What is Aircraft TBO and what is its function?

Aircraft TBO (Time Between Overhauls), also known as the time before overhaul, is a critical factor in determining the lifespan of an aircraft's engine. The recommended time or cycle between engine overhauls is established by the engine manufacturer and is essential for maintaining the engine's longevity.

The determination of an Aircraft Engine's TBO involves a comprehensive process. The engine manufacturer sets TBO based on data collected during the new engine's operation under various conditions and flying environments. This data, which includes materials research, flight testing, and field experience, is then submitted to the FAA for approval. The FAA conducts regular reviews every five years to ensure the continued accuracy of TBO. If revisions are necessary, the FAA collaborates with the manufacturer to update TBO. However, any attempts by manufacturers to increase TBO without additional research are not approved by the FAA.

Most piston-powered aircraft engines have a TBO ranging from 1,800 to 2,400 hours, while high-performance engines may reach TBOs as high as 3,600 hours. Turbine-powered engines typically have a TBO between 3,500 and 6,000 hours. Exceeding the recommended TBO poses the risk of irreparable engine damage, emphasizing the importance of tracking TBO and scheduling regular maintenance.

TBO extensions

TBO extensions are possible through reputable programs that can lengthen the time between overhauls by up to 2,000 hours, providing a cost-effective alternative to major engine overhauls. The FAA allows continued operation past TBO as long as the engine meets mandatory service bulletins, airworthiness directives, and is used in Part 91 or Part 135 operations. Confirmation of airworthiness during inspections by a mechanic is also crucial.

To extend an aircraft engine's TBO, owners can follow the manufacturer's recommended maintenance schedule or opt for a TBO extension program. Regular maintenance, adhering to the manufacturer's specifications, and timely inspections are vital to ensure the engine's peak performance and longevity.

Time Since Major Overhaul (SMOH) is a distinct concept from TBO, representing the time passed since a major overhaul was performed on an engine or its components. While a low SMOH can be advantageous when purchasing an aircraft, it is essential to recognize that SMOH and TBO are not interchangeable terms.

TBO Maintenance

Regular maintenance is key to prolonging an aircraft engine's life. In addition to following the manufacturer's specifications and maintenance schedule, operators can enhance engine longevity by operating within approved power ranges, avoiding prolonged operation at low power settings, flying in moderate climates, keeping the aircraft clean, using quality aviation fuel, and proper storage when not in use.

A Hot Section Inspection (HSI), conducted at half the recommended TBO interval, ensures the turbine section's proper condition. Overall, these measures contribute to the safety and effectiveness of aircraft operations.