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.
Recommendations for Executive Action
|Department of Transportation||1. 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.|
|Department of Transportation||2. 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.|
|Department of Transportation||3. 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.|
|Department of Transportation||4. 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.|