Graham Warwick/ATLANTA
MORE THAN a decade before the aircraft is due to enter service, pilots are flying simulated Joint Strike Fighter (JSF) missions to ensure that the aircraft meets its primary objective - to be affordable. These simulations, which will continue for years, are intended to ensure that the avionics functions provided meet the operational requirements - and that the operational requirements do not drive up avionics costs to the point where the JSF becomes unaffordable.
Affordability is vital if the JSF is to replace 3,000 US Air Force Lockheed Martin F-16s, US Navy Grumman A-6s, US Marine Corps McDonnell Douglas (MDC) AV-8Bs and F-18s and Royal Navy British Aerospace Sea Harrier F/A2s, beginning around 2008. Teams lead by Boeing, Lockheed Martin and MDC are competing for two JSF concept-demonstration contracts to be awarded in November.
"This programme is indeed different," says Chuck Peterson, JSF manager at Hughes Radar & Communications Systems. He highlights the potential scale: "3,000 aircraft at $30 million apiece equals $90 billion - an avionics content of around 28% equals $25 billion." The JSF will not be affordable if it is "business as usual," he says: "The real bottom line is that a 5% change in avionics cost has a $1.25 billion impact."
For the first time, the cost of individual avionics functions is being quantified early in the programme, when design flexibility is greatest and the cost of making changes least. "Virtual prototypes" are being used to measure the impact on aircraft operational effectiveness of varying avionics performance parameters - with the aim of defining the lowest cost suite meeting the requirements.
BUCKING THE TREND
JSF programme managers are trying to buck a trend, which has seen avionics content, as a percentage of flyaway cost, rise from 12% in the MDC F-4 to 30% in the F-18, primarily because of avionics functional requirements. Avionics weight growth is also an issue.
The JSF programme office calculates that the F-16 has grown by nearly 0.5kg a day since it entered service, mostly because of added avionics. Compared with 1990s' technology, the JSF approach promises to reduce avionics life-cycle costs by more than 30%, and to cut mission costs by 50%, says Ciro Luis Pinto-Coelho, manager for advanced strike systems at Northrop Grumman's Electronic Sensors and Systems division. Central-bay avionics will be common to the three JSF variants, he says, while antennas will be tailored to the services' specific requirements, and functions added or removed as "plug-in/pull-out" software modules.
Alan Johnson, business-development manager at the Texas Instruments Advanced Programmes division, says that the JSF approach could reduce avionics flyaway costs by 30-40%. Increased integration makes it easier to tailor common, core avionics to different service requirements.
"In a federated system, add functions and you add apertures. Integrated multi-function apertures lower the total cost," he says.
Hughes' Peterson says that integration at chip, module and system levels increases multi-function capability and improves reliability by reducing interconnections. The JSF avionics architecture will distribute functions across common modules, and share their resources between functions, providing fault tolerance and increased reliability, he says. An avionics architecture is being defined which addresses:
Commonality: 90% avionics commonality between the three JSF variants will be achieved using common hardware and software modules;
flexibility: software which is independent of the hardware will allow processor upgrades without the need to rewrite expensive code;
scalability: adding or removing modules will allow the avionics suite to be expanded or contracted for specific variants, or for growth.
All-important affordability is being addressed in several ways:
increased integration of avionics functions will result in a smaller, lighter system, with fewer modules to develop, build and support;
software and hardware re-use between avionics functions and aircraft variants, and the JSF and other aircraft, will reduce costs;
an open-system architecture based on commercial standards will reduce component costs, overcome obsolescence and simplify upgrades;
rapid, virtual, prototyping will allow avionics changes to be made early on, when design flexibility is greatest and cost impact least.
The starting point for the JSF architecture is the Lockheed Martin/Boeing F-22 avionics suite. This marks the first major step in the integration of previously separate avionics functions, with consolidation of signal and data processing into the common integrated processor (CIP). Electronic-warfare (EW) and communication/navigation/identification (CNI) systems are also integrated, but still separate.
The F-22 CIP is built up from a small number of common line-replaceable modules which are not dedicated to one particular avionics function, but instead shared. Similarly, with the EW and CNI systems, resources such as antennas and receivers are shared.
Avionics integration takes a major leap forward with the JSF. At the heart of the aircraft is the integrated core processor (ICP). This is essentially similar in concept to the F-22 CIP, but includes EW and CNI signal and data processing. Like the CIP, the ICP is a liquid-cooled rack housing plug-in common modules.
Alongside the ICP is the integrated sensor system (ISS), essentially the support electronics for the JSF's radio frequency (RF) systems - radar, EW and CNI. The ISS has been described as, the analogue equivalent of the digital ICP - a rack of plug-in common modules, which handle all pre-processing of RF signals from the aircraft's various antennas.
The major source of those signals is the multi-function nose array (MFA). More than just a radar, the MFA is an electronically scanned active array which also handles electronic support-measures (ESM) and communications, in conjunction with other apertures around the aircraft. The array generates multiple, sequential, beams which provide the pilot with near-simultaneous air-to-ground and air-to-air radar modes, high-gain ESM and wide-band datalinks.
Complementing the RF system is an electro-optical/infra-red suite using shared electronics and apertures for a targeting forward-looking infra-red (FLIR) and a situational-awareness infra-red sensor search-and-track (IRST).
Use of information from off board sensors is central to the JSF avionics concept, and to keep costs down by reducing the requirements placed on the sensors on board the aircraft. The data, for situational awareness, threat warning, sensor cueing and targeting, may come from another JSF, or from surveillance aircraft, unmanned air-vehicles or satellites.
REDUCING RISK
Demonstration programmes are already under way to mature certain JSF avionics technologies - low technical risk at entry into engineering and manufacturing development in 2001 is a prerequisite of the programme. The biggest of these is the Multi-function Integrated Radio-Frequency System (MIRFS) technology-demonstration.
MIRFS contracts were awarded earlier this year to Hughes Aircraft ($55 million) and Northrop Grumman ($48 million), under which two teams will build and test multi-function nose arrays. Hughes Radar & Communications Systems is leading a team which includes ITT, TRW and the UK's Defence Research Agency, while Northrop Grumman Electronic Sensors and Systems (formerly Westinghouse Electronic Systems) is to manage a team which includes Litton, Raytheon and GEC-Marconi.
The basic functions of the MFA are synthetic-aperture-radar (SAR) imaging, ground moving-target indication (MTI) and ground mapping. The latter will be used to target the Joint Direct Attack Munition. Ultra-high-resolution SAR images, with MTI data on slow-moving vehicles superimposed, will be used to target the Joint Stand-Off Weapon.
Almost simultaneously, the MFA will provide air-to-air search and track modes for self-defence, with ultra-high-resolution SAR and high-gain ESM modes being used to identify targets. The nose array will also provide the datalink which is required to update the Advanced Medium-Range Air-to-Air Missile en route to its target.
Each MIRFS team will build an MFA for ground testing and subsequent flight-testing and demonstration of a suite of air-to-ground modes. Northrop Grumman plans to re-use software from its existing APG-76 SAR/MTI and APG-77 (F-22) radars in development of its MFA, which is scheduled to be flown on a BAC One-Eleven testbed in late 1999.
Hughes will use experience gained on an earlier wideband integrated-forebody technology-demonstration. This combined an electromagnetically accurate model of a Hughes very-low-signature multi-function aperture with a Boeing chined, "clear" (wideband), radome. Radar cross-section tests showed an "extremely low" signature, says Hughes.
While the MIRFS effort is concentrating on the RF section, accounting for about 30% of the JSF avionics cost, other demonstrations are looking at core processing, which accounts for almost a quarter of the cost. The emphasis here has been on using commercial standards and components so that affordable digital processors can be produced.
STARTING POINT
An initial architecture dubbed Version 1 has been defined by the JSF programme office, as the starting point for avionics development, by the weapons system contractors, during the forthcoming concept-demonstration phase. At the same time, the JSF programme office has defined the process by which the contractors will tailor the architecture and demonstrate their avionics suite.
This iterative process involves the evaluation of a virtual-avionics prototype (VAP) by pilot-in-the-loop simulation. Pilots will fly the VAP on simulated missions to determine the operational effectiveness of the JSF avionics suite.
Contractors will repeat these simulations many times, each time varying one avionics performance parameter, while holding the others steady, to measure the impact on lethality. This will enable the cost and benefit of a particular avionics capability to be determined.
This process was demonstrated under the JSF Avionics Virtual-Systems Engineering and Prototyping (AVSEP) contract awarded to a team consisting of Texas Instruments (TI), Honeywell, Litton and TRW. The AVSEP effort took the Version 1 JSF avionics architecture through one cycle of the iterative process, says TI's Johnson.
In piloted simulations using a virtual avionics prototype, the AVSEP team varied the SAR resolution to determine the impact on cost and effectiveness. This showed that the resolution of SAR images presented to the pilot could be lowered, from 0.3m to 0.9m, without affecting the aircraft's lethality. The reduced resolution requirement, in turn, resulted in lower avionics costs.
Johnson says that the weapons-system contractors will now use the same process to tailor avionics architectures specific to their aircraft. Each will conduct numerous piloted simulations, while periodically updating its virtual prototype to make it more and more like the aircraft. Initially, the avionics functions will be simulated, but an increasing amount of hardware will be incorporated as the concept-demonstration phase progresses, he says.
At several points during concept demonstration, the weapons-system contractors will be required to link their VAPs into combat simulations run by the JSF programme office. These campaign simulations, hosted at NAS Patuxent River, Maryland, will enable programme officials to evaluate the effectiveness of the competing JSF designs in a "virtual fly-off".
A key feature of the JSF avionics concept is the ability to determine the cost of individual avionics functions, so that trade-offs between cost and performance can be made. Under the AVSEP contract, the TI-led team produced not only a cost estimate for the complete JSF avionics suite, but also a breakdown of the cost of each function making up the system.
Based on historical data, the JSF programme office estimated the avionics content of aircraft flyaway cost at around 28%, or $8-9 million. The avionics cost estimate emerging from the AVSEP effort, of around $6 million, represents a reduction of 20-30%, Johnson says.
The estimate was built up function by function, beginning with the core ICP and ISS, which are common to all three JSF variants, and then adding options, all costed, such as: identification friend-or-foe; SAR; targeting FLIR; radar-warning receiver; satellite communications; helmet-mounted display; situational-awareness IRST; towed decoy; and weapons-control datalink.
TRADING PERFORMANCE
This building-block approach to arriving at the total cost has also enabled the AVSEP team to develop estimates for avionics suites providing the differing functionality required by the three services. This has resulted in an estimated avionics flyaway cost of $5.94 million for the $27.5 million US Air Force JSF, $5.97 million for the $32.3 million US Navy JSF, and $6.13 million for the $30.4 million US Marine Corps JSF, Johnson says.
This is the starting point for the two teams, which win the JSF concept-demonstration contracts. They will tailor the initial architecture to match their specific designs, under cost pressures which are unlikely to relax - and very likely to increase - as the JSF programme moves towards the $16 billion development phase scheduled to begin in 2001.
Source: Flight International
