Arbitrary Escalation Caps (AES)

Transcription

1 White Paper By Ed Adams, Senior Consultant and Dave Nakata, VP Consulting Services Operator maintenance program escalation proposals of greater than ten percent often elicit grave reservations from a variety of sources. These concerns intensify when the escalation involves an entire C or D check. To some degree, the concerns may be raised because the regulatory authority or other interested parties do not have confidence in the operator s processes and motivations. Perhaps, the operator has a history of making escalations with inadequate quantitative and qualitative justification. Considering these reservations, the current financial state of the airline industry and a growing awareness of the human factors impact on aircraft maintenance, scheduled maintenance task or check interval adjustments need to be planned to yield optimal intervals. New business practices and modern Continuing Analysis and Surveillance System (CASS)-based reliability policy and programs are needed to provide the means for operators to make significant and justified adjustments to scheduled maintenance task or check intervals. Today, some operators are able to adopt the revised Maintenance Review Board (MRB) Report s check interval changes with minimal effort, while other operators navigate through an extremely challenging and timeconsuming process to gain the same benefit. In some instances, operators have been significantly tested to demonstrate that an escalation, based on the MRB, will not increase safety risks or have a negative effect on operational performance. Conversely, some operators have made scheduled maintenance task or check escalations beyond MRB recommended intervals using their best judgment and regulatory authority approved processes. An escalation greater than the MRB interval can be a long and arduous task and in some cases has made for contentious relations between the operator and their regulatory authority. In order to preclude or minimize this type of issue, best business practices need to be combined with engineering expertise, risk analysis, science, critical thinking and logical rules to provide a means for operators to optimize scheduled maintenance task and check intervals.

2 Best business practices are the key to optimizing scheduled maintenance task and check programs. These practices are needed for a number of reasons including: 1. The industry is in financial distress and most operators must reduce costs across the board in order to survive and be competitive. 2. A major aircraft safety incident or crash would likely be very harmful or fatal to an operator in today s competitive marketplace. This is especially true if an escalation was found to be a contributing factor. 3. An operator s scheduled maintenance program must be optimized to minimize the number of aircraft removed from revenue service for planned maintenance. 4. The scheduled maintenance requirements must be optimally effective to minimize aircraft downtime and unscheduled out of service time. Best business practices leading to optimally scheduled maintenance task and check interval escalations start with an approved CASS-based reliability program. Program elements and expected benefits associated with this program highlighted in the following table. Continuing Analysis and Surveillance System (CASS)- Based Reliability Program Program Elements Critical Thinking Logical Processes Risk Analysis Quantitative Measurements Qualitative Information Ongoing Surveillance Other Functions, As Required Benefits Enhanced Safety Margins Dynamic Decision Making Process Reduced Risk Improvement in Operational Performance Increased Cost Effectiveness If an operator has an approved CASSbased reliability program that meets or exceeds FAA s Air Transportation Oversight System (ATOS) expectations, scheduled maintenance task and/or Ideally an operator only takes an aircraft out of service for scheduled maintenance at an optimal interval, i.e., every task is planned and accomplished at precisely the time needed to maintain the aircraft s inherent levels of safety and reliability.

3 Unfortunately, the need to group tasks to accommodate planning, staffing, facilities and aircraft routing limitations causes some loss of efficiencies. In addition, determining the exact moment a failure will be detectable and repairable is not likely because most components on an aircraft exhibit complex failure modes and varied failure distributions. Those failure causes are usually dispersed over a wide time span and seldom show a direct correlation of failure to time. Therefore, the grouping of tasks into a check requires rigorous policies and procedures that provide an optimal time for task accomplishment without increasing safety risks or degrading operational performance while still minimizing out of service time. Every scheduled maintenance task that is a candidate for escalation needs to be analyzed to assess the impact on operational performance (while maintaining the inherent level of safety and reliability) and on out of service time reduction. Operational performance will improve to some degree with a check escalation because fewer maintenance events equals fewer opportunities for failures early in the component s life and human factors influences will also be minimized. Less is better and If it isn t broke don t fix it definitely and correctly apply to this situation. To simplify the escalation justification process, scheduled maintenance tasks should be categorized and different types of analysis processes should be accomplished on each task within a task category. Assuming this proposed process is approved or allowed by the operator s Operation Specifications, the task analysis could be categorized as follows: 1. The first task category is mandatory, safety-sensitive tasks. Included in this category are tasks such as: Certification Maintenance Requirements (CMR), Airworthiness Limitation Items (ALI), Airworthiness Directive (AD), Life Limited Parts (LLP), and unique national requirements. For example, national requirements apply to the cockpit voice recorder (CVR) and flight data recorder (FDR). Tasks in the mandatory category have a legal basis of origin and the tasks are accomplished by their own specific rules. These tasks should not be embedded in a check or automatically included in a check escalation. These mandatory tasks are generally beyond an operator s authority to revise. Authority to make change is in the hands of the type certificate holder or the regulatory authority. 2. The second category of scheduled maintenance tasks can simply be classified as other. Other tasks include scheduled maintenance tasks derived from Maintenance Steering Group 3 (MSG-3) analysis and reflected in an approved MRB report. In addition, other tasks include scheduled maintenance tasks self-imposed by the operator based on historical justifications, experience, operating environment, and unfortunately sometimes, emotion. Examples of how an operator s program justifies escalations to tasks or intervals in this category include the following:

4 a. For scheduled maintenance tasks like checks, inspections and lubrication of systems that maintain or verify the continued reliability of items like flight controls, engines, auxiliary power units, customer preference items such as passenger seats and inflight entertainment equipment and landing gears, valid sampling of historical data providing a ninety-five percent confidence factor in the data should be used to identify failure modes and the distribution over time of those failures. b. For scheduled maintenance tasks involving structure, the Corrosion Prevention and Control Program (CPCP) rules that require an operator to prevent level two or three findings and maintain level one or better should be followed. c. Other special considerations apply to some types of structure tasks. For example, fatigue-sensitive structure inspections (ALI) should not be considered candidates for interval adjustment by an operator s program. The above groupings were made broad; specific task analysis will vary by task category because one size does not fit all, which is the concern raised when a check is escalated without a task-bytask analysis. From an advanced task/ maintenance program analysis perspective, there are other analyses and justification methods that could be used to justify check escalations. For example, a matrix of indices that consider every four-digit Air Transport Association (ATA) subject could be used to filter out specific ATA subjects that do not need a detailed analysis if certain conditions are quantified. Although, for those ATA subjects that don t satisfy the conditional requirements, a detailed failure mode, corrective action, final fix and probability of failure distribution analysis process could be justified. Historically, MRB task and check intervals are conservative because they are founded on little or no actual operational experience and the working groups derive them through consensus. Limiting all operators to some arbitrary escalation cap such as no more than a ten percent escalation of those conservative intervals can create problems. For example, in most instances, a ten percent escalation will not move most operators out of the planning window used to schedule aircraft into check. In some instances, operators bring aircraft into check at ninety percent of the approved interval. Therefore, they will not surpass the original interval except in a few instances. It is hard to justify the effort to develop an escalation with so little to gain. With a ten percent escalation cap, an operator would need to justify a minimum of five escalations to achieve a one-day gain for a task that is scheduled and being accomplished on a daily basis. Many perspectives are needed in the check escalation analysis process. The following examples highlight some possible process considerations: 1. TScientific methods are used to determine remaining useful life for oil and air filters, which quantitatively determines how many additional flight hours the filter could remain in service.

5 2. Engineering expertise is used to measure cabin door assist bottle leak rates based on how often bottles have been serviced. 3. Reliability analysis is used to find unscheduled maintenance actions that are related to tasks in the check. Critical thinking must be used to determine if change can be made to a scheduled maintenance task or check interval. For example, the following types of decision tree questions should be asked: 1. Are the failures random in nature or somewhat predictable? 2. Are the failure consequences purely economic or do the failures ever lead to an operational difficulty event? 3. Could an improved failure-finding task be added to the maintenance program? 4. Could a modification be more effective to improve inherent levels of reliability than an on-going maintenance task? Finally, operators must use their talents and expertise wisely and continuously to minimize safety risks, improve operational performance and reduce maintenance costs. The airlines need to apply best business practices and a modern CASS-based reliability program to dynamically adjust their scheduled maintenance requirements in a professional, safe and realistic manner. Ed Adams, Senior Consultant Mr. Adams has over forty years of aircraft maintenance experience in roles ranging from mechanic and crew chief to manager of reliability programs. He has been a member of numerous industry working groups defining best practices for maintenance and reliability programs. Dave Nakata, VP Consulting Services Mr. Nakata is a thirty-eight year veteran of the aviation maintenance industry. He is a recognized authority in development and implementation of approved maintenance, CASS, reliability and quality assurance programs.