There has been a lot of discussion on the future of aircraft MROs, and who is going to provide maintenance for future generation civil airliners. The big two OEMS, Airbus and Boeing are moving into this space, currently occupied by major flag carriers and the large independent groups. At margins of the debate, there are issues surrounding the appropriate metrics being used today and in the future.
The existing metrics are simple yes/no metrics; did the aircraft depart or arrive on-time? There was a report issued recently by the American Transport Association, congratulating themselves on an on-time arrival rate of 85%, what it does not mention is the effect of the other 15% being late; it doesn’t quantify the delay. Were people late by 15 minutes, 1 hour or possibly longer? Was the flight cancelled?
Can one deduce from the on-time data that 15% flights left late? It is logical that if your flight departs on-time, you should arrive on-time. From an operator’s perspective, on-time departure is more important, why was it late, how long was it late, how much did it cost, will it happen again?
Concentrating on the technical side of the debate, Technical Availability is the ratio of the available time against the unavailable time due to maintenance; most operators would provide a maintenance window, typically 2359-0600. Availability becomes:
F*D – (T)/F*D
Where:
F – Fleet size on the day
D – Normal operating day
T – Total time out of service in the day
As can be readily seen, the greater the duration of the technical delay the lower the availability; by simply multiplying by the available fleet size gives the total availability for the day. Aircraft off-line for scheduled maintenance are not included in the available fleet for the day; aircraft late off maintenance are included.
Example 1
F = 5
D = 18 hours = 1080 minutes
T = 4 hours = 240 minutes
Total number of rotations = 45
TDR = (45-2)/45
= 95.6%
Technical availability = (5*1080)-240/(5*1080)
= 95.5%
Example 2
F = 5
D = 18 = 1080
T = 14 = 840
Total number of rotations = 45
TDR = (45-2)/45
= 95.6%
Technical availability = (5*1080)-840/(5*1080)
= 84.4%
In example 2, one aircraft suffered a major un-serviceability of 11 hours, including diagnosis, component change and system testing. With the same TDR as example 1, the flying days would appear similar, how would you incentivise the supplier based on TDR?
Availability must be tracked daily to have any meaning. “Incentives” will be based on a rolling average. The airline and MRO will agree a target and a series of bands above and below the target that will be assigned incentives, those bands below the target will incur a greater negative incentive the further away from the target they are! The contract should be based on the headline Technical availability figure; it is not for the contracting airline to get involved in the MROs departmental KPIs required to achieve the headline figure.
As can be seen in the examples above, the simple TDR rates trumpeted by the major OEMs are not going to cut it in this future environment; the OEMs will need a culture change across the organisation, designing for a 98% TDR is not the same as designing for a 98% technical availability target where trouble-shooting, component accessibility and reliability are all affecting the organisations performance. Can avionics designers and structural designers cooperate to the required degree? As someone who has spent his entire career at the operational end of aviation, I doubt it!
From the OEMs perspective embarking on this process, there will be a step change in the organisation, there is a degree of agility required to respond to a airline opening a new route, night-stopping location or overnight maintenance facility, the airline, for marketing reasons may not provide significant notice of the changes, get one over the competitors! Low cost carriers will have no hesitation when cutting any of the above, regardless of the investment put in to support the operation, what counts to them is he load factor! Do the OEMs have the necessary MRO infrastructure, to meet the needs of the airlines, in particular the low cost carriers; they will not dead-leg an aircraft for maintenance, unless the cost of the two empty sectors is covered by the MRO! They want maintenance carried out in the network, where they can schedule aircraft in and out of maintenance straight on to a revenue service.
As always, I look forward to your comments and feedback!
