Graham Warwick/Fort Worth
Risk will be a deciding factor in who wins the competition to develop the Joint Strike Fighter (JSF). An unprecedented effort is under way, therefore, funded by government and industry, to reduce the risk attached to technologies judged critical to meeting the affordability and performance goals set for the JSF.
In addition to a substantial technology-maturation (Tech Mat) effort funded by the JSF programme office, the competing Boeing and Lockheed Martin teams plan unique demonstrations of technologies critical to their designs - some funded by industry in an additional effort to reduce the risk attached to engineering and manufacturing development (EMD).
Examples of risk include problems with aircraft weight, aerodynamic loads and radar signature which forced costly redesigns during development of the Lockheed Martin/Boeing F-22. If the JSF affordability goals are to be met, redesigns late in development must be avoided.
The Tech Mat effort is co-operative, with the competing contractors sharing the results, while the unique demonstrations are tailored to each team's preferred weapon-system concept (PWSC). Results from the Tech Mat programme, unique demonstrations and concept-demonstrator aircraft will feed into refinement of the PWSCs, leading up to submission of the EMD proposals in 2000.
Lockheed Martin identified 16 technologies and processes as critical to its JSF, some of which it will not reveal for competitive reasons. "What was 'critical'?", says Frank Kirkland, product manager, JSF unique demonstrations and technology maturation, at Lockheed Martin Tactical Aircraft Systems in Fort Worth, Texas. "They had to offer value - they had to be essential to affordability and/or vital to functionality - and they had to have high or moderate risk." Each will contribute to reducing JSF life-cycle cost (LCC) by at least $1 billion, he says.
The company developed a risk "waterfall" which outlines how each Tech Mat and unique demonstration, the concept-demonstrator aircraft (CDA) and PWSC maturation efforts will contribute to reducing risk in the 16 areas to an acceptably low level by the start of the EMD. For some technologies, it will be the major Tech Mat demonstrations which will provide most of the risk reduction. For others, it will be building and flying the CDAs. The unique demonstrations have been selected, therefore, to cover technology "deep holes", Kirkland says.
ALL ELECTRIC
One of the bigger demonstrations planned by Lockheed Martin comes under the Tech Mat banner, and involves the flight testing of an all-electric flight-control system in a modified F-16 - part of the JSF Integrated Subsystem Technology (J/IST) demonstration programme. Integrated subsystems, including electric actuation, are projected to reduce JSF weight, size and cost by eliminating the hydraulic systems, auxiliary and emergency power-units, environmental-control system and accessory-drive gearboxes now required.
Lockheed Martin will modify the existing F-16 Advanced Fighter Technology Integration testbed with fault-tolerant 270V DC electric power-generation and flight-control actuation, replacing the hydraulic system. The J/IST flight test will be the first to involve electric actuation on all axes - previous efforts have been limited to one set of control surfaces - and will focus on the practical aspects of packaging, installing and operating electric actuators.
The primary power source will be an engine-driven switched-reluctance starter/generator. This Sundstrand-developed unit acts first as a motor, to start the engine, then as a generator, to drive the actuators, and provides two independent channels of 270V DC electrical power. Five electro-hydrostatic actuators (EHAs) will be installed to drive the flaperons, horizontal tail and rudder.
Each Parker Bertea EHA incorporates an electrically driven hydraulic pump which is powered up to move the control surface. The EHAs will be detuned to match the performance of the hydraulic actuators they replace, and issues to be addressed, Lockheed Martin says, include the effect on aircraft handling-qualities, which are intended to be unchanged, and the potential for electro-magnetic interference caused by the rapid switching of "enormous" currents at the EHAs.
Six months of flight testing are planned, beginning in January 1999, involving 60 sorties covering the full F-16 flight-envelope. In a parallel Tech Mat demonstration, Northrop Grumman - soon to be merged with Lockheed Martin and already a member of the company's JSF team - will ground test a complete aircraft electrical system. This will include high-power, JSF-sized EHAs developed by Moog and Sundstrand starter/generators driven by both the engine and the thermal- and energy-management module (T/EMM). Being developed by AlliedSignal, the T/EMM combines the functions of auxiliary and emergency power-units and environmental-control system. Northrop Grumman will also be involved in a final J/IST ground demonstration planned for early 2000 at Pratt & Whitney, in which the F119 JSF engine will be integrated with the T/EMM, starter/generator, fan-duct heat-exchanger and thermally efficient fuel pump.
LIGHTER AHEAD
Lightweight, low-cost structures are key to achieving the JSF affordability and performance goals, says Kirkland. Lockheed Martin has several demonstrations planned involving technologies and processes for the design and manufacture of advanced structures. While its two concept-demonstrator airframes will incorporate some of the technology planned for the EMD design, ground demonstrations will investigate higher-risk approaches.
In producing the CDAs, Kirkland explains, the team was faced with the choice of building high-fidelity prototypes, and so freezing the design and technology earlier in the programme, or focusing the CDAs on those areas requiring a flying demonstrator, such as the propulsion system, while continuing to pursue technologies that could increase affordability and reduce cost. Lockheed Martin opted for the latter approach, and its eventual PWSC will be evolved from the CDAs to incorporate design and manufacturing technologies that will be matured through ground tests.
One such effort is the Airframe Affordability Demonstration. This is a unique demonstration intended to reduce the cost and risk of the baseline airframe, Kirkland says, and will involve building a large section of the airframe - the wing carry-through using the manufacturing processes planned for EMD. This project will "benchmark" the selected technologies and substantiate the cost estimates for EMD, he says. Higher-risk, higher-payoff approaches will be evaluated for possible EMD use under another project, the Composites Affordability Initiative.
Supporting Tech Mat projects include the Advanced Lightweight Aircraft Fuselage Structure programme, in which Northrop Grumman is participating. This has involved the "clean sheet" redesign of the centre-fuselage/inner-wing structure of the Boeing (formerly McDonnell Douglas) F-18E/F using fibre-placement and fibre-steering techniques for the low-cost manufacture of large-scale "unitised" composite structures.
Lockheed Martin, meanwhile, is progressing through a series of increasing complex demonstrations under the Simulation Assessment Validation Environment (SAVE) programme, a Tech Mat project to integrate software tools for virtual product-development. The effort is aimed at developing an infrastructure and methodology enabling various design tools to "plug and play" together, with an industry standard for "SAVE compliance" to be available for use in EMD, Kirkland explains.
FLYING AVIONICS
Perhaps the most costly of the unique demonstrations planned by Lockheed Martin is the Co-operative Avionics Testbed (CATB), a joint effort with Northrop Grumman to flight test the JSF avionics architecture. This is an industry-funded project, and involves the modification of Northrop Grumman's BAC One- Eleven testbed with the sensors, processors and software for the proposed mission avionics.
The majority of testing, however, will involve a series of increasingly realistic virtual avionics prototypes, culminating in an integrated hardware prototype. At the heart of the system is the Texas Instrument integrated core processor (ICP), which will handle all digital signal and data processing for the Northrop Grumman multi-function nose array (MFA), electro-optical/infra-red shared-aperture sensor and electronic-warfare system.
The ICP is to be available early in the programme so that software development can be carried out on the target hardware. It is being designed so that the software is independent of the hardware, and commercial processors will be used. A key demonstration goal will be to prove that new processor technology can be inserted without perturbing the application software, Kirkland says. Another will be to show that "legacy" software, from aircraft such as the F-22, can be reused in the JSF to reduce costs. The ICP and the MFA, an active electronically scanned array combining radar, electronic-warfare and communications functions, will be key elements to be ßight tested in the CATB beginning in mid-1999.
Source: Flight International
