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Maintenance

Practice of evolution

Keeping the A330 family of aircraft flying, including the neo, has seen steady progress in escalating maintenance intervals, to the benefit of airlines. Ian Goold reports
 
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 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." >>
 

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