Reliability Based Aircraft Maintenance Optimization and Applications

He Ren, Xi Chen, Yong Chen

• Éditeur: Academic Press
• Année: 2017
• ISBN:
  9780128126691
• Sujet: Tecnología e ingeniería
• Sous-sujet: Transporte y navegación

Reliability Based Aircraft Maintenance Optimization and Applications presents flexible and cost-effective maintenance schedules for aircraft structures, particular in composite airframes. By applying an intelligent rating system, and the back-propagation network (BPN) method and FTA technique, a new approach was created to assist users in determining inspection intervals for new aircraft structures, especially in composite structures.

This book also discusses the influence of Structure Health Monitoring (SHM) on scheduled maintenance. An integrated logic diagram establishes how to incorporate SHM into the current MSG-3 structural analysis that is based on four maintenance scenarios with gradual increasing maturity levels of SHM. The inspection intervals and the repair thresholds are adjusted according to different combinations of SHM tasks and scheduled maintenance.

This book provides a practical means for aircraft manufacturers and operators to consider the feasibility of SHM by examining labor work reduction, structural reliability variation, and maintenance cost savings.

• Presents the first resource available on airframe maintenance optimization
• Includes the most advanced methods and technologies of maintenance engineering analysis, including first application of composite structure maintenance engineering analysis integrated with SHM
• Provides the latest research results of composite structure maintenance and health monitoring systems

Chapter 1

Introduction

Abstract

This book is going to determine flexible and cost-effective maintenance schedule for aircraft structures particular in composite airframes. By applying an intelligent rating system, the back-propagation network (BPN) method, and FTA technique, a new approach was created with a powerful learning ability and a flexible data fusion capability, to assist in determining inspection intervals for new aircraft structures, especially in composite structure. Also, this book discusses the influence of Structure Health Monitoring (SHM) on scheduled maintenance. An integrated logic diagram was established incorporating SHM into the current MSG-3 structural analysis, based on which four maintenance scenarios with gradual increasing maturity levels of SHM were analyzed. The inspection intervals and the repair thresholds are adjusted according to different combinations of SHM tasks and scheduled maintenance. This book provides a practical means for aircraft manufacturers and operators to consider the feasibility of SHM by examining labor work reduction, structural reliability variation as well as maintenance cost savings. Finally, A380 Reliability and Maintainability program, as an example, is explained in this book.

Keywords

life-cycle cost

Maintenance Engineering Analysis (MEA)

maintenance review board (MRB)

composite materials

reliability engineering

Structure Health Monitoring (SHM)

Chapter Outline

1.1 Challenges of Modern Developing Commercial Aircraft

1.2 Evolution of Aircraft maintenance Process

1.3 Aircraft Composite Structures

1.4 Reliability-Centered Maintenance

1.4.1 Reliability Design

1.4.2 Reliability-Centered Maintenance

1.5 MSG-3 Structural Analysis

1.6 A380 Maintenance Programs

1.7 Summary

1.1. Challenges of modern developing commercial aircraft

In the new millennium, economy and development have grown significantly to accommodate a rising number of air travelers. Future demands for increased convenience and safety in the aviation industry will be prompted by new developments in aircraft technologies. Driven by a strong economy, new entrants, large emerging markets, and increasing liberalization, air travel has grown nearly 30% since 2000, the strongest recovery in aviation history [1]. According to the forecast by Airbus, world passenger traffic is expected to increase by 4.8% per annum. In the largest emerging market, China, aviation passenger traffic volume grew 3.6 times, greater than the growth in railway and highway traffic volume during the period of 2001–12 [2]. It is estimated that more than 3000 new aircraft are needed in the next 20 years for the domestic market alone, and that by the year 2032 the volume of passenger traffic will account for 16% of the world’s total, approaching the scale of the North America region [3].

To meet the booming civil aviation demand, new generation aircraft with modern technology is designed to be safer, more comfortable, and with greater fuel efficiency. The number and scale of the airport is being expanded to increase the capacity of airplane accommodation. Moreover, the operation efficiency is of key importance as the operational cost accounts for a large portion of the life-cycle cost. From the perspective of system engineering, a scientific maintenance strategy that is determined at the beginning or is updated in time can assure cost-effective aircraft operation and high flight safety. A typical figure indicating the cost relationship is shown in Fig. 1.1 [4].

Figure 1.1 Opportunity for affecting logistics and system effectiveness.

Aircraft maintenance is developed to be an independent multidiscipline subject. For example, Maintenance Engineering Analysis (MEA) is carried out to synthesize many programs from different disciplines, such as failure mode and effect analysis, damage and special events analysis, logistic-related operations analysis, and software support analysis, and so on. Then a systematic analysis is conducted in order to make proper maintenance plans and activities.

A continuous airworthiness maintenance program is a compilation of the individual maintenance and inspection functions utilized by an operator to fulfill total maintenance needs. Authorization to use a continuous airworthiness maintenance program is documented and is approved by the Federal Aviation Administration (FAA). The basic elements of continuous airworthiness maintenance programs comprise aircraft inspection; scheduled maintenance; unscheduled maintenance; engine, propeller, and appliance repair and overhaul; structural inspection program or airframe overhaul; and required inspection items. A traditional deviation of maintenance activity is shown in Fig. 1.2 [5].

Figure 1.2 Types of maintenance activity.

Following approval by the FAA, engineering provides the work package to the maintenance units and monitors standards. Engineering tasks include providing technical documentation, technical fleet management and planning, airworthiness control, schedule planning, reliability monitoring, quality assurance, and training. Engineering is much more than a “technical function.” It is a “knowledge function” that works very closely with the maintenance function to optimize maintenance programs, increase fleet reliability, and facilitate flexible deployment.

With the fast development of modern technology, new materials and design concepts are being integrated into new aircraft and, thus, the traditional or existing maintenance programs may not be competent to the new requirements. For example, advanced sensors and data processing capability are promoting innovative monitoring methods, which may exert a profound influence on the current scheduled maintenance.

1.2. Evolution of aircraft maintenance process

The principle behind the construction of modern aircraft maintenance schedule is a documentation produced by Air Transport Association (ATA) maintenance steering group (MSG). The concept started in the 1960s by FAA on the first generation of wide body aircraft, that is, the Boeing 747, DC10, and L1011. Before the application of MSG Logic, hard time (HT) principal was in use, which based maintenance for the aircraft on the theory of preventive, yet expensive, replacement or restoration of components [6].

The process-oriented approach to maintenance uses three primary maintenance processes to accomplish the scheduled maintenance actions. These processes are called HT, on-condition (OC), and condition monitoring (CM) [7]. The HT and OC processes are used for components or systems that, respectively, have definite life limits or detectable wear-out periods. The CM process is used to monitor systems and components that cannot utilize either the HT or OC processes. These CM items are operated to failure, and failure rates are tracked to aid in failure prediction or failure prevention efforts. These are called “operate to failure” items.

The process used involved six industry working groups (IWGs), which includes structures, mechanical systems, engine and auxiliary power unit (APU), electrical and avionics systems, flight control and hydraulics, and zonal. Each group addresses their specific systems in the same way to develop an adequate initial maintenance program. The first MSG focuses on developing how to conduct a logical decision process to develop efficient, cost-effective maintenance routines that are acceptable to operators, manufacturers, and regulating authorities. The IWGs analyze each item using a logic tree to determine the requirements in the areas of functions, failure modes, failure effects, and failure causes. This approach to maintenance program development is called a “bottom up” approach because it looks at the components as the most likely causes of equipment malfunction [7].

Over time, the MSG process has evolved from a hard-time concept to CM. The process allows malfunctions to occur and relies upon the analysis of information about such malfunctions to determine the proper actions. To improve upon this method, MSG-2 was designed and then modified in 1980 in a document released by the ATA. Then, MSG-3 was built upon the existing framework of MSG-2. It adjusted the decision logic to provide a more straightforward and linear progression through the logic. MSG and MSG-2 are both bottom-up approaches; in contrast, the MSG-3 process is a top-down approach or consequence-of-failure approach. The component failures or deteriorations are not the main focus of the process; instead, the consequences of the failure and how it affects aircraft operations is considered. The idea is to cover and analyze each task based upon these three dimensions across the full decision tree. A simplified diagram [8] is shown in Fig. 1.3.

Figure 1.3 MSG-3 logic diagram.

The result of the MSG-3 analysis constitutes the original maintenance program for the new model aircraft and the program that is to be used by a new operator of that model. The tasks selected in the MSG process are published by the airframe manufacturer in an FAA-approved document called the maintenance review board (MRB) report. This report contains the initial scheduled maintenance program and is used by those operators to establish their own FAA-approved maintenance program as identified by the operations specifications. The MRB report, the manufacturer publishes its own document for maintenance planning. For manufacturers like Airbus or Boeing, this document is called the maintenance planning document (MPD). This document often groups maintenance as an alphabetical checklist with hours, cycles, and calendar time. These estimated times must be altered by the operator to accommodate the actual task requirements when planning any given check activity.

1.3. Aircraft composite structures

Composite materials are a new generation of materials that are increasingly used in the aviation industry. Since the 1970s, composite materials were first used on nonload bearing structures, such as radomes, fairings, and for inner decoration. In the 1980s, secondary structures began to be constructed with composite materials, but their use was still limited in structures like control surface panels. In the new millennium, the use of composite materials has shifted from secondary structures to primary structures. Typical examples are the world’s largest aircraft, the Airbus 380, and the most advanced aircraft to date, the Boeing 787. More precisely, the composite structures used in the Airbus 380 weigh more than 30 tons, comprising 25% of the total airframe weight. The entire center wing box is made with composites [9]. The Boeing 787 adopts composite materials for the entire fuselage. Besides this, many components on the wing and nacelle are built with composite materials, so that composites account for 50% of the airplane [10]. Recently, the first prototype of the A350 was manufactured and the use of composite materials accounts for up to 52% of the plane [11], which marks very significant progress for Airbus and for the entire aviation industry. The development of composite materials by two leading aircraft manufacturers over the past two decades is depicted in Fig. 1.4....