March 31, 2017, ©. Leeham Co: In the last Corner, we showed flight hour graphs for wide-body engines. Now we will deduce the market for engine overhauls from these graphs.
It will show which engines are still in engine manufacturer care, in their main maintenance cycle and in the sun-set phase.
The phase the engine is in and its future flight hour development will decide the attractiveness of the engine for overhaul organizations.
To understand the engine maintenance market for the wide-body engines, we will now deduce the number of shop visits per year from the engine flight hour graphs we showed last week.
The use of wide-body engines is different from the single-aisle. Most wide-body aircraft have an average flight time of over six hours. This means the deterioration from the flight hour is a more important trigger for maintenance actions than flight cycles.
For the early life of engines, the deterioration from, for example, erosion might trigger a shop visit before the first Life Limit Part (LLP) is forcing the engine off the aircraft. As engine families mature, most workshop visits will be the result of LLP limits being reached, unless the engines are operated in a harsh way (short flight times or polluted air areas).
The time on wing for an engine will depend on the flight time-to-cycle ratio. Engines which operate in domestic traffic with short flight times (like ANA’s Boeing 787) will have much shorter time on wing than engines operated mainly on long-haul routes.
The notes about overhaul strategy made in Part 3 for short-haul engines is also valid for wide-body engines. Engines which are in the introduction phase are handled by the OEMs, on power by the hour contracts.
Mature engines which are popular create an overhaul market with several players competing for the jobs. The cost for overhauls in the wide-body market is high. A complete LLP stack for an Airbus A330 engine cost around $8m and for the Boeing 777 around $12m. With LLP flight cycle limits varying from 3,500 flight cycles to 20,000 cycles and the typical wide-body flying around 700 flights/year, the engines will have consumed the low-rate LLPs several times over before the complete stack has been changed.
A typical shop visit for an A330 engine will cost between $5m to $8m dependent on engine and use, whereas a GE90 visits cost $10m or more.
Engines in the sunset phase are maintained by shops which certified on the engine during its hey-day. Overhaul strategies for such engines will be time and material. Used parts will be built into the engine, so when the engine goes end of life, the LLP value is at a minimum.
If we assume the average time on wing for long-haul engines is around 20,000 flight hours, we get the shop removal picture in Figure 1.
Assuming 20,000 flight hours for an engine between shop visits is a rough measure. Typically, two-shaft engines are below that and three-shaft above (to avoid discussion, this is not coming from Rolls-Royce, but from independent engine MRO surveys that we have access to).
For our purposes, a global mean of 20,000 flight hours to generate the shop visit picture is OK.
It’s clear the wide-body engine overhaul market is smaller than the single-aisle. We have less than half the number of shop visits. Single-aisle engines had a total of 3,665 shop visits; for wide-body we count 1,440 for the past year.
If we again assume that an engine maintenance organization would like to have at least 50 overhauls of an engine family per year, with a minimum of 10-20, there can’t be too many shops competing for jobs outside of Trent 700 and GE90.
We will discuss the engine shop structure for wide-bodies more in detail in the next corner.