Excluding retrofits or airworthiness-directive compliance, the worldwide market for overhauling Rolls-Royce (R-R) Trent 700-series turbofans is projected at about $2 billion for the next three years, with Asian carriers accounting for the largest share of the work.

A 2009 retrofit kit for the engine, which improves efficiency by 1%, is proving popular, however, and adds to the potential value of each shop visit for those engines undergoing the modification. Moreover, R-R expects to have another retrofit kit available by 2015, the final year of the forecast period, to incorporate technologies from the Trent 1000, Trent XWB and BR725 engines. The final shape of that package, unveiled during this year’s Farnborough air show, is still being determined.

In addition, high- and intermediate-compressor airworthiness directives still in force also could add to the costs of Trent 700 shop work during the forecast period.

Hong Kong’s Cathay Pacific Airways, which launched the 70,000-lb.-thrust-class Trent 700 17 years ago, will require the largest single share of overhauls—9.5% of the 610 overhauls projected to be needed during the forecast period by the 50 operators tracked—according to Aviation Week’s MRO Prospector tool. Emirates Airline and Etihad Airways in the UAE come in at second and third place, with just under 7% of the total overhauls for the period.

Like its RB211 predecessor, the Trent features a stiff, three-shaft spool arrangement, and also like its predecessor, its large Asian and Middle Eastern market presence means lots of service hours on long routes. R-R reports that the 700 accrues about 250,000 service hours each month, and the 700 series already boasts 4.5 million cycles.

Cost Estimates

MRO Prospector uses an hours-and-cycles model to project the likelihood of maintenance events for each operator and aircraft, while using a regional assessment of in-house and third-party shop labor and component rates to estimate the potential cost of each shop visit.

The analytical tool projects that Cathay’s installed base of Trent 700 turbofans should generate the need for 58 overhauls during the three-year forecast period beginning with June of this year, at an estimated cost of just over $200 million. Cathay is expected to require 22 overhauls during the first 12 months of the forecast period, 12 in the next 12-month period and 24 in year three.

Cathay outsources its R-R overhaul work to the Hong Kong Aero Engine Services Ltd. (Haesl) joint venture of R-R (45%), Hong Kong Aircraft Engineering Co. Ltd. (Haeco) (45%) and Singapore’s SIA Engineering Co. (10%). R-R also owns a stake in Singapore Aero Engine Services Ltd. (Saesl) and in German overhauler N3, a joint venture with Lufthansa Technik, so a considerable chunk of the overhaul market is controlled by R-R itself.

Of the other two Hong Kong carriers flying Trent engines—Dragonair and Hong Kong Airlines—only Dragonair is projected to require overhauls during the period, an estimated 16 overhauls in total at a cost of about $54 million. As R-R notes in its fact sheets on the engine, Cathay, together with sister airline Dragonair, is the leading Trent 700 operator, with 48 Trent 700-powered Airbus A330s in service and another 19 of the engines on firm order.

Although Cathay represents the largest single overhaul requirement for any operator, mainland China represents the largest overall market, with 116 overhauls expected worth an estimated $382.7 million. Air China and China Eastern Airlines are expected to require the lion’s share, at 38 and 36 overhauls, respectively, during the forecast period, worth $126 million and $118.6 million. China Southern Airlines needs 28 overhauls worth $92 million and Hainan is projected to require 10 at just under $33 million.

Asian operators make up 48.5% of the market by number of projected overhauls, and 48.2% of the projected value. Aviation Week projects the three-year overhaul market value for the Trent 700 in Asian markets at $984.4 million through the first part of 2015.

Along with the major airframers, R-R agrees that Asia remains the largest growth opportunity for the next two decades. In its recent market outlook, R-R forecast that Asian air traffic will be double that of either the North American or European markets by 2031. Asia eclipsed North America as the largest single air traffic market in 2010. Growth is widely expected to balloon in the long-haul markets, particularly in the developing regions of Asia and Latin America, rather than in the mature North American and European markets, which are uniformly expected to grow only modestly during the next few years.

Other significant Trent 700 operators include Fly Asian Xpress in Malaysia, projected to require 36 overhauls during the forecast period at nearly $118 million, just under 6% of the overall three-year market; Germany’s Lufthansa, accounting for 30 overhauls or just under 5% of the market at $103 million; Garuda Indonesia with 22 overhauls; and Aeroflot and Swiss International Air Line, with 20 each.

Work In Americas

There will be significant overhaul work in the Americas as well. Air Canada is projected to require 16 overhauls during the period at just under $56 million. Half of those are expected during the next 12 months or so, with the balance in the second half of 2014 and the first half of 2015. Canada’s Air Transat comes in with a projected 10 overhauls at $26.6 million, all near the end of the three-year period.

Like Air Canada, Avianca in Colombia is also projected to require 16 overhauls, at $52.5 million, and US Airways is expected to require 14 overhauls, beginning next year, at a cost of just over $45 million. Hawaiian Airlines is seen requiring six overhauls at just over $19 million between the second half of 2014 and the first half of 2015.

It is unknown which of these airlines, if any, have installed or intend to install the Enhanced Performance, or EP, Trent kit, which incorporates many of the features of the EP standard for new-build 700s that R-R introduced three years ago. R-R does not identify which customers bought the retrofit kit, although the enginemaker reports that 12 carriers so far have purchased it.

Though the EP kit does not turn the older Trent 700 into today’s build, it comes pretty close. Like the new-build engine, the EP kit features the aerodynamically enhanced compressor blade shape R-R developed for the latest Trent 1000 and Trent XWB engines. Elliptical leading edge profiles improve efficiency for these blades, which are installed on all of the engines’ intermediate- and high-pressure compressor blades. High-pressure turbine blades, plus the high-pressure and intermediate-pressure nozzle guide vanes, are super-polished, and there are other HP compressor quality improvements.

There are a few items the kits do not contain, however, such as optimized HP turbine clearances, optimized fan tip clearances or a pocket-less spinner fairing.

With another kit in the offing promising another 1% efficiency improvement, it is likely more operators will move to add the kits during a shop visit.

The Trent 700’s most high-profile airworthiness issue actually grew out of an incident involving its higher-thrust successor, the Trent 800. The January 2008 crash of a Trent 800-powered British Airways Boeing 777 was pegged to a specific combination of factors that allowed ice to form within the fuel system and collect on the front of the fuel-to-oil heat exchanger (FOHE), limiting fuel flow.

In-Service Data

Engineers looked at in-service data from the seemingly innocuous go-around of an Airbus A330 in May 2009, which led the European airframer to conclude that the problem could exist on Trent-powered A330s and A340s as well. An airworthiness directive followed, AD 2009-0257, ordering upgraded FOHEs on Trent 700s and 500s.

Among other actions in the 700’s history, the European Aviation Safety Agency (EASA) in 2009 mandated (AD 2009-0187R2) inspections and possible replacements of front combustion liner (FCL) head sections after routine inspections detected cracked FCL heads. R-R service bulletin instructions outline acceptance criteria for any damage found.

In 2007, EASA ordered inspections of intermediate-pressure compressor rotor Stage 2-3 interstage spacers after one was found cracked on an in-service Trent 700.

In 2005, a series of in-service oil loss events prompted an emergency AD (2005‑0025) ordering oil filler caps on all in-production Trent engines replaced. The problem was traced to a manufacturing defect on a batch of the caps.

Also in 2005, a Trent 700 was removed due to oil loss and low oil pressure. The oil leak came from an oil feed tube damaged by an outer head shield. EASA ordered inspections in 2006 and followed up with a directive (2007‑0260) that included a termination action. Modifications must be done at the next intermediate-pressure (module 05) overhaul or by May 31, 2014.

A number of low-power surges prompted the U.K. Civil Aviation Authority (CAA) to order surge tests and eventual replacements of high-pressure compressor Stage 1 casings and intermediate case outer location rings in late 2003. An EASA AD (2007-026) superseded CAA’s directive and extended the terminating action compliance window to 6,300 cycles from 4,500 cycles.