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…