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IN FOCUS: Very large airliners

Boeing's 747-8 programme passed a major milestone on 1 June, when the Intercontinental passenger variant entered revenue service with Lufthansa, flying from Frankfurt to Washington DC.

By the end of September, the German airline had received three of its 20 ordered ­747-8Is. A total of four aircraft of the type had been delivered to undisclosed VIP customers, the first having been handed over in February. Cargolux took delivery of the first 747-8 Freighter in October last year, and by September 30, Boeing's -8F output had reached 23.

Nippon Cargo 747-8 Boeing

 Boeing

Delivery of a 747-8F to Nippon Cargo Airlines marked the 747-8's Japanese debut

But there have been setbacks along the way. On 4 October, General Electric ordered inspections on all 120 GEnx engines operating on Boeing 747-8s and 787s to check for installation errors of a component now linked to an engine failure in China in September.

The service bulletin calls for a one-time inspection of the first stage low-pressure turbine (LPT) nozzle, a non-rotating part that directs the air flow into the trailing LPT stages. GE issued the bulletin four days after completing a teardown inspection of a GEnx-2B turbofan that was damaged during a rejected take-off by an AirBridge Cargo 747-8 in Shanghai.

The National Transportation Safety Board and the US Federal Aviation Administration initially linked the incident to two other LPT failures of GEnx engines in late July and early August. These were caused by cracks on the forward end of the fan midshaft, which connects the LPT to the inlet fan. But closer inspections of the AirBridge Cargo engine revealed no cracks or fractures of the fan midshaft, which pointed to an installation problem within the LPT itself.

GE has emphasised the GEnx engine family's reliable safety record, despite the high-profile contained engine failures on the 747-8 and 787. The engine fleet has achieved a dispatch rating of 99.9% with 225,000 flight hours in less than two years of service.

In September, the fan midshaft cracking and fracturing incidents were traced to a new, lead-free coating that allowed the component to corrode rapidly under certain conditions. GE switched to a leaded coating already used on the GE90 to correct the problem. To ensure the performance of 747-8s delivered from 2014 will be "within 1%" of the original target, Boeing, in conjunction with GE, is working on a package of engine, aerodynamic and weight improvements to address all the issues. The 6-12 November issue of Flight International will include a full technical description of Boeing's 747-8.

The other contestant in the market for very large airliners, Airbus, has delivered 20 A380s this year - and is aiming at a figure of 30 for the full year. Emirates is set to get five more in 2012, while Thai Airways, Malaysia Airlines and Korean Air are also due to receive examples. A met target of 30 would bring total A380 deliveries to 97 over the full life of the programme. Singapore Airlines has already received its initial complements of 19 A380s.

WING MODIFICATIONS

British Airways, due to receive its first superjumbo in July 2013, has opted to ensure its A380s are delivered from the outset with full-life wings, incorporating the modifications developed in the wake of a bracket-cracking problem on the type. The airline, which is taking a new 575t higher-weight version of the aircraft, will have the affected wing-rib bracket components replaced at Toulouse.

BA's A380 schedule enables the carrier to take advantage of the repair as well as the introduction of the permanent production wing from 2014. Airbus expects the permanent A380 wing fix to secure certification towards the end of this year.

VLA data

The European Aviation Safety Agency had, in June, determined that repetitive inspections were required on Airbus A380s to check for the cracking problem. Its directive was updated to require high-frequency eddy current inspections at intervals of 560 cycles, as well as an initial inspection within 1,300 cycles of first flight. Certain jets which have had lower panel rib boom sections replaced are subject to a slightly different inspection regime. EASA deemed the revised inspection order an "interim action" pending approval of a permanent solution to the cracking problem, identified after cracks were initially discovered in a Qantas example and further inspections turned up problems on additional aircraft.

Lufthansa, meanwhile, has had its own issues with the A380. The German carrier has experienced a number of incidents of odours in the cabin air of Rolls-Royce Trent 900-­powered A380s, but cautions that it is not clear whether all of the events involved engine oil fumes. It plans to introduce onboard equipment to measure potential contamination levels on an ad hoc basis.

The carrier asked Rolls-Royce to develop a modification, which has now been installed on several engines in the airline's 10-strong A380 fleet. The modification comprises a cover for the bleed air extraction outlet, which should stop oil particles from entering the cabin air system. It is based in principle on a similar shield that was developed for Trent 500 engines on the Airbus A340-600.

The cabin odour issue appears to arise during engine start-up. Lufthansa is developing a new start-up procedure together with Airbus and Rolls-Royce, whereby the bleed air supply to the cabin will be temporarily interrupted as the engines spool up. This procedure has yet to be approved, however. In the meantime, airline technicians are manually cleaning the affected engine areas at short intervals to avoid any residual oil outside the regular lubrication system.

Lufthansa has contracted German research centre Fraunhofer Institute to develop portable measuring equipment to determine cabin air contamination levels.

For all the A380 programme's travails, dispatch reliability appears to be going in the right direction. At September's ILA air show in Berlin, Airbus underlined the positive effect of retrofit measures on various systems. A380 marketing head Richard Carcaillet said that these had raised the dispatch reliability rate by a percentage point, to 99.3%, from the beginning of 2012.

Thai A380 Airbus

 Boeing

Thai Airways International received its first A380 in September

The improvement had been notable during the course of delivery of the past 25 aircraft, he said. Modifications had been made to systems such as landing-gear door sensors which, he says, were "a bit too twitchy" as well as fuel pumps, electro-hydraulic actuators and door systems.

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