JSF PROGRAM // X-32 & X-35 Back in 2000, the most THE valuable fi ghter fl y-offs in modern times took place between the Boeing X-32 and Lockheed X-35, as Gerard MATCH Keijsper explains T DOES NOT seem so long ago, The fi nancial situation was tight successful supersonic but it is almost 30 years since because of the peace dividend – the STOVL fi ghter. For this reason, the Defense Advanced Research Berlin Wall had fallen just a couple of DARPA assigned an experimental ’X’ Projects Agency (DARPA) issued years earlier – and no one wanted to designation for the prototype: the X-32. a Request for Proposals for the put budgetary pressure on the F-22 General Dynamics had been testing a Advanced Short Take Off and program. DARPA pointed out that the full-scale E-7 ejector propulsion model in IVertical Landing (ASTOVL) aircraft USMC had a similar problem, but there NASA’s 80ft x 120ft wind tunnel but, technology demonstration program in could be co-operation if the extra fuel in the end, it off ered a fan-in-wing 1992. The aim was to build a supersonic tank was replaced by a lift fan to off er the propulsion concept similar to the Ryan STOVL fi ghter with an empty weight of supersonic STOVL capability desired by XV-5A. McDonnell Douglas went in with 24,000lb, similar to the F/A-18C Hornet, the service. The USAF showed interest, an off er for both a SDLF (shaft driven to keep the weight and cost in check. asking DARPA to provide the technology lift fan) and GDLF (gas driven lift fan) by the end of the 1990s. propulsion system. Northrop off ered a Financial constraints similar propulsion solution as the Russian The USMC was having trouble getting STOVL testing Yakovlev Yak-38: the lift + lift-cruise Above: The Boeing political support for the Bell Boeing V-22 Many agencies had tried to develop a system. Boeing off ered the Harrier X-32A performed Osprey, with then-US Vice President Dick supersonic STOVL fi ghter and the history propulsion system called ’direct lift’. up-and-away fl ight Cheney one of its fi ercest critics, and books are full of examples of experimental The Lockheed and McDonnell Douglas demonstrations for the US Navy, as well they could not aff ord to fund another failures, including the Hawker Siddeley designs could remove the lift fan for the as fi eld carrier high-profi le program on their own. USAF P.1154; Dassault Balzac V; EWR VJ-101 (tilt conventional fi ghter and Northrop could practice landings Brig Gen George Muellner, then Deputy engines and lift engines); Rockwell do the same with the lift engine. Boeing Boeing Chief of Staff for Requirements at Air International XFV-12A and British didn’t have this advantage, so selected Combat Command, Langley Air Force Aerospace (BAe) P.1216, but problems a delta wing as these could hold a larger Right: X-35A mostly Base (AFB), received a presentation from such as hot gas ingestion, suck-down fuel volume. A requirement set by DARPA did up-and-away fl ights for the Lockheed/DARPA about a replacement forces, and the fountain forces made was that a full-scale model had to be USAF requirement. for the F-16, but with more range. them unsuccessful. Hot gas ingestion, developed to prove the design could Lockheed managed a This was the kind of range the USAF the transition from conventional fl ight to carry its weight in the STOVL fl ight very aggressive fl ight schedule, putting craved, even if it didn’t have the funding hover and managing to lift its own weight regime to prevent a repeat of the Boeing under pressure to mount another project, owing to the at the same time had proven to be the Rockwell International XVF-12A, which Lockheed Martin cost of the F-22A Raptor. three biggest problems in developing a could not lift its own weight. 90 August 2021 // www.Key.Aero Right: A 1996 wind with a full-scale model prepared for testing. tunnel model of the X-35. Note the McDonnell Douglas had selected the Skunk Works and General Electric YF120 for their GDLF. X-32 stickers above the model. The inlet design was that of The dream team the F-22 NASA Lewis McDonnell Douglas and BAe teamed Research Center up with Northrop Grumman to form the dream team, as all western operational STOVL and recent naval STOVL experience was now under one roof. The McDonnell Douglas team abandoned the GDLF concept, much to the chagrin of NASA, and adopted the lift + lift cruise propulsion system that Northrop had pursued. The dream team did not bother with a full-scale model for In March 1993, Lockheed’s SDLF point coming when General Dynamics the lift + lift system as they reasoned they propulsion system and McDonnell Fort Worth missed out on a possible F-16 were developing a proven propulsion Douglas’ GDLF system were selected, replacement and was subsequently sold capable of lifting its own weight. At with General Dynamics, Boeing and to Lockheed. the same time as changing propulsion Northrop losing out. Boeing rallied their Two years before the Advanced systems, it changed its propulsion US Senate representatives, arguing Tactical Aircraft (ATA) program, General provider, as they now wanted to off er a that the sole proven concept had been Dynamics’ A-12 Avenger II project had lower risk and a proven engine: the Pratt & rejected. Through the Senate, Boeing got been cancelled. The F-16 production was Whitney F119. Both Boeing and Lockheed an agreement with DARPA to continue expected to come to a halt soon as the had selected the F119 engine from the but they had to fund 50% of the costs USAF had opted to stop buying them. outset and, as such, there was never a themselves; Northrop continued with With General Dynamics losing out on this competitive engine off ered for the JSF. its own money. DARPA contract, it was expected that Fort Lockheed was already in talks with Worth could soon be out of business. Joint Strike Fighter General Dynamics over acquiring the McDonnell Douglas was co-operating The DARPA program was eventually Fort Worth division, with the tipping with BAe in an exclusive deal on the GDLF, absorbed by the Joint Advanced Strike www.Key.Aero // August 2021 91 JSF PROGRAM // X-32 & X-35 replace the entire US Inventory of fighter Left above: X-32A aircraft. Indeed, no new fighter designs seen here with a gaping hole through were expected for another 30 years. the middle allowing McDonnell Douglas had once been the imagination a major company on the civil side of to work out the size of the engine aviation, but that had been diminished by in proportion of competition from Boeing and Airbus. So, the aircraft. The soon after, McDonnell Douglas was sold demonstrator aircraft would have a to Boeing. BAe and Northrop Grumman minimum of mission decided to join Lockheed. systems Boeing The prototypes (or concept demonstration aircraft, as they were officially called) had to prove that the design would be stealthy, could replace the Harrier by landing vertically, have a short take-off run, and be launched Left below: The large- from a conventional aircraft carrier while scale powered model seen here right after having a fighter performance equal to roll-out at the Skunk the F-16. In short, they should fulfil all Works in Palmdale. Its the requirements of the three US armed designation was the X-32 and it was used services and many exports were expected at the NASA Ames to follow automatically. Outdoor Aerodynamic Research Facility’s wind tunnel. This The Lockheed effort model can now be The task at hand was not an easy one found at a scrapyard but Lockheed’s Advanced Development at Fort Worth right beside the HALO Company – better known as Skunk model of the F-35 Works – was on the job with innovative Lockheed Martin proposals. For the lift concept, new SDLF technology from Skunk Works was met with some optimism as it seemed to tackle most of the issues. The SDLF design was refined by engineer Paul Bevilaqua’s team and patented in 1993. To reduce cost, the Technology (JAST) program, which meant Strike Fighter (JSF) program. initial design was borrowed from the F-22. the two downselected contractors would Both Boeing and Lockheed Martin were get the chance to build a demonstrator downselected on November 16, 1996, The Boeing effort aircraft. As a result, the X-35 designation and received a contract to build and test Boeing was not accepted by DARPA as was added. The fact that the demonstrators two prototypes on what was to become it was not offering “new technology”. Its were to be built under JAST meant the JSF. McDonnell Douglas supplied propulsion unit was a modern version of they would become more than simply the fighter powerhouse, the legacy of the Harrier system. Boeing reasoned that technology development – they would be the F-4 Phantom II, F-15 Eagle and the their offer was less risky as it had already an actual aircraft demonstration. To reflect F-18 Hornet, but had no other work in proven itself and, as such, only had to this, the name was changed to the Joint the future as the F-22 and the JSF would solve the hot gas ingestion problem. The Left: The X-35B with the hat-trick tail was a sign of the confidence the Skunk Works team had in their aircraft.