Microwave Landing Systems:

Additional Systems Should Not Be Procured Unless Benefits Proven

RCED-88-118: Published: May 16, 1988. Publicly Released: May 24, 1988.

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Pursuant to a congressional request, GAO reviewed the Federal Aviation Administration's (FAA) National Airspace System Plan, focusing on: (1) the justification and requirements for replacing improved instrument landing systems (ILS) with microwave landing systems (MLS); (2) potential MLS operational and economic benefits; (3) the MLS siting strategy; and (4) industry and user association views of ILS and MLS.

GAO found that FAA: (1) first justified its need for MLS in 1969, citing concerns about ILS reliability and limitations and projected large increases in air traffic volume; (2) planned to replace ILS with MLS, although it did not reassess its needs by taking into consideration substantial ILS improvements and lower-than-projected traffic volumes; (3) experienced significant delays and increased program costs for MLS production and testing; (4) has not adequately assessed potential MLS benefits or identified its limitations; (5) requested $20 million to initiate a second MLS procurement and to develop the avionics to demonstrate MLS benefits; (6) is developing plans to test MLS at two airports; and (7) developed its list of MLS implementation sites without considering test results, cost benefits, and user support. GAO also found that: (1) both national and international air carriers were generally satisfied with ILS capabilities; (2) regional and commuter airlines generally supported MLS; and (3) commercial and general aviation pilots' views toward MLS differed.

Recommendations for Executive Action

  1. Status: Closed - Implemented

    Comments: FAA concurred in this recommendation. A detailed plan for the second MLS procurement, approved by the Deputy Secretary on December 6, 1988, provides for integration of the demonstration project into the overall MLS implementation strategy. A final report on FAA plans for MLS was issued on April 3, 1992.

    Recommendation: The Secretary of Transportation should require the Administrator, FAA, to reassess the requirements to replace ILS with MLS, recognizing improvements to ILS and current and expected air traffic growth. The reassessment should consider: (1) improved ILS reliability; (2) increases in the number of available ILS channels; (3) reduced ILS siting problems; and (4) the ability of aircraft to land using ILS in lower ceiling and visibility minimums than previously possible.

    Agency Affected: Department of Transportation

  2. Status: Closed - Implemented

    Comments: A detailed plan for the second MLS procurement, approved by the Deputy Secretary on December 6, 1988, provides for integration of the demonstration project into the overall MLS implementation strategy. The demonstration project consists of nine projects, all of which have been completed. A final report from the demonstration program was issued on April 3, 1992.

    Recommendation: The Secretary of Transportation should direct the Administrator, FAA, to demonstrate MLS benefits by testing the system in the challenging airport environments in which it is to be used. This should be done before proceeding with further MLS procurements. The operational tests should involve: (1) wide-bodied aircraft; (2) landing at major hub airports having difficult and complex operating requirements; (3) both good and poor weather conditions; (4) both curved and segmented approaches; and (5) operating under the control of FAA traffic controllers and interfacing with the air traffic control environment.

    Agency Affected: Department of Transportation

  3. Status: Closed - Implemented

    Comments: The contract has been terminated for cause. Two replacement contracts for a limited number of commercial systems to satisfy the requirements for the demonstration program are underway. They will be deployed in the manner recommended by GAO, beginning in mid-1992. A full development, limited production contract for additional MLS was awarded in June 1992.

    Recommendation: The Secretary of Transportation should direct the Administrator, FAA, not to proceed with the planned second MLS procurement unless the assessment of ILS improvements and air traffic growth, as well as the operational testing of MLS, has been completed. In the interim, FAA must accept delivery of 178 MLS and should use them: (1) in operational tests; (2) on some international runways, if internationally scheduled airlines are willing to acquire the necessary on-board avionics; (3) at locations that qualify for a precision landing system, but where FAA can clearly show that ILS cannot be sited because of terrain or obstacles in the approach or missed approach path; and (4) at heliports.

    Agency Affected: Department of Transportation

  4. Status: Closed - Implemented

    Comments: FAA issued its precision approach and landing system policy stating that ILS will be protected through January 1, 1998, and optionally retained through January 1, 2000. ILS will be maintained until parity with MLS is achieved, around the year 2015. At that time, a decision will be made on when ILS will be removed from service.

    Recommendation: The Secretary of Transportation should require the Administrator, FAA, to take the action necessary to maintain ILS as the primary landing system nationally and internationally until the assessment, analysis, and demonstrations have been completed.

    Agency Affected: Department of Transportation

 

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