This Is How Aircraft Are Kept Reliable

This Is How Aircraft Are Kept Reliable

Aircraft maintenance is made up of a number of elements: apart from the actual physical act of maintaining aircraft, a great deal of planning and careful consideration have gone into laying out the maintenance process. From the Maintenance Planning Document, to the Approved Maintenance Program, and all the details in between, aircraft maintenance constitutes a complex tree of processes, procedures, and parts. One such part is the reliability program.

Source: Sassofia


Reliability programs are mandatory and serve an important purpose. Their basic functions are to reflect the effectiveness of the maintenance program and the way in which maintenance is carried out. They are meant to provide significant and timely technical information to aid in improving aircraft reliability. While reliability programs are developed by the a Continuing Airworthiness Management Organization (CAMO), the responsibility ultimately lies with the operator.

Often times, changes made to the maintenance program are justified by data from reliability programs. These changes may be to escalate, de-escalate, remove, add or vary maintenance tasks. Data extracted from the program is a combination of statistical monitoring and recording, based on events associated with the airworthiness of the aircraft in the fleet.


Data Collection

Primarily, reliability programs collect data. Through the analysis of this data, feedback on issues, irregularities and inefficiencies can be identified. The basis of this data collection relies heavily on various parameters, such as flight hours and cycles, technical delays, pilot reports (PIREPS), mean time between unscheduled removals (MTBUR) and shop visits.


Useful Comparisons

Source: Medium

In the airline industry, constant comparisons with other airlines – also known as benchmarking – serve a helpful purpose. This is where reliability programs come in useful: by helping airlines determine how well they fare, in comparison to their fellow peers and competitors. When it comes to reliability, comparisons for the same type of aircraft can be classified into four main indicators:

  1. General aircraft reliability

Includes indicators such as aircraft availability, and aircraft despatch reliability (the probability that the aircraft will take off on scheduled time).

  1. Systems reliability

Data for systems reliability from pilot reports (PIREPS) is collected and classified accordingly under the individual aircraft systems (relevant ATA Chapters, which include hydraulic power, flight controls, and so forth). Each operator sets their unique Alert Level, based on aircraft utilisation. The PIREPS rates are compared to the set Alert Level, and from this, trends can be studied to identify any signs of impending failure.

  1. Aircraft component reliability

The reliability of each aircraft component is determined by the number of unscheduled removals. The Unscheduled Removal Rate (URR) of each component is compared against the Alert Level to identify which components fail too frequently and require investigation.

  1. Power plant reliability

Data pertaining the reliability of power plants are obtained by monitoring shop visits, in-flight shutdowns and unscheduled removals.


Data Analysis

Source: dashboardinsight.com

After collecting the required data mentioned above, we can then determine the state of the system. Basing off results from the indicators, the system can be labelled as stable, unstable, and critical.

  • Stable: reliability indicators exist within control levels
  • Unstable: the parameter exceeds control levels, or enters the critical zone, but returns below control levels.
  • Critical: reliability is compromised

For a given fleet, feedback on flight operations and maintenance programs play a large role in maintaining airworthiness. Not only will the operator achieve refined levels of safety as a result of a functional reliability program, manufacturers, too, can make use of results obtained from the reliability programs of various operators. Reliability programs help detect defects, leading to modifications and installations to improve later versions of aircraft that roll off the production line.

An operator that has a solid reliability program is benefited in terms of optimized aircraft utilization, which translates to higher revenue because fewer aircraft are left in downtime. Moreover, airlines can also save on avoidable maintenance costs. A good reliability program helps the operator reduce delays, keeping both brand image and passenger satisfaction high – nobody likes flying with a constantly delayed airline!

All in all, reliability programs help keep the operator’s maintenance program in check by assessing its effectiveness. In turn, this keeps the fleet in a reliable state. And besides safety, reliability programs enhance the airlines’ revenue, brand image, customer satisfaction, maintenance and overall continuity of operations.

More information regarding aircraft maintenance and CAMO services, can be found at www.dviation.com.

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