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Rolls-Royce and LHT partner on Trent shop

 - November 11, 2007, 7:04 PM

N3 Engine Overhaul Services–a joint venture between Rolls-Royce (Stand W206) and Lufthansa Technik (Stand C518)–opened officially in September. It is the latest in a global network of Trent engine overhaul facilities.

Built from scratch at Arnstadt in the central German state of Thuringia, N3 accepted its first engine in April, immediately after receiving approval from the European Aviation Safety Agency to operate as an EASA Part 145 engine maintenance facility for Trent 500 engines. By the time of its official opening, the new facility had already shipped two engines back to customers. But it is still ramping up both its services and its staff.

By September the company employed around 270 of a workforce expected to reach at least 500. The Trent 500 is specific to the Airbus A340 airliner, and approval expected next year to overhaul the A330’s Trent 700 will mean a much bigger customer base. Approval for the A380’s Trent 900 should follow in 2009.

The company expects capacity to be 200 engines per year. About 40 percent are expected to come from Lufthansa aircraft, the rest from other operators in Europe, North America, Africa and the Confederation of Independent States. Engines inducted so far have come from Iberia and South African Airways as well as Lufthansa itself.

Engine overhaul, with its reliance on sophisticated processes, expert skills and high-value equipment–more than 20 percent of the o100 million ($140 million) investment that N3 represents was spent on machines, including o8 million for cleaning and nondestructive testing alone–is probably the most lucrative activity in the commercial aircraft maintenance, repair and overhaul industry. It is certainly important to Rolls-Royce: aftermarket services account for fully 53 percent of the group’s $15 billion revenue and 38 percent of its $53 billion order book.

N3’s name is a reference to the three-shaft configuration that Rolls-Royce uses for all its big turbofans, both the Trent series and the earlier RB211 line. The Arnstadt facility complements existing overhaul facilities at the manufacturer’s home base in Derby, UK, and joint ventures with Cathay Pacific maintenance affiliate Haeco in Hong Kong, SIA Engineering in Singapore and American Airlines in Dallas.

As the newest, it is naturally the most modern and it has been laid out with a U-shaped flow line. The line, with stops for disassembly, examination, cleaning, crack detection, repair, storage and assembly, was devised to ensure optimum material flow and short travel distances. It also makes maintenance progress clearly visible.   

Overhauling Trent Engines the N3 Way

Engine overhaul is one of the most lucrative aspects of the aircraft maintenance, repair and overhaul industry. But what does the process involve?

After arriving by truck, each engine is placed on a disassembly stand and examined for concealed damage. The production planners then translate the work specified in the customer’s order into detailed work plans, taking into account legal requirements and the manufacturer’s instructions.

Once nonmodular components such as piping have been removed, the engine is hoisted into a vertical position using a crane and disassembled into its eight modules. Vertical stripping and reassembly is an innovation: traditionally the procedures have been carried out with the engine in a horizontal positåion, but new engines are built vertically, and during reassembly the upright position means gravity helps with the joints.

The individual modules are then taken to disassembly booths where they are further dismantled into their individual parts and components–as many as 15,000 of them in total–for cleaning and crack detection. Each part is then assessed in comparison with permissible tolerances as serviceable, repairable or scrap.

Serviceable components are stored ready for assembly, while components to be repaired are either taken to N3’s internal repair shop or dispatched for external revamp. Specialist repairs such as turbine blades, for example, are carried out at the appropriate center of excellence, while LHT’s own engine shop at Hamburg has the special facilities needed for the Trent 500 combustor case.

The engine’s modules are then rebuilt using a combination of undamaged, brand-new and refurbished components. The mechanics carrying out this stage also handle grinding and balancing. When the modules have been inspected and passed, they are delivered to final engine assembly.

Once the engine has been rebuilt and checked by N3’s product quality team, it can be taken to the new test cell. One of the biggest and most sophisticated in the world, the test cell has an intake tower 75 feet high and an exhaust stack 30 feet taller. Able to sustain an airflow of more than 100,000 cu ft per second, it can be used to test engines with up to 150,000 pounds of thrust.

After testing, the engine and its documentation are examined one more time before being given a certificate of airworthiness. The engine is then prepared for dispatch and returned to the customer.