F-22 Raptor Support System
The F-22 is more reliable than the aircraft it replaced, and it requires significantly less support resources than the F-15 while providing unequaled operational capability. It is a true force multiplier.
From the outset, the F-22 was designed for supportability and self-sufficiency, with reduced logistics costs. The improvements designed into the F-22 are predicted to save more than 50% of the operations and support costs of the F-15 over a 20-year period.
Unlike in past programs, where supportability was almost an afterthought in the design process, on the F-22, maintainers worked with designers and manufacturing representatives to ensure that a part or system was designed correctly, could be manufactured, and could be maintained while that part or system was still on the drawing board.
As two examples, the slings used to hoist the canopy into position on the assembly line is the exact same sling design that are used in the field. The same sling used to place the wing leading edge flap is also be used to hoist the flaps and flaperons.
The F-22 provides significantly more sorties each day than current fighters. It can be flown on twice as many consecutive sorties, is twice as reliable, require 1/2 the direct maintenance man-hours per flight hour, and 2/3 the turnaround time for its next combat sortie as the F-15C. Also, a 24-aircraft F-22 squadron would require less than 1/2 the C-141 airlift support to deploy for 30 days than is presently required by a comparable F-15 unit (about 7.8 C-141 loads to deploy an F-22 squadron versus the 16 C-141 loads for an F-15C).
Additionally, to deploy an F-22 unit, there would be fewer shops required (such as wheel and tires, ejection seat, and pilot equipment), and reduced spares as well.
There are five key design features that makes the F-22 more supportable than any previous fighter: access/maintainability; fault detection and isolation; self sufficiency; improved combat turn; and high reliability.
Access/Maintainability: The bottom of the F-22 sits only 36 inches off the ground, allowing maintainers to have shoulder-height access (or lower) to nearly every component or system ( such as avionics racks, engines, airframe mounted accessory drive system (AMAD), and weapons) without the use of ladders or workstands. In addition, the aircraft's modular avionics allow the maintainer to pull out a non-functioning module and plug in another in rapidly.
Fault Detection and Isolation: There is an extensive Built-In Test (BIT) capability inherent in the F-22. In fact there is so much capability that the diagnostics system can go down to the Line Replaceable Module (LRM - the individual electronics cards - level to determine faults. There are also built-in test sensors; fault filtering, that is, the system determines whether a fault is significant enough for the pilot to receive a Caution or Warning in the cockpit; a significant failure data recording, to allow maintainers to know exactly when a part failed.
Self-Sufficiency: The F-22's On-Board Oxygen Generating System (OBOGS) provides breathable air to the pilot, so there is no need for ground-based liquid oxygen (LOX) equipment; likewise, the F-22 has an On-Board Inert Gas Generating System (OBIGGS) that is used to fill the fuel tanks with nitrogen as a safety measure as the fuel is depleted on a flight; the aircraft has an Auxiliary Power Unit (APU), so there is no need for a ground power cart; and as much 'housekeeping' as possible has been eliminated - for instance, it only takes four simple steps to take the aircraft from cold metal to engines running.
Integrated Combat Turn: The Integrated Combat Turn (ICT) is the military equivalent of a pit stop in auto racing - the aircraft is refueled, rearmed, and sent back into combat. The F-22 allows for simultaneous gun ammunition and missile reloading, a process that normally goes in sequence only. The Raptor has single-point refueling and a single-point consumables (oil, chaff, flares, etc.) status check point. It also has pneudrallic extend and retract missile launchers, which means that there are no pyrotechnics to be concerned with while the aircraft is being turned.
Reliability: The F-22's systems are highly reliable, requiring fewer spare parts and less airlift support. The F-22 has fault-tolerant liquid-cooled avionics. When one card fails, the system automatically reconfigures itself. These lower operating temperatures extend avionics life. Also, during development, systems went through comprehensive analysis, development tests, and full-scale tests. These accelerated life tests were more severe and of longer duration than traditional military standard (MIL STD) tests. For example, electronic tests included ten times the number of thermal cycles and ten times the vibration duration at higher vibration levels than MIL STD tests.
The F-22 Integrated Maintenance Information System (IMIS) integrates the Tech Order Data (TOD), maintenance forms, the aircraft itself to provide the maintainer a single source of maintenance information.
There are three main components to the F-22's IMIS: the Portable Maintenance Aid (PMA); the deployable, squadron-level Maintenance Support Cluster (MSC), and its back shop counterpart, the Maintenance Work Station.
The Portable Maintenance Aid (PMA) is a ruggedized computer that a maintainer would take out to the aircraft. It serves as the primary maintenance interface with the aircraft and its systems. The PMA displays Interactive Electronic Technical Manuals (IETMs), has the capability to order parts, and supports the recording of maintenance actions in maintenance forms.
The PMA, built by AlliedSignal, weighs 9.85 pounds, is fully sunlight readable, and runs on nickel-metal hydride batteries. It has a keypad and function keys to support data entry.
One of the biggest advances the PMA offers to the F-22 maintainer is the use of IETMs that display on the IMIS equipment. IETMs are a set of detailed instructions that tell the maintainer how to inspect, troubleshoot, and replace a component. These instructions are interactive, and offer the user "branches" of information depending on situations that may be encountered during the maintenance action. IETM graphics are taken from the three-dimensional computer database used to design the aircraft. The graphics are translated to a simplified two-dimensional drawing for ease of use and technical clarity. IETMs displayed on IMIS eliminate the cumbersome paper-and-paper change process in use today that often results in big-city sized phone books on flightlines.
Approximately 3,200 of these packets have been written already, and this represents only about 20% of the total to be written before the aircraft is operational.
The PMA works like this. The maintainer goes out to the aircraft and plugs the PMA into a data port on the aircraft (located in the wheel wells and cockpit) that would accept commands. The maintainer can first use the PMA to stimulate a system to perform a BIT check to verify a failure. If the maintenance instructions call for opening the weapons bay doors, for instance, the PMA allows the maintainer to open the door without having to get in the cockpit.
As this is an electronic system, the PMA has been updated with the latest TOD, and it displays only those instructions. At the aircraft, the maintainer can scroll through and look at the entire task before going back and checking off the individual steps.
If there are questions, the graphics in the PMA would let the maintainer zoom in on a specific part or pan out to see the entire system. If the action requires parts, a message can be sent back to maintenance control and the part is ready once the maintainer gets back. He then heads out to the flightline and replaces the part. Once the maintenance action is complete, the PMA records it, and sends the information back to maintenance control. Other data such as failures, parts usage, and consumables data can also be sent via the PMA.
The PMA can also be used to load Operational Flight Plan (OFP) software into the aircraft through another data port on the aircraft. In fact, the first software loaded on to the first F-22 while it was in final assembly was done through the PMA.
The Maintenance Support Cluster (MSC) and the Maintenance Work Station (MWS) are both computer packages that are the center of the IMIS. The two systems use the same basic commercially available components, but the MSC is packaged in rugged containers so that it can be deployed. These containers also offer the computer hardware protection against out-of-the normal hangar environments. The MWS system would remain at the main operating base.
The basic functions of the MSC include:
Analyzing Diagnostic Data: When a pilot returns from a mission, the data transfer cartridge (DTC) in the cockpit is removed and brought to maintenance. If any failures occurred on the mission, those fault codes are noted on the DTC and that data is downloaded into the MSC computer. The cause of the failure is identified, and a course of recommended corrective action is taken.
Prepare for the Task: The maintenance task is scheduled, resources (parts, etc.) are identified, instructions for that task are reviewed and checked for currency, and then a PMA is loaded with the instructions so the maintainer can take the PMA out to the flightline and complete the task.
Collect Maintenance Data: The data collected - what is failing on the aircraft, how long it is taking to repair the aircraft, parts usage, etc. - is all collected and is used to generate reports and summaries. A basic tenet of the F-22 support system is to collect the data once and then reuse it as much as possible.
Support Maintenance Planning and Analysis: The data collected is also used in planning, as it is used to schedule inspections and to schedule time change maintenance.
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