This report examines what, if any, trends may be emerging as a result of the introduction of NAS stage 2b from 27 November 2003. Four indicators - airprox, breakdown of separation (BOS), resolution advisories (RA) and violation of controlled airspace (VCA) - were analysed to assess any net effects resulting from NAS 2b changes. There was no significant change in the rate of airproxes per aircraft movement in the 180-day period after NAS 2b was introduced relative to the 180-day period immediately before. There was also no significant change in airproxes involving RPT aircraft. There was a reduction in the rate of BOS incidents per aircraft movement in the post-NAS 2b period compared with the period immediately before, but this was not statistically significant. Analysis of RA incidents indicated no statistically significant change in the rate per movement reported after NAS 2b was introduced compared with the period immediately before. Overall, the report concludes that data currently available do not enable reliable conclusions to be drawn about NAS 2b safety trends.
|Type:||Research and Analysis Report|
|Publication date:||24 July 2004|
|ISBN:||1 877071 77 3|