Retrofit Capability To Be Withdrawn

Wingbox Modifications Negate Fuel Burn Savings

Weight Penalty Increases With Re-Engined Models

Airbus’ ongoing trade studies on the winglet or “sharklet” designed for the A319, A320 and A321 have all but concluded that retrofitting the device may not be feasible or cost effective given that the raft of changes needed to the centre wingbox modifications, front wing spar and pylons.  The level of design changes required negate the fuel burn savings identified versus those of new build airplanes that have the strengthened components built-in from the outset during assembly.

On the A319 specifically, retrofitting the winglets/sharklet was described by an one engineer as a “non-starter” given that the outboard wing bending relief required much greater stiffening than first thought to counter the moment arm of the shorter airplane. The jet maker has no plans to incorporate winglets to the A318, either on existing or new build airframes. Airbus had encountered similar issues when trialling previous winglet designs, electing to drop those proposals as weight and stiffening requirements adversely affected the front and rear spars of the A320 wing, including greater torsional forces and stresses on the unstrengthened centre wing box.

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Airbus had noted at the Dubai Air Show last fall that additional wingbox strengthening would involve another “200kg” weight, however, the reinforcements could be as much as 350kg. Offsetting some of this weight would emerge through ongoing program weight saving, although it is not clear whether the efforts would be enough to maintain the 3.5% fuel burn reduction and still deliver the boost in range.

Airbus states that there would be a range increase of up to 150nm or a corresponding payload increase of half a ton, depending on configurations of each model. On a comparative basis:

• The 737-700 would still have a 7% range advantage (3440nm) over the A319WE (Winglet Equipped)
• The 737-800 would still have a 5% range advantage (3115nm) over the A320WE (Winglet Equipped)
• The 737-900ER* would still have a 15% range advantage (3115nm) over the A321WE (Winglet Equipped)

Winglet equipped A320′s would also incur additional weight penalties for the planned re-engine strategy which Airbus hopes to finalise this year. Qatar Airways had been seen as a prime candidate as launch customer for the A320 re-engine model, however the airline is poised to announce an order for the lacklustre CSeries at the Farnborough Air Show in two weeks time.

One major US-based A320 operator has baulked at Airbus’ plans for both the winglet and re-engine moves claiming that the weights being advertised are so heavy, that the dual-wheel landing gear legs need to be substituted for a four wheel bogey to compensate for the increase in weight as a result of the major wingbox and wing changes needed to fit the Pratt & Whitney PurePower GTF engine.

Despite being lighter, the CFM International LEAP-X engine option would still require significant beefing up of the wingbox, pylon, wing spars to accommodate the engine.

The gap between the fuel burn dynamics on the A320 and 737 families widens next year with the introduction of the CFM56-7BE engine (formally known as the Evolution) which aims to deliver a further 2% fuel consumption improvement (with aerodynamic changes). CFM is also using the CFM56-7BE platform to target further efficiencies with PIP upgrades with a view to attaining another 2% or more cut in fuel burn from the engine alone, however it has no plans to offer the same on the A320 engines as of yet.

While Airbus has opted to concentrate its near-term efforts on integrating the wing tip device for its new build jets, it is “continually looking at ways” to reduce the weights involved in the strengthening of the wingbox and surrounding structures to eke out more aerodynamic efficiencies.

*Range does not include two optional fuel tanks