Airspace System:

Emerging Technologies May Offer Alternatives to the Instrument Landing System

RCED-93-33: Published: Nov 13, 1992. Publicly Released: Nov 13, 1992.

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Pursuant to a congressional request, GAO reviewed aircraft landing systems, focusing on: (1) capabilities and costs; and (2) potential consequences of the FAA approach to developing these systems.

GAO found that: (1) the current instrument landing system (ILS) cannot be adapted to use enhanced systems features, is limited in coverage area, cannot be used in all locations, and is sensitive to signal interference; (2) ILS, with a flight management system (ILS/FMS), permits some but not all enhancements, and has all other ILS limitations; (3) the microwave landing system (MLS) meets the full range of operational requirements for precision landing systems, but it may not be fully used by the aviation industry because of the availability of other systems and the cost of installing instrumentation; (4) FAA is developing a satellite-based navigation system that could potentially provide all the capabilities of the other systems plus airport surface and air route navigation, service to all runways within an airport, and service to both ends of the runway; (5) the satellite system will require technically challenging enhancements for a precision landing system; (6) FAA estimates that the cost of maintaining, replacing, and adding new ILS equipment will be $360.9 million between 1992 and 2000, and users' costs will range from $3,600 for general aviation aircraft to $107,00 for some commercial aircraft; (7) FAA costs for ILS/FMS include maintenance of ILS ground stations, procedures development costs, and certification of FMS equipment, and users will spend between $500,000 and $750,000 for FMS packages plus certification costs; (8) FAA costs for MLS include those for ILS, plus $2.6 billion for development, procurement and installation, and additional costs for increased staffing, certification of on-board instrumentation, and lighting systems; (9) the satellite system's costs are not directly comparable because the system will perform functions beyond just precision landings; and (10) the Department of Defense will spend $10 billion for development and implementation of the satellites and FAA will spend up to $315.8 million for ground stations and additional funds for developing approach procedures and equipment certification.

Recommendations for Executive Action

  1. Status: Closed - Implemented

    Comments: In June 1994, FAA determined that satellite technology, with augmentations, and the current instrument landing system (ILS) could best meet the users precision landing needs. As a result, FAA has cancelled the MLS program. In regard to funding, FAA has requested a significant increase in funding for satellite technology in FY 1995 and continued funding for ILS, albeit to a lesser degree. Because the MLS program was terminated, no funding was requested.

    Recommendation: To determine which alternative precision landing systems will best meet the requirements for precision landings, the Secretary of Transportation should direct the Administrator, FAA, to provide full budgetary support for the development of all alternative systems so that by the mid-1990s decisionmakers will have a meaningful basis for comparing the systems' capabilities, benefits, and costs.

    Agency Affected: Department of Transportation

  2. Status: Closed - Implemented

    Comments: In June 1994, FAA terminated its development contracts for MLS because satellite technology, with augmentations, and the current instrument landing system, could satisfy all precision landing needs.

    Recommendation: To determine which alternative precision landing systems will best meet the requirements for precision landings, the Secretary of Transportation should direct the Administrator, FAA, to prepare a mission need statement for precision landing systems in general that is based on a runway-by-runway determination of which system, or mix of systems, provides the most benefits at the lowest cost to both FAA and the system's users. This general mission need statement should be ready when FAA selects the precision landing system that will replace the ILS.

    Agency Affected: Department of Transportation

 

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