Raegan Reber

FRS 142

4/5/04

Currently, in most navigation and landing, airplanes use ground based navigation radar and vocal communication,

but a new system using GPS is being implemented and has the potential to revolutionize air traffic.

This new system combines two GPS based systems: Wide Area Augmentation System (WAAS) and Local Area

Augmentation System (LAAS).

Constraints on Current Air Traffic Control Systems

The current navigation system can’t support the predicted air traffic growth

There are limitations of the line-of-sight systems in terms of propagation distance, accuracy, and reliability

There is difficulty implementing the current system in a consistent manner around the world.

Limitation of voice communication

Lack of digital air-ground data interchange systems to support automation in the airplanes and on the ground.

Wide Area Augmentation System (WAAS)

WAAS is a GPS-based navigation and landing system that provides precision guidance to aircraft at thousands of airports and airstrips where there is currently no precision landing capability

It is a satellite based augmentation system designed to improve the integrity of the information coming from GPS satellites.

What is it?

The Federal Aviation Association uses WAAS to provide a Lateral Navigation/Vertical Navigation capability.

Testing in September 2002 revealed accuracy 1-2 meters horizontally and 2-3 meters vertically.

How does it work?

WAAS provides augmentation to GPS receivers to enhance the accuracy and reliability of position estimates. The signals from GPS satellites are received across the National Air Space at many widely spaced Wide Area Reference Stations (WRS).

The WRS locations are precisely surveyed so that any errors in the received GPS signal can be detected. Unlike traditional ground-based navigation aides, WAAS covers nearly all of the National Air Space System.

What are the benefits of WAAS?

1. Greater runway capability

2. Reduced separation standards which allow increased capacity in a given airspace without increased risk.

3. More direct enroute flight paths.

4. New precision approach services

5. Reduced and simplified equipment on board aircraft.

6. Significant Government cost savings due to the elimination of maintenance costs associated with older, more expensive ground-based navigation.

Local Area Augmentation System (LAAS)

What is it?

An augmentation to GPS that focuses its services on the airport area (approximately 20-30 mile radius).

It broadcasts its correction message via a very high frequency radio data link from a ground based transmitter.

Provides the ability for more flexible, curved approach paths.

Accuracy has been determined to be less than 1 meter both horizontally and vertically.

How does it work?

Local Area Augmentation System Ground Facility (LGF) includes 4 reference receivers (RR), RR antenna pairs, redundant Very High Frequency Data Broadcast (VDB) equipment feeding a single VDB antenna, and equipment racks.

LGF receivers decode and monitor GPS satellite information and produce correction messages. To compute corrections the ground facility calculates position based on GPS and then compares this position to their known location.

What are the benefits of LAAS?

1. Makes curved precision approaches possible.

2. Approaches are redesigned to avoid obstacles, restricted airspace, noise sensitive areas, or congested airspace.

3. LAAS will only need one LAAS ground station for all runways in an airport. This is different from the current instrument landing systems which require multiple installations

Application of GPS

Automated landing in hijacking situations: “dead-man switch”

In the wake of 9/11 airline executives began to investigate ways to prevent overrun of airplanes. One way they suggested doing this is to install an onboard GPS based automated landing system.

The system would broadcast mayday to Air Traffic Control, search the database for the nearest airport, alert the airport, receive clearance to land, and land there.

During these operations, no one onboard would be able to gain control of the aircraft, not even the pilots. No amounts of violence would allow the hijackers to use the airplane as a missile.

Is this workable?

The Federal Aviation Administration is focusing on both WAAS and LAAS GPS measures to implement this idea and in testing both have been found to be extremely accurate.

However

Look ma! No hands!

Obstacles!In a situation in which the “dead-man switch” was improperly used how would the pilot regain control of the aircraft?

What if the terrorists tap into the power source for the GPS and therefore disable it?

What if the terrorists used a jammer to interrupt the GPS?

What happens if the airport denies clearance to a plane?

Suggested Solutions

In the occurrence of mistaken use of the switch a "multiple key" arrangement could restore manual control with codes from the pilot, the co-pilot, and the ground-based ATC

operators. Ground control would contribute its code only when absolute sure that the aircraft could not be used to attack a population center.

To protect it from being disabled, the system would require a hardened compartment not accessible from the cabin and an autonomous power source not controlled from the

cockpit circuit breaker panel.

A jammer could only cause the aircraft to fly long enough to run out of gas and fail to land, but the terrorists would not be able to direct the plane as a missile.

If permission to land was denied, the system would search its database for the next best place to land.

“SATELLITES GUIDE RESCUE HELICOPTER REACH FIRST WEST COAST SERVICE CERTIFIED TO USE GPS

TECHNOLOGY, GREATLY EXPANDING FLIGHT POTENTIAL”

December 11. 2000, The Press Democrat (Santa Rosa, California) reported that without the aid of an onboard GPS navigation based system, transportation of critically injured patients in poor weather would have been impossible!

The GPS system had been implemented only days earlier and had it occurred before that time, the patients would have had to wait for transportation to the hospital or would have had to rely on much slower ground transportation.

“WAAS charts new course in air navigation history” by Paul Lowe

July 10 2003, the FAA implemented its wide-area augmentation system (WAAS) which will potentially open up thousands of runways at 5,400 public-use airports for near-precision approaches in both lateral and vertical guidance modes.

The implementation took longer than previously thought, because it is a system that has never been tried before. One of the biggest challenges was correcting the GPS signals that are distorted by the ionosphere. Scientists came up with a special software program that continuously tested the integrity of the WAAS system.

CO$T

Initial developmental costs in the area of $790 million dollars beginning in 1994

Total life cycle costs (to 2020) are predicted to be around $3.2 billion

Stand alone WAAS receivers are predicted to cost around $8,000, but prices were expected to drop as other avionics manufacturers increased production within the following six months.

“Now that the FAA has turned on the signal, the agency has to accelerate charting new approaches at those airports that don’t have them now”, “The FAA must take innovative steps, such as turning to the private-sector survey, and design these approaches.” Marion Blakey

Aviation International News Online, “WAAS charts new course in air navigation history” by Paul Lowe

Sources

Goel, Sanjeev. “Opportunities in Aviation and GPS”. Center For Technology Training. 2000. Accessed 3/24/04. [http://www.gisdevelopment.net/technology/gps/techgp0037.htm]

Lowe, Paul. “WAAS charts new course in air navigation history”. Aviation International News Online. August 2003. Accessed 4/3/2004.

[http://www.ainonline.com/issues/08_03/08_03_waaschartsp6.html]

Luccio, Mateo. “GPS and Aviation Safety”. GPS World. October 1, 2001. Accessed 3/24/04. [http://www.gpsworld.com/gpsworld/article/articleDetail.jsp?id=1804]

Norberg, Bob. “Satellites guide rescue helicopter reach first west coast service certified to use GPS technology, greatly expanding flight potential”. The Press Democrat (Santa Rosa, California). December, 11 2000: Business D1.

Wheeler, Shelby, compiler. “Federal Aviation Administration Satellite Navigation”. Federal Aviation Administration. November 2003. Accessed 3/24/04.[http://gps.faa.gov/]