Air Traffic Management Concept Baseline Definition - The Boeing ...

Broadcast (ADS-B), V6.0). Individual radar sensors can support availability on the order
of 0.999. However, to achieve the overall system level availability, dual surveillance
coverage is usually required. This is currently not a problem at high altitudes since dual
radar coverage or better is available throughout the NAS. At low altitudes, and in the
terminal maneuvering areas this requirement is difficult to achieve and an availability of
0.999 is currently considered acceptable, except at the major hub airports. This level of
availability is probably adequate for future systems, except that traffic growth may extend
the need for higher availability in more terminal areas. Continuity of function is often
included in the availability metrics and in future system planning considerations.
Integrity Metrics
Integrity is usually measured in terms of undetected errors in surveillance system outputs.
Desired system level integrity is on the order of one undetected error in 10 7 scans/output
reports. At the sensor level, clutter detections and fruit replies can lead to large
spontaneous errors at much higher rates. The tracking and data fusion software typically
provides the added integrity to achieve the desired system level performance. Future
systems will probably require equivalent integrity, although the use of multi-sensor
processing and integrity checking could yield higher integrity than current systems.
Latency Metrics
Latency is a measure of the acceptable delay between successive surveillance reports on
the average or at a specified probability level. (For example, with en route radars the
probability of reception per scan is on the order of 98%, and the latency between
successive scans is 12 seconds at the 98% probability level.) This metric is typically
specified by a stressing application such as separation assurance at a typical range between
the aircraft being tracked and the tracking sensor. For close range applications such as
parallel approach monitoring and collision avoidance, a typical latency requirement is a
one second report updating at a 95 to 99 percent probability of reception. For other
applications latency requirements increase with separation range and size of minimum
separation standards, e.g. latency may be 15 minutes with ~95% reception probability for
an oceanic ADS system supporting horizontal separation standards on the order of 30
miles. This does not include transmission latency, which is a measure of the time delay in
actually receiving the report at the data fusion center, or latency error, which is a measure
of the time stamping error associated with a surveillance report. These metrics are also
useful in quantifying system performance.
5.1.5 Aviation Weather Performance
Weather has a major impact on the safety, efficiency, and capacity of aviation operations.
Accidents and incidents continue to be caused by adverse weather. Runway acceptance
rates and other capacity metrics are reduced in IMC. According to some studies, 40-65
percent of delays that affect U.S. domestic airlines are caused by adverse weather, at
annual direct costs ranging from $4-5B per year (Evans, 1995). In addition, passengers
are inconvenienced by flight delays and cancellations or diversions due to weather, and are
uncomfortable when turbulence is encountered during a flight. The expected future
growth in air traffic will only exacerbate all these conditions, imposing constraints on the
63