A pair of six-foot-tall appendages sprouting from the wingtips of an A320 immediately caught the attention of plane spotters scanning the ramp outside Airbus’ Toulouse headquarters last month. The winglets, part of a program to improve the economics and cabin comfort of the single-aisle family, will contribute to a 4- to 5-percent fuel burn improvement targeted for one of the few Airbus programs that hasn’t created a storm of controversy lately.

Dubbed the A320 Enhanced, the project isn’t the giant leap forward analysts predict Airbus will one day need to take with its single-aisle jets, but part of a maturation process designed to ensure, in the words of Airbus COO for customers John Leahy, “at least ten more years of A320 dominance over the 737.”

Of course, Boeing can just point to a history of units sold to debunk Leahy’s claims of dominance. Still, few would deny the A320’s role in Airbus’ remarkable emergence from bit player on the world civil aerospace stage to Boeing’s co-star in a matter of a decade. Last year alone Airbus counted 21 new operators of the venerable single-aisle jets. So the company’s reluctance to abandon the A320’s basic framework should come as no surprise, at least until competitive circumstances change dramatically.

“If you can come up with 10 percent better economics than the A320, then maybe you have a case,” said Leahy. That, of course, would require a new engine. Because of higher maintenance costs, neither the General Electric GEnx nor the latest Rolls-Royce Trent design will work on a single-aisle jet, he added. “The engine manufacturers are trying to figure out how to get there without increasing maintenance costs…maybe by 2014 or 2015.”

In the meantime, the world’s airlines will have to make do with a newly designed cabin, some incremental engine improvements, a few minor drag reduction items and, of course, the aforementioned winglets.

In the cabin, a new ceiling panel will include a lamp screen for better lighting and less noise, while a modification of interior supports will increase overhead storage by 10 percent, enough space for five “Travel Pro Type 22” roller bags. Other improvements include a new overhead grip rail that will allow for integrated seat row numbering and optional LED illumination, a new passenger service unit channel design modeled after that in the A380 and new sidewall/window panels that will create another inch of shoulder space. All told, Airbus expects the changes, available by the middle of next year and retrofitable into existing aircraft, to result in a one decibel drop in noise and 110 pounds of weight savings.

By the middle of last month, the winglet-equipped A320 test article flew roughly 30 hours during 10 flights, the longest lasting five hours and five minutes. After evaluating structural and aerodynamic data of the first design, Airbus planned to fly an alternative configuration this month.

Other airframe modifications will include a lower-drag fuel surge-tank vent at the wingtips, a redesign of the upper wing-to-fuselage fairing and a new engine pylon shape. Planning to freeze the design by the end of this year, Airbus expects the aerodynamic changes alone will result in a 1 percent improvement in fuel burn.

Meanwhile, CFM International and IAE continue work on their respective engine efficiency improvement programs, both of which they expect to make available by late 2008. Both International Aero Engine’s V2500Select and CFM International’s Tech Insertion packages promise lower maintenance costs and less fuel burn, while CFM also promises reduced nitrogen oxide emissions. Engine modifications would account for two thirds of the A320’s fuel efficiency improvements, according to Airbus CEO Gustav Humbert.

This year Airbus expects to see the A320 line benefit from a 0.1-mile required navigation performance (RNP) approach certification. All Airbus aircraft equipped with dual flight management systems and global positioning systems have won certification down to RNP 0.3 in approach. Most Airbus fleets can therefore already fly instrument approach procedures published under ICAO PANS OPS (or TERPS) criteria. At airports where terrain or environmental constraints such as noise, traffic or security issues restricts access, lower RNP values and/or curved final segments can reduce approach time and fuel consumption while improving safety.

Other planned navigation improvements include the introduction of head-up displays in the Airbus Corporate Jetliner family by the end of the year and the entire A320 line by 2008.

Now building 30 A320-family airplanes a month, Airbus has managed to cut production time by four days thanks to a new moving production line in Hamburg, Germany. It plans to increase production to 32 by early next year, then again to 34 with the help of techniques developed for the A380 program.