MAX KINGSLEY-JONES / LONDON
The German-built A318 makes its public debut as Airbus reworks the programme following the delay to the Pratt & Whitney PW6000
The A318, the latest and smallest member of the Airbus A320 family, will enter service in the middle of next year with CFM International CFM56 power. That is six months later than planned and with a totally different engine to the one originally specified, after problems with Pratt & Whitney's new PW6000 powerplant.
Airbus has reshuffled the programme, however, and remains confident it will be able to ride out the delay. "Given the situation after 11 September, some airlines have been less concerned about the delay than perhaps they would have been," says one Airbus source.
The company's decision to develop an A320-based 100-seater followed abortive plans in the mid-1990s to create anall-new family of 80-100 seaters with China under the Airbus Industrie Asia (AIA) AE317/AE318 designation (Flight International 9-15 June, 1999). In parallel with these studies, Airbus had devised a plan to remove four-and-a-half fuselage frames from the 124-seat A319, providing a genuine A320-based 100-seater to tackle the Boeing 717 and 737-600, and new-generation large regional jets.
Airbus linked up with P&W, which was looking for an application for its PW6000 engine, and the two were able to offer a highly competitive 100-seat aircraft to the market. It was unveiled in September 1998, adopting the A318 designation with the PW6000 as the only engine option. By the time of the launch in April 1999, the A318 had taken 109 orders and commitments from six customers.
Although the PW6000 was "the engine of reference" for the programme from the beginning, Airbus left the door open for the incumbent A320 family powerplants (the CFM International CFM56-5 or International Aero Engines [IAE] V2500) to be offered to provide commonality for existing operators. While IAE (in which P&W is a shareholder) decided against offering an engine, CFMI joined the programme in July 1999, when major CFM56-operator Air France specified its engine for the 25 A318s it had on order and option.
This decision to offer an alternative engine on the A318 would later be of great benefit when the PW6000 ran into major technical problems (see panel). Although the first A318 is equipped with the PW6000, the CFM56 version will fly in late August and this combination will now lead the programme.
In its effort to gain a foothold in the market, P&W designed the PW6000 as a simple engine to keep maintenance costs to a minimum, and developed its "power-by-the-hour" fleet management programme. "This takes away a lot of the potential down-side resulting from the lack in engine commonality," says Stuart Mann, product marketing director of the A320 family.
According to Airbus chief engineer single aisle family Wolfgang Engler, the PW6000-powered A318 equipped with the definitive version of the engine will have around 2% higher fuel consumption than the CFM56-version - but its 6% lower maintenance costs ensures direct operating cost is below that of any of its competitors, including the CFM56 version.
Two-class layout
The 4.5 fuselage frame reduction over the A319 - 1.5 frames forward of the wing, and three aft - reduced the A318's overall length to 31.45m (103ft 2in). This enables to 107 passengers to be accommodated in a standard two-class layout, or 129 in a high- density configuration - similar to the rival Boeing 717 and 737-500/600.
"To compensate for the shorter moment-arm, the surface area of the vertical stabiliser is increased through the incorporation of a 0.7m [28in] extension of the fin tip," says Engler. This provides greater stability and control at low speeds, and enhances the A318's field length capability. "We have also reinforced the nose gear to compensate for the higher loads," he adds.
The A319's 34.1m-span wing is unchanged, with the single-slotted flaps and leading-edge slats retained. "With A318 production not expected to exceed four per month, we made no structural changes to the wing or fuselage to reduce weight as it would have been too costly from an industrial perspective," says Engler.
Airbus has introduced new production techniques with the A318 at its plants in Einswaden and St Nazaire. These will reap benefits in the longer term. "We have replaced riveting with laser-welding on parts of the lower fuselage shell - this will reduce production costs and help maintenance as the structure is much cleaner," says Engler, adding that the engine pylon and interfaces are identical to the current aircraft, with an adopter plate bolted to the existing pylon for the PW6000 installation.
The belly cargo doors are each one frame narrower to ensure that the nacelle and wing-trailing edge clearances are maintained during ground handling. Six maximum take-off weight options are offered on the aircraft from the baseline 59t up to 68t - the latter providing a maximum range with 107 passengers of 6,013km (3,250nm) with CFM56 engines (see table).
Airbus Deutschland was designated to undertake final assembly at its Hamburg Finkenwerder plant alongside the A319 and A321. Assembly of the first example, powered by the PW6000, began last August, and this aircraft flew on 14 January.
Delays
By then, it was clear the PW6000 was not going to meet its performance guarantees, so Airbus decided to delay the programme for that version of the A318. "We didn't want an aircraft that couldn't perform as advertised out of the box," says Mann. "P&W remains steadfastly behind its performance predictions," he adds.
This has resulted in the PW6000-powered A318's in-service target being delayed from early next year to mid-2005 as the engine undergoes a major redesign. Although the delay was a major blow, as most A318 customers had specified the P&W engine, Airbus has coped by reshuffling the programme, and PW6000 customers Frontier Airlines and International Lease Finance have switched to the CFM56. Of the 108 A318s on order, around two-thirds are now CFMI powered.
Flight-testing of the first aircraft at Airbus's centre in Toulouse is going well, says Engler, with 80h accrued to date. "The engine is performing very well. There have been no snags or isolated problems and the engine has been very reliable so far."
The first phase of the certification programme has been completed. It involved exploring and exceeding the normal flight envelope. The aircraft has been operated beyond its normal Mach 0.78 cruise speed to M0.87. Auto-land and auto-braking systems have also undergone initial tests.
The first A318 is concentrating on tests of the engine/aircraft and nacelle integration for the PW6000, as well as the powerplant's new Papillion thrust reverser developed by Hurel-Hispano. The second aircraft, also fitted with PW6000s, will join the flight-test programme in June, when the prototype will be grounded for re-engining with CFM56s at Hamburg. This aircraft will resume flying in late August.
"The 'identification' of the A318 [ie the defining of the control laws for the fly-by-wire control system] and aero-elasticity testing will be completed by June using the PW6000 version," says Engler.
The third aircraft, the first production CFM56-powered version, is due to fly in May next year and will be used for a "very small" function and reliability test programme. The CFM56 model is due for certification in May next year, with deliveries commencing the following month to Frontier. This has been brought forward by three months to compensate for the delay.
Meanwhile, the prototype A318 will be grounded again and returned to P&W power with the revised production standard PW6000. "This is due to take place by October 2004," says Engler. The entire flight-test programme will total 1,050h, he adds, of which around 450h will be flown by the CFM56 version and the remainder by the PW6000 model.
| TABLE: Airbus A318 orderbook | ||
|
| Orders | Engine selection |
| Air China | 8 | PW6000 |
| Air France |
| CFM56 |
| America West |
| PW6000 |
| British Airways |
| PW6000 |
| CIT Aerospace |
| N/A |
| EgyptAir |
| PW6000 |
| Frontier Airlines |
| CFM56 |
| GECAS |
| CFM56 |
| ILFC |
| CFM56 |
| Total | 108 |
|
| Note: N/A - not announced | ||
Source: Flight International
