Beyond the XLR: Stepping-up the next design evolutions across the A320 Family

Since its launch more than 40 years ago, the A320 Family Programme has continuously evolved and improved. Its latest family member, the A321XLR, entered into service in late 2024 with launch customer Iberia. Now the scene is set for the next set of evolutions to all the A320 Family – so the best gets even better.

While the A321XLR was still in the design and production phases, the teams had already initiated the next evolution projects to incrementally improve the A320 Family platform even further, connecting today and tomorrow – and most importantly, improving its producibility and keeping it competitive beyond 2030.

Those projects have been labelled as incremental ‘STEPs’. Although not normally spoken in full, 'STEP' stands for "Synchronized Targeted Embodiment Point". In this case, “STEP4” represents the latest package of improvements for Airbus’ Single-Aisle Family: the A320neo, A321neo and A321XLR.

A321XLR – the new baseline for Single-Aisle Family commonality

The first ‘quick-win’ of STEP4 is to take some of the new features which have already been developed for the A321XLR and infuse them back into the A321neo and A320neo – while keeping operational commonality with A320 Family aircraft already in operation.

The transferable design features applicable to the A321neo variant include: the XLR's lighter and simplified wing with a single-slotted inboard flap design (replacing the A321neo's double-slotted inboard flap); the forward cabin temperature zones; the new e-Rudder (which provides weight savings versus the legacy unit, as well as improved reliability and reduced maintenance costs); new 'generic' flight control laws; a new flight data management unit; and updated Multi-Functional Runway Lights (MFRL).
 

Structural improvements

Torsten Hartung, Head of A320 Family Development, summarises the onward evolution rationale: “We are putting the good ingredients from our XLR development on our high-volume platform onto the A321neo. How do we do that? By ‘marrying’ various new features – including the improved wing – which we have developed for the XLR onto the A321neo.” 

Single-slotted flaps

Putting these back into the A321neo will not only bring significant benefits for airline operations and maintenance, but for Airbus they also bring higher commonality in production and as well in design. This helps the A320 Family rate ramp-up in support Airbus’ target of 1,000 overall deliveries per year.

He adds: “The A321neo, being an established programme, was a prime candidate to benefit from modernisation of its flight controls and other aspects. It was logical therefore to take features (ie. the wing, e-Rudder and the associated control laws) which have already been developed for the XLR and then implemented back into the A321neo.”

e-Rudder

In addition to these, the A321neo will also receive from its XLR sibling (via STEP4): the optional forward temperature zone; the “Enhanced Takeoff performance Improvement package” (ETOC); and the new “Multi-Functional Runway Light” (MFRL).

ETOC, which was first introduced on the A350 and then on A330neo, improves the take-off performance and optimises the payload by introducing intermediate flap positions. It is now being adapted for the A321neo and works together with the new inboard single slotted flap.

Brand new evolutions for all the A320 Single Aisle Family – including the XLR

Cobra duct

The STEP4 package of improvements does more than borrow the evolutions developed for the XLR and apply them across the Family. Rather, it goes beyond the XLR by introducing additional new ones, and thus answering positively to the airlines’ requests.

To this end the A321XLR and A321neo will both receive, in addition to those items already mentioned: a new “Cobra Duct” APU air intake relocated at the top of the fuselage which will result in cabin air quality enhancements; new corrosion prevention enhancements (including improvements to the cabin floor, cargo bay, and Doors 1 & 4); cabin floor reinforcement providing additional loading flexibility for customers; and increased use of LED technology (e.g. the aircraft’s runway and beacon lights).

The new corrosion protection improvements will comprise new upper deck and lower deck corrosion protections. For the upper deck they include full titanium seat rails and titanium cover sheets on aluminum lavatory and galley rails; and for the lower deck they include a combination of solutions including improved drainage, sealants and panel sills.

Anti-corrosion improvements

Another notable item in STEP4 is a standardised “Flight Data Interface and Management Unit” (nFDIMU) for all the A320 Family. This device enhances data processing capability, improves in-service flexibility and increases common part numbers across the A320 Family. 

A320neo: increased commonality with A321neo plus brand new features

The A320neo programme benefits too: STEP4 will bring over as much commonality as possible from the updated A321XLR and A321neo to the smaller A320neo. This will include most of the items listed earlier in this article – except for the A321-specific features such as the XLR’s new wing, ETOC and cabin temperature zones.

The applicable features will be phased gradually onto A320neo. These will start with the common structural and improvements packages (the Cobra Duct, corrosion-prevention enhancements etc.) before applying as a next step a few years later: the new flight controls; the e-Rudder; and the cabin floor reinforcements (for the changing passenger-plus-baggage weight industry standards).

STEP4 industrialisation approach: Focus on the A320neo initially…

The STEP 4 programme's industrialisation is focusing initially on the A320neo since it presents a lower volume production, and the Final Assembly Line teams can thus learn from it before exposing the upgrades to the full rate of the A321. Following the A320neo implementation, implementation will move on to the A321neo, including the XLR common wing. Finally in a third phase, Airbus will apply the new improvements described above (Cobra Duct etc...) to the XLR too.

The way to achieve a phased introduction of the STEP4 items, explains Martin Schnoor, A320 Family Programme Development STEP Leader, is through the use of ‘pilot’ aircraft fleets, which progressively introduce into production the components of STEP4.

"For the A320 stream we have selected the first ‘pilot’ aircraft fleet. Deliveries are starting with the first STEP4 A320s. This will be followed a year later by the first STEP4 A321neo and the first A321XLR."

“The baseline A320neo is the first model to incorporate and ‘prove’ the new modifications – such as the new titanium seat rails, the APU Cobra Duct, and the corrosion improvement package.”

He adds: "Where we physically change the aircraft we decided to apply it first on A320neo in order to learn and see how well things are going, and that's the reason why we have pilot aircraft."