develop the technology sufficiently enough so that when we started the next phase it would be a lower risk program. We didn’t spend a lot of time looking at what the proposed prototype airplanes would do in terms of performance."

Defining the Team

Soon after the team met in California, workers split into two basic groups. One group addressed interfaces, costs, and teaming issues for the prototype and, later in the dem/val phase, for the preferred system concept. After splitting the work, the companies went into a difficult and complex process of validating the dollar amounts that each team member associated with its portion of the work. The calculations were complicated by many factors, including differing labor rates and unique estimating processes.

The other group focused on those seven categories of task assignments as apportioned in the teaming agreement, which established the basic relationship among the three contractors. The fifty-page document spelled out the roles and responsibilities of the team leader; the division and assignment of work among the team members; the preparation of future proposals; the handling of proprietary information and patents; the procedures for resolving disputes, cost sharing, and cost reporting; coordination of publicity; and termination procedures for the agreement itself.

Each company had provided its own list of task assignments should it win the award for the dem/val phase (and, therefore, become the team lead). These assignments fell into six categories: weapon system integration, airframe design/systems, avionics, system test, manufacturing, and supportability. A seventh category, systems engineering, was added after the dem/val contract was awarded.

As the team leader, Lockheed’s plan for dividing the work carried the most weight. Accordingly, Lockheed claimed the forward fuselage and nose landing gear, all the specially treated edges and low-observable antenna integration, cockpit, controls and displays, core processing for the avionic systems, final assembly and checkout of the airplane, and leadership of flight test.

Boeing got the aft fuselage and the wings, fire protection system, life support system, auxiliary power system, arresting gear, radar, infrared search and track system, mission software, flying avionics laboratory, and the biggest share and leadership of the training system.

General Dynamics got the mid-fuselage and all of the subsystems in it, main landing gear, horizontal and vertical tails, flight controls, communication-navigation-identification system, electronic warfare system, inertial reference system, stores management system, the infrared portion of low observables, and the biggest share and leadership of the support system. This basic division of work, with some minor revisions, exists to this day on the F-22 program.

The teaming agreement also established the proposed design from the winning party as the starting point for the dem/val phase. The agreement carried the following stipulation: "Such a proposal may be revised to incorporate aspects of the other parties’ proposals for the dem/val phase as such incorporation may be requested by the Air Force or agreed by the parties and concurred in by the Air Force." In simple terms, the team was encouraged to draw from the strengths of all three individual companies to come up with a winning ATF design.

"After the contract was awarded, it took us two years to figure out the design," explains Dick Hardy, the ATF program director for Boeing. "We decided that we shouldn’t build a demonstrator until we knew what the production configuration looked like. The Northrop team ran off and made a demonstrator and then tried to figure out the production configuration. When it came time for the downselect for the next program phase, they had to change the location of their weapon bays and a whole bunch of other things. We wanted the data we derived from building and testing the demonstrator to apply to the production version. That relationship was the whole purpose of flying the demonstrators—to produce data useful to the final design."

When the team first met in Burbank, the winning Lockheed design was represented by an internal arrangement and external line drawings labeled Configuration 090P and a detailed three-view drawing called Configuration 090P/092. Configuration 090P designated the Lockheed ATF proposal for the dem/val phase. Configuration 090P/092 contained changes that occurred during the months the proposals were being evaluated by the Air Force. The differences included a revised inlet and small changes in wing and tail sweep angles. The vertical tails were also moved farther outboard and the chine was narrowed slightly.

The transformation of 090P into Configuration 1132, what is better known as the F-22 prototype or YF-22, involved some of the most concentrated work in the history of aircraft design. The transformation got off to a strained start as the team members sized up their relative strengths and weaknesses and argued for and against a variety of design features. "The period was intense," says Paul Martin, Lockheed’s deputy chief engineer for technology and design during the period. "We spent a lot of time convincing each other what great he-men engineers we all were."

The posturing was fed by the sheer amount of material available to scrutinize as all three companies placed their work on the table. Every one of the designs proposed by the three teaming companies had its share of problems and advantages. As the official starting point, however, Lockheed’s design was open to the most scrutiny and criticism.

"After studying the design of Configuration 090P," recalls Murff, "we soon realized that the airplane would not fly. Its huge forward glove made the design uncontrollable in the pitch axis. The internal arrangement would not go together. The large rotary weapon bay pushed engines and inlets outward, which produced an excessive amount of wave drag. And the rear-retracting landing gear design was not suited for a fighter."

"After the General Dynamics team had been out in Burbank for about two weeks, they sent home a set of drawings of the winning design," remembers Kevin Renshaw, the configuration design lead for General Dynamics. "The first task for the engineers in Fort Worth was to put the aircraft drawings into the computer to provide a base for analysis. The immature status of the Lockheed design became immediately apparent. The plan view, profile view, and sections on the drawings had only a rough relationship to each other. After analyzing the design, it became obvious that the aerodynamic and weights data in the proposal had been ‘goal’ levels with little actual relationship to the drawings. The design turned out to be a series of unconnected sections drawn around individual portions of the aircraft’s subsystems. Lockheed had a concept for an aircraft, not a point design. However, that approach won the competition."

The 090P design may very well have been less defined than the design submittals from Boeing and General Dynamics. But in Lockheed’s defense, the company had gotten off to a relatively late start on its design because it had changed its basic approach just after the last phase of the ATF program. That change catapulted Lockheed from last to first place in the evaluation of the dem/val proposals. Conversely, Boeing and General Dynamics had placed too much value on point designs when the Air Force evaluators were more interested in a solid plan for reducing risk for the dem/val phase.

"General Dynamics historically has focused on the configuration," says Kent. "We went into enormous detail on the structural design, the aerodynamics, and the wind tunnel testing to present a creditable story that our design would do what we said it would do. We understood that the Air Force evaluators were as interested in detailed dem/val planning as they were in the configuration. In our view, however, we believed that valid trade studies could be made only from a solid configuration starting point. It turned out that we probably misread the Air Force’s emphasis. They were more interested in the details of the dem/val planning than in the validity of the baseline configuration for the trade studies."

"Configuration 090P was not a point design by plan," explains Mullin, "not by accident. Our proposal supported what the customer wanted to do and what we needed to do to win the competition. If the customer wants two years of good system engineering and not a lot of point design, then it’s not a bad idea to propose two years of system engineering and not a point design.

"Our team had a big problem at the beginning with system engineering," Mullin continues. "A lot of the engineers wanted to design an airplane to the stated requirements instead of performing trade studies and allowing Air Force officials to adjust the requirements where they felt the impact was worth the change. One of the main themes of 1987 was to get everyone adjusted to the fact that none of the requirements should be viewed as final. Trade studies and risk-reduction were more important."

"Everyone was a little defensive of his design at first," recalls Hardy. "In retrospect, the team did a great job coming together and reaching an agreement. Mullin did a great job. He kept everyone focused on the design and on the program. He kept arguments from getting personal, and he always focused on what was best for the program." Mullin led the ATF program for the Lockheed-Boeing-General Dynamics team through the dem/val phase. He had the unenviable task of creating a cohesive group from three divergent corporate cultures that had each spent years evolving its own unique ATF design.

"I think I was reasonably fair with all," Mullin explains. "On an average week, I had just as many Lockheed engineers upset with me as I did Boeing and General Dynamics engineers. Everyone believed that his own way of approaching a design was practically biblical. I had to convince people from Boeing and General Dynamics that I was playing fair and square and that I did not have a Lockheed bias. That was not easy. However, I developed a very productive relationship with Hardy, Kent, and with many others. We became a cohesive team, and that was a key factor in winning the competition. We did not change each other’s organizational culture very much. We simply learned to live with each other and work together. Al Pruden, as the system engineering team director, had the tough job of getting this done right."

"The three company program managers Mullin, Hardy, and Kent formed a complementary set," observes Bill Moran, who attended the initial meetings in 1986 and still works on the program. "Mullin is excitable, ebullient, and fascinated with technology. Hardy is fiscally sensitive, hardheaded, and laconic with a droll sense of humor. He was the perfect counter to Mullin’s excitability. Kent is reserved, intellectual, and dedicated to producing a real airplane that excels in flight test and in eventual operations. He kept the other two pointed at the ultimate objective of the program: to produce an operational weapon system. Watching these leaders interact was always exciting and instructive. Seeing how well they got along, even when they disagreed, was good for the whole team. As with any other group of several thousand people, some pairings worked and some didn’t. But upper management’s lead established the right tone for success. I haven’t been on any other team, but I’ve heard stories about other teams that make it clear that a team won’t work unless it has strong examples at the top.

"Jim Fain, who commanded the ATF system program office during dem/val, also deserves a big share of the credit for making this program and this team work," Moran adds. "He turned out to be even smarter than most of us originally perceived. And he was a fearless innovator. When he joined the program as a colonel at the beginning of dem/val, he announced that he was never going to make general so he was going to run this program the way he thought it should be run. Fain eventually was promoted to brigadier general in the middle of the dem/val phase and retired as a lieutenant general. He personally forced the team to work on both the Air Force side and the contractor side. He used competition between the two teams rather than program direction to get what he wanted. With the help of Rick Abell and Col. Tom Bucher, he introduced many of the acquisition reforms that were made across the Department of Defense several years later."

The Design Process

Mullin, Hardy, and Kent became the ultimate arbitrators in a design process that required new levels of tact, efficiency, and arbitration for the Lockheed-Boeing-General Dynamics team.

"The working troops would communicate disagreements through their company chief engineer, who worked for one of the three program directors," explains Kent. "If they could not come to a resolution, they had to work first through their respective chief engineers. If they still couldn’t decide, the issue was kicked up to the Mullin-Hardy-Kent level. No matter how good an engineer was, he had to learn how to sit down, let the other person speak, treat him with a certain measure of respect, and not ridicule him. We removed people who could not get along. Some of the best technical contributors had the hardest time living with their counterparts. We all came to the table with traditional ways of doing things and with different backgrounds from different airplanes. I began to sense that we were becoming a more cohesive team when the aerodynamicists from all three companies began voting against the structural engineers from all three companies."

The design process was influenced by regular contact with USAF representatives and by more formal USAF reviews. "The Air Force controlled the evolution of the ATF with a draft specification that spelled out the initial requirements for the aircraft," Abell explains. "We adjusted the system specifications once a year during the dem/val program as studies came in and alternatives were evaluated. In our system requirements reviews, we took the operations analyses and the results of tests and other information and determined if we were asking for too much or too little. We adjusted the specification accordingly. If members of one team had trouble making a requirement and we didn’t change it, they soon appreciated that maybe the other team was meeting the requirement. When a requirement changed, both teams knew it was hard for everyone to meet."

For example, the Air Force initially required that eight missiles be carried internally in the main weapon bay. "One team thought it could be done," says Abell, "but it didn’t know for sure. Consequently, we didn’t change the requirement to six missiles until both teams decided that eight could not be carried effectively. In another example, short field requirements were changed to eliminate thrust reversers because the benefit was not worth the price we had to pay for the capability."

"The evolution of the production configuration involved an annual thrash on system requirements with the ATF System Program Office and with Tactical Air Command," adds Moran. "Each year of design work produced refined weight, cost, performance, and effectiveness estimates. These estimates led to changes in the requirements, which required new design work, which led to new changes in requirements, and so on."

Air Force involvement in the design process during dem/val was, therefore, somewhat indirect. "Our biggest influence on the program was allowing the companies to explore and develop rationale and reasons for specific systems," says Abell. "Our involvement in the technical aspects was more to understand the design concepts and the approaches being taken. We were always asking, ‘Why are you doing that?’ Not so much suggesting, ‘Why don’t you do this?’ We were more interested in the processes and the reasoning behind the designs than in any particular detail. If anyone on my team said ‘Do this,’ I shot him. We could not give direction."

Design Challenges

The basic challenge of the ATF design was to pack stealth, supercruise, highly integrated avionics, and agility into an airplane with an operating range that bettered the F-15, the aircraft it was to replace. The F-22 also had to have twice the reliability and half the support requirements of the F-15.

"One problem we typically face when trying to stuff everything inside an airplane is that everything wants to be at the center of gravity," Hardy explains. "The weapons want to be at the center of gravity so that when they drop, the airplane doesn’t change its stability modes. The main landing gear wants to be right behind the center of gravity so the airplane doesn’t fall on its tail and so it can rotate fairly easily for takeoffs. The fuel volume wants to be at the center of gravity, so the center of gravity doesn’t shift as the fuel tanks empty. Having the center of gravity move as fuel burns reduces stability and control. We also had to hide the engine face for stealth reasons. So, these huge ducts had to run right through the middle of real estate that we wanted to use for everything else. The design complexities result in specialized groups of engineers arguing for space in the airplane. That was the basic situation from 1986 through 1988."

As the design progressed, weight became the most difficult design challenge. "We were never able to design an airplane with a 50,000-pound takeoff gross weight that came close to meeting the Air Force requirements," Mullin admits. "After two years of hard work, we convinced the Air Force that it was not possible. The weight requirement was changed.

"Getting the right inlet design was very difficult as well," Mullin continues. "The aerodynamic, structural, low observable, and producibility requirements conflicted with each other to a significant degree. We took about three years and performed a lot of analyses and wind tunnel testing before we achieved a fully acceptable inlet design. In the end, the performance was excellent."

The first major change in the Lockheed-Boeing-General Dynamics configuration came in February 1987, when a more space-efficient flat weapon bay was substituted for the rotary weapon bay found on 090P. The change marks the transition to Configuration 095. The deletion of the rotary weapon bay allowed the engines to be moved closer together, which reduced wave drag.

The large hooded strake was narrowed to reduce the planform area ahead of the airplane’s center of gravity and to push the vortex generated by the strake farther back. These changes were essential for controlled flight at higher angles of attack. Engineers also worked to repackage the forebody to reduce cross-sectional area to improve high alpha capability and to reduce wave drag and weight. The engine inlets were also redesigned. Configuration 095, however, retained the trapezoidal wing and tail design found on 090P.

At about this time, the configuration evolution was split into two families. The first family, denoted with a 1000 prefix, represented the prototype design (called the prototype air vehicle). The second family, with a 500 prefix, represented the preferred system concept—the design that would be carried into the proposal and the next phase of the program. Configuration 095 thus became 1095 (prototype) and 595 (production).

Minor iterations within a configuration were represented with dashed numbers. In July 1987, for example, the preferred system concept was Configuration 595-6. As the dem/val phase progressed, these two design families grew further removed. The prototype design was frozen so the design could be built and flight-tested during dem/val. The preferred system concept evolved toward a production design for the next program phase (the full-scale development phase, a term later changed to engineering and manufacturing development phase).

The first requirements review with the Air Force came in May 1987 and lasted about a week. "The first review was a communication session to make sure that we were on the right track," Mullin recalls. "I think we all came out of the first review feeling good about our design. However, at that point, optimism still reigned supreme. No one was ready to admit that our ATF was not going to be a 50,000-pound airplane. We had not done enough of a detailed design and weight analysis to get a good set of weights."

The Great Configuration Chase

The team got those weights in late June 1987, just before a three-company executive meeting in Fort Worth on 10 July. "We were almost 9,000 pounds off on gross weight and $5 million off on unit cost," recalls Kent, "but we were still making all the maneuver parameters. We had a pretty good airplane except for the weight and cost problems. We wanted to relax the fuel load at max g requirement. We wanted to let gross weight be a fall-out from meeting the other requirements, delete a couple of the missions, and work on cost by simplifying the avionics requirements."

When those compromises were not forthcoming, the team decided to step back and open up the design to more fundamental changes. "After a bloody debate, we agreed to trash the current design and start over," says Mullin. "Over that weekend, we brought in a new director of design engineering, Dick Cantrell, flew in people, and started a ninety-day fire drill. Work started on Monday 13 July. That date marks one of the most creative periods of conceptual design for any fighter aircraft. We looked at different inlets, different wings, and different tail combinations. One configuration had two big butterfly tails and looked somewhat like the F-117, though people did not know that since the F-117 was still highly classified. The configuration search was wide open, but the biggest single change that resulted from it was to go with diamond-shaped wings."

The concentrated configuration search began with a slew of possible designs. The search complicates the numbering scheme considerably, as diamond wings, twin tails (two tails instead of four), various inlet shapes, and various forebody shapes were all considered and reconsidered simultaneously in the summer of 1987.

Configuration 595-7, with trapezoidal wings and four tails, was the starting point for these studies. Configuration 608A, labeled the baseline equivalent, represented a similar shape with six instead of eight missiles in the main weapon bay (all the design alternatives assumed this loading).

Configuration 608 had a trapezoidal wing and twin tails. Configuration 607-0 introduced the diamond-shaped wing similar to the General Dynamics proposed ATF, but with four tails instead of one. Configuration 607-11A had a diamond wing and twin tails. Configuration 611A had a diamond wing, twin tails, and the large chine reminiscent of 090P. Configuration 609A looked a lot like the Boeing proposed ATF with its trapezoidal wing, twin tails, and single chin inlet.

Configuration 610A was a Boeing/Lockheed hybrid with trapezoidal wings, twin tails, and twin side inlets.
Computer-aided design proved critical to completing these configuration studies. The ATF effort was one of the first fighters to be designed from the beginning with computers. At first, the team used CADAM, a relatively fast two-dimensional drafting package.

"CADAM was better suited to designing detailed parts, not iterating design concepts," explains John Hoffschwelle, a configuration designer for General Dynamics who spent months in Burbank working the ATF design. "We quickly realized that we needed ACAD and our Perq computers to speed up the design process. We had them flown out from Fort Worth and approved by Lockheed security, which was no small feat. About six of us Fort Worth engineers went to work in a small office, or big closet. ACAD allowed us to look at more ideas and at each idea in greater detail."

ACAD, a three-dimensional software package developed by General Dynamics, was used for conceptual and preliminary design. (A much improved version is in use today.) The team also used a process that linked ACAD with CATIA, a high-fidelity three-dimensional software package developed by Dassault. CATIA can output data directly to numerically controlled machining equipment. The ATF designers would do a first-generation lines database on ACAD so they could be iterated quickly. These files would then be translated into a master CATIA database.

"We also had datalinks so that design data and other data could be moved digitally among all three sites," Mullin adds. "This network, set up early in the program in 1987, was created in the days of mainframes, not workstations. The datalinks were secure and encrypted. An engineer in Fort Worth could share design-related data at Burbank or Seattle." By mid-August 1987, the configuration choices had been narrowed to five, represented by Configurations 595-7 (baseline with trapezoidal wings, four tails, and eight missiles); 612 (baseline equivalent with six missiles); 613 (trapezoidal wings and twin tails); 614 (diamond wings with four tails); and 615 (diamond wings, twin tails, and twin side inlets). By late August, the diamond-wing four-tail Configuration 614 won out.

"The fundamental reason for going to a diamond wing was that it provided the lightest configuration and gave us the best structural efficiency and all the control power we needed for maneuvering," Mullin explains. "The biggest consideration was its light weight. Weight drove the decision."

"A diamond wing has more square feet of surface area, but is more structurally efficient," adds Renshaw. "The longer root chord provides a more distributed load path through the fuselage. Multiple bulkheads carry the bending loads. The design provides more opportunity to space the bulkheads around the internal equipment. It also provides more fuel volume."

"The structural engineers wanted a diamond wing because it provides a larger root chord, which carries bending moments better," Hardy notes. "The aerodynamicists wanted a trapezoidal wing because it provides more aspect ratio, which is good for aerodynamics. Dick Heppe, the president of Lockheed California Company, made the final decision, and he was right. The aerodynamics were not all that different, but the structure and weights were significantly better. So we went to a diamond shape. The big root chord, though, moved the tails back. Eventually we even had to notch the wing for the front of the tails. If the tails moved farther back, they would fall off the airplane."

The Tail Chase

Once the wings were set with Configuration 614, subsequent configurations dealt with the tail arrangement. "We spent a lot of wind tunnel time looking at the tails," recalls Lou Bangert, the chief engineer for engine integration from Lockheed. "From late 1987 to early 1988, we were engaged in what we called ‘the great tail chase.’ We knew we would have four tails, but where they would go was a big deal. A small change in location often made a huge difference. We had to look at performance effects, stealth effects, stability and control, and drag at the same time. The tail arrangement and aft end design were important design considerations for all of these effects."

Wind tunnel results showed an ultra-sensitive relationship between the placement of the vertical tails and the design of the forward fuselage. The interactions could not be predicted accurately by analysis or by computational fluid dynamics. The airflow over the forebody at certain angles of attack affects the control power exerted by the twin rudders on the vertical tails. Getting the airflow right was critical.

The cant and sweep angles of the vertical tails could not be altered too much because such changes increased radar signature. In finding a suitable arrangement, the control system designers were constrained by the radar signature requirements to moving the tail locations laterally or longitudinally and to shrinking or enlarging them while holding the shape essentially constant. By the end of the dem/val phase, the team had accumulated around 20,000 hours in the wind tunnel. A lot of this time was devoted to tail placement studies.

Configuration 614-6, with trapezoidal horizontal and vertical tails, represented the starting point for the tail chase in December 1987. After many intervening configurations, the vertical tails had evolved to a diamond shape by February 1988 in Configuration 630. The wing area was also reduced in Configuration 630. The size of each vertical tail increased by seven square feet in Configuration 631. The rudder size was also increased slightly and the cant angle of the verticals went from thirty degrees to twenty-eight degrees. The prototype design was frozen at this shape (Configuration 1131) in March 1988.

The prototype design was unfrozen at the last minute in May 1988 after the Air Force eliminated the requirement for thrust reversing for short-field operations. The change allowed the team to alter the external mold lines on the aft fuselage and nozzles in the area around the thrust reversers. The trimmed aft end reduced drag significantly. "We never had an airplane with the right supersonic drag until May," Mullin explains. "We scared the Air Force when we unfroze the prototype design at that late date. The supersonic drag was still too high to supercruise. A team led by Ed Glasgow, our chief flight sciences engineer, redesigned the forebody and aftbody. Suddenly we had acceptable supersonic drag levels that ensured that the airplane would supercruise."

The final design freeze for the prototype occurred at Configuration 1132 in May 1988. Besides the reshaped forebody and trimmed aft section, the horizontal tails also changed from trapezoidal to diamond in the transition from Configuration 1131 to 1132.

The Prototypes

The first drawings were formally released for YF-22 production on 1 April 1988. Construction of the first of two YF-22s began in Fort Worth with the rough-cutting of the titanium 631 bulkhead of the mid-fuselage on 27 April. The mid-fuselage was built in the main factory in Fort Worth in a secure area at the north end of the final assembly line for the F-16. Production of the forward fuselage began soon after with the nosewheel forward bulkhead at Lockheed facilities in Burbank. The aft section and wings took shape during the same timeframe at Boeing facilities in Seattle, beginning with the flaperon torque arm assembly. Fabricating the prototypes consumed the next two years.

The various sections of the prototypes came together in Palmdale, California. The first mid-fuselage was shipped to the West Coast in a Lockheed C-5A Galaxy on 12 January 1990. Shortly after taking off from Carswell AFB, the big cargo plane was struck by lightning. Undeterred, the mid-fuselage was readied to mate with the forward fuselage later that night. The forward fuselage was brought up from Burbank on a truck a few days earlier. Boeing shipped the aft fuselage down from Seattle on a truck the same day the mid-fuselage arrived.

"The mating of all these major structural components was rapid and as smooth as silk," Mullin recalls. "The use of CADAM software for the detailed design of both the airplane and the assembly tools at all three locations really paid off."

The YF-22 was unveiled to the public on 29 August 1990 at Skunk Works facilities in Palmdale. The prototype took to the air for the first time on 29 September from Palmdale when Lockheed test pilot Dave Furguson flew it to nearby Edwards AFB. The second prototype flew for the first time on 30 October. The flight test program that followed was one of the most concentrated efforts in aviation history.

The flight rate ramped up from thirteen in October, to twenty-two in November, to thirty-eight in December. The team accumulated over ninety flight hours in seventy-four flights as the YF-22s expanded flight envelopes beyond Mach 2, seven g’s, and sixty degrees angle of attack. The flight test program included the live-firing of both AIM-9M Sidewinder and AIM-120 AMRAAM missiles.

Supersonic flight without afterburners, or supercruise, was demonstrated with both the Pratt & Whitney engines and the General Electric engines. "After we finally made our first flight, our flight rate was extremely high," Kent says. "It had to be since we had less than three months to fly. In the back of our minds was the YF-16 and YF-17 contest for the Air Force’s lightweight fighter program. General Dynamics had a much higher flight rate on the YF-16 than Northrop had on its YF-17. We wanted to repeat that performance for the YF-22 flight test program, and we did. We had a very experienced set of flight test personnel from Lockheed, Boeing, and General Dynamics. We had a lot of experienced field service personnel as well. Lockheed’s Dick Abrams did an outstanding job as head of our flight test team at Edwards."

The flight test program required that the teams demonstrate performance and handling qualities representative of the ATF requirements, including supercruise. Thrust vectoring, while not a requirement, was fully demonstrated through post-stall maneuvering. Low-observable requirements were evaluated on radar ranges with full-scale pole models.

"The Northrop-McDonnell Douglas team got off the ground a month ahead of us and executed a perfectly normal and successful short flight test program," Moran says. "We showed up late and crammed more into three months of flight testing than had ever been imagined. And we pulled it off without a hitch."
Production Design Evolves
The production design continued to evolve after the prototype design was frozen. The dem/val evolution post-Configuration 1132 accounts for most of the external differences between the YF-22 and the F-22. By July 1988, Configuration 632 had evolved into Configuration 634, which had a relocated cockpit, a shortened inlet, and an improved structural arrangement. More importantly, it had a $9 million cap on flyaway cost for avionics. The cost cap on avionics had a profound effect on the program.

"The avionic requirements were growing and growing," Mullin explains. "Senior USAF officials met in January 1989 and decided on the avionics cap. At the time, we had paper designs of avionic systems that were over $16 million per ship. The cap sent a shockwave through the program, as much through the Air Force as through the two teams. The infrared search and track system bit the dust and so did a lot of other systems, including the side-looking radar apertures. That limit is probably one of the best things that happened to the program. Avionic growth had gotten out of control before that point. The Air Force solved a lot of problems by putting one simple number on the table."

By the fall of 1989, Configuration 634 had given way to Configuration 637, which had different forebody shaping, a new weapon bay design, and a new systems arrangement. Configuration 638 arrived in early 1990. The leading edge wing sweep was changed from forty-eight degrees to forty-two degrees. The inlet moved farther aft and the cockpit farther forward. The vertical tails became smaller. The wingtip trailing edge was clipped. The overall length of the airplane was shortened from sixty-four to sixty-two feet. A variation of Configuration 638 was the final design submitted in the proposal for the next phase of the program. The proposal was delivered to the Air Force at Wright-Patterson AFB, Ohio, on the last day of 1990.

The Win and After

Secretary of the Air Force Donald Rice announced the winner of the ATF program on 23 April 1991. Rice noted that the Lockheed and Pratt & Whitney designs "clearly offered better capability at lower cost, thereby providing the Air Force with a true best value." The original full-scale development contract called for nine single-seat, two two-seat, and two ground test F-22 aircraft. The subsequent production phase originally included the production of 750 fighters with first delivery scheduled for 2005. Late in dem/val, the total was reduced to 648 aircraft. Subsequent post-Cold War funding and threat analyses have now reduced the planned buy to 339 aircraft. However, the potential for an air-to-ground version of the F-22 to eventually replace the F-15E is favored by the Air Force. Sales to US allies is another long-term possibility.

Since the Air Force did not provide a detailed evaluation of the proposals to the contractors after the selection, the reasoning behind the Lockheed-Boeing-General Dynamics win is open to some interpretation. Sherm Mullin explains it this way: "Our goal was to beat the Northrop-McDonnell Douglas team in every aspect of the competition, not just to focus on some selected areas. We used the team investment, which had grown to $675 million, to implement an across-the-board strategy. We had a balanced design for our production configuration. Our prototype performance was almost exactly as we predicted to the Air Force. Our full-scale pole models showed that radar signature objectives were achievable with low risk. Our approach to integrated avionics was demonstrated in our ground-based and flying laboratories. We prototyped an enormous amount of avionics software in realtime, and it worked well. Reliability, maintainability, and supportability features were designed into the F-22 with an intense focus on self-sufficient operations. And we rigorously complied with every detail in the Air Force’s request for proposals for the engineering and manufacturing development phase."

The F-22 program begins the transition from development to production this fall with the award of long-lead contracts for the first lots of production aircraft. Though the design currently stands at Configuration 645, the external lines have changed very little from Configuration 638, the design proposed for the engineering and manufacturing development phase in December 1990.

Eric Hehs is the editor of Code One.
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