NextGen Performance Snapshots
Cloudy Day is A-OK at Half Moon Bay
Cloudy Day is A-OK at Half Moon Bay
On the edge of the Pacific, about 20 miles south of San Francisco in San Mateo County, Calif., sits Half Moon Bay Airport. Built in 1942 as a U.S. Army training facility, it is now home to about 80 aircraft and the staging point for emergency services, such as air ambulances and Coast Guard sea rescue operations. The airport is also a source of education and training for pilots, mechanics and airport employees, making it an important economic resource for the county.
In the early mornings and late afternoons, heavy cloud banks roll in off the cold waters of the Pacific, obscuring the view down to the runway at Half Moon Bay. But Half Moon Bay is also home to two NextGen landing procedures that allow pilots to land even when visibility is low.
These NextGen procedures use GPS signals enhanced by the Wide Area Augmentation System (WAAS) to provide a precise landing path that pilots see on their cockpit instrument panel. Master flight instructor Max Trescott, who teaches general aviation pilots how to fly these kinds of NextGen approaches, explained that without them, pilots would not be able to land at Half Moon Bay when visibility to the runway is hidden by the clouds.
Known as Localizer Performance with Vertical Guidance (LPV) procedures, they enable pilots of WAAS-equipped aircraft to descend to as low as 200 ft. before the pilot has to see the runway to land. This is important because when visibility is obscured, for example by clouds hovering at 200 ft. above the ground, WAAS sends signals to the plane's onboard instruments to guide the pilot on the descent to the runway until the aircraft gets out of the clouds. On a day when the cloud cover descends low to the ground, the lower the plane can get using instruments, the more opportunities there are for the plane to be able to land. The availability of LPVs, which require no equipment on the ground, has improved safety and access to Half Moon Bay and more than 1,500 other small and medium-sized airports around the country in use by general aviation: small planes, air taxis, helicopters, and law enforcement and rescue aircraft.
The FAA has produced almost 3,000 LPV approach procedures around the country since WAAS became available for operational use in the National Airspace System in 2003. More than 1,800 of those procedures are for runways that have no Instrument Landing System (ILS) installed, which means the LPV is the only way for aircraft to land.
The FAA plans to publish another 2,000 WAAS LPVs by 2016 so that every runway in the nation that qualifies for an LPV approach will have one.
Another benefit of LPVs is that they are just as accurate at 30 nautical miles from the airport as they are directly over the runway, just as GPS systems we use in cars are always providing information no matter how far away from our destination we are. By comparison, signals from traditional ground-based navigation and landing equipment, such as Instrument Landing Systems, become less accurate as distance from the runway increases. And if the airport is surrounded by mountains, the signal can become disrupted and unavailable. In that scenario, aircraft are not able to land at all when visibility is low. Satellite procedures offer more flexibility to small airports where ground-based equipment may be too expensive to install and maintain.
So how important is an LPV approach for pilots? Well, imagine you're in your car on your way home and 500 feet from your house you suddenly get to an area with heavy fog. For a pilot, that would mean having to turn around and go to another airport. But using an LPV approach, the pilot can fly through the clouds just as easily as you drive through the fog.
Given the advantages of LPVs, pilots and owners of general aviation aircraft have been early adopters of WAAS technology and the primary users of the procedures. Almost all general aviation aircraft in the U.S. that fly using instruments have GPS and 60 percent of them have WAAS as well. This is nearly 55,000 aircraft. In addition, 3,800 corporate business aircraft and 200 regional jets are equipped with WAAS.
Click here to find out where WAAS LPV procedures are available in your area.