MRO Management

A380 undergoes review of maintenance procedures

A380, maintenance review

With just over a decade in service, the A380 is undergoing a review of maintenance procedures.

This month (September), revised A380 maintenance and other technical documents are expected to follow analysis of Airbus full-scale fatigue testing (FSFT) of its flagship very large airliner. Publication will reflect the impact of the FSFT teardown and results of a fleet operational survey.

Almost 11 years after the double-deck design entered service, Airbus reports constantly improving operational reliability (OR), the rate of aircraft-related technical delays (of 15 minutes or less).

A380s with 575-tonne maximum take-off weight (MTOW) – the production standard since mid-2013 – have a 99.2 per cent OR, compared with a global fleet rate of exactly 99 per cent, according to the European manufacturer. (OR should not be confused with operational availability (OA), a measure of days/year that aircraft are available for operations.)

Lufthansa, whose fleet includes older examples of the A380, cannot quite match the performance of younger machines; after starting operations with an impeccable 100 per cent OR during the first five months of service in 2010, the European carrier has seen a slight decline in despatch reliability.

It then maintained 99 per cent, a little above its current 98.6 per cent average. Engineering arm Lufthansa Technik (LHT) says operational performance is “as expected, with good dispatch reliability – but a high maintenance load, which is especially driven by engine issues”.

With the benefit of more than a decade’s operational experience since Singapore Airlines (SIA) inaugurated A380 services, Airbus has been extending inspection intervals as it optimises maintenance schedules.

“We have been continuously working to improve operations, facilitate maintenance and increase profitability of the aircraft – in particular with an optimised cabin space,” according to former A380 programme head Alain Flourens (now Airbus Helicopters executive vice president, engineering and chief technical officer).

Such optimisation has been supported by the manufacturer’s gathering of scheduled and unscheduled maintenance data, including that from aircraft of different ages, configuration, and utilisation.

A380, maintenance review

Since 2008, International Maintenance Review Board Report (MRBR) Policy Board issue paper 44 (IP44) on the establishment of inspection intervals has required “sufficient in-service data [from a] sufficient number of [maintenance] task occurrences,” says Airbus maintenance engineering.

Under MRBR procedures setting minimum requirements for scheduled maintenance of certificated aircraft (and derivatives), A380 task intervals are defined in the maintenance planning document (MPD) by useage parameters: flight hours (FH), flight cycles (FC) or calendar age.

For example, checks of aircraft structures are prescribed at six-year (6YE) intervals. Likewise, in standard flight operations, block check maintenance was initially required every 1,000FH for light A checks and every 24 months (24MO) or 6,000FH for heavy C checks.

Airbus points out that for the A380 there are only two engineering shop visits ahead of the first 6YE intermediate layover (IL) structural check, rather than three on other types subject to an 18MO schedule.

LHT’s A380 maintenance policy essentially follows the Airbus MPD, but is ‘enriched with LHT experience’. It says that, through evolutionary exercises, Airbus and the industry have successfully increased A check-equivalent intervals from 750FH to 1,000FH and C check-equivalent tasks from 24MO to 36MO intervals.

The key MPD changes are driven by Airworthiness Limitation Section (ALS) Part 2 updates as results of the fatigue testing,” according to LHT. “Besides the MRBR changes, which include the interval evolution, ALS Part 2 remains the main driver for MPD changes with new requirements and revised intervals.”

How did LHT, which has so far performed all A380 checks up to 6YE inspections, prepare for maintenance of the behemoth, and how has it evolved with experience?

LHT established a maintenance readiness project involving about 50 people. “[Our] focus has been gaining maturity of all systems and always concentrating on the mechanics’perspective. Dedication to this model was continued ever since.”

By the beginning of June, the A380 ‘lead’ aircraft logged over 45,000FH/6,000FC, while the global fleet of 224 aircraft had accumulated more than 4.9 million FH. As of August, some 229 examples had been delivered and 227 were in service with 14 operators (with an additional two ex-SIA machines in storage.

A380, maintenance review
Line maintenance on an Airbus A380 at Lufthansa Technik in Frankfurt

For its part, by late July, Lufthansa had recorded 405,000FH and 41,000FC with an average of 9.8 hours daily utilisation among its 14-strong A380 fleet. This usage compares with an initial utilisation of 14+ hr/day in 2012 after about two years of operation.

LHT says A380 maintenance is conducted “basically in-house”. Engine work is “contracted with Rolls-Royce, and component repair/overhaul is split between [ourselves] and AFI KLM E&M for the Spairliners share”.

Maintenance training for its Frankfurt base was “obtained on all required levels for the handpicked and most experienced crew”. The company invested more than €10 million in A380 ground support equipment. Additionally, the Frankfurt maintenance facility was built to cover fleet expansion over the next years, at a cost of more than €70 million.

Since March this year, five A380s have been operated from Munich, where LHT has invested in two external tail docks’ to accommodate an A380 inside. For A380 line maintenance, the company bought an inflatable mobile tent for engine change and a lift for maintenance work, representing a further €400,000 investment.

LHT Philippines (LTP), a joint venture established between LHT and Philippines-based MacroAsia Corporation in 2000, offers a wide range of A320 Family, A330 and A340 base maintenance and modification services. Since 2012, this has included A380 work – capacity that has been developed to include C4 heavy check approval for the past four years.

In 2015, a second A380 bay was added to permit maintenance on two aircraft simultaneously, which began in October 2016 with Lufthansa’s first 6YE IL checks, performed on its two oldest aircraft. The work included passenger-door, flap track 6, inboard outer fixed leading edge and cruciform frame 56 modifications.

LTP, which includes Air France and Asiana Airlines as base maintenance customers, has performed at least 100 A380 door modifications and also completed a wing rib modification campaign.

A380, maintenance review

Airbus partnered with several airlines on OA, the number of days every year when an aircraft is free to fly, uninhibited by maintenance or technical considerations. “To improve A380 OA and maintenance costs, Airbus launched a project to optimise scheduled maintenance programme intervals,” according to A380 cabin customisation managers.

OA targets included increasing A check intervals by a third, from 750FH to 1,000FH, and C check intervals by 50 per cent, from 24MO to 36MO; this has reduced maintenance events in the first six years from three to two.

Standard MRBR procedures saw the optimised A check schedule adopted at the end of 2016 (under MRBR Revision 8), with the enhanced C check interval approved late last year (and included in Revision 9).

Airbus says operators’ actual data was a key element in achieving maintenance schedule optimisation, which includes engine, systems and zonal inspection work.

It covers some certification maintenance requirements and the manufacturer also aimed to reduce structure inspection items under airworthiness limitation items (ALIs). CY Airbus cabin customisation officials attribute inspection interval extensions to several factors:

  • validated identification of margins (through tests or in-service monitoring)
  • detailed assessment of operational feedback (including particular requests about “experience on filter clogging [and] drain bottle liquid levels”)
  • correlation of full-scale fatigue test findings against aircraft configuration and actual loads
  • adoption of non-destructive testing in place of visual inspection
  • use of structural modifications (some for retrofit) to enhance design and remove ALIs or prospective escalation of threshold interval checks.

The optimisation exercise was launched in June 2015, with related A380 maintenance working group (Mwg) and industry steering committee (Isc) activities following in 2016. By mid-2017, some 95 per cent of A check tasks had been increased to 1,000FH (or more).

Nevertheless, Airbus has not yet been able to introduce lessfrequent6YE/ILinspectionsthatcover, for example, light structures maintenance (including primarily corrosion and zonal inspections).

“The number of [such] events up to [2018] does not permit [us] to demonstrate compliance [with] IP44 for [a longer] interval,” says Airbus, which is keen to synchronise [the 6YE interval with] the 12YE period between structures maintenance tasks and landing gear overhauls.

Reviewing more than 10 years of A380 operations, Airbus says the A380 MRBR is continuously updated to take account of aircraft configuration changes, operational feedback and regulatory changes.

Operators, airworthiness authorities and the manufacturer have shared experience with the MWG and ISC.

Optimisation of task intervals is driven by IP44: “This method, based on statistical approach, requires sufficient in-service data from operators and sufficient maintenance task occurrences in associated maintenance events.”

Airbus says that last year’s MWG/ISC activity was dedicated to optimising equivalent C checks and aimed to increase intervals from 24MO to 36MO. “Associated results have been promulgated through MRBR Revision 9, approved [at the] end of 2017.”

“Implementation of the so-called C check evolution programme [has been] the main change,” according to LHT. “This leads to interval updates for approximately 200 tasks (from 24MO to 36MO or from 48MO to 72MO). In a few cases, the interval had to be decreased due to in-service experience.”

Most recently, the ISC’s work has considered “the impact of design changes on the MSG3, landing gear sampling and [maintenance] WG reviews”.

Broadly, what changes are being considered for MRBR Revision 10, which is scheduled for publication in February 2019? The revised document will be linked to four changes, according to Airbus:

  • results from modification follow-up
  • removal of some structure/zonal tasks from the 6YE check
  • access changes based on customer queries
  • addition of a new “interval to be managed at component level” note for some system tasks.

LHT has experienced fewer ‘findings’ than it expected during 6YE IL checks on eight A380s, the MRO noting “especially the [passenger-cabin] floor structure [that] was in very good condition”.

It says that the work involved, mainly driven by structure improvements and cabin refurbishment, has grown, but this has been offset by accumulated knowledge of the A380.

“There has been an increase in the number of [Airbus] service bulletins (SBs), thus increasing the downtime. Our vast experience in IL and C checks has contributed to the reduction of downtime,” according to LHT.

A380, maintenance review

Greater experience has been gained by the LTP joint venture in Asia, which is LHT’s ‘preferred’ location for A380 maintenance. Overall, LTP has performed 60+ checks, of which 17 have been C4/6YE work.

“Depending on the extensiveness of the check, workload and customer requirements/preferences, the typical downtime can range [between]14-18 days for C1 checks, 28-35 for C2 checks and 48-80 days for C4 checks,” says LTP. It has two A380 lines operating simultaneously.

LTP’s 50th A380 layover was a C2 check last year for Qantas that included Flap Track 3 and 4 and door modifications.

The Australian carrier has contracted LTP to provide all required base and heavy maintenance for its 12 A380s, including various modifications and C1, C2, C4 and, in future, C8 checks. What work will be involved in upcoming 12YE checks (including structures work and landing gear overhauls), expected to begin in mid-2019?

Airbus has previously identified a few fatigue ‘items’ for which the manufacturer has been finalising relevant inspections.

“We are [also] working on future modifications that will allow cancelling these inspections,” says Airbus, which hopes to release improvements before 12YE checks begin. The manufacturer is in the final stages of landing gear ‘sampling’ conducted to confirm the 12YE overhaul target.

“Two samples [have been] completed and a third [was to be] taken in August. No unexpected failures or damage that could affect the sampling programme validation results [have] been experienced,” according to Airbus.

It expects the third sample to endorse landing gear overhaul plans. To complete validation of the sampling programme, Airbus will review the overhaul report from the landing gear of a fourth ‘pre-selected’ aircraft.

Earlier this year, in a 14-day exercise, Emirates Engineering replaced an A380 undercarriage for the first time. “The first complete replacement of [all five] landing-gear [units] is an important milestone for us,” according to Mohammad Jaffar Nasser, senior vice president, engineering maintenance at Emirates.

Two more Emirates A380s are scheduled for the same work before the end of the year. In addition to investing in related infrastructure and facilities (including specialist tools), Emirates Engineering worked closely with Airbus and suppliers Field International, Safran and UTAS.

Analysis of the A380 FSFT was expected to yield results – and publication of updated ALS Part 2 and MPD documents – this month (September), following EASA approval in July.

These publications reflect the impact of the FSFT teardown and results of a fleet operational survey on maintenance of airframes that have recorded up to 9,500FC or 70,000FH (that is, half the 19,000-FC/ 140,000-FH design service goal [DSG]).

Airbus says that the work will continue over the coming 12 months, with the impact above the half-DSG thresholds expected to be published in late 2019 or early 2020.

Maintenance objectives had a major influence in establishing the A380’s DSG, which has been used to set an initial inspection threshold and repeat intervals for structures items.

“Extensive fatigue testing has demonstrated remarkably slow crack growth, such that there is no need to inspect for fatigue damage throughout normal [aircraft] life,” says Airbus. “Corrosion resistance [is] superior to conventional aluminium.”

To comply with European and US standards for widespread-fatigue and fatigue and damage-tolerance (F&DT), full-scale testing was performed up to 3.2 x DSG.

This exercise, which began in September 2005, involved some 47,500 simulated “flights” and was performed by engineering specialist IABG and testing services partner IMA in Germany.

It was followed by full test, ‘teardown’, and inspection of the structure (including residual strength tests, non-destructive testing inspections, fractographic analysis and damage assessment). The data has been combined with the results of an A380 fleet operations survey to validate F&DT maintenance requirements.

Airbus expects a full overview of the updated inspection plan and related modifications, both of which are expected to become available next year, to be in airworthiness limitation changes. (The manufacturer has not yet revealed any plans or work underway to establish an extended service goal for the A380.)

Airbus continues, of course, to develop the A380 – with particular attention to increasing reliability and reducing maintenance costs. For example, for high-slip induction motor fuel pumps the manufacturer has adopted “A350-like technology having almost no electronic parts”.

It says that improved pump-maintenance cost emanates directly from better reliability reduced mean time between unscheduled removal of the simpler technology, “significantly reducing current operational interrupts (delays and cancellations) caused by the [existing] more complex electronic units”.

Some hardware improvements, modifications and upgrades are first available only as a production line fit [or have been candidates for possible line fit], while others can be incorporated during maintenance. Changes such as flight management system upgrades, being software, are available for retrofit.

Airbus explains that such availability is driven by ‘business case’ decisions that take account of aircraft downtime, labour, SBs, parts kits and other considerations, compared with the return on investment.

At the 2017 Paris Air Show, Airbus revealed development studies for an enhanced ‘A380plus’ that involved aerodynamic wing refinements that, with maintenance optimisation and cabin improvements revealed at last year’s Aircraft Interiors Expo in Hamburg, would offer a claimed 13 per cent cost per seat reduction over current models.

Airbus tells MRO Management that the A380plus ‘brand’ is not being marketed, but it is continuing with the related ‘cabin efficiency enablers’, including a new forward staircase, nine-abreast premium economy seats, internally wider upper deck, aft galley stair module and combined crew rest area.

The new forward stairs option remains a project study (after discussion with potential customers), but could become a line-fit option ‘if some customers are interested’. The proposed nine-abreast main deck ‘premium economy’ seating (forward of Door 2 and available as a line-fit and for retrofit) requires installation of an additional seat rail.

An upper-deck cabin-width modification that removed sidewall stowage capacity (to make space for up to 10 more seats, in conjunction with a ‘herringbone’ business-class cabin layout) became standard fit last year.

Airbus has not developed a previously revealed potential line fit main deck ‘sidewall rotation’ because of ‘limited benefit and high cost’. The aft galley stair module, available for line or retrofit, has been selected by a customer and is planned for introduction in 2019. It features “a U-shaped stair and integrated galleys”, permits removal of galleys near main deck Door 4 and allows up to 14 more seats.

Originally presented as retrofittable, a proposed combined crew rest compartment is seen as more appropriate as line fit equipment, being otherwise too large an investment to be justified to generate space for just three more seats.

To obtain the best OA, lowest initial investment, and predictable maintenance and service entry costs, the manufacturer says that A380 operators can select customised modular-service support packages.

Airbus has flight hour services (FHS) agreements with five operators, that have 53 A380s (of which 48 are in service). The FHS-Components core module of such contracts provides component repair by-the-hour, exclusive on-site stock at the customer’s main base and inventory pool spare parts availability.

Under a 10-year partnership agreement involving its engineering division, launch operator SIA receives Airbus engineering, maintenance, reliability and supply chain management services.

SIA has a full FHS-Tailored Support Package (TSP) that includes airframe, engineering and line maintenance elements. Elsewhere in Asia, Bangkok-based Thai Airways has a ‘light’ TSP module that covers auxiliary power unit (APU), logistics, nacelles and tools.

China Southern has APU and escapes slides cover and, in Europe, British Airways has logistics support from Airbus – both under FHS agreements.

TSP contracts generally provide tailored maintenance and engineering services that include fleet technical management. “The latter are managed and contracted for the operator customer by Airbus, [which] for TSP subcontracts with an agreed MRO provider to perform the MRO,” says Airbus.

An additional (non-airline) FHS-Component contract covering Trent 900 engine mounts is also available with Rolls-Royce. TSP airframe maintenance modules include scheduled line, base and heavy checks, with advanced fleet technical management (including airworthiness review, engineering support, maintenance planning and reliability programme) being covered by the engineering module.

“A full TSP ‘solution’ can provide a guarantee of aircraft availability on-time performance covering technical, logistics and maintenance delays,” concludes Airbus.

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