Flight Redemptions

What is MTBUR in Aviation? (Mean Time Between Unscheduled Removals)

Updated: March 05, 2024

The Importance of Mean Time Between Unscheduled Removals (MTBUR) in Aviation

Aviation is a complex industry that relies on the safe and efficient operation of aircraft. One crucial factor in ensuring the reliability of an aircraft is the Mean Time Between Unscheduled Removals (MTBUR). This term, often abbreviated as MTBUR, refers to the average time that elapses between two consecutive unscheduled removals of a component or system from an aircraft. In this article, we will explore the significance of MTBUR in aviation, its impact on safety and maintenance, and how it is calculated.

Understanding Mean Time Between Unscheduled Removals (MTBUR)

Mean Time Between Unscheduled Removals (MTBUR) is a metric used in aviation to assess the reliability and maintenance requirements of aircraft components and systems. It measures the average time that a component or system can operate without experiencing a failure that requires its removal from the aircraft for repair or replacement. MTBUR is an essential parameter in aviation maintenance planning, as it helps determine the frequency of inspections and the replacement schedule for components and systems.

MTBUR plays a vital role in aviation safety. By monitoring and analyzing the MTBUR of various components and systems, maintenance personnel can identify potential reliability issues and take proactive measures to prevent failures during flight. This proactive approach helps minimize the risk of in-flight failures, which can have catastrophic consequences. Additionally, maintaining a high MTBUR reduces the frequency of unscheduled maintenance events, which can disrupt flight schedules and increase operational costs for airlines.

The Calculation of MTBUR

The calculation of MTBUR involves collecting data on the number of failures and the total operating time of a component or system. The formula for calculating MTBUR is:

MTBUR = Total Operating Time / Number of Failures

For example, let's consider an aircraft's hydraulic system. If the hydraulic system operates for a total of 10,000 hours and experiences 20 failures during that time, the MTBUR for the hydraulic system would be:

MTBUR = 10,000 hours / 20 failures = 500 hours

Therefore, the hydraulic system has an MTBUR of 500 hours. This means that, on average, the system can operate for 500 hours before experiencing a failure that requires its unscheduled removal for repair or replacement.

The Significance of MTBUR in Aviation Maintenance

MTBUR is a critical parameter in aviation maintenance planning. It helps maintenance personnel determine the optimal inspection intervals and replacement schedules for components and systems. By considering the MTBUR of different aircraft parts, maintenance teams can prioritize their efforts and allocate resources efficiently.

High MTBUR values indicate that a component or system is reliable and can operate for extended periods without requiring unscheduled maintenance. In such cases, maintenance teams may opt for longer inspection intervals or delay component replacement until it reaches its expected service life. This approach can help reduce maintenance costs and minimize disruptions to flight operations.

On the other hand, low MTBUR values can indicate reliability issues with a component or system. If a particular part consistently experiences failures and has a low MTBUR, maintenance personnel may need to increase inspection frequency or consider replacing the component earlier than planned. This proactive approach helps identify and address potential safety risks before they lead to in-flight failures.

Implications for Aviation Safety

The MTBUR of aircraft components and systems directly impacts aviation safety. Unscheduled removals and failures during flight can pose significant risks to the aircraft, crew, and passengers. By monitoring and analyzing MTBUR values, maintenance personnel can identify components or systems with low MTBUR and take appropriate actions to mitigate the associated risks.

For example, if a critical system, such as the aircraft's engine, consistently exhibits a low MTBUR and experiences frequent failures, maintenance teams may decide to replace the engine earlier than scheduled or implement more frequent inspections. These proactive measures help ensure the reliability and safety of the aircraft, reducing the likelihood of in-flight failures that could lead to accidents.

Overall, MTBUR serves as a valuable tool in aviation maintenance, allowing for effective planning and resource allocation. By considering the MTBUR of aircraft components and systems, maintenance teams can enhance safety, minimize disruptions to flight operations, and optimize maintenance costs. Regular monitoring and analysis of MTBUR values contribute to the continuous improvement of aviation safety and reliability.


FAA Advisory Circular AC 20-152
Reliability analysis and optimization of aircraft systems - ScienceDirect

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