Horizon using new guidance system for bad weather landings



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Posted on February 23, 2010 at 6:32 PM

PORTLAND - Life for pilots would be wonderful if every day were sunny and clear, free of haze and darkness. In the Northwest, that tends to be more of an exception. In this part of the country, rain, fog and low-hanging clouds can stick with us for months. Add in long nights and you begin to get an idea.

When you step into the cockpit of a Horizon Airlines Q-400 turboprop, you quickly get an idea of the tools that are brought to bear to fight back. The airline was an early adopter of Heads Up Displays, or HUDs, that project  instrument information onto a piece of glass the captain looks right through so he or she doesn't have to take their eyes off the ground or the runway.

Its planes are equipped with Required Navigational Precision (RNP), a technology pioneered in the 1990s by its sister carrier Alaska Airlines. It  allows a plane to fly precise and often irregular routes to get into an airport through lousy weather and thread through difficult terrain. 

But now, Horizon is at the head of the pack as it adopts the Wide Area Augmentation System (WAAS). Simply put, WAAS is a system that enhances the accuracy of the Global Positioning System as it's used in WAAS equipped aircraft.

The accuracy of GPS signals can be rendered less than reliable because of effects in both the atmosphere and ionosphere. For the GPS unit in your car, it's not as big a deal as trying to land a plane in crummy weather.  WAAS works because a series of some 27 ground stations in the U.S. measure the accuracy of the GPS signals, and if something is off, those ground stations send corrected information through other satellites that go back to the WAAS systems on planes.

 "Where in the old days of ground based navigation systems, you were close, you were in the neighborhood, but you were not spot on. And that's not what we do today," says Perry Solmonson, Horizon's director of flight standards and training. She is fluent when discussing the leading edge of technologies in the cockpit.

It's the "spot on" nature of WAAS that makes it appealing. An airplane using WAAS could safely land in weather where the clouds hang just 200 feet over the runway with a mere half-mile of visibility.

WAAS is part safety tool and it helps boost the airline's schedule reliability in bad weather, reducing fewer cancellations and delays because of bad weather.

While WAAS is a new system for full-fledged, Part 121 airlines like Horizon, it's been in the works for years and was used primarily by corporate jets heading to remote airports before now. The reason it's of interest to regional carriers like Horizon is the similar need to get into smaller airports that lack much of the precision, ground-based technology that's taken for granted at big airports like Sea-Tac and PDX in Portland. Solmonson says WAAS builds on the airline's history of technology adoption and, "Makes the aircraft self contained as a navigation system."

WAAS-approved airports don't have to do anything but have their charts certified that they are exactly where they say they are. So, when a pilot pops out of low hanging clouds and expects a runway underneath his or her plane, there really is a runway where the GPS says it is.

Horizon training pilot Steve Bush says he's done plenty of those landings.

"I was involved in the flight test certification for this aircraft and have complete confidence in the system." says Bush.

One Horizon air Q400 is certified and equipped with WAAS at the moment.  Six more are scheduled to be upgraded by April and the balance of the airline's fleet of some 50 jets will have it by the end of 2011.

Horizon continues to work with the FAA, sharing what it learns particularly at those smaller airports not equipped with expensive instrument landing systems.