When conducting inspections and maintenance of an aircraft, there are often two categories it can fall into. The first category is scheduled maintenance which is conducted annually, before flights, on timed intervals, or any other pre-scheduled time by the pilot and/or technician. The other type is unscheduled maintenance and is conducted whenever a problem arises and needs to be checked and solved. Understanding the two is very important for pilots for safe flight and preservation of their equipment.
Scheduled aircraft maintenance services are conducted regularly to ensure that aircraft always remain airworthy and safe for operation. Before each and every flight, checks are done to scan the aircraft for obvious malfunctions, defects, damages, etc. Checklists are often implemented and referred to as to ensure that there is nothing missed by the pilot. These lists are comprehensive as a pilot is to check areas such as the battery, aircraft cockpit, cabin, and more.
Maintenance may also be done on certain timed intervals, such as 50/100 hours and annual inspections. Commercial aircraft often undergo checks every 50 hours, and then required to have inspections every 100 hours. 50 hour checks include changing oil, cleaning, replacing damaged components, and more. 100 hour inspections are much more in-depth as they are required by the FAA and involve removal and testing of various components. Annual checks are similar to 100 hour inspections, though they are much more comprehensive as engines, logbooks, flight controls, and other systems are inspected.
Unscheduled maintenance can arise at any time and should be done whenever there is an assumption or indication that a component is malfunctioning. Unscheduled maintenance can come about if a problem is found during normal scheduled inspection as well, as any problem demands immediate attention and MRO before flight is permitted. When these problems arise, the aircraft is grounded until a technician can address the issue and deem the aircraft airworthy again.