THE LEADING GLOBAL PUBLICATION FOR OPERATORS OF AND INVESTORS IN AIRCRAFT AND ENGINES

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ISSUE FIFTEEN JULY/AUGUST 2013

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30 Airline Economics July/August 2013 www.airlineeconomics.co

A380 ENGINES

When Airbus decided to launch the A380 it was generally agreed by the industry that this aeroplane was

not going to sell in the same quantities as previous wide-bodied aircraft such as

Boeing’s 747, 767 or the Douglas DC10 / MD11 family. After years of cutting each other’s throats trying to win market share on aircraft offering engines from all three major suppliers, the engine manufacturers realised that they could not continue with this war of attrition,

especially on an aircraft with such limited sales potential, even though it was a four-engined aircraft. Assuming that Airbus would surely select Rolls-Royce as the European engine supplier the two remaining manufacturers, GE and Pratt and Whitney, were faced with

Powering the superjumboDavid Cook, president of ASM Consulting, offers his advice to Doric on engine choices for the A380

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a dilemma – who was going to be the America supplier?

In a rare example of good sense and commercial reality they agreed to compromise and formed a joint-venture, Engine Alliance, to provide an American engine to compete with Rolls-Royce. The

British manufacturer was already up and running, promoting the Trent 900 as the lead engine for the A380. In a project similar in engineering and structure to GE’s flagship CFM programme, the Engine Alliance developed an engine in a 50/50 joint venture managed by an independent organisation populated by personnel from both companies. Without wishing to sound over simplistic, this engine is similar to the CFM in that it takes an existing GE core, that of the GE90, and mates it with a low pressure system coming from Pratt and Whitney’s successful PW4000 engine family. At 70,000 lbs thrust it was baptised – inevitably – the GP7000. Basic characteristics of both engines are listed above:

Both engine types, as would be expected, comply with all current noise operating restrictions in place at major airports and have extremely efficient, low emissions combustion chambers providing comfortable margins relative to current CAEP limits. It is a little known fact (identified by the Society of British Aerospace Companies) that if an A380 were to overshoot the runway at Heathrow and end up taxiing through the centre of London it would be exempt the Central London Emissions Charge in view of the fact that an A380 produces

only 75 gms of CO2 per passenger kilometre compared to central London’s limit of 77 gms CO2 per passenger kilometre!

Both engines demonstrate the classic architecture of their parent companies. Rolls Royce has always believed in the three-shaft concept where fan, Intermediate compressor and HP compressor are driven by different turbines on different shafts. The greater aerodynamic efficiency produced by such a system has generally produced a range of engines which are more fuel efficient than their competitors at similar thrusts while taking a small penalty in weight due to the additional hardware. This is not the case on the A380: the GP7000 is longer, larger and heavier, using a classic two-shaft engine configuration and incorporating an additional rotating stage compared to the Trent 900. Nonetheless it has established a reputation in the market as being more fuel efficient than its three-shaft competitor and the reason for this probably lies in the higher Overall Pressure Ratio and higher operating temperatures permitted by the more sophisticated materials used in the GE90-derived core.

Fuel efficiency is of critical importance on a long-range aircraft such as the

A380 ENGINES

ROLLS ROYCE TRENT 900 V ENGINE ALLIANCE GP 7000

Rolls-Royce Trent 900 Engine Alliance GP7000Certified thrust ratings 75,152 lbs (970-84)

76,752 lbs (972-84)78,304 lbs (970B-84)80,213 lbs (972B-84)

74,735 lbs (GP7270)

Development capability (thrust ratings already certified)

80,781 lbs (freighter)83,835 lbs (freighter)84,098 lbs (stretch)

80,290 lbs (freighter)

Length 179” 187”Overall diameter 118” 124”Dry weight 14,190 lbs 14,800 lbsOverall Pressure Ratio (OPR) 37-39 43.9Bypass Ratio (BPR) 8.5 – 8.7 8.7Fan 116” diameter,

24 hollow titanium blades116” diameter, 24 hollow titanium blades

Intermediate (IP)/ Low Pressure (LP) compressor

8 stage IP compressor 5 stage LP compressor

High Pressure compressor 6 stages 9 stagesShafts 3 shafts,

counter-rotating core2 shafts

High Pressure Turbines 1 stage HP turbine1 stage IP turbine

2 stage HP turbine

Low Pressure Turbines 5 stage LP turbine 6 stage LP turbine

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A380 ENGINES

2010. Groundings, engine removals, modification programmes, claims for damages and compensation ensued, making 2012 a particularly difficult year for Rolls-Royce but sales do not appear to have suffered due to the slow market for the A380. Enough has been written about this incident already (it was, in fact, due to a manufacturing quality issue) and there is no need to go into further details here but it does highlight a fundamental problem concerning the continued development of either engine on the A380. Engine manufacturers ‘de-bug’ their engines through accumulated experience, building up operational hours and cycles through the use of their products by the airlines. Four-engined aircraft are particularly good at this, generating twice as much experience as a twin-engined aircraft, and both engine types on the A380 have already

0.5 – 0.8%.Being the lead engine in the aircraft

certification process, the Trent 900 did pick up the majority of early customers. However, Engine Alliance turned the situation around at a stroke by securing a massive 90 aircraft order from Emirates. Considering the recent Doric order, but ignoring recent possible cancellations the situation currently stands at: Trent 900 – 38% of firm engine orders, GP7000 – 50% of firm engine orders, and 12% undecided.

As regards in-service experience, both engines have experienced some problems. The in-flight shut down of a GP7000 was the cause of an Emirates precautionary landing in India in October 2011 but this incident pales in comparison to the uncontained engine failure which struck a Trent 900 powered Qantas flight departing Singapore in November

A380 and both engine manufacturers continue to leap-frog each other in their claims for having the best fuel performance. The GP7000 engine’s fuel performance has, according to its manufacturer, been revised downwards three times since it entered service, improving on the originally specified fuel consumption by 1.2%, while Rolls-Royce continues to improve the Trent 900 by recycling technology developed for other engines in the Trent family such as the Trent 1000. New engines delivered since 2012, referred to as the Trent 900EP, incorporate improvements such as elliptical compressor blades, reduced low-pressure turbine tip clearances and improved coatings on the high pressure compressor drum to improve clearances. Additional improvements are expected to be brought in by mid-2014, which will further improve fuel burn by between

A380 engine - paris air show 2011 (ea engine)

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become a very expensive liability. Disregarding the operational aspects

of these agreements, they can also create difficulties in terms of the management of the aircraft, and engines, as assets. Some progress has been made recently in making aircraft Fleet Support Agreements more ‘lessor friendly’ providing for more flexibility should the aircraft move from one airline operator to another. The same can not be said for engine Fleet Support Agreements. While the engine manufacturers have proposed similar flexibility to their agreements, such proposals have received a lukewarm response from the engine leasing and financing community and more needs to be done to allay fears of a closed market which diminishes the value of the engine as an asset. We all understand that the value of any asset is the price a willing buyer is prepared to pay for that asset. We have all sat through presentations at aviation finance conferences showing aircraft value depreciation curves where, after 20 or so years, the residual value of the aircraft is, in fact, the value of the engines installed on that aircraft. But what is the value of those engines if the only possible buyer is the engine manufacturer that controls the spare engine or spare parts market? Besides looking at traditional engine evaluation factors such as fuel burn, reliability and maintenance costs it may be useful for a lessor such as Doric to investigate which of the respective engine manufacturers will offer the greatest comfort and flexibility in terms of assuring the residual value of their products in 20 years time.

A380 ENGINES

performance data, it would be impossible to judge which engine will offer the best fuel burn in the future. But will these manufacturers continue to invest in their engines? If sales remain sluggish then manufacturers could be forgiven for concentrating on more exciting programmes such as Boeing 777Xs, 787s or Airbus A350s. Could we, for example, expect GE and Pratt and Whitney to continue to transfer technology from their headline engine programmes into a joint-venture product with limited potential? The launch of an A380 Freighter, or a stretched passenger aircraft, could actually be counter-productive in this regard if it was not accompanied by a very strong demand from the market and good early sales.

The other key element in an engine selection would be engine reliability and, by implication, maintenance costs. Even if maintenance cost data was publicly available it would be far too early in these engine programmes to come to any long term conclusions as to which engine would be the cheaper to maintain. Both manufacturers do, of course, offer Fleet Support Agreements, so should the airlines care? It all depends on what is written in the small print and exactly what the agreement covers. An engine beset with reliability problems will normally have maintenance and modifications costs covered under such an agreement but the airline will still have to bear the costs of disruption to their operation caused by an unreliable engine. An A380 with over 500 passengers on board which does not push-back on time can suddenly

exceeded two million flight hours of in-service operation. However, the A380 is operating over extremely long flight sectors and so in-service flight cycles remain very low. The Trent 900 fleet leader, for example, has amassed over 22,000 flight hours in just six years of operation but only 3,500 cycles. In engine terms it is hardly run-in. Slow sales, and delayed deliveries due to the A380 wing cracks problem, ensures that the fleet is still relatively small and so it should be considered that both engines are still relatively immature and capable of creating surprises as the cycles build up.

But as a lessor, what sort of engine choices should Doric be making in terms of its engine selections? For an aircraft with such a long sector length as the A380, then fuel consumption would be foremost in any potential lessee airline’s consideration. As mentioned previously, both engine manufacturers are continuing to invest heavily in modifications to improve the performance of their engines and, without access to the very latest aircraft

The nacelles for the A380 posed a particular challenge for their manufacturer, Aircelle, a subsidiary of the French aerospace group Safran. In awarding the nacelle supply contract in July 2001 Airbus had decided that, contrary to the practice at the time, the A380 would only be equipped with thrust reversers on its inboard engines. This made the design of inboard and outboard nacelles different which, combined with the choice of two engine types, generated a requirement for four completely different nacelle designs on the same aircraft, an unprecedented challenge. Furthermore, the situation was further complicated by the proposal that, in order to improve reliability, the nacelle manufacturer would dispense with the

traditional hydraulic actuation system for the thrust reversers and develop an electrical actuation system, something which had never been done before.

In the following four years leading up to the aircraft’s first flight on 27th April 2005 Aircelle, which had been created following the fusion of Hispano-Suiza Aerostructures and Hurel Dubois, struggled to respond to the challenges it had been set. The ETRAS, Electrical Thrust Reverser Actuation System, was a particular problem. Even though the thrust reverser translating cowls were made of ultra-light carbon fibre it still represented a significant mass which had to be moved rearwards smoothly and reliably in just a couple of seconds. This required the generation of an enormous

amount of electrical power which, in turn, generated significant amounts of heat from the control unit and motors which had to be dispersed rapidly to avoid it damaging the composite structures around it. Hispano Suiza, the Safran Group’s equipment specialists, toiled on this problem for the best part of 5 years before the system was finally certified in 2006, long after the first flight of the A380. Honeywell, specialists in mechanical actuation systems, provided the power transmission system and thrust reverser actuation mechanism.

The development of the ETRAS was a huge mountain for Aircelle to climb but now they can consider themselves pioneers in this particular technology and, by all accounts, the system is performing safely and reliably in service.

ETRAS – a difficult birth.

“Even if maintenance cost data was publicly available it would be far too early in these engine programmes to come to any long term conclusions as to which engine would be the cheaper to maintain”

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