As Southwest Airlines moves ahead with plans to implement new fuel-saving navigation procedures, the airline is finding the process challenging.

The low-cost carrier is investing $175 million over the next six years to implement required navigation performance procedures at the 64 airports it serves after receiving US Federal Aviation Administration approval to conduct such operations.

"Our RNP programme is, without a doubt, the most complicated and time-consuming project that Southwest has ever embarked upon. Southwest Airlines has learned that it's difficult, complicated and expensive to implement RNP," carrier senior director of flight operations Jeff Martin wrote in testimony to a 29 July US House Aviation Subcommittee hearing.

Each of Southwest's more than 500 aircraft require some type of modification to conduct RNP procedures, which has "consumed" more than 80% of the airline's NextGen budget, Martin added at the hearing.

Last month the Dallas-based operator completed autothrottles and vertical navigation (VNAV) modifications on its fleet, enabling pilots to fly more precise speeds and to use optimum descent profiles.

Nearly 300 of the airline's Boeing 737-700s are RNP-capable today, Martin says.

In addition, Southwest plans to retrofit its remaining 215 737-300s with GPS receivers, software upgrades and necessary avionics in the next four years to fly more direct and efficient RNP procedures, he adds.

Developing a pilot training curriculum for the new navigation procedures took 19 months and "consumed" 13% of the airline's NextGen budget, Martin says.

Southwest is in the midst of training its nearly 6,000 pilots on the use of automation, VNAV and autothrottles.

Training on autothrottles began last year as they were deactivated on Southwest's Next Generation fleet because, until then, flightcrews had all been standardised on the classic 737 cockpit.

Next, the carrier will train pilots to perform basic GPS approaches followed by RNP flight procedures. All training is expected to be complete next year in order for the airline to begin flying RNP procedures by October 2010, Martin says.

Meanwhile, Alaska Airlines is expanding its use of fuel-saving RNP arrivals to Seattle, having already recorded benefits of the procedure elsewhere. It used RNP more than 12,300 times throughout last year generating system-wide savings of a little more than $8 million, says the airline.

The Seattle-based operator, which has been using RNP since 1996, began testing RNP procedures with optimised profile descent, also known as continuous descent approaches, at its home base in June.

The carrier is aiming to obtain FAA approval next year.

Source: Flight International