DEVELOPING SUPPORT and training systems concurrently with the aircraft and engine has allowed designers to take advantage of the capabilities of the F-22's integrated avionics. The aircraft has extensive onboard diagnostics, required for sensor fusion and fault tolerance, which can be used to eliminate ground-support equipment, while the flight software is being designed so that it can be used also in training simulators.
The support system has been designed to reduce dramatically the personnel and equipment required to keep the F-22 flying. The need to reduce support equipment forced the integration of aircraft and support-system design, says Chester Hardy, support-system team leader at Lockheed Martin Tactical Aircraft Systems. "There is major support capability in the aircraft which we did not want to duplicate on the ground," he says.
"This is the first programme to ever really achieve concurrency in design of the support system with the aircraft," says Art Vogan, deputy support-system team leader, noting that some support equipment is already in use on the assembly line. "We have moved the entire support-system structure up enough in the programme to use it from day one," he says.
Two features of the F-22's design help reduce support requirements, says Hardy. The aircraft is self-sufficient, with an auxiliary power-unit (APU) and onboard oxygen and inert-gas generators, which "drastically reduces" the number of powered carts required, and therefore the number of transport aircraft needed to support deployment of the F-22. The aircraft's highly reliable avionics, meanwhile, provide fault isolation to a line-replaceable module and eliminate the need for an intermediate-level avionics shop.
"The aircraft needs to know which module has failed and which functionality is missing [for sensor fusion and avionics reconfiguration]," says Vogan. As a result, the F-22 has "-tremendous diagnostics. There is no need for an off-aircraft test facility. We can do on the aircraft almost everything that the F-15 [support crews] can do off the aircraft," he says. Eliminating the avionics shop substantially reduces support costs.
Technology is used to improve the maintainer's "situational awareness", Hardy says. The F-22's integrated maintenance-information system (IMIS) "-tells me what the health of the aircraft is and where I go to fix it," he explains. Three elements make up the IMIS: the maintenance support cluster (MSC), which is deployed with the aircraft; portable maintenance aid (PMA), which is taken out to the aircraft; and the maintenance workstation, which is used in an office.
The MSC analyses diagnostic data downloaded from the aircraft via the data-transfer cartridge, extracts the fault information, calls up the corrective actions, schedules maintenance tasks and loads the PMA. The maintainer takes the PMA out to the aircraft. The hand-held PMA displays detailed instructions specific to that aircraft and records maintenance actions as the maintainer steps through the instructions.
The maintenance concept is based on an alphanumeric accounting system which identifies each part, its location, its failure modes and the corrective actions required, Hardy says. "We define the aircraft as 2,000 parts which can be taken out," he says. Failure codes are reported in flight to the data-transfer cartridge, which is removed on landing and plugged into the MSC.
Essentially a ruggedised lap-top computer, the PMA presents electronic technical-order data, including graphics based on simplified CATIA data. It weighs less than 4.5kg, and is powered from the aircraft when plugged into a data port. Only data relevant to the configuration and condition of the aircraft being maintained are displayed. A radio-frequency link to the MSC is used to order parts, download updated forms or access information on another aircraft.
All control of the aircraft for maintenance is through the PMA. The device is used to initiate built-in test, or request door movements. This keeps the maintainer out of the cockpit and on the flightline, and improves efficiency so that fewer people are required to maintain the aircraft, the designers say.
The F-22 training system has been fully integrated into the development effort from day one. "This is the first time that a training system has been bid as part of a total weapons contract," explains Robert Jenkins, product manager for the Boeing-led F-22 training system.
Boeing built its proposal on four major elements: commercial training technologies developed mainly for the 777 airliner, use of best commercial practices, commercial off-the-shelf (COTS) hardware, and effective re-use of realF-22 hardware and software. The cost savings of this combination appear to be startling. The development-cost estimate was less than 50% of that for previous training systems. Today, the production cost estimate for the average training unit is 56% below programme goal.
"We are totally integrated into the team and are networked with all parts of the IPT [integrated product-team environment]. It's been very cost effective because we have been able to identify training requirements and flow them out to, say, avionics or any other part of the aircraft," says Jenkins. Programmers developing software for all aspects of the F-22 placed "hooks" into the code for use by the training system. "We simply rehost operational software on COTS hardware. Once we have the hooks in place, we tap all the laboratory software. All you've got to do is tweak some design software, but otherwise it's identical." For example, 99% of the software written for avionics core-processing is re-useable by Hughes Training, which is developing the pilot and maintenance training-devices.
The system is divided into two parts: pilot and maintenance training, with four second-tier functions. Of the latter, one covers training on support systems like the IMIS, while another - the training management system - deals with student and schedule management. "It will have a database of all maintainers, for example, so if we had another Desert Storm it will pull out all the relevant trained people," says Jenkins.
The pilot and maintenance training concept is structured to reflect the Air Force's drive towards "base level" training with smaller, low-cost, but high-fidelity, training devices. These will be located at several operational bases, rather than having a much larger, dedicated, Wing-level training base equipped with simulators costing five times as much.
Computer-based training (CBT), derived directly from the 777 programme, forms the heart of the system for aircrew training. "Advanced, multi-media, interactive CBT courseware is being developed to make learning more interesting, and because it drives down some of the 'doing' part of it. Say you're teaching a pilot to start the APU. By the time he goes to the simulator, he's already practised those tasks on the CBT," says Jenkins. The use of CBT in the 777 syllabus has produced a 30% reduction in the time to train a pilot to proficiency, says Boeing. "We expect to train F-22 pilots in around 104 days, or roughly the same time as for an F-15, yet it is much more complex," Jenkins adds.
Three main types of training device make up the pilot-training system; a full-mission trainer, a weapons and tactics trainer and an egress-procedures trainer. Entry-level pilots will use the devices at formal training units before passing on as mission-capable crew to further unit-level training. Texas-based Hughes Training will produce all 78 pilot-training devices.
Nine main types of devices complete the maintenance-training ensemble. Entry-level maintenance students will train at a resident training centre, before passing on to unit-level training as mission-ready technicians. Hughes is producing 47 maintenance-training devices, while USM of Texas is making three devices.