Out with the old, in with the new

Transcription

1 Out with the old, in with the new The retirement of ageing early-series Boeing 747s is freeing up maintenance capacity that can now be used to meet the increasing needs of later variants, which are beginning to reach maturity, albeit with less demanding maintenance requirements than their predecessors. Ian Goold investigates Hangar space used for around 250 Boeing 747SP, -100, -200, and -300 Classics is being shared with younger s that are subject to less intensive maintenance. More D checks on s delivered in the past five years will be accommodated by the capacity vacated by retiring 747 Classics, says Boeing Commercial Airplanes maintenanceeconomics director Khwaja Ali. The older 747s take significantly longer time in D checks due to their ageing, whereas the newer D checks are expected to [take fewer] than 25 days. By , about 111 such D checks a year will be performed on s, up a sixth on the 95 typically carried out annually since 2005, according to Ali. We need to account for longer 8 MRO Management

2 (photo: Lufthansa Technik) [maintenance] duration in the third D checks, which start occurring in [the coming five years]. Viewed alone, it would indicate a need for 25% additional 747 hangar capacity, but the [space] being vacated by accelerated retirement of 747 Classics easily absorbs this demand. The s unique calendar-driven inspection schedule means that peaks and troughs in MRO demand are not influenced by different aircraft usage among operators. D check requirements will be largely governed by delivery dates (and rates), with calendar frequency determined by the maintenance programme. Reduced requirements Since boeing instituted a revision of inspection requirements for all 747 series aircraft, using us Air Transport Association Maintenance Steering Group Level 3 (MSG-3) standards about 10 years ago, two significant trends have emerged: lower D check downtime and reduced frequency of heavy maintenance events. boeing has offered Classic operators an MSG-3 programme that reduces average D check time by eliminating many tasks and extending many intervals, says Ali. The non-routine findings continued to grow due to ageing, [but] the net result was still a reduction in D check [time of] about five days freeing about 5% of hangar capacity. The revised maintenance programme has been available since 2002, with boeing saying that it has given participating operators reduced maintenance labour-hours, as well as increased aircraft availability. The programme provides flexibility to operators to package tasks based on their business requirements and can vary. Ali suggests it would be reasonable to suppose that the ageing of the 747 Classics fleet implies that hangar downtime for D checks increases by 50% for third (and subsequent) D checks, compared with a s first two such inspections. The longer time implies a more expensive job and the need for more hangar capacity, but boeing analysis shows that accelerated retirement of older 747s more for fuel burn efficiency than higher maintenance costs frees more hangar space than is lost to D check time escalation. Of the 959 active boeing 747s (as at December 2010), some 29.5% or 283 units are Series 200s or 300s, which are being retired at a rate of 37 a year. The fleet is expected to decline to 818 over the next six years, says Ali. Since entering service with Northwest Airlines in January 1989, the has seen a steady increase in scheduled maintenance intervals, with myriad improvements and modifications extending airframe and engine life, as well as reducing overhaul costs. Initial scheduled requirements were: A check at 300 flight hours (FH), C check at 15 months (but not to exceed 3,000FH), and D check at five years (but not to exceed 25,000FH). The model s maintenance review board (MRb) has increased Maintenance Planning March MRO Management 9

3 LHT confirms an industry trend for D checks to take place in Asia, where manhour rates are much lower than elsewhere. It is the main source of European C check capacity following AFI KLM E&M s decision to drop such maintenance (photo: Lufthansa Technik) Data document (MPD) intervals to: A check 1,000FH, C check 24 months (but not to exceed 10,000FH), and D check eight years, explains BCA maintenance-engineering director Larry Slate. After two D checks (D1 and D2), eight-year inspections become six-year inspections for relevant structures. Ali points out that not all interval improvements arose from MPD changes: In many cases, lead operators were supported to analyse and increase their check intervals based on their own experience. He says that the current inspection schedule and escalation of individual intervals implies a 15% reduction in scheduled tasks over the life of an aircraft and a corresponding reduction of about 5% in hangar space demand. Alternative approaches Different operators or MRO providers may use different schemes, according to a small random survey by MRO Management. For example, in Europe, the Lufthansa Technik (LHT) schedule involved A checks every 700FH, C checks every 21 months, and D checks every six years, although it has now adopted the MRB/MPD programme with the exception of the C check 10,000FH restriction. The German MRO performs D checks per year on a single line, says D2 or D3 checks should require 40 to 45 days, and at the beginning of 2011 still had slots available in the middle of the year. Middle East maintenance provider El Al Technical (EAT), whose parent airline group operates seven s (including one freighter) with an average age of 10 years, has not adjusted its inspection schedule over time, according to information provided by maintenance-marketing manager Eli Uziel, aircraft overhaul-division production-service manager Moshe Tabib, maintenance-specification manager Shaul Peri, and aircraft-structure, Interior, and non-destructive testing engineering manager Oren Jerasi. EAT has adopted C check intervals of 16,000FH (or 18 months whichever comes first) and D checks every 25,000FH (or 72 months), and has performed about 10 D checks Engine services with the global wingspan to reach anywhere you fly, day or night. It s in our power.

4 including one third-party contract for a foreign carrier. The MRO schedules approximately 15 days (around 13,000 hours) for full C checks and 25 or 50 days (around 27,000 hours), respectively for partial or full D checks. This year s slots are sold out and it is accepting enquiries for Before the parent company grounded its fleet of one and three -400s as an economy measure, the technical division of South African Airways (SAA) divided A check, 650FH-interval work into two separate maintenance jobs: the airframe check (CKA) plus weekly engine items, and the engine check (CKE) plus weekly airframe items. C checks were performed every 6,500FH, or 18 months, and D checks at a maximum of six-year intervals. SAA Technical has capacity for up to four 747 D checks a year, with no current backlog. One still in service was due for a C check in March 2011and a D check in July next year. Aircraft not in operation are subject to weekly checks and SAA has carried out How is the Boeing expected to compare? (photo: Boeing) Boeing concedes that since the new (marketed as the 747-8) is a larger aircraft than the current (an extra 51 seats and an 18ft longer fuselage), its maintenance costs would normally be expected to be higher. However, due to system, structural, and maintenance-programme improvements, the airframe maintenance cost is expected to be 3% lower than that of the -400, says Boeing Commercial Airplanes maintenanceeconomics director Khwaja Ali. Technology improvements reduce cost by 5% and maintenance programme by 3%. Size (weight and passengers) increases cost by 4% for [a] net cost reduction of 3%. Service soars with the Eagle. Our more than 50 locations across the globe stand ready to provide dependable services that anticipate needs, create value and keep aircraft flying anywhere, anytime. With more than 85 years of experience producing and maintaining dependable engines, Pratt & Whitney Global Service Partners combines the experience of an OEM with the flexibility of an MRO, defining the service standard for all commercial engines including our competitors. Discover the OEMRO advantage at pw.utc.com/oemro. MAINTENANCE REPAIR OVERHAUL

5 third-party work for Lufthansa, Saudi Arabia s Kingdom Holding, Saudi Arabian Airlines and TAAG Angola Airline. Scheduled maintenance for the is generally similar for all sub-variants, with some differences on systems-inspection requirements based on production improvements and service-bulletins (SBs) or modifications. Although system and structure SBs have been raised to improve performance, these have not had a significant impact on scheduled maintenance, according to BCA maintenance engineering director Larry Slate, who confirms that incorporation of relevant bulletins can allow some tasks to be eliminated or some intervals to be increased. Continuous improvements in materials and corrosion-prevention measures have contributed to the escalation of structural inspection intervals from six to eight years. Operationsperformance data and subsequent analysis have resulted in optimisation of scheduled maintenance [requirements], according to Slate. All corrosion-prevention and control-programme (CPCP) work mandated by airworthiness directives (ADs) were incorporated with re-analysed MRB structural- and zonal-programme requirements. This produced a streamlined baseline programme that has eliminated overlapping and duplicate maintenance requirements, and has also seen incorporation of SFAR88 requirements into the schedule. Annual delivery rates of the have fluctuated in response to airline demand, which in turn follows passenger traffic trends that typically follow (and, in fact, exaggerate) swings in global economic trends. Deliveries have varied from over 60 in the early 1990s, through 30 or less in the middle years of the last decade, to much lower rates more recently. Indeed, Ali confirms that in the past five years, just 65 have been delivered scarcely more than one a month. The first of these will start coming in for D checks after eight years, in Boeing s calendar-based heavy-maintenance schedule means that cycles in demand for D check capacity will reflect those in deliveries, with Ali reporting plenty of overall MRO capacity. There was sufficient capacity for the estimated 150 D checks in 2010, and the additional 13 aircraft expected in each year from 2013 is equivalent to demand for slightly less than a two-bay hangar. The increase in required capacity will be offset by that left vacant by 37 Classics being retired each year. Powering improvement Owners and operators of the Boeing have benefitted from improvements to each of the three offered engines, as well as airframe and systems maintenance requirements, according to Boeing Rolls-Royce RB in 1998, Rolls-Royce incorporated Trent engine technology and upgraded the RB s high-pressure compressor (HPC), combustor, and HP turbine (HPT) to produce the -T variant. Boeing says that this resulted in a significant increase in exhaust-gas temperature (EGT) margin and decreased shop maintenance. The powerplant manufacturer also introduced (photo: Lufthansa Technik) fan-blade modifications to decrease inspection and lubrication maintenance requirements and increase blade life by 67%. A new compressor drum standard introduced in 2006 increased the component life by 43%. Pratt & Whitney PW4000 Boeing says that the PW inch advantage performance upgrade (APU) kit, covered by a September 2010 service bulletin, has been developed to provide up to 1% fuel savings and significant HPT-durability improvement. The kit represents targeted technology insertion from the PW inch ADV70 engine. The durability improvements include a 1/2K thermal-barrier ceramic, new blade outer air seals, reduced first- and second-stage HPT blade clearance, and increased second-stage blade cooling flow. General Electric (GE) CF6-80C2 GE s continuing engineering focus is on areas such as Tech CF6 HPT blades, enhanced compressor technology, and thrust-reverser systemreliability improvements that reduce cost of ownership and maintenance requirements and increase reliability and durability, says Boeing. The CF6-80C2 s time-on-wing has continued to grow 6% a year since 1992 and averages about 13,000 hours for a mature shop visit. [It] combines a proven core with the latest technical innovations to offer the highest reliability, longest life, and lowest fuel burn in its thrust class. Geographical distribution But will maintenance demand be global or regional. And how balanced are regional capacity demand and supply? And what factors drive regional differences? There is sufficient capacity for D checks in all regions, says Ali. Most [aircraft] are in Asia Pacific, with the second largest concentration in western Europe. Nevertheless, south Asia remains short of MRO capacity for large machines, says Ali: Infrastructure has not been able to keep pace with the [region s] burgeoning aviation growth. He explains that for reasons other than capacity s are typically flown to low labour cost areas for D checks, other major work, and modifications. LHT confirms an industry trend for D checks to take place in Asia, where manhour rates are much lower than elsewhere. United, for example, is sending [its] complete fleet to Ameco in China. Under a five-year contract agreed in March 2010, United s 747s began to go to Ameco Beijing last October for heavy maintenance and C checks, with the MRO also performing maintenance and cabin upgrades on the US carrier s Boeing 777s. 12 MRO Management

6 Significant tasks and service bulletins With boeing development benefitting from myriad improvements and modifications, Lufthansa Technik (LHT) lists more than 1,000 service bulletins (Sbs), many of which have had an impact on operational reliability and maintenance costs. The German MRO identifies the most significant tasks: A2507/airworthiness directive (AD) stretched upper-deck tension-tie inspection and repair; A2218/AD DSb underwing mid-spar fitting inspection and modification; A2563 scribe line inspection; A2784 bs320 crown-frame web inspection and replacement; A2331 wing landing-gear support-beam end fitting; Ageing airplane safety rule; Widespread fatigue damage rule; and Supplemental structural-inspection document (SSID) programme. Asked about the most significant, or critical, Sbs (those most frequently specified in third-party maintenance contracts) and ADs, SAA Technical nominates these modifications: Cockpit door surveillance; Enhanced ground-proximity warning systems (EGPWS); Fuel-jettison wiring; Emergency locator transmitter (ELT); 8.33kHz radio-frequency channel spacing; Integrated drive generator (IDG) power feeder cable; and Pylon leading-edge wiring. Regular work in recent years for El Al Technical has been modification of overhead crew rest areas above Door 5, a 150-manhour exercise carried out during C checks. In , it introduced a cabin-upgrade programme to replace premiumclass seats and to install power points in the economy-class sections. In-flight entertainment systems were also enhanced, while the package also included new seat fabrics, carpets and curtains. beyond the crew rest area AD, El Al sees most such mandatory work as structural strengthening of the aircraft. The us SFAR88 requirement (introduced following the TWA Flight 800 accident) was regarded as a hot issue that required a lot of manhours, a sentiment that has been echoed by LHT. by the time a receives its second C check (C2), about 40% of MRO activity is non-routine, says El Al. A typical example of such non-major maintenance is CPCP work in the cargo compartment. Ali says that any spare hangar capacity released elsewhere by s going to Asia Pacific for maintenance is being used by smaller aircraft that cannot fly to lower-cost areas. LHT sees a lack of European C check capacity, with its own facilities comprising the main supply following AFI KLM E&M s decision to drop such maintenance. SAA Technical expects global maintenance capacity will be reduced due to the declining 747 market. Reliability How has despatch-reliability performance evolved as the has matured, and do these improvements vary between operators? In 2008, boeing told MRO Management that, as the fleet had matured, reliability had remained fairly stable [at] between 98.4% and 98.6% over many years. Now, schedule reliability has improved to around 99%, as measured during the 12 months from November 2009 to October 2010, according to Ali. Improvements have come from regular product [development], better support in spares, and [the] increased experience of airlines and technical departments. boeing says that variation in schedule reliability among operators may be due to a number of factors, including stage-length differences and daily utilisation. Ali points out that one consideration is the speed of aircraft turnaround, since longer times permit more maintenance, which in turn is driven by the number of mechanics available, the quality of their training, and the availability of spares. Others are: the extent and quality of repairs performed during overnight maintenance [and] the extent [to which] the airline uses its despatchdeviation guide. In LHT s experience, reliability as usual for commercial aircraft initially dropped and then increased before subsequently decreasing as the airframe and components have matured. El Al Technical has performed about 10 D checks including one third-party contract for a foreign carrier. This year s slots are sold out and it is accepting enquiries for 2012 (photo: El Al Technical) 14 MRO Management

7 LHT says that the most recent MRB report revision was in May 2009, when letter checks were optimised, with temporary revisions following in December 2009 and July 2010 to meet the requirements of FAA Advisory Circular using the MSG-3 enhanced zonal procedure (EZAP). The MRO says that the D check escalation represents the latest maintenance development from the industry steering committee (ISC). According to Boeing s Slate, there are currently no major changes being considered by the ISC. When the was designed in , direct maintenance costs (DMCs) at entry into service (EIS) were foreseen as being 10% lower than those of the , but in practice were actually 26% less. The airframe maintenance cost has been as expected and in cents/available seat-mile basis is among the best of all airplanes, claims Ali. The cost of ageing How have DMCs for mature s compared with expectations, and how will these change as the fleet ages further? As airplanes age, we expect the maintenance cost to grow above the mature maintenance cost after the second D check by about 3% per year, explains Ali. This is without accounting for any inflation in material or labour costs. So, a 25-year-old airplane would cost about 30% more to maintain than a mature airplane younger than 15 years. Meanwhile, Boeing is charting mature airframe maintenance costs, which are said to be reducing by 0.5% per year. During the last 15 years, mature maintenance cost (as measured between the first two D checks) has reduced by 7% from what was initially modelled, says Ali. The reduction is due to a combination of product improvement, check interval improvements, and better product support. Further cost reductions have usually resulted No significant structural cracking within 20,000-cycle DSO To stay ahead of the most active (or oldest) airframes, Boeing continuously evaluates fleet reports for potential improvements that can be incorporated into new production aircraft or additional maintenance actions for in-service machines. The is a derivative of the original 747 [that] is proven by static- and fatigue-test data, as well as fleet data, says the manufacturer. For validation of the redesigned Section 41 forward fuselage modified after structural-cracking problems with early airframes and now the baseline for the Boeing has carried out additional fatigue testing. This demonstrated no significant cracking [ahead of the 20,000-cycle] design service objective (DSO) [but] did define maintenance actions and inspections for airplanes operating past the DSO. In addition, Boeing has conducted tear-downs of a and a forwardfuselage fatigue-test article, which (with the extra testing) has been used to define maintenance actions or inspections. Boeing has issued further service action to instruct operators of high-cycle or high-hour s to remove fasteners from specific critical structural joints, perform intensive inspections, and report any findings to Boeing. As of January 2011, there had been no significant findings from these inspections to generate additional fleet action. Boeing says that the DSO is a concept useful for assessing the economics of airplane structural maintenance: Continued airworthiness up to, and beyond, the DSO is assured by effective scheduled maintenance and compliance with mandatory actions. The s 20-year, 20,000 flight-cycle DSO may be summarised as the minimum period of service during which at least 99% of primary structural details (or 955 over 30 years) remain free of detectable fatigue cracks with 95% confidence. Boeing has subjected the complete-airframe fatigue-test specimen to 20,000 cycles, with the fuselage receiving 20,000 additional pressure cycles, while the forward-fuselage Sections 41 and 42 have undergone a further 20,000 pressure-test cycles. The manufacturer says that the s airframe structure is designed to exceed the DSO with modest increase in maintenance costs. from increased competition as additional MRO players have entered the component overhaul/ repair business. LHT confirms that DMCs may be managed, and that increases are not inevitable. [Such costs] can be controlled as cost-increasing factors [such as] ageing are reduced, or even equalised by applying Lean methods in maintenance or setting up reliability programmes. In recent years, the MRO and sister company Lufthansa have introduced improvement programmes (such as check or limit escalation) that have helped to keep costs in line with internal targets. However, this is offset by the potential for other airframe problems to develop. The is a challenging aircraft concerning DMCs as several structural items are developing over the period, warns LHT; both LHT and SAA Technical benchmark their maintenance costs against those of competing MROs through analysis of industry media publications. Boeing fleet* and fleet leaders Orders 694; Deliveries 671; Backlog 23 Category Delivery Age Cycles Hours Oldest aircraft 26/01/ years 11,876 91,024 Aircraft with most flight cycles 13/10// years 32,047 43,461 Aircraft with most flying hours 26/10/ years 13, ,041 *As at January 2011 (source: Boeing) 16 MRO Management