Line-replaceable units (LRUs) are commonly used in airplanes. Also known as line-replaceable items and line-replaceable components, they consist of aircraft components that can be removed and replaced on the fly.
Airplanes are complex vehicles with many different components. When taking into account fasteners and other small components, some airplanes have millions of components. Fortunately, there are certain components that technicians can easily swap out. Known as LRUs, they generally consist of four types of components.
#1) Avionics
There are avionics components that fall under the category of LRUs. Avionics are electronic devices and systems in airplanes. Some of them are used for communication purposes, whereas others are used for navigation and flight management purposes. Avionics components that can be removed and replaced on the fly without disassembling other components are considered LRUs.
#2) Mechanical
Some LRUs are mechanical. Mechanical LRUs include components that move during operation. Landing gear actuators and flap actuators, for instance, move during operation. They can typically be replaced on the fly — just like the aforementioned avionics components. Therefore, landing gear actuators and flap actuators are classified as LRUs.
#3) Powerplant
There are also powerplant LRUs. Powerplant LRUs involve propulsion systems, such as propellers and engines. All airplanes have a propulsion system. Certain components of the propulsion system may be classified as LRUs, assuming they can be removed and replaced on the fly.
#4) Electrical
Finally, there are electrical LRUs. Not to be confused with avionics, electrical LRUs include individual electrical components, such as circuit breakers and generators. Circuit breakers are safety devices that are designed to protect against overcurrent. Generators, on the other hand, are devices that generate electricity. On some airplanes, electrical components such as these can be swapped out on the fly, so they are classified as LRUs.
Why Airplanes Use LRUs
You might be wondering why airplanes use LRUs. For starters, they allow for faster and easier maintenance. Technicians can replace LRUs on the fly. They don’t have to disassemble other components. Rather, technicians can pull out the old or damaged LRU and replace it with a new one.
LRUs also offer cost-saving benefits. Airlines can save money on maintenance expenses by using them instead of other, more permanent components. LRUs even help to prevent flight delays. If there’s a problem with a particular LRU that’s keeping the airplane on the tarmac, the airline can swap it out, resulting in a shorter delay.
