World's First RNP: Juneau, AK

Overview of Juneau Airport showing Gastineau Channel to the Southeast.

Problems   Mountainous terrain surrounding the Juneau airport prevented the installation of traditional precision approach aids such as an Instrument Landing System (ILS). Alaska Airlines, the main carrier serving the airport, was forced to use a variety of non-precision procedures with high Decision Altitudes (DAs), which combined with frequent low ceilings to cause diversions or cancellations affecting 10% of flights into Juneau. If an aircraft did make it in and the weather conditions deteriorated, departure procedures also were subject to disruptions. It was not unusual to have departures delayed by days while waiting for enough visibility to fly out of the area.   Crews executing missed approach procedures had to make nerve-wracking, high bank-angle, 180 degree turns over unlit mountainous terrain. When winds dictated the use of Runway 08 for departures, Alaska utilized a series of low-speed, high bank-angle turns to get the airplane headed in the opposite direction and away from the mountains to the East of the airport.

Solution   Steve Fulton, an Alaska Airlines technical pilot at the time, knew that RNP had been used to reduce aircraft spacing for transoceanic operations. Using a combination of GPS and the Inertial Reference System (IRS), aircraft could fly navigation procedures requiring performance measured in tenths of a mile rather than the many miles then allocated for traditional navigation methods.   Fulton, together with Hal Andersen, another Alaska technical pilot, proceeded to develop the world’s first terminal area RNP procedures. For approaches, RNP enabled them to create flight paths around mountains and other obstacles so that aircraft could safely descend through the clouds to be properly positioned for touchdown on the runway. On departure, with the tight tolerance enabled by GPS/IRS positioning Alaska crews could depart from Runway 08 without having to use the series of low-speed manuevers to turn around. Instead, they could fly down the narrow Gastineau Channel, confident that they would avoid the terrain on both sides of the airplane.   Revenue service using the new RNP procedures began in 1996. Fulton and Andersen quickly saw the benefits add up. Schedule reliability improved dramatically as RNP approaches allowed for significantly lower DAs. Safety improved as crews were given positive guidance around terrain in missed approaches and departures. Removing the need for tight turns at low speed over challenging terrain increased the amount of payload aircraft could carry.

View from aircraft approaching Juneau runway 08, mountains loom behind the clouds.

View approaching runway 08 on a rare clear day with mountains visible to the East.