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CAD cuts cost for fighters and airborne lasers

CAD cuts cost for fighters and airborne lasers

The last production fighter Boeing built was the P-26 Peashooter, an open-cockpit monoplane with wire-braced wings that first flew in 1932. During the opening weeks of the Pacific theater in WWII, Mitsubishi Zeros rapidly swept the handful of Peashooters still flying from the skies. Now Boeing is back with the F-22 Raptor, a twin-engine air-superiority fighter with titanium and composite wings being built in partnership with Lockheed Martin. If they perform as advertised, Raptors will have everybody else ducking for cover.

With the McDonnell Douglas merger, the Seattle commercial airplane giant is poised to strike deeper into the high-intensity marketplace for tactical aircraft. Boeing's candidate for the Joint Strike Fighter (JSF), a multi-service, multi-national attack plane, features a one-piece, all-composite delta wing, stealthy angles, and a variant with short take-off and vertical landing (STOVL) performance. Larry Winslow, vice president of engineering at Boeing's Defense & Space Group, sees McDonnell Douglas' experience with hot gas diversion technologies implemented on its AV-8 Harrier as key to a JSF win.

Meanwhile, Boeing is leveraging its commercial airplane expertise to develop the Airborne Laser (ABL), once again in partnership with Lockheed Martin. TRW is also playing a major role. The ABL will mount a megawatt laser aboard a 747-400F intended to shoot down theater ballistic missiles in their boost phase. What's more, just as Boeing breaks back into the fighter business, Paul Shennum, executive director of the ABL team, is only half-kidding when he claims derivative laser-armed aircraft one day will render the conventional fighters his company makes obsolete.

The appointment of Alan Mulally (Design News Engineer of the Year in 1996) as head of the Boeing Defense & Space Group signals a renewed emphasis on the business of building military aircraft. The man who shepherded the 777 from CAD geometry onto the world's airways will now see "commercial best practices" implemented on the military side of the company. Every program, it seems, is permeated with "Triple Seven" spirit.

Achieving technical superiority. The premier military aircraft program of the Defense & Space Group currently is the F-22 Raptor. Boeing claims the F-22 is a leap forward in aircraft technology, as much ahead of the F-15 as the latter is ahead of the WWII-era P-51 Mustang.

In the past, air-superiority was accomplished in a stand-up fight. This probably will not be possible in the future with a flood of Mach 2 fighters coming on the market from many nations, particularly Russia. The tactics for Raptor-drivers will be to sneak up on their adversaries, close with "supercruise" engines that produce Mach 1+ speed without fuel-gulping afterburners, and hit them with an AMRAAM before ever showing up on the other guy's radar.

At Boeing, core competency has come to mean wings and systems integration, and digital design definition. Rather than simply accept an off-the-shelf design and manufacturing package when embarking on the 777, the company leveraged its aerospace engineering expertise and experience in assembling aircraft to develop FlyThru. This home-grown, dynamic modeling application enables engineers to produce digital mock-ups from CATIA solid models. In effect, engineers use FlyThru to pre-assemble aircraft on the screen.

FlyThru digital mock-ups have all but eliminated physical prototyping on the F-22 for the purpose of proofing assemblies. Boeing only had to build one physical mock-up, the engine bay, and that was to proof an engine trailer design and to demonstrate quick removal and replacement of the Pratt & Whitney F119 turbofans.

If the 777 program set new standards for digital design definition, the engineers beneath the Raptor's wings are working to make those standards yesterday's news. "Our goal has been to do an even better job of integrating design and manufacturing on the F-22 than the commercial side did on the 777," says Regina Fritz-Ruddy a lead systems engineer on the program. "We took lessons learned and improved on them. On the F-22, we have reduced fitting errors by 90% and cut drafting time as much as 50%."

The F-22 program is not the Military Airplane Division's first exposure to CAD. Boeing is a subcontractor on the B-2 Spirit bomber program, of which Northrop Grumman is the primary. Northrop Grumman uses its proprietary NCAD design software, and Boeing maintains a design staff fluent with the system to perform its contract work. However, NCAD is regarded as "old school" by the F-22 team.

Lockheed Martin also uses Boeing's code. Engineers at the Fort Worth, TX, facility responsible for the central fuselage section, and at the Marietta, GA, facility responsible for the forward section, control surfaces, and stabilizers, are all on CATIA. There are many points on the plane where work originating at all three facilities comes into contact, such as at the wing roots. The Pratt & Whitney F119 engines and other subcontracted systems must be accommodated as well. Fritz-Ruddy says a common design and system network environment makes it possible for designers in distant locations to work together effectively.

According to Douglas Wise, Boeing's integrated product team manager for the F-22's aft fuselage, a key improvement in the program over earlier efforts involved co-locating the design, manufacturing, and tooling engineers. "We sit together," Wise says. "And we share design/build responsibility. The team's charter is not just to lay out the design, but to figure out how to build it. All development teams have similar charters. That's what really makes the F-22 product work."

The conceptual leap where a "weapons system" became a "product" is more profound than mere words suggest. It is a recognition that the Boeing Defense & Space Group does not occupy some lofty position in the firmament. It is a business, like its commercial sibling, that competes and builds and delivers goods for customers. "With development costs these days you have to--otherwise it's bid, lose, disband," says Engineering VP Winslow. "Boeing succeeds by stressing a strong systems engineering approach with the customer in mind. We stress product integrity and safety in flight."

The integrated design/build product teams enacted on the F-22 include unionized, hourly-wage personnel who specialize in assembling the finished product. Mark Knoll, a systems installer, credits his access to FlyThru data with avoiding grief on his end. "Digital mock-ups even help with tooling," Knoll says. "In reviewing a design for a frame intended to hold the wing up, we noticed the tool only had six inches clearance, which was not sufficient for somebody to get under it. They were able to revise the design before the frame was built."

Of course, the Raptor is a special breed of product and not every design/build issue can be resolved digitally. The design for the intermediate wing spars, for example, originally specified composite materials. Weight considerations encouraged Boeing to use composites wherever possible, and about a third of the F-22 is either epoxy, BMI, or thermoplastic. Further evaluation of the spars in question prompted a switch to titanium construction for certain sections. Did analyzing an electronic mock-up lead the design/build team to make this change?

"We fired a 30 mm cannon shell at a full size wing test section," reports Jeffery Stone, manufacturing manager on the F-22. "This produced catastrophic damage in the all-composite assembly, so we went with titanium for some spars. We hit the new assembly with another round, and it held up."

The last of warbirds. One of the challenges in applying commercial best practices to the business of building military aircraft is the nature of the customer. With the notable exception of the F-4 Phantom, which flew in USAF, USN, and USMC colors and under many foreign flags, building a fighter plane that appeals to multiple services and foreign customers is a difficult challenge.

This fact tends to rob an aircraft program of the very thing it needs to be cost effective: production numbers. When Cold War defense budgets lavished money on the armed forces, each service with a jet-fighter arm ordered its own preferred aircraft. There was some room for overlap: Both the Navy and the Marines operate the F-18 Hornet in the strike-fighter role. However, wherever possible, each service sought its own unique planes and, because the money was available, generally got them.

This will no longer be possible in the foreseeable future. The F-22 may very well be the last single-service, front-line fighter produced in the United States. As it stands, the Air Force is likely to purchase fewer than 500 of the $70 million plane. And this required the Pentagon to reduce the Army's ground forces to pay for them. "Future aircraft are going to have to cost one hell of a lot less than the F-22," observes Engineering Vice President Winslow, candidly.

Economics have forced the relevant branches of the armed forces to see the need to standardize on one airplane in order to achieve economies of scale. A Defense Advanced Research Projects Agency (DARPA) study on the feasibility of a multi-service strike aircraft eventually led the Department of Defense (DOD) to award contracts to Boeing and Lockheed Martin to develop their own concepts for the Joint Strike Fighter. The JSF is intended to fill the roles held by aircraft as diverse as the A-10, F-16, F-18, and the Sea Harrier. It may become the ubiquitous combat aircraft of the 21st century.

The base JSF version is the Air Force model. It will be supersonic and designed to carry the GPS-guided Joint Direct Attack Munitions and other ordnance in internal bays. The Navy version is similar, but with strengthened landing gear and a tail hook for conventional carrier landings. Its footprint will be small enough that folding wings won't be necessary. Both the U.S. Marines and the British Royal Navy have nearly identical JSF requirements, and will buy a STOVL model of the winning design. This aircraft will have slightly clipped wings, enabling it to fit on the deck elevators of the former's amphibious assault ships and the UK's Invincible-class carriers. Despite these differences, the exterior lines of all JSF versions will be essentially identical.

Shared parts. Boeing, in partnership with McDonnell Douglas, has come up with a JSF design that has 90% commonality of parts between the versions for each service. Boeing is designing a single production facility capable of producing all three versions. Also, the aircraft will be powered by a single F119 engine, the same engine used on the F-22, which is intended to further reduce the cost of acquisition and maintenance. The STOVL version will carry a Rolls Royce vertical lift system similar to the one employed on the Harrier.

The most unique aspect of Boeing's candidate for the JSF is its single piece, all-composite wing. "Our JSF is a wing with an airframe attached," says Randy Harrison, a senior manager in the Military Airplanes Division. The wing is a huge composite structure that also serves as a fuel tank." This approach has enabled Boeing to break the JSF down into four manageable sections, which should simplify manufacturing.

The company has invested $450 million in composites technology, plant, and equipment, including building the two largest autoclaves in the world in Seattle. Some of the company's expertise comes from its work on the B-2 program, and some of this is paying off in the V-22 Osprey tilt-rotor program at Boeing's Helicopter Division in Philadelphia. The company also has adapted much of the technology and engineering practices perfected on the F-22 to the JSF. The integrated product teams, many of whose members are Raptor veterans, are using CATIA and FlyThru.

With affordability and performance mandated by contract, and with as many as 5,000 units at stake over a 50-year program, competition for the JSF prize will be fierce. In terms of dollars, JSF is potentially the largest aircraft contract in history. Both development teams are scheduled to roll out flyable prototypes for evaluation in 1999. Both teams are confident of victory (For more information on the JSF, see "Engineers battle for the right to design next-generation fighter jet" by Marne Turk, DN, 2/17/97).

Peace through light. At the other end of the military procurement spectrum is the Airborne Laser. Here, Boeing, Lockheed Martin, and TRW are cooperating closely on bringing this revolutionary weapon system to bear (somehow, calling the ABL a product doesn't quite fly). The extensive research and development effort and low expected production numbers place the program in a more "high risk" design category in terms of payback.

Listen to its boosters at Boeing, however, and the ABL will have an impact on warfare akin to gunpowder. "The ABL will revolutionize the way wars are fought," says ABL Executive Director Shennum. "We're battling politically and scientifically to make that clear."

The sharp end of the ABL is a flyable chemical oxygen iodine laser (COIL) under development by TRW. In action, the COIL would destroy enemy theater-range ballistic missiles (TBM) as they rise after launch. Actually, the ABL has to get the missiles on the way up or it won't work. "Our kill mechanism is catastrophic destruction of the booster," Shennum explains. This means the ABL would not be effective against incoming warheads and re-entry vehicles. It would, however, play a key role in a "tiered" missile defense system, where ship and ground based interceptor missiles would handle the ones that got away from ABL.

The questions of what targets the ABL engages and when are important from a political as well as military standpoint. The aircraft is intended to fly over friendly territory and shoot down missiles about 400 kilometers away. Thus, Boeing says the ABL does not have the range to be used against intercontinental ballistic missiles (ICBMs), which would put it in violation of the Anti-Ballistic Missile (ABM) Treaty signed by Russia and the United States. "Not unless the Air Force wants to attempt penetration flights," Shennum muses.

The COIL emitter is located in a streamlined turret in the nose of a 747-400F freighter aircraft. Much of the center and aft sections of the fuselage are packed with the laser equipment, which includes tanks of chemicals (enough for about 40 shots before reloading). The chemicals used do not produce a combustible mixture and the exhaust from a shot is water, iodine, and chlorine. The COIL will be fired at altitudes in excess of 35,000 feet since the ABL needs to engage targets above cloud cover.

Targeting is accomplished through an infrared search & target (IRST) system similar to the one carried by the F-14 Tomcat that guides an illuminator laser. The automatic beam control system, being developed by Lockheed Martin, tracks the fiery plume of a missile as it rises. Pattern recognition algorithms determine where on the target missile the illuminator laser should focus. This is the spot the high-energy laser needs to hit to cause critical cracking of the booster stage. Returns from the targeting illuminator laser are also compared with a database of local atmospheric conditions to identify turbulence between the ABL and the missile. A deformable mirror developed by Xinetics Inc., Littleton, MA, focuses the kill laser, compensating for turbulence. Zap! Then it's on to the next missile.

"The deformable mirror is a key component," Shennum says, indicating that it is crucial for focusing the required amount of energy on target. Lockheed Martin faces one of the most significant design challenges. The company is charged with developing the wavefront sensor that measures returns from the illuminator laser. This sensor will help determine how the deformable mirror should be focused. "Success also is driven by how good your turbulence model and atmospheric database are," Shennum adds. He indicated the U.S. Government currently is collecting atmospheric data on regions where enemy TBMs are likely to be used, such as North Korea and Southeast Asia.

Studies and physical tests have verified the concept and many of the individual components of the ABL. A flying laser laboratory program in the 1970s and early 80s successfully destroyed a number of Sidewinder missiles. A ground-based version of the COIL has destroyed static and flying targets, including "hard" targets such as metal cylinders representing rocket stages. Existing adaptive optics hardware exceeds ABL requirements. Shennum says the ABL can overcome countermeasures, such as reflective or ablative coatings or missile rotation, by holding the beam on target longer.

True to its core competency philosophy, Boeing is performing the systems integration work on the ABL. "The real design challenge is integrating all this technology into an aircraft," Shennum says. "This is what Boeing does best."

Lessons from Boeing Military

  • Integrated "design/build" product teams reduce errors and engineering time.

  • Identify your "core competencies" and focus on them.

  • Know when to risk a radical design approach and know when to keep it simple, stupid.


Osprey: a Marine bird gets off the endangered species list

President Truman once remarked the U.S. Marine Corps had a propaganda machine second only to Joseph Stalin's when he tried to disband the service after the Second World War. Thanks to leatherneck stubbornness, the Corps lives, and so does Bell/Boeing's V-22 Osprey tilt-rotor.

Boeing's Helicopter Division, a unit of the Military & Space Group, was in a lot of trouble with the V-22, which it is developing in partnership with Bell. Two crashes, one that killed seven, were never adequately explained: Combustion of an indeterminate liquid was suspected in the fatal one. Dick Chaney, secretary of defense under President Bush, ordered the Pentagon not to fund the tilt-rotor program any further. The Osprey was all but dead, except for one thing: The Marines wanted it.

The Osprey, which can take off and land like a helicopter and transition to level flight like an airplane, has the capacity to carry 25 troops over 500 miles at 300 miles per hour. Ospreys would permit U.S. Marines staging from their amphibious assault ships to "hit the beach" from much farther off shore. In fact, the Marines could bypass the beach all together to secure objectives well inland. They made their point, and the Osprey was back. The first production units are now being built at Boeing Helicopter in Philadelphia.

"Fortunately, new technologies were available that enabled us to improve the V-22 when support for it picked up again," says Allen Schoen, director of mobility/maneuver concepts at Boeing Helicopter. The reborn Osprey is lighter than its predecessor, thanks to replacing large sections of the airframe with composites. Cocuring and bonding techniques permit Boeing to produce larger structures, and eliminate tens of thousands of fasteners. These fasteners had caused numerous alignment problems on the previous design. High-speed machining techniques permit those aluminum parts remaining to be manufactured faster and more accurately. Declares Schoen: "We have simplified the design and made it stronger in the process. Now assembling an Osprey is just like putting a Fisher Price kit together on Christmas Eve!"

Well, maybe not. But the spirit of tilt-rotors yet to come is proving inspirational at Boeing Helicopter. A civil tilt-rotor is in development, the Model 609, that is smaller than the Osprey but shares its versatility. The slender craft is being positioned as an alternative to the cumbersome business jet, which requires extensive runways. The 609 would be able to operate in crowded urban areas, such as the Northeast Corridor in the U.S., where air traffic is dense and airport facilities fetch premium prices. At the recent Paris Airshow, 30 customers plunked down $100,000 each for options to buy the first 609s that come off the assembly line.


Defense

With its engineering work on the Joint Strike Fighter, the F-22 Raptor, the Airborne Laser, and the V-22 Osprey, the Boeing Defense group is at the forefront of modern military technology. And, the company is cutting the costs of that technology by implementing what it has learned in the commercial sector.

TAGS: Aerospace
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