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JSF Rivals Face off

Aerospace America January, 2001

by Ben Iannotta, contributing writer

In competing for the biggest aircraft contract in history, Lockheed Martin and Boeing have taken radically different design approaches

The Joint Strike Fighter (JSF) program is the largest procurement effort in the history of aviation, and one that requires the U.S. military services to embrace a completely new approach to aircraft development. The services must work together to select the design for a single airframe that can be modified to meet the highly divergent demands of the Air Force, Navy, and Marines, as well as the British Royal Navy. For the U.S., the program is the heart and soul of its tactical aviation modernization plan. A total of 3,002 planes will be built, with the first becoming operational in 2008.

The rationale for the new joint development approach, industry officials say, is to cut manufacturing costs. Each service's JSF variant will be built on the same production line with the same tooling; they will share 70-90% of their hardware in common. "Where you incur your cost is when you build different parts for different airplanes on different lines," explains Charles "Tom" Burbage, executive vice president for customer requirements at Lockheed Martin in Fort Worth, Texas.

The Navy wants a new carrier-based fighter; the Air Force wants a light, agile fighter to replace the F-16; and the Marines want a short takeoff/vertical landing (STOVL) plane with better range and bomb-carrying capability than the AV-8B Harrier. If separate planes were built to meet those requirements, the cost to the government would be almost twice as much, officials at the JSF program office have told Congress.

Still, estimates for the cost of developing and manufacturing all 3,002 planes range upwards from $ 200 billion. The General Accounting Office has warned that costs could soar wildly if government managers push ahead on the program before technologies are ready.
Enormous stakes

With so much aviation work residing in one program, the stakes are equally huge for Lockheed Martin and Boeing. The two are locked in an old-fashioned fly-off for the lucrative contract to develop and build the JSF. Boeing flew its first JSF demonstrator on September 16; Lockheed Martin's flew for the first time on October 24. The down-selection is scheduled for some time this year, with production beginning in 2005. At its peak, the program will be worth more than $ 3 billion a year. Although the loser of the competition will probably survive as a major subcontractor, the competition is still a fierce one.

"This program is very, very important to Boeing. In fact, you might say it's the number one priority. It's the biggest procurement program in the history of aviation," says Frank Statkus, vice president and general manager for the JSF program for the Boeing Military Aircraft and Missile Systems Group in Seattle.

Boeing and Lockheed Martin are each building two demonstrators to test the basic aerodynamic handling of all three JSF variants. Officials from both companies are quick to point out that their demonstrators are not intended to be production prototypes, although pieces of the planes can be considered prototypes.

Instead, the goal is to focus on the riskiest technologies. For instance, the two competitors will test radically different approaches to the STOVL problem. Both companies will also show that their JSF airframe can handle low-speed carrier landings. Neither, however, will demonstrate radar-evading stealthy flight. Program managers at both companies are banking that the stealth issues have been resolved through their work on the B-2 stealth bomber and the stealthy new F-22 Raptor. And both say they have tested the stealthiness of full-scale models of their JSF planes in the laboratory with great success.
X-32 vs. X-35: Different strategies

Beyond those similarities, Boeing and Lockheed Martin have chosen very different strategies to show off their JSF capabilities. The Boeing X-32A will test conventional flight from land-based runways and also slow-speed carrier landings. The latter will be conducted in the safety of Edwards AFB rather than on an actual carrier.

Boeing's demonstration of Harrier-like short takeoffs and vertical landings will have to wait until its second craft, the X-32B, is ready to fly.

By contrast, Lockheed Martin's first demonstrator, the X-35A, is demonstrating only conventional runway operations. Once those flights are complete, the plane will be returned to the shop and outfitted with an innovative lift-fan system that will demonstrate hovering STOVL flight. By converting the same airframe for STOVL demonstrators, company officials say they are showing the commonality between the two variants. On the outside, the conventional and STOVL planes will have the same dimensions and aerodynamic design, spokesman John Kent says. The second demonstrator, the X-35C, is finished and is now being readied for a series of flights to demonstrate the slow approaches necessary for carrier landings.
Carrier landings

Achieving these slow, reliable carrier approaches without sacrificing too much commonality is the challenge for the JSF carrier variant (CV). The Air Force wants to replace the F-16 -- which has only one engine -- with a light, affordable fighter. In the past, Navy officials have balked at the idea of landing a single-engine fighter on the deck of a pitching carrier loaded with planes, jet fuel, and personnel. Both the F/A-18 and F-14 Tomcat have twin engines partly so that if one engine fails, the aircraft still has power.

Nevertheless, both Lockheed Martin and Boeing plan to power their JSF planes with single Pratt & Whitney F119 engines. According to Lockheed Martin's Burbage, "Engine reliability is so great today that there's no significant difference in terms of reliability between one and two engines." He also points out that single-engine attack planes have landed on carriers.

Beyond their common engines, the two competing carrier variants diverge greatly. The Lockheed Martin X-35C, which will demonstrate the CV requirements, has a wingspan of 43 ft, which is a full 8 ft wider than the conventional X-35A. It will have "bigger wings to get the landing speed lower," explains Burbage.

Boeing officials, however, have made no such concession on wingspan, spokesman Chick Ramey says. The company will demonstrate both the conventional and CV requirements with the same plane: the X-32A, whose wingspan is 36 ft.

"Just because a wing is larger doesn't mean the aircraft will have better low-speed handling characteristics," Ramey notes.

Lockheed Martin's Burbage says that it makes more sense to keep the Air Force variant as lightweight as possible while building a larger, stronger variant for the Navy. He says costs can be controlled by building both with the same production tooling.

In particular, the CV version must be strong enough to withstand catapult takeoffs and tailhook landings. To achieve that, Lockheed Martin will build its carrier variant with a thicker undercarriage and support structures. "They're the same parts cut on the same tool, but we make them thicker," Burbage explains. "You wouldn't want to produce an Air Force plane with that kind of load path."
Outdoing the Harrier

Nowhere do the Lockheed Martin and Boeing approaches differ more than on how to meet the Marine Corps-Royal Navy requirement for a fixed-wing plane that can come to a hovering stop in midair and land vertically like the Harrier. Both companies studied all the possible options but came to diametrically opposed conclusions on what would be the best technology for the STOVL variant.

Boeing engineers have adapted the tried-and-true Harrier approach, called direct lift, to their STOVL plane. In direct lift, air passing through the engine is redirected or vectored downward to provide vertical thrust. One difference from the Harrier is that the Boeing plane will hover on three thrust posts instead of four. Two pivoting nozzles will be installed on the fuselage at the center of gravity. A third nozzle will provide lift at the front of the fuselage just behind the cockpit. The plane also will have smaller nozzles on the wing tips and the front and rear of the fuselage to control rocking motions or roll, pitch, and yaw.

Also, with the Boeing design, making the transition between horizontal and vertical flight will entail less work for the pilot, says Statkus. Nevertheless, he notes, the biggest advantage is that the technology is proven. "After having looked at all the possible combinations, the absolute least risk system -- and you can take that to the bank -- is direct lift," he says.

Lockheed Martin engineers, on the other hand, studied the existing technologies and became convinced that a completely new system would be necessary to meet the rigorous JSF requirements. After all, the plane not only must hover like the Harrier but also must fly supersonically, be stealthy, and carry more weight. "It's our opinion that we're about at the limit of what direct lift can provide. There's just a fundamental difference in philosophy," Burbage says.

Unlike a direct-lift plane, the Lockheed Martin STOVL variant will not rely exclusively on air traveling through the engine. Instead, the front of the aircraft will be kept aloft by a separate, downward-pointing adjustable-lift fan that is attached to the F119 engine via a shaft. The shaft will engage and turn the fan during STOVL flight only. "It's a little more complex than a clutch in a car, but it's the same principle," Burbage says.

At the rear of the plane is a three-bearing swivel duct that deflects exhaust from the F119 engine downward to support the tail of the aircraft. The design of this duct was inspired by the Russian YAK-141 STOVL plane, Burbage says. The Lockheed Martin STOVL variant will also direct thrust from the engine to two roll ducts on the wings to control side-to-side motion.

In November 1999, Lockheed Martin published a paper arguing that its "shaft-driven, lift-fan concept" would generate 60% more vertical thrust from the F119 than the existing direct-lift approach. Although their STOVL variant will weigh 4,000 lb more than their conventional variant, the extra weight is worth it, because the STOVL plane will carry more payload than the Harrier, contend Lockheed Martin officials.

Nevertheless, Boeing's Statkus vows the company's direct-lift approach will meet the military's requirements with less risk than the Lockheed Martin approach. "We looked at all the options and we chose direct lift," he says. "While you can understand the physics that take place [with a lift fan], in order to come up with the right answer you have to define the risk."
Keeping the program together

Given the stakes of the program and the challenges facing the JSF competitors, industry leaders and observers expect loud debate this year when military officials select a single contractor to take the program into the engineering, manufacturing, and development (EMD) phase, which is a precursor to production.

Delaying the program would give military planners headaches, because the Pentagon's tactical modernization plan is counting on timely development of the JSF to keep the average age of its planes within acceptable limits.

The JSF schedule "includes a very short development period for a fighter, compared with recent experience, so a delay in the program would not be surprising. If that happens, the aging of DOD's fighter fleets will continue unchecked until deliveries of the JSF or a replacement begin," warned Eliot Cohen of the Johns Hopkins University School of Advanced International Studies, testifying before Congress in 1999.

Not everyone agrees that speedy development is most critical. Lou Rodrigues of the congressional General Accounting Office is convinced that Pentagon program managers are pushing ahead too rapidly. Major cost overruns lie ahead in the EMD phase, because numerous technical issues are not being addressed in the current program, he warns. Once the program enters the EMD phase, annual expenditures on the JSF will climb to $ 1 billion and eventually to more than $ 3 billion, Rodrigues notes. "You make a mistake then, and you're now carrying a $ 4-billion program," he says.

In March 2000, Rodrigues told two subcommittees of the House Armed Services Committee: "GAO believes that program managers should continue to focus on risk-reduction efforts by maturing critical technologies before entering engineering and manufacturing development, and be allowed to do so without the penalty of withdrawal of funding support."

The JSF program has seen the first seeds of cost overruns, but managers say the numbers are relatively low for a program its size. The overrun is "in the low tens of million of dollars on a program that's $ 730 million of effort over four and a half years," Boeing's Statkus says.

No matter how those issues are resolved, analysts agree that the contractors have a major balancing act in front of them. They must keep costs down by keeping the three JSF variants from devolving into separate planes. On the other hand, they must come up with a plane that satisfies the vastly different demands of the Air Force, Navy, Marines, and Royal Navy. "How do you avoid coming up with a [Joint Strike Fighter] that nobody likes, or a fly-off that turns out to be a fly-apart? That's the question," says John Pike of the Federation of American Scientists, an independent watch-dog group in Washington.
Air Force1,763 JSF conventional takeoff
and landing variants to replace
A-10s and F-16s
Navy480 carrier variants to
complement F/A-18E/F
Super Hornet
Marine Corps609 STOVL variants to replace
AV-8B Harriers and F/A-18s
British Royal Navy150 STOVL variants to replace

Lockheed MartinBoeing
X-35A CTOL demonstratorX-32A CTOL and CV demonstrator
 Wingspan: 35 ft  Wingspan: 36 ft
 Length: 50.5 ft  Length: 45 ft
 Weight: 26,500 lb  Weight: Proprietary
X-35B STOVL demonstratorX-32B STOVL demonstrator
 (X-35A outfitted with STOVL system)  Wingspan: 30 ft
 Wingspan: 35 ft  Length: 45 ft
 Length: 50.5 ft  Weight: Proprietary
 Weight: 30,697 lb
X-35C CV demonstrator
 Wingspan: 43 ft
 Length: 50.8 ft
 Weight: 30,618 lb

GRAPHIC: Picture 1, no caption; Picture 2, Both JSF competitors will be powered by Pratt & Whitney F1119 engines; Pictures 3 and 4, Boeing's second plane the X-32B, will demonstrate Harrier-like short takeoffs and landings. Lockheed Martin's first plane, the X-35A will initially conduct conventional runway operations only; it will then be outfitted with an innovative lift-fan system that will demonstrate STOVL flight.

Copyright 2001 American Institute of Aeronautics and Astronautics, Inc.;