Line-replaceable unit
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A line-replaceable unit (LRU[1]) is a modular component of an airplane,[2] ship or spacecraft[3] that is designed to be replaced quickly at an operating location. An LRU is usually a sealed unit such as a radio or other auxiliary equipment. LRUs are sometimes described as "black boxes" despite the fact that they aren't necessarily black.
LRUs improve maintenance operations, because they can be stocked and replaced quickly from on-site inventory, restoring the system to service, while the failed (unserviceable) LRU is undergoing maintenance. Because they are modular, they also reduce system costs and increase quality, by centralizing development across different models of vehicles.[4]
[edit] Definition and Specifications
While the term LRU has been in use for decades, MIL-PRF-49506, Notice 1 of 18 Jan 05, the Performance Spec for Logistics Management Information defines an LRU as:
An LRU is an essential support item which is removed and replaced at the field level to restore the end item to an operational ready condition. Conversely, a non-LRU is a part, component, or assembly used in the repair of an LRU, when the LRU has failed and has been removed from the end item for repair.
LRUs are designed to common specifications, with cannon plug input/output interfaces. Specifications also define the tools necessary to remove and replace (R&R) the unit and the bulk and weight (they typically need to be transportable and fit through a door or hatchway). There are also requirements for flammability, unwanted radio emissions, resistance to damage from fungus, static electricity, heat, pressure, humidity, condensation drips, vibration, radiation and other environmental measurements.
Many LRUs for commercial aircraft are designed according to ARINC specifications, such as ARINC 404 and ARINC 600. LRUs are also defined by manufacturers like Airbus and Boeing and by various military organizations. In the military, electronic LRUs are typically designed to interface according to data bus standards such as MIL-STD-1553.[5] On the International Space Station, LRUs are referred to as Orbit Replaceable Units.
[edit] See also
- Annex: Acronyms and abbreviations in avionics
- Avionics
- Source, Maintenance, and Recoverability Code
- Spare part
- Two-Level Maintenance
- Three-Level Maintenance
- Line-Replaceable Module (LRM)--commonly a circuit card component of a LRU designed to be repaired at the organizational Level (O-Level Maintenance).
- Shop-Replaceable Unit (SRU)--commonly a circuit card component of a LRU designed to be repaired at the field Level (at a backshop, known as I-Level Maintenance).
[edit] References
- ^ [1]
- ^ A comparative evaluation of the reliability improvement in line replaceable unit
- ^ Welcome to IEEE Xplore 2.0: Line Replaceable Unit (LRU) Analysis in the Space Shuttle Orbiter Electrical Power System
- ^ A Cost Trade-Off Analysis of F-16 Line Replaceable Unit (LRU) Packaging Options
- ^ "The B-52H Integrated Weapon Interface Unit (IWIU) program is a newly developed Line Replaceable Unit (LRU) which will replace the current 1980s developed LRU’s which are becoming unsupportable. The LRU’s currently installed in the Stub Pylon/Heavy Stores Adapter Beam (SP/HSAB) provide the command and control link between the B-52H Offensive Avionics System and all “smart” MIL-STD 1760 current and future weapons carried on the B-52H." United States Department of Defense Contracts, No. 615-07, May 21, 2007
