LRU is an acronym which stands for Line Replaceable Unit.
An LRU can be a Rotable, Repairable or Expendable inventory item of the aircraft or the engine that can be removed and installed. These are modular components that are designed for quick replacement.
If a component fails to operate, it could be a better option to invoke an MEL or replace the failed LRU by a serviceable unit and dispatch the aircraft. The intent is to improve aircraft serviceability (operations) and to reduce delays and cancellations.
LRUs have fasteners and connectors for easy and quick installation and removal.
LRUs are sealed units with easily identifiable part number and other essential details for tracking and other logistics requirements. The tracking is done individually and does not necessarily follow the operation cycle of the higher assembly or the aircraft.
LRUs can be stocked and replaced quickly from on-site inventory, restoring the aircraft back to service, while the failed (unserviceable) LRU can be repaired later.
Coordination to dispatch the unserviceable (U/S) inventory for appropriate repair or overhaul, sourcing a replacement and managing the inventory level involve a combination of technical and commercial skill.
Different LRUs are manufactured by different manufacturers (OEM) and airlines for ease of operation, and might provide a contract to a single agency who can repair / overhaul most of the LRUs.
Awareness about LRU repair agencies and different types of contracts becomes an important part of aircraft maintenance engineer courses.
The LRU repair agencies are FAA 145 / EASA 145/ DGCA 145 approved repair stations.
As per the published records, for airline operations, fuel expense accounts around 37 percent of operating cost. Aircraft and component maintenance stand second. Hence, operators aim to achieve longer operation time and minimum downtime for maintenance to reduce maintenance overhead.
To achieve this quick dispatch of aircraft, it requires availability of a pool of parts or components at strategic locations. The airline can then request a component from this pool. The requested ’serviceable’ component is then exchanged for their ’unserviceable’ component. The unserviceable component is shipped back to the MRO provider, repaired, and finally restocked to be further exchanged in the future.
While the Airline gets the liberty to choose the MRO service provider, there are certain governing parameters which airlines evaluate.
Few parameters are listed below.
| Age of LRU |
| AOG support |
| Approvals from EASA / FAA / GCAA / DGCA |
| Compensation clauses for premature failures |
| Contract termination clauses |
| Cost per hour of operation |
| Force majeure clauses |
| Handling cost |
| Local presence as per the regulations and national requirements |
| Location of inventory warehouse |
| Modifications, Upgrade, work scope and service bulletin incorporation |
| No Fault Found (NFF) removal rate |
| Rouge criteria |
| Scope of coverage |
| Scope of maintenance (work scope) |
| Shipment cost |
| Special investigations |
| Technical support |
| Technical Support and documentation |
| Turnaround time (TAT) for repair |
| Usage of PMA parts |
| Warranty support |
What is a Rotable and what are its key characteristics
Rotables are aircraft parts that are purchased, placed into inventory as assets, and persist in the inventory system until scrap.
Rotables are treated as assets on the balance sheet of a company.
Have a repair process per a maintenance manual and can undergo from one or more repairs or
overhauls during its lifespan. Rotables accumulate depreciation expense to a residual value during their lifetime.
A proper understanding of all these terminologies is critical and Aircraft Maintenance Online courses essentially help to build and enhance skills in this domain.
by Sumanth Eswar
Ex Assistant Manager-Technical Services, Jet Airways
14 years of industry experience in various sections under Engineering and Maintenance department such as Engineering Planning, Technical Services Engineering including Structures, Cabin Maintenance, Airframe and Systems, Base Maintenance, Powerplant, Reliability, Aircraft Weighing, Rotable Management. Years of Safety Office experience and was a surveyor for Aircraft Insurance