The avionics suite of the F-35 Joint Strike Fighter (JSF) will probably be the most extensively tested of any aviation electronics, with much of the work performed before systems fly on the intended airframe. Indeed, risk reduction is a focal point of the $45 billion development program led by Lockheed Martin.
"We have a risk-reduction philosophy of ‘defense in depth.’ Defense against failure at each juncture, particularly out in the field," said Eric Branyan, Lockheed Martin vice president of F-35 mission systems. "We have to understand the issues from the past. On the F-35, we did a lot of analysis on root causes (of faults) on legacy programs. Our team has a lot of strength in that area."
In recent interviews, Branyan and Doug Pearson, a retired major general who serves as vice president of the F-35 Integrated Test Force for Lockheed Martin, discussed the risk-reduction strategy and progress of the F-35 development effort. Avionics also spoke with BAE Systems, a principal partner responsible for the JSF’s electronic warfare (EW) suite.
JSF is a huge challenge in avionics integration and processing centralization. Common modules are used where possible, such as in the aircraft’s integrated core processor (ICP), and a 2 gigabit per second Fiber Channel provides near instant communication among the ICP, sensors, communications, navigation and identification (CNI) system and displays. The electronically scanned radar array, controlled by the mission system software, can perform EW functions to supplement the aircraft’s EW system, which shares some of the com/nav/identification apertures.
Systems integration on the JSF will produce a leap forward in situational awareness. Radar, electro-optical, EW, CNI and off-board data will be fused and presented as an intuitive, tactical picture on the head-down display. The pilot will have a helmet-mounted display system (HMDS) that provides an infrared picture along with tactical, flight and safety symbology. The HMDS also will provide high-angle off-bore sight targeting.
"We had to find a way to take the risk out of these complex avionics systems before we install them on the airplane," said Pearson. "By the time we’re building and flying the F-35, we need to have a high degree of confidence that the systems are going to perform as designed. You can have many individual systems that perform fine alone, but when you try to integrate them on one platform — well that’s the challenge."
Although there are three variants of the F-35, the avionics are largely the same across all three, and the temptation to vary them has been resisted. "We’re going to have the same avionics on all three variants," Pearson said. "One could have argued that the STOVL (short takeoff/vertical landing) needs a different suite from CV (carrier variant) which needs a different suite from the CTOL (conventional takeoff and landing). If we had not been careful, we could have ended up with three different mission systems. To reduce risk we have one. It’s one of the most powerful common elements across all three variants and a big risk reducer."
Lockheed Martin wrote requirements for JSF that take into account issues that may have been problematic in previous programs. It doesn’t tend to be the mission-related elements that cause problems. It tends to be the less interesting activities such as how should the system start and how should it shut down? How should it report faults? Can you start it up gracefully, shut it down gracefully and capture faults?
Legacy systems have not always been so good at endurance. "One of the checks we had on them was, could they run under the most stressing scenarios for six hours? That was a significant lesson learned from legacy aircraft where we didn’t do that kind of check. That retires a lot of risk early on," Branyan said.
Lockheed Martin was responsible for avionics architecture development and functional design on the F-22 Raptor, which also faced development challenges. The CNI suite, for example, represented a significant leap in technology.
"We’d have only two to three hours of stability before we’d have a fault in the avionics system. That was about 10 years into the program," said Branyan. "Now we can run (the JSF’s) CNI for better than six hours without a fault. Two years before the first flight of a mission systems F-35 we’re better then they (the F-22 team) were several years into the flight-test program."
Extensive testing of component systems in an accurate simulated environment has been crucial. Lockheed Martin prescribed to suppliers extensive tests that must be accomplished before equipment is shipped for integration. The EW suite, for example had to perform in a simulated threat environment that was "very rigorous and very stressing," Branyan said.
Components are joined in the mission systems lab as an integrated set of avionics. That brings together EW, CNI, radar, sensors, multifunction displays, ICP and all related software. It’s an extensive simulation and stimulation environment.
"Before we put the first aircraft up (AA1), we performed Mission Alpha in the labs," said Branyan. "We had all of the avionics up, all of the power, electrical, and thermal systems that were representative of an F-35. We had a full iron aircraft on the ground. It was flown by a pilot in the mission profile. That way you’re executing the pilot/vehicle interface, all of the hardware/software interfaces, in a simulated airborne environment, just like flying that first mission. We know how it’s going to perform on the aircraft before it gets there."
BAE Systems is responsible for the EW package, including a passive situational awareness suite, direction finding and geolocation capability, a response and resource management system and multispectral countermeasures, said Dan Gobel, JSF vice president for BAE.
"Our philosophy when we started the design was to get our prototype hardware done fast early in the program and to fly it as often as we could," Gobel said, describing BAE’s approach. "As a result, about 30 months into the program, we built our first proof-of-design systems. They were 90 percent on performance but 100 percent on form, fit and functionality. Thirty months into the program we’d built four systems and we did quite a bit of integration on them in the integration labs as well as integrity testing. This allowed us to stress the system out from an overall lifetime perspective and to integrate our integrity results back into the next generation hardware."
In keeping with its "fly as early as possible" philosophy, BAE flew the system on a T-39 twinjet about 42 months into the program. The company has flown every component of the EW system in some way, shape or form. It was delivered to Lockheed Martin’s integration lab in April 2006, allowing it to interface with mission avionics.
At the same time, Gobel said, BAE started work on proof-of-manufacturing systems, which were completed at the end of 2006. The company built four systems that year, and is building eight this year.
"One of key lessons learned that we had going into this program was to have the proof-of-design systems built by operations from the start," Gobel said. "On other EW programs, we built our first systems with the engineers and we would design a system that was very difficult to transition into production. Our manufacturing has gone superbly. The number of changes required to any of the hardware has been minimal. We’re experiencing some very high-quality systems coming out of operations."
BAE also emphasized cost, another tenet of the EW development program. The contention was that 80 to 90 percent of the cost of the system is set by the critical design review, and if the company didn’t have cost worked out of the system by then, it would be very difficult to achieve cost targets.
"When we went through our critical design review we were around 20 percent below our cost targets," Gobel said. "Since then the cost has crept up a little bit, but we’re still within the target cost that was set for us at the beginning of the program. This was essentially lower than anything that’s out there right now from an EW perspective.
"Everything we’ve done on our proof of manufacturing units is coming in within the targets that we’ve set forth. We’re below our weight target by about 16 percent. We’re meeting all the performance parameters with margin. I’m confident we’re going to do what we said we’re going to do on time."
Even with extensive ground testing, there are things that only flying the kit can reveal. As part of the JSF risk reduction effort, BAE carried out the modification of a Boeing 737-300 known as the Co-operative Avionics Test Bed (CATB), or CATBird, which serves as the F-35’s avionics integration testbed. The aircraft completed its first flight Jan. 23 at Mojave, Calif.
With CATBird, Lockheed Martin can fly JSF systems to instrumented ranges and evaluate them in real-world warfighter conditions. The company can evaluate the functionality of a system and develop characteristics of its robustness and durability.
"The flying done on the testbed was very important" in the case of the EW suite, Gobel said. "As much as I’d like to tell you that the lab environment tells us all the problems, you really learn a lot every time you put it on an airplane. That’s why we wanted to put it on the T-39. We realized it wasn’t a CATB, it wasn’t putting it on an F-35, but it did give us integration experience. When we do go to the CATB, there’s less likelihood that we’ll see unknowns that usually pop up with integration."
Getting the EW system to function with the rest of the mission avionics is a vital step. "Tying the EW in with the rest of the mission systems is the biggest unknown, and that’s the beauty of what CATB brings to the system," Gobel said.
"It allows us to put all the systems on an integrated testbed. It allows us to stress-out how they all operate together and in unison. I think we’ve done an excellent job of wringing out the EW system by itself; but how does it play with others?"
By the end of the year Lockheed Martin will have a fully representative F-35 pole model with all the sensor apertures and the right wiring line length in place. That will allow the company to evaluate systems in an open-air environment with the random emissions that are in the area.
"We’re on a joint Reserve base, so we’ve got military traffic 25 miles away, we have Dallas/Fort Worth Airport with a lot of commercial traffic, then there are cell phones, and other RF emissions. We’ll be able to evaluate the system under those conditions," Branyan said.
"Finally, we’ll put [systems] on the F-35," said Branyan. "In late 2008, early 2009 we’ll have the first mission systems F-35 flying and by then we’ll have significant amounts of ground testing and air testing. Right now we’re in the labs with all the sensors two years before the first flight of a mission F-35. We’ll have a known pedigree before they have to go airborne. The philosophy is ‘know before we fly.’" An
Since its initiation, the F-35 Joint Strike Fighter (JSF) program has been an international endeavor. The United States and eight international partners — the United Kingdom, Italy, the Netherlands, Turkey, Canada, Denmark, Norway and Australia — have joined the program.
Lockheed Martin is the F-35 prime contractor, with Northrop Grumman and BAE Systems as principal partners. Pratt & Whitney and the GE/Rolls-Royce Fighter Engine Team are working with the JSF program to design and build interchangeable powerplants for the F-35. The first flight of the JSF "AA-1" aircraft, powered by a Pratt & Whitney F135 turbofan, took place Dec. 15 last year in Fort Worth, Texas.
"Lockheed Martin has an extensive background in building aircraft such as the F-16, F-117 and now the F-35," said Eric Branyan, the company’s vice president of F-35 mission systems. "But we also have Northrop Grumman, which was strong on the B-2, a low observable aircraft with a significant systems integration challenge, and BAE Systems which is coming off a 4th Gen fighter development program with the Eurofighter Typhoon."
Variants of the JSF will be flown by the U.S. Navy, Air Force and Marine Corps and the U.K. Royal Navy and Royal Air Force. Other international customers are likely to follow with the industrial partner nations being strong candidates.
A Helmet Mounted Display System (HMDS) manufactured by Vision Systems International (VSI), of San Jose, Calif., the joint venture of Rockwell Collins and EFW, an Elbit Systems subsidiary, flew for the first time on the F-35, VSI said in April.
The HMDS has been in development for five years and recently completed all required safety-of-flight tests, allowing in-flight seat ejections up to 450 knots equivalent air speed (KEAS). It has demonstrated structural integrity to 600 KEAS as a critical risk mitigation step toward full-flight certification, VSI said.
Principal suppliers include Elbit Systems, which provides the Display Management Computer for the helmet containing advanced graphic processing and head tracking; Rockwell Collins, which builds the helmet mounted display, including advanced optical design; and Helmet Integrated Systems Ltd., of the United Kingdom, providing the helmet shell and pilot personal fitting system.