Low Maintenance Costs And
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717-200: LOW MAINTENANCE COSTS AND Low airplane maintenance costs and high dispatch reliability are key to the financial success of any airline. Both these perfor- mance measures are central to the design of the 717-200, the newest Boeing twinjet airplane for the short-haul, high-frequency, 100-passenger market. Airline experience to date indicates that the 717 is exceeding its economic performance targets. RANDY HEISEY REGIONAL DIRECTOR MAINTENANCE MARKETING–AIRLINE ECONOMICS BOEING COMMERCIAL AIRPLANES 18 AERO No.19, July 2002 HIGH DISPATCH RELIABILITY In the competitive airline dispatch reliability requires a discus- Direct airframe and engine maintenance costs are the costs of industry, low direct operating costs sion of the following: the labor and materials required to (DOC) are key to airline profitabil- 1. Industry definition of mainte- perform servicing, repair, modifica- ity. The five elements of DOC are nance costs. tion, restoration, inspection, test, ownership costs, flight and cabin and troubleshooting tasks during 2. Airplane maintainability and on-airplane and shop maintenance crew costs, fuel costs, maintenance reliability by design. activities. Maintenance overhead costs, and other costs (fig. 1). costs are unallocated labor costs and 3. In-service support. Maintenance costs are a signifi- the expenses for maintenance super- cant part of DOC. In fact, the 4. 717 operator experience to date. vision, training,and planning; equip- ment rental; and utilities. Overhead world’s airlines spend more than costs do not include capital expenses INDUSTRY DEFINITION OF for facilities, spares, test equipment, $40 billion on airplane main- 1 MAINTENANCE COSTS tenance each year. Depending maintenance tooling, and ground- The air transportation industry support equipment. on airplane age, type, and range, describes airplane maintenance costs To help operators and manufac- maintenance costs typically as the expenditures required to restore turers understand the relative main- represent 10 to 20 percent of or maintain the systems, components, tenance costs of airplane features DOC. Understanding how the and structures of an airplane in an air- and the factors that influence those worthy condition. These costs include costs, the total cost of maintaining 717-200 provides operators with expenses for direct airframe and engine a specific airplane model can be low maintenance costs and high maintenance and maintenance overhead. subdivided several ways. One method 20 AERO No. 19, July 2002 1 AIRPLANE DIRECT OPERATING COSTS FIGURE Flight and cabin crew Ownership Fuel Maintenance 10% to 20% Direct airframe** 4.5% of DOC* Direct engine** 5% Other Maintenance overhead 7.2% *Varies by airplane type and range **Part of contracted maintenance TOTAL DIRECT AIRPLANE MAINTE- TOTAL DIRECT AIRPLANE MAINTENANCE is to divide maintenance costs 2 NANCE COSTS BY ATA CHAPTERS 3 COSTS BY ROUTINE/NONROUTINE ACTIVITY according to airplane systems, FIGURE FIGURE as defined by Air Transport Association (ATA) chapters (fig. 2). Cost data at the ATA Auxiliary chapter level are used to analyze power unit the effects of design choices Equipment and Routine furnishings and project maintenance costs for new and derivative airplanes. Structure Another approach is di- Landing gear viding total direct airplane maintenance costs according to routine and nonroutine activity Systems (fig. 3). Routine maintenance comprises scheduled tasks outlined in airline maintenance Nonroutine programs. Nonroutine main- tenance involves unscheduled on-airplane repairs and the Represents total Represents total removal and restoration of Engines components. Nonroutine labor and material costs are the primary causes of increasing maintenance costs as an airplane ages. Operators and manufacturers strive to reduce nonroutine maintenance because of its effect on schedule reliability and airplane downtime. No. 19, July 2002 AERO 21 2 AIRPLANE MAINTAINABILITY Involvement of AAGs. maintenance program development. AND RELIABILITY BY DESIGN Unlike AAG participation in earlier Airplane design. The first step in During design of the 717, Boeing airplane programs, the 717 AAGs not the airframe design process was to focused on the interrelated aspects of only reviewed airplane designs but also examine the causes of nonroutine maintainability and reliability. The made design recommendations during maintenance on previous Douglas- design team sought to reduce part the airplane design phases. The most designed twinjet airplanes. MD-80 counts, reduce the number of mainte- important considerations were airplane dispatch delays were attributed to nance and inspection tasks, minimize maintainability, reliability, and main- 1,699 components (i.e., 1,699 six-digit downtime, increase ease of access, tenance costs. AAG meetings focused ATA chapter classifications). Of these, increase commonality of components on numerous improvements to flight 116 components caused 50 percent deck, interior, and airplane system and procedures among 717 systems, of the delays, and their improvement designs, many of which were expected consider human factors related was given the highest priority by the or had been shown to reduce mainte- to maintenance tasks, and improve 717 design team. nance costs and improve reliability in fault-isolation capability. The team also focused on retain- service. For example, the wheel brake The design team implemented ing airplane design elements that mounting was redesigned to signifi- the following key steps to ensure had proved successful on previous cantly reduce removal and installation continuous focus on its design goals: Douglas-designed twinjet airplanes, time. A new design for the potable including the 100,000-cycle airframe ■ Establishment of maintenance cost water system incorporates integrally structural design and the simple, and reliability baselines and targets. heated hoses that eliminate cold- reliable, low-maintenance primary weather cracking and resultant leaks in ■ Involvement of airline advisory flight control system. Figure 4 shows the cargo compartment. A new, sealed groups (AAG). some of the significant 717 airplane flap-position transmitter on the wing design improvements made to lower ■ Assignment of a chief mechanic. protects electrical contacts from ex- maintenance costs and improve posure to the corrosive environment. ■ Continuous focus on maintainability reliability. and reliability targets. Assignment of a chief mechanic. System design. System designs on A chief mechanic was assigned to the 717 predecessors were revised to Establishment of maintenance cost improve component-level design and and reliability baselines and targets. 717 design team to serve as an airline advocate during the design process, ease of maintenance on the 717: Because dispatch reliability and main- specifically in the areas of mainte- ■ The environmental control system tenance costs are directly related and nance and operations. As a peer of the uses three-wheel air-cycle machines, can be improved through increased chief engineer on the design team, which eliminate the need for air- component and system reliability, the chief mechanic ensured that all cycle machine ground cooling fans the 717 design team reviewed the design decisions considered mainte- and reduce scheduled maintenance. dispatch reliability of another Douglas- nance costs, dispatch reliability, and The system has 27 percent fewer designed twinjet airplane, the MD-80, the perspective of airline mechanics, line-replacable units (LRU) than whose design was based on that of the and he was able to increase the team’s the DC-9 and MD-80 design. DC-9. The MD-80 fleet represented a awareness of fleet problems experi- mature airplane program from which enced on previous Douglas-designed ■ The integrated electrical system to draw reliable data. With 1.5 million twinjet airplanes. The chief mechanic reduced the number of major dispatches annually, the MD-80 fleet also monitored changes made during components from 60 to 9, which had a 98.9 percent dispatch reliability the design process to ensure that they eliminated 150 wires compared with at the time that the 717 was designed. had a neutral or positive effect on dis- the DC-9 and MD-80 design. The Using this information, the 717 patch reliability, focusing on the master 717 system features an integrated design team established targets of a minimum equipment list and the con- drive generator, no-break power 0.2 percent improvement in dispatch figuration deviation list. transfer, and interchangeable power reliability (99.1 percent, later revised conversion distribution units. to 99.17 percent) and a related Continuous focus on maintainability 20 percent reduction in maintenance and reliability targets. ■ The airplane interior features re- costs. Engine manufacturer Rolls-Royce To help ensure that established goals movable window escutcheons that also adopted these reliability and would be met, the design team focused permit inner and outer windowpane maintainability goals for the 717 power on airplane design, system design, replacement without the removal plant, the BR715. power plant design, and scheduled of seats or sidewall panels. 22 AERO No. 19, July 2002 4 EXAMPLES OF 717 DESIGN IMPROVEMENTS FIGURE ■ Electrically controlled aileron trim, single-point aft servicing and is ■ The engine modules are prebalanced, rudder trim, and spoilers simplified designed for corrosion prevention. which allows for quick replacement. the flight deck pedestal, or aisle stand, ■ Built-in test