REDUCING VERTICAL SEPARATION

Current vertical separation minima (2,000 feet) were created more than 40 years ago when altimeters were not very accurate above FL 290. With better flight and navigation instruments, vertical separation has been safely reduced to 1,000 feet in most parts of the world, except Africa and China.

RVSM airspace has already been implemented over the Atlantic and Pacific Oceans, South China Sea, Australia, Europe, the Middle East and Asia south of the Himalayas. Domestic RVSM (DRVSM) in the United States was implemented in January 2005 when FL 300, 320, 340, 360, 380, and 400 were added to the existing structure. To fly at any of the flight levels from FL 290 to FL 410, aircraft and operator must be RVSMapproved. [Figure 6-10]

REDUCING HORIZONTAL SEPARATION

The current oceanic air traffic control system uses filed flight plans and position reports to track an aircraft’s progress and ensure separation. Pilots send position reports by high frequency (HF) radio through a private radio service that then relays the messages to the air traffic control system. Position reports are made at intervals of approximately one hour. HF radio communication is subject to interference and disruption. Further delay is added as radio operators relay messages between pilots and controllers. These deficiencies in communications and surveillance have necessitated larger horizontal separation minimums when flying over the ocean out of radar range.

As a result of improved navigational capabilities made possible by technologies such as GPS and CPDLC, both lateral and longitudinal oceanic horizontal separation standards are being reduced. Oceanic lateral separation standards were reduced from 100 to 50 NM in the Northern and Central Pacific regions in 1998 and in the Central East Pacific in 2000. The FAA plans to extend the 50 NM separation standard to the South Pacific. Because flight times along the South Pacific routes often exceed 15 hours, the fuel and time savings resulting from more airplanes flying closer to the ideal wind route in this region are expected to be substantial. Separation standards of 30 NM are already undergoing operational trials in parts of South Pacific airspace for properly authorized airplanes and operators.

DIRECT ROUTING

Based on preliminary evaluations, FAA research has evidenced tremendous potential for the airlines to benefit from expected routing initiatives. Specifically, direct routing or “Free Flight” is the most promising for reducing total flight time and distance as well as minimizing congestion on heavily traveled airways. Traditionally,

pilots fly fixed routes that often are less direct due to their dependence on ground-based NAVAIDs. Through Free Flight, the FAA hopes to increase the capacity, efficiency, and safety of the NAS to meet growing demand as well as enhance the controller’s productivity. The aviation industry, particularly the airlines, is seeking to shorten flight times and reduce fuel consumption. According to the FAA’s preliminary estimates, the benefits to the flying public and the aviation industry could reach into the billions of dollars once the program is fully operational.

Free Flight Phase 1 began in October 1998 and launched five software tools over the next four years. These were Collaborative Decision Making (CDM), the User Request Evaluation Tool (URET), and the previously discussed SMA, TMA, and pFAST.

CDM allows airspace users and the FAA to share information, enabling the best use of available resources. It provides detailed, real-time information about weather, delays, cancellations, and equipment to airlines and major FAA air traffic control facilities. This shared data helps to manage the airspace system more efficiently, thereby reducing delays.

CDM consists of three components. The first component allows airlines and the FAA’s System Command Center in Herndon, Virginia, to share the latest information on schedules, airport demand, and capacity at times (usually during bad weather) when airport capacity is reduced. This shared information is critical to getting the maximum number of takeoffs and landings at airports. The second component creates and assesses possible rerouting around bad weather. This tool enables the Command Center and busy major ATC facilities to share real-time information on high-altitude traffic flows with airline operations centers, thus developing the most efficient ways to avoid bad weather. The third component provides data on the operational status of the national airspace system. Examples include runway visibility at major airports and the current availability of Special Use Airspace.

URET allows controllers to plot changes in the projected flight paths of specific airplanes to see if they will get too close to other aircraft within the next 20 minutes. URET means that controllers can safely and quickly respond to pilots’ requests for changes in altitude or direction, which leads to smoother, safer flights and more direct routings. During trials in the Memphis and Indianapolis en route centers, the use of more direct routes made possible by URET was found to save airlines about $1.5 million per month.