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GPS IN AVIATION AND THE COMING AGE OF AUTOMATED LANDING SYSTEMS. By Pete Hand FRS 144 April 17 th , 2006. Outline. A Brief History of GPS used in aviation Goals and Objectives GPS Aviation Technology throughout the years ILS MLS WAAS LAAS. Outline Continued. Automated Landings

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gps in aviation and the coming age of automated landing systems


By Pete Hand

FRS 144 April 17th, 2006

  • A Brief History of GPS used in aviation
  • Goals and Objectives
  • GPS Aviation Technology throughout the years
    • ILS
    • MLS
    • WAAS
    • LAAS
outline continued
Outline Continued
  • Automated Landings
    • In the Military
    • For Commercial use
    • The future of automated landing systems
    • TALS
a brief history
A Brief History
  • June 1991Portable/panel mount GPS that interfaces with autopilot
  • On February 10th, 1993, the National Aeronautic Association selected the Global Positioning System Team as winners of the 1992 Robert J. Collier Trophy, the most prestigious aviation award in the United States. This team consists of researchers from the Naval Research Laboratory, the US Air Force, the Aerospace Corporation, Rockwell International Corporation, and IBM Federal Systems Company
  • February 17, 1994 The Federal Aviation Administration announces that GPS is operational an integrated as a part of the U.S. air traffic control system.
  • In 1998, Vice President Al Gore announced plans to upgrade GPS with two new civilian signals for enhanced user accuracy and reliability, particularly with respect to aviation safety.
    • Wikipedia entry and
history continued
History continued
  • Originally only used by the military (Air Force), but the FAA has approved its use in commercial aviation
  • Commercial GPS uses a different frequency from the Air Force uses
  • First commercial GPS use in 1996
gps in commercial aviation
GPS in Commercial Aviation
  • “The objective of NAS Implementation is to develop the operational infrastructure to support the certification process for satellite navigation and provide the technical basis for the development of GPS operational procedures for all phases of flight. NAS Implementation communicates and cooperates with numerous governmental and non-governmental agencies to pave the way for a smooth transition to satellite navigation.”
    • - National Airspace System
  • Ultimately, the FAA, NAA, NAS, etc. wish to have GPS-based aviation systems which operate all flights
  • Would create the possibility for “drone commercial aviation” – highly unrealistic, but a rising possibility
  • Would make it virtually impossible or terrorists to hijack planes – although if they ever did they could control every plane in the sky…
  • Ethical problems? Economic problems? Safety problems? All an issue…
improvements in landing technology
Improvements in Landing Technology
  • Selective Availability technology – used by the gov through 2000 – accuracy only to 100 meters
  • 2001 – best non-SA accuracy only to 15 meters
  • Differential GPS – used by the Gov until late 2001 – up to10 meters accuracy
  • WAAS – still used by the gov – able to attain accuracy of up to 3 meters
  • LAAS – developed in 2001 – current accuracy is 16 m laterally and 4 m vertically – but goal is go have both accuracies down to 1 meter
early gps ils
Early GPS - ILS
  • Instrument Landing System
    • 2 separate systems – one vertical guidance and one horizontal guidance systems
    • Localizer antenna located at the end of the runway – 2 signals transmitted on a carrier frequency between 108 MHz and 111.975 MHz
    • Localizer receiver on the aircraft measures difference in depth of modulation – when the difference is 0 the localizer is in line with the center line of the runway
ils continued
ILS continued
  • glideslope antenna array is sited to one side of the runway touchdown zone – follows the path of an aircraft down the center of the runway
  • The GS signal is transmitted on a carrier frequency between 328.6 MHz and 335.4 MHz
  • uses a technique similar to that of the localizer
ils in use
ILS in Use

Localizer Antenna at Whiteman Airforce Base

  • Microwave Landing System – developed by FAA NASA and the Department of Defense

-“designed to provide precision navigation guidance for exact alignment and descent of aircraft on approach to a runway”

- provides azimuth (The angle of rotation (horizontal) that a ground based parabolic antenna ), elevation and distance

- supplements ILS – has both vertical and horizontal guidance systems

- MLS use suspended by FAA in 1994 in support of then new WAAS technology

  • “WAAS is a GPS-based navigation and landing system that is meant to improve safety by providing precision guidance to aircraft for all phases of flight at thousands of airports and landing strips where there is no ground- based landing capability. WAAS consists of 25 ground reference stations, 2 leased geostationary satellites, 2 master stations, and 4 uplink stations. The ground reference stations are strategically positioned across the United States to collect GPS satellite data. WAAS is designed to improve the accuracy, integrity, and availability of information coming from GPS satellites and to correct signal errors caused by solar storms, timing, and satellite errors. Unlike conventional ground-based navigation aids, WAAS provides curved precision approach paths in order to avoid obstacles, restricted airspace, noise-sensitive areas, and congested airspace.”
how it works
How it Works
  • 25 ground stations through out the United States – compare GPS signal with known coordinates
  • Report to WAAS Master Station – sends singal to WAAS satellite
  • WAAS satellite sends signal back to plane
  • “The WAAS-enabled GPS receiver adds the correction factor to the GPS signals to derive a corrected GPS signal which is far more accurate than the original GPS signal.”
history of waas
History of WAAS
  • Developed by the DOT and the FAA in early 1995
  • First precision approach technology was Instrument Landing System – a glide path, laser guided system
  • Soon replaced by MLS – Microwave Landing System in the late 80’s which used microwaves to locate the aircraft
  • Soon replaced by the highly more accurate, and much cheaper WAAS system
more history
More History
  • July 10, 2003 – WAAS signal activated for general aviation
  • March 2005, FAA leases services of WAAS geostationary satellite from Lockheed Martin through 2016
  • 2006 – WAAS available in 99% of the continental United States
problems with waas
Problems with WAAS
  • Signal often affected by cloudy weather
  • Signal affected by “jamming” – not so much a problem anymore with new technologies, but was a problem at the start of GPS landing systems
  • System can only cover a limited amount of the country due to possible receiver locations – however this percentage has reached 99% of the country
  • “LAAS is a precision approach and landing system that relies on the Global Positioning System (GPS) to broadcast highly accurate information to aircraft on the final phases of a flight. LAAS is being developed specifically to augment GPS satellites to support precision approaches and landing capability to aircraft operating within a 20- to 30-mile radius of the airport. LAAS approaches will be designed to avoid obstacles, restricted airspace, noise-sensitive areas, or congested airspace.”
history of laas
History of LAAS
  • Concept first in 1992
  • System requirements first analyzed in 2001 – developmental stage begins
  • Developed in late 2001
  • Due to be implemented in 2006, however due to the FAA budget the project has been deferred to 2009
  • Only 18 million left in the budget as of the end of 2004 – will only carry LAAS development through 2005 – implementation will require 600 million dollars
how it works23
How it Works
  • “The Local Area Augmentation System (LAAS) will augment the Global Positioning System to provide an all-weather approach, landing, and surface navigation capability. LAAS focuses its service on a local area (approximately a 20-30 mile radius), such as an airport, and broadcasts its correction message via a very high frequency (VHF) radio data link from a ground-based transmitter.”
problems with laas
Problems with LAAS
  • Only covers 20-30 miles around a single airport – WAAS covers much more of the country and is much more effective
  • VHF uplink signal currently slated to share the frequency band from 108 MHz to 118 MHz with existing ILS localizer – users will have to own more than one set of radio gear to operate the system
  • potential for a single point of failure – caused by weather, solar activity, or jamming – airports with LAAS have no back up…if the system goes you’re out of luck!
automated landings
Automated Landings
  • Auto-pilot can already do take-offs, and in-flight performance – the one untested area is landings
  • When automated landings are perfected, un-piloted flights may become a reality.
  • LAAS has brought automated landings into possibility – with 1 meter accuracy as opposed to the 100 meter accuracy of less than 15 years ago
possibilities with waas and laas
Possibilities with WAAS and LAAS
  • WAAS and LAAS, or a combination of the two are bringing ever closer the idea of unmanned flight – both in the military and civilian realms
  • Greatly reduces the risk of terrorism involving planes, but also puts human lives in the hands of robots
  • Not yet at the level where we can abandon pilots
  • New LAAS system – if it is ever implemented would make it possible to have un-piloted flights
to summarize
To Summarize
  • Technology has gotten much better in the past 10 years
  • LAAS accuracy can not be beat, but WAAS coverage can not be beat, thus…
  • Final system likely to have LAAS at major airports with WAAS around the rest of the country
auto landings history military
Auto-landings history (Military)
  • In 1947, The UK Blind Landing Experimental Unit (BLEU) was established within the Royal Aircraft Establishment, now QinetiQ. BLEU conducted the world’s first fully automatic landing in 1950 and had significant involvement in the development programme for the world’s first Cat IIIb landing system for civil airliners.
  • Later technology developed by QinetiQ's predecessor include the Microwave Aircraft Digital Guidance Equipment (MADGE), developed as a tactical approach and landing system and was subsequently adopted by the Royal Navy for precision recovery of aircraft to the INVINCIBLE class aircraft carriers.
  • Recent work by QinetiQ's forebears on automatic landing systems has focussed on the use of differential and relative-GPS systems. A number of flight trials were conducted during the 1990s to explore the use of GPS as a means for recovery of helicopters to restricted sites, concentrating particularly on ship operations.
  • QinetiQ's recent ship trial aboard HMS INVINCIBLE has demonstrated the world’s first fully automatic STOVL shipboard recovery and landing.
    • Taken from
automated landing systems big news
Automated Landing Systems – Big News
  • “September 25, 2002 -- San Diego, California. General Atomics Aeronautical Systems, Inc., the leading manufacturer of unmanned aircraft systems, has successfully landed its IGNAT unmanned aircraft using a company-developed automatic landing system. Aeronautical Systems has funded and has now fully demonstrated the capability of automatically landing its aircraft without the direct control of the pilot. The automatic landing software uses differential global positioning system (GPS) which provides an accurate cross section of where the aircraft is in space and in relation to the ground. Using this formula, the aircraft descends at a pre-programmed rate to a fixed point on the ground. This company-funded effort resulted in the first automatic landing of the IGNAT on 12 September.”
new landing systems
New Landing Systems
  • “the means for guiding and controlling aircraft from an initial approach altitude to a point where safe contact is made with the landing surface. Such systems differ from low-approach systems in three major respects: (1) They furnish not only guidance but control of the aircraft as well. (2) They furnish information on the aircraft's position with respect to the terrain below it, and the rate at which the landing surface is being approached. (3) They do not require the pilot to assume manual control near the ground”
  • Tactical Automated Landing System – currently the only commercially-oriented automated landing system
    • Not available for commercial use but currently in development for commercial use
    • Designed by the army to reduce dangers of landing at night, but becoming more and more commercially oriented
    • Could be used in planes as early as 1212 – radar landing system dependent on LAAS technology