Understanding Scheduled and Unscheduled Aircraft Maintenance

All aircraft need periodic inspections and maintenance in order to ensure they are airworthy and safe to fly. Some of that maintenance is pre-scheduled and known to both the pilot and aircraft technician. Other types of maintenance are sudden and unscheduled, which can be due to problems found by the pilot or by the A&P performing an inspection. For pilots and aircraft owners, it is important to understand the differences between scheduled and unscheduled aircraft maintenance.

Understanding Scheduled Aircraft Maintenance

Scheduled aircraft maintenance is preventative maintenance that is performed at regular intervals. This type of maintenance generally includes 100-hour inspections, annual inspections, and progressive inspections as well as preflight checks to ensure the aircraft is airworthy and ready to be flown.

1. Preflight Checks

Every pilot is required to perform certain preflight checks in order to make sure the aircraft is ready to be flown and that there are no obvious defects or malfunctions. When a pilot or student pilot performs a preflight check, he or she must use a checklist in order to ensure nothing is forgotten. Preflight checks include walking around the aircraft and inspecting all the major components of the fuselage and flight control surfaces for defects, wear and tear, and other deformities that may impede the safety of the flight. The cockpit, cabin, avionics, and battery are also checked and tested for proper operation and function prior to the flight. If any abnormalities are found, the pilot does not depart and instead contacts a maintenance technician for repairs.

2. 50 and 100 Hour Inspections

Aircraft that are flown for hire or for flight instruction are required to have 50-hour checks and 100-hour inspections. It’s important to understand that the 50-hour inspection isn’t FAA mandated. However, aircraft owners should still consider it due to the fact that the oil must be changed every 50 hours. In addition to changing the oil, the 50-hour inspection may also include examining, cleaning and gapping the spark plugs and checking the engine for wear and tear. If any excessive wear and tear or problems are found, those components are replaced in order to maintain the aircraft’s airworthiness. This is also a good time to address any problems or minor maintenance issues noticed by the owner or pilot of the aircraft.

100-hour inspections are required by the FAA, and those regulations can be found under FAR 91.409b. During a 100-hour inspection, all inspection plates, access doors, cowlings and fairings are removed, and all of the major components of the aircraft are inspected. This typically includes the fabric and skin of the fuselage, the windows, cabin and cargo doors and the flight control surfaces as well as the tires, brakes, struts and landing gear.

Inside the aircraft, the cabin and cockpit are inspected for any potential issues such as loose controls and objects and seat and seat belts malfunctions. The avionics, yoke, fuel switches, flight controls and battery are also inspected and tested. The engine and engine area are also inspected and routine maintenance is performed, such as cleaning the spark plugs and changing the oil. If defect or damage is found, repairs are made to ensure the aircraft remains airworthy in accordance with all applicable FAA regulations.

3. Annual Inspections

Annual inspections are performed once every 12 calendar months and are required for all aircraft, regardless of whether they are used for hire, flight instruction or for recreational use. FAR 91.409a sets up the requirement for an Annual Inspection while FAR 43 Appendix D outlines the detail and scope of the inspection itself.

Annual inspections are typically more detailed than 100-hour inspections. The annual commonly includes all of the inspections performed in the 100-hour, such as, review of all the aircraft logbooks and testing and inspecting the engine, flight surfaces, flight controls and avionics. If obvious defects and/or problems are found during the annual inspection, they are noted so that they can be repaired and the aircraft airworthiness restored.

4. Progressive Inspections

Progressive inspections are also known as phase inspections, and they are typically utilized when an aircraft can’t afford to spend a lot of time in the maintenance hangar due to its flight schedule. These inspections also occur at regular intervals. For example, a progressive inspection may be performed every 25 or 50 hours. During each inspection, certain components of the aircraft are examined and tested for proper operation. The inspections are also performed in an organized manner so that all of the requirements for 100-hour and annual inspections are completed on-time.

Understanding Unscheduled Aircraft Maintenance

Unscheduled aircraft maintenance occurs anytime a component has malfunctioned or is suspected of malfunctioning, and by definition, this maintenance is unforeseen. It can occur after the pilot finds a problem during the preflight inspection, as the result of an in-flight malfunction, or as the result of problems found during 100-hour, annual, and progressive inspections.

Examples of unscheduled maintenance could be anything from a worn tire, low landing gear strut, or sheared vacuum pump to in-flight issues such as a rough running engine or high magneto drop during run-up. Upon discovery, the pilot would report the problem to the A&P technician and fill out a maintenance request. At this point, the aircraft would be grounded until the problems are repaired and the aircraft is deemed to be airworthy by the technician.

Getting Your Scheduled and Unscheduled Maintenance Performed at Double M Aviation

Our A&Ps at Double M Aviation in Lakeland can perform all of your scheduled and unscheduled maintenance in a timely and affordable manner. We offer 50-hour, 100-hour, annual, and progressive inspections as well as efficient responses to all unscheduled maintenance. Every aircraft is personally flown by our IA after each scheduled inspection so you can be confident that your aircraft is airworthy and ready for your next flight.

To learn more about our inspections and to schedule an aircraft inspection or maintenance, call us at 863-940-3450.


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