Keeping the Airbus A330 family of aircraft flying, including the neo, has seen steady progress in escalating maintenance intervals to the benefit of airlines.

About 90 Airbus A330 are expected to undergo second structural inspections this year, according to the European manufacturer, which sees expanding global MRO capacity ‘well aligned’ with upcoming demand.

With around 70 qualified MROs in this market, Airbus reports price levels as “very competitive, which is to the benefit of our customer airlines”.

The story of A330 maintenance is about the practice of evolution, of which the twin-aisle twinjet’s C check requirements provide a good example, according to A330/A340 maintenance programme manager Alan Smith.

C check evolution has been a two-phase exercise, conducted in 2012 and during 2017-18, with the manufacturer very dependent upon operator cooperation.

The initial interval targets selected by the A330 Industry Steering Committee (ISC) for C and 2C checks covering powerplant (engine/APU), systems and zonal tasks, were to escalate from 18 months (18MO)/36MO to 24MO/48MO.

But these targets were not reached, owing to a lack of data at sufficiently high intervals, and check intervals were consequently cancelled in the A330 Maintenance Review Board Report (MRBR) Revision 13.

Each former C or 2C interval task was then expressed in its most appropriate usage parameter(s): calendar time, flight-hours (FH), flight-cycles (FC), or a combination.

“The first phase of the C/2C-evolution exercise was introduced in the maintenance-planning document (MPD) Revision 19, in February 2012,” says Smith.

Respectively, these were: systems/powerplant – former C interval 24MO or 10000FH, former 2C interval 42 MO or 20000 FH; and zonal – former C interval 24MO, former 2C interval 42MO.

“The 42-MO target interval was not reached, mainly due to most reported 2C data being at low intervals. The 2C interval was therefore limited to 42MO.”

The second phase of the exercise addresses the ‘drop out’ tasks that previously remained at 18MO (C check) and 36MO (2C) after the first exercise, with the aim to achieve: former C interval 24MO or 12000FH, and former 2C interval 48MO or 24000FH.

The next update will be MRBR Revision 18, for which the draft was submitted to the European Aviation Safety Agency (EASA) last December, with approval expected in April, and the corresponding MPD Revision 24 becoming available about four weeks later, according to Smith.

Spanish MRO Iberia Maintenance says the new revision will differentiate between parts to be managed at component levels, and those at aircraft level.

Operator response to data requests for the 2017-18 evolution exercise was better, although it ‘still required several reminders and extensions’ to achieve target figures. “It has historically been difficult to get reported operator data for scheduled maintenance,” says Smith.

Nevertheless, Airbus is confident that this situation will be resolved following introduction of its new Skywise data platform.

Have airlines remained willing to report maintenance related data continuously, and have they taken up benchmarking? “Some operators report sporadically, but a growing number are now reporting continuously,” confirms Smith. “Airbus is confident that this will further increase very significantly [with full implementation of] Skywise, [which] also allows a much wider range of functions for benchmarking.”

The A330 maintenance executive says ‘a small number’ of C check drop-out tasks at 18MO, 36MO, 42MO, 100FH, and 2000FH remain outstanding. The number for an individual current A330neo is approximately 15 tasks for a C1 check, slightly higher for an older aircraft.

“These tasks generally have quite low access and man-hours, and can be scheduled in A checks. Operators will be able to resynchronise the C and 2C checks at 24MO/48MO.”

Some operators have justified higher-than-scheduled intervals to national airworthiness authorities (NAAs), and Airbus is aware of several who have achieved ‘a 1000-FH A check interval and 24MO/48MO C/2C interval frame based on evolution of their own data with [NAA] approval’.

Airlines extend their intervals with processes agreed with NAAs, generally without Airbus help or involvement, according to Smith. Some have received manufacturer assistance ‘on a customised basis’.

When developing their maintenance planning, many airlines also break down the A events into overnight work packages to accomplish tasks during otherwise lost time, while maximising aircraft availability.

Some operators equalise A, 2A, 4A, and 8A checks to balance the maintenance workload or aircraft ground time (thus ensuring an even spread of resource requirements, whatever the check) – although this philosophy has not been seen for heavier maintenance, according to Smith.

Many operators are known to have equalised C and 2C checks, so that each event is C1 + half of 2C. “However, as far as we are aware, all A330 operators have kept a block C concept, as the downtime allows sufficient time to perform tasks, corrective action, partial cabin refurbishment, service-bulletin embodiment, paint ‘touch-up’, and more.”

Different aircraft configurations drive different requirements, says Smith. “Configuration is typically broken down as follows: ALL, A330-200, and then further in terms of pre- or post-modification (Mod) and weight variants (WVs).

“During an evolution exercise, a candidate [task] list is usually identified at the start, based on an interval range. For example, the last C/2C evolution exercise included all systems/powerplant tasks with interval C and 2C, and FC and FH equivalents.

“In many cases, there were [multiple] similar tasks with different Mod applicabilities, [and] the Mod is usually linked to a product improvement. The different tasks may have similar intervals, depending on the nature of the Mod.

“To ensure a possibility to increase [all these task] intervals, we ensure that we have enough feedback from a wide variety of different aircraft with good modification coverage. In certain cases, we have identified certain aircraft and operators, and requested specific feedback.”

The current A330 MRBR Revision 17 was approved in August 2018. Smith says the main changes were introduction of maintenance tasks for the re-engined A330-800 and -900 variants with Rolls-Royce Trent 7000 powerplants, while Iberia Maintenance adds that it also reduced the frequency of selected low-interval tasks to 10DY and 42FC.

These developments had been preceded in April 2017 by Revision 16, which introduced new extended twin-engine operations (ETOps) policy and tasks (using newer A350-derived methodology), and replaced intervals NR and VR with numerical intervals in the systems section.

The next A330 Industry Steering Committee (ISC) meeting, scheduled for June this year, will aim to complete the A check evolution activities to increase the interval from 800FH to 1000FH for planned publication in MRBR Revision 19 during October-December 2019, according to Smith.

Iberia Maintenance notes other publication updates, including A330 Airworthiness Limitations Section (ALS) Part 1 Revision 10 last October, which ‘mainly introduced the A330-941’, as well as the Variations 9.1, 9.2, and 9.3.

It also covered ‘mandatory instructions and airworthiness limitations applicable to ATA57 components, and resulting from extended service goal (ESG) activities’.

Other subjects included ‘a new [landing-gear] bogie-beam pivot pin and four new bogie-beam part numbers’. The life limit of the aft pintle bearing on Enhanced A330 variant main landing-gear units has also been increased to full life, says IM.

Current published aircraft-maintenance requirements use ‘limit of validity (LOV)’ terminology in place of previous references, such as ‘design service goal (DSG)’, or – less accurately – ‘aircraft life’. This follows a rather different maintenance evolution: that in industry-wide consideration of airworthiness assurance (that is, ageing-aircraft – or ‘geriatric jet’ – issues).

These have been covered by US Federal Aviation Administration (FAA) and EASA widespread fatigue damage (WFD) regulations.

Indeed, A330 LOV values and definitions have changed following Airbus discussions with EASA and FAA for compliance with FAR 26 WFD requirements. Each DSG and related interim (ISG) and ESG value has now been replaced by the generic term Publication Trigger (PT).

What were the A330 DSGs (age/FH/FC), and how have these changed over time? Smith says the A330 DSG was 60000FH/40000FC, while (pending completion of a full ESG study) an ISC exercise was aimed at a short-term FH extension as a trade-off between those values and 100000FH/33000FC. (The Enhanced A330 enjoyed higher DSG values, equal to the ISC target values.)

Last October’s ALS Part 2 Revision 3 retains earlier LOV terminology, adding the A330-900 to which the same values apply.

The document says that LOV reflects ‘the engineering data that supports the structural maintenance programme, which corresponds to the period of time during which it is demonstrated that Widespread Fatigue Damage will not occur’.

For A330-200, -200F, -300, and -900 variants, this is 180000FH/60000FC, whichever occurs first.

The ALS continues: “Published maintenance programme content is provided in compliance with JAR/CS 25.571, JAR/CS 25.1529, and JAR/CS 25 Appendix H, for aircraft operating up to the Publication Trigger [FH/FC value] quoted… Operation beyond these values requires an update of the ALS Part 2 data… approved by EASA. Should any operator envisage future operations beyond the quoted values, they much first contact Airbus for advice.”

Defined by an airframe’s sub-variant status and modification standard, a range of such trigger points apply to the A330: 100,000FH/33,000FC and 130,000FH/40,000FC for Series 200 and 900 aircraft, and 100,000FH/33,000FC and 126,000FH/44,000FC for Series 300s.

Aircraft operations marketing head Bert Stegerer outlines improvements that have contributed most to reduced A330 direct maintenance costs (DMC) or increased intervals: “Since entry into service, we achieved a 20 per cent reduction in DMC [at the] aircraft level. Increased check intervals led on the airframe to significant improvements.

“New technology applications like the fly-by-wire rudder, LCD cockpit displays, LED cabin light, T3CAS, or enhanced electronic instrument system led to savings on the components cost.

“All three engine suppliers drove their development to reduce maintenance cost. P&W introduced the Advantage 70 programme for the PW4000 family, GE developed the TechCF6 improvement for the CF6, and R-R invested in the Enhancement programme for the Trent 700EP.

“Lower DMCs come mainly from the improvements applied on the MPD and the components. These are reflected in the ten-day maintenance-free operating period for line maintenance, new interval escalation for the 2C [check] from 42MO to 48MO, and the lack of fatigue-sampling tasks.

“A further reduction of A330 and A330neo airframe maintenance costs is planned for 2019 onwards with the escalation of the A check to 1000FH. Specific to the A330neo, new redesigned parts have target check intervals established at 6MO or 2000FH. For the components, the new engine bleed air system and full cabin LED lighting will increase the reliability reducing the labour cost,” concludes Stegerer.