717-200: LOW MAINTENANCE COSTS AND

Low 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 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

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 equipment is an integral and eliminated many cables compared ■ The use of digital and hardware element of many 717 digital com- mockups early in the design process with the DC-9 and MD-80 design. ponents, reducing troubleshooting helped ensure LRU accessibility. ■ The in-line (i.e., straight-shaft), and inspection times. In addition, the engine-driven hydraulic pumps have integrated centralized fault display ■ The use of lock wire on engine higher reliability than the bent-axis system (CFDS) receives inputs from LRU installations was minimized. (i.e., articulated-shaft) pumps on ear- more than 30 LRUs and presents lier airplanes. The flareless fittings information on the flight deck multi- ■ With the exception of integrated in the hydraulic lines significantly function control and display units drive generator servicing, only improve reliability because they are for ease of line maintenance. standard hand tools are required to less prone to cracking and leakage. ■ The auxiliary power unit, based on perform engine maintenance. a proven design, requires no special- ■ The integrated flight deck has state- ■ Repair of the all-aluminum cowling of-the-art displays, communication ized ground-support equipment for transport. requires no specialized materials or and navigation equipment, and digital skills. To expedite line maintenance flight guidance system, which cumu- ■ The 717 structures are based on the tasks, the cowling is designed for latively reduce the number of flight proven design of its predecessors, use as a mechanics’ stand and can deck LRUs by 57 percent, compared with improved corrosion protection support two mechanics and a toolbox with the DC-9 and MD-80 design. and appropriate material choices. (fig. 5, p. 24). ■ The landing gear system incorporates Power plant design. Rolls-Royce ■ The majority of the LRUs are steel brakes that are attached with focused on power plant maintainability, located on the bottom of the engine 10 pins rather than traditional fasten- low maintenance costs, and high for ease of access. ers, which reduces installation time reliability throughout the design of by 60 percent, compared with the the BR715 engine. ■ To prevent contamination, the DC-9 and MD-80 design. ■ The wide-chord fan is highly pneumatic elements are located on ■ The vacuum waste system, which resistant to damage from foreign the top of the engine, away from features modular lavatories, permits object debris. fluids on the bottom.

No. 19, July 2002 AERO 23 ■ The fan blades have been designed 5 BMW ROLLS-ROYCE ENGINE COWLING FOR THE 717 to allow on-wing replacement within FIGURE 60 min. ■ The full-authority digital electronic control isolates and annunciates faults and interfaces with the CFDS. Unambiguous NO DISPATCH and TIME-LIMITED DISPATCH messages are displayed to the flight crew on the engine alerts display. ■ The latest generation engine vibra- tion system permits data sampling for use in balancing blades. ■ Extending replacement intervals for life-limited parts (LLP) reduces the materials costs of engine main- tenance. LLPs on the BR715 engine have target cycle limits of 25,000, 30,000, and 50,000 cycles, com- pared with 19,000 cycles for LLPs on the DC-9 Pratt & Whitney (PW) JT8D-15/-17 engine and 20,000 and 25,000 cycles for LLPs on the MD-80 PW JT8D-219 engine. Scheduled maintenance program development. The scheduled mainte- nance program for the 717 significantly reduces maintenance labor-hour requirements (figs. 6 and 7), thereby 717 cowling is lowering total maintenance costs. designed for use as The labor-hour reduction results from a mechanic’s stand improved scheduled maintenance to expedite line- programs and new design initiatives. maintenance tasks. The 717 scheduled maintenance programs were developed using a pro- cess established by the Maintenance Steering Group (MSG), a committee of airframe manufacturers, airlines, and U.S. Federal Aviation Administration maintenance programs. (This process ■ A single point of entry for representatives. Through the MSG also was used during development of maintenance inspections. Level 3, Revision 2 (MSG-3 Rev. 2) the 777 and 737-600/-700/-800/-900 process, maintenance programs are maintenance programs.) In addition, ■ Time-saving CFDS inspection developed using a top-down, systems- the MSG-3 Rev. 2 process integrates procedures (e.g., checking the proper level approach, rather than the bottom-up, aging airplane maintenance programs, rigging of all 14 landing gear, component-level approach used in the such as the Corrosion Prevention and 4 slat, and 8 door proximity sensors development of MSG-2 maintenance Control program, which eliminates is accomplished from the flight programs. Only tasks deemed applicable some duplication of tasks (e.g., entry deck in moments, rather than and effective are included in the and access tasks). inspecting each at its location). maintenance programs, which reduces The time needed to conduct scheduled scheduled maintenance activities by maintenance tasks also was reduced on ■ Single-switch activation and reset extending maintenance intervals and the 717 compared with its predecessors of all cabin reading and call lights eliminating some tasks required by earlier through several design features: during service inspections.

24 AERO No. 19, July 2002 6 REPLACEMENT OF LRUS ON BYPASS DUCT 7 REPLACEMENT OF CORE LRUS FIGURE FIGURE

100 100 100% 100% 80 80 74% 60 60 53% 40 40 40%

20 20 Percent replacement of LRUs Percent replacement of LRUs 10% 0 0 Under 15 min Under 30 min Under 60 min Under 15 min Under 30 min Under 60 min

Figure 8 illustrates the time-saving airplane design improvements, the 717 than a scheduled engine overhaul improvements in the 717 scheduled requires 45 percent fewer cumulative program, thereby allowing extended maintenance programs. The conversion labor-hours than does an MD-80 on intervals between shop visits. Engine of an MD-80 maintenance program to the an MSG-3 maintenance program. condition analysis includes monitoring MSG-3 approach results in a 35 percent The scheduled maintenance of the of exhaust gas temperature, engine reduction in cumulative MD-80 sched- 717 power plant is similarly efficient. vibration, and spectrometric oil uled maintenance labor-hours during a The BR715 engine features an on- analysis program parameters. Internal 10-year period. In addition, because of condition maintenance program rather engine borescope inspections can be

AIRPLANE SCHEDULED MAINTENANCE PROGRAMS — 8 LABOR-HOURS PROJECTED FOR A 10-YEAR PERIOD FIGURE 20,000

MD-80 MSG-2 cumulative labor-hours 17,500 MD-80 MSG-3 cumulative labor-hours 717 cumulative labor-hours

15,000 35% 12,500

10,000 45% 7,500 Cumulative labor-hours

5,000

2,500

0 15 30 45 60 75 90 105 120 Months

No. 19, July 2002 AERO 25 9 717 DISPATCH RELIABILITY — BASED ON DELAYS OF MORE THAN 15 MIN AND FLIGHT CANCELLATIONS FIGURE 100.00 Fleet monthly values Fleet 3-month moving average

99.50

99.00 Dispatch reliability, % Dispatch reliability,

98.50

98.00 Apr 01 May 01 Jun 01 Jul 01 Aug 01 Sep 01 Oct 01 Nov 01 Dec 01 Jan 02 Feb 02 Mar 02

accomplished quickly through numer- Rolls-Royce supports the BR715 power greater than that of its MD-80s during ous access ports. plant at its Dahlewitz, Germany, facility, the latest six months. which is the coordination point for all Maintenance costs. 3 IN-SERVICE SUPPORT in-service issues and spare parts provi- sioning. The engine manufacturer’s field Early data indicate that operators with By providing in-service support, Boeing service representatives coordinate with both 717s and DC-9s are experien- helps 717 operators to attain low main- the Dahlewitz team. cing significantly lower maintenance tenance costs. Support programs for all costs on their 717s (fig. 10). Because Boeing commercial airplanes include 4 717 OPERATOR EXPERIENCE reported maintenance costs for on-site service representatives, a TO DATE first-year operations are excluded business-to-business web portal, and To date, 717 operators are experiencing from any maintenance cost analysis, maintenance services. Boeing also offers dispatch reliability and maintenance maintenance data reported to the services that support operators’ airplane costs that meet or better program targets. U.S. Department of Transportation are maintenance programs, including engi- just becoming statistically significant. Dispatch reliability. neering support; program management; (The inclusion of first-year data skews quality support; recovery and modifi- According to statistics reported to reported costs because of the variable cation; repair, overhaul, and exchange; Boeing, 717 fleet dispatch reliability effect of airplane newness on mainte- and worldwide spares distribution. is exceeding the final design target of nance activity.) In addition to the standard services 99.17 percent for on-time departures In addition, reports from one 717 available to all Boeing operators, Boeing (fig. 9). Dispatch reliability has exceeded operator, who also operates DC-9s, offers an integrated services program 99.2 percent, and several operators indicate that in-service experience is for 717 customers in Europe. Customer are experiencing reliability greater exceeding Boeing forecasts: Operation Support (COS) supports than 99.5 percent. One operator is 717 customers’ daily operations with a experiencing a 717 dispatch reliability ■ The operator’s 717 in-service checks pool of high-value rotable spare parts, 1.37 percent greater than that of its require significantly fewer labor- inventory management, and the repair DC-9s. Another operator reported its hours than for its DC-9 fleet. During and overhaul of the COS program parts. 717 dispatch reliability was 1.10 percent a period of 550 flight-hours, the

26 AERO No. 19, July 2002 cumulative total of labor-hours for ■ Regulatory authorities extended For example, the operator uses 717 in-service checks is 200 less the operator’s check intervals reduced engine power settings on than that of the DC-9. based on the operator’s in-service takeoff (i.e., derate) to extend engine experience with the 717. The life considerably, thereby lowering ■ Out-of-service time for the opera- A-check interval increased from engine maintenance costs. tor’s 717s is 80 percent less than for 450 flight-hours to 500 flight- In addition, the digital technology its DC-9s. Extensive maintenance hours, and the C-check interval allows the operator to know how inspections performed on a periodic increased from 3,600 flight-hours each system and each component basis (e.g., C-checks) average (15 months) to 4,500 flight-hours within a system are operating. As a 3 days for the 717 compared with (18 months). result, the operator anticipates prob- 21 days for the DC-9. lems before they occur and replaces ■ The operator’s BR715 power ■ The operator’s intervals between 717 units before functionality or perfor- plant sustains far less damage mance is degraded. This proactive C-checks are more than 8 percent from foreign object debris than longer than those of its DC-9s. maintenance capability increases the PW JT8D on its DC-9s. reliability and lowers the cost of line ■ C-check costs for the operator’s Another 717 operator has found maintenance staffing and inventory 717s are only 10 percent of those that the 717 allows it to reduce requirements associated with for its DC-9s. maintenance costs several ways. unexpected part failures.

10 DIRECT MAINTENANCE COSTS — U.S. DEPARTMENT OF TRANSPORTATION FIGURE 700

Reported direct maintenance costs from operators of both 717s and DC-9s Engine contract based on U.S. Department of Transportation (Form 41) data. Engine material 600 Engine labor Airframe contract Airframe material Airframe labor

500

400

300

U.S. dollars per flight-hour (2001 data) 200

100

0 717 DC-9 Note: Values shown are based on a weighted fleet average.

No. 19, July 2002 AERO 27 28 AERO No. 19, July 2002 SUMMARY

Maintenance costs for the 717 are the lowest of any 90- to 120-seat airplane operating today. Lower costs were achieved through a concentrated focus during airplane design on maintainability and reliability and through in-service support following airplane delivery. The 717 design team focused on the correlation between airplane dispatch reliability and nonroutine maintenance costs, which led to many system improve- ments and also validated the incorporation of the best features of 717 predecessors. Specific considerations during airplane design included airplane accessibility and ease of troubleshooting, inspection, and repair. The 717 scheduled maintenance program was de- veloped using the MSG-3 Rev. 2 maintenance process, which minimized tasks and maximized the intervals between inspections. Boeing in-service support helps ensure that airlines minimize 717 maintenance costs while maximizing reliability. To date, 717 operators report that they are experiencing high airplane dispatch reliability and relatively low maintenance costs.

No. 19, July 2002 AERO 29