Another notable episode was associated with low and fog partially covering the aerodrome on 18 June 2013. Although the duration of this episode was sixth in descending order of magnitude, it accounted for the third highest number of aircraft expected to arrive. This was due to the weather coinciding with morning peak aircraft arrival times. This weather episode contributed to a serious safety incident. Two aircraft en route diverted to Mildura, and also encountered conditions below the landing minima at that location. This was the subject of ATSB investigation . Table 4: Top 10 weather episodes by expected number of aircraft arrivals during reported conditions below the landing minima – Adelaide Airport 2009 to 2013 Date time End time Hours below landing minima Expected aircraft arrivals Reported weather phenomena Landing minima Rank by weather duration 07-Dec-10 1330 0200 8.73 55.7 Rain Thunderstorms 1 03-Aug-12 0500 1118 6.3 46.4 Fog and mist Low cloud and visibility with strong winds affecting lowest possible instrument approach 3 18-Jun-13 0745 1200 4.25 42.4 Partial fog Low cloud and visibility 6 19-Jul-10 0008 1013 8.08 37.1 Patches of rain, fog and mist Low cloud and visibility 2 05-Nov-12 1600 2230 3.73 31.7 Rain Thunderstorms 8 03-Sep-10 1034 0830 3 24.7 Drizzle and rain Thunderstorms and tailwind or low visibility 11 14-Mar-12 0212M 1921 2.25 24.2 Rain Thunderstorms 14 04-Aug-12 0530 1055 4.48 23.3 Fog and mist Low and visibility with strong winds affecting lowest possible instrument approach 5
Appendices Appendix A – Selected TTF, TAF and results 8: Overview of landing minima parameters for periods below the landing minima at Adelaide Airport 2009 to 2013 Episode landing minima Number of episodes Landing minima observed at the same time Duration (minutes) Expected aircraft arrivals Thunderstorms 42 Thunderstorms 2,345 242.4 Ceiling and visibility 7 Ceiling and visibility 1,006 89.9 Ceiling 271 31.6 Visibility 46 1 Ceiling, visibility and tailwind 2 Ceiling and visibility 259 23 Ceiling and tailwind 124 20.9 Visibility 120 6 Tailwind 99 14.3 Ceiling 45 5.4 Ceiling 4 Ceiling 425 30.1 Visibility 6 Visibility 338 6.6 Visibility and thunderstorms 2 Thunderstorms 171 17.2 Visibility and thunderstorms 20 2.5 Thunderstorms and tailwind 1 Thunderstorms 167 23.3 Tailwind 13 1.4 Ceiling and tailwind 1 Ceiling 88 2.9 Tailwind 67 9.4 Tailwind 7 Tailwind 129 15.3 Crosswind 8 Crosswind 123 17.1 Thunderstorms and crosswind 3 Thunderstorms 51 6.3 Crosswind 25 3.2 Thunderstorms and crosswind 2 0.4 Thunderstorms, crosswind and tailwind 2 Crosswind 24 2.1 Thunderstorms and crosswind 17 0.3 Thunderstorms 17 0.2 Thunderstorms and tailwind 10 0.2 Tailwind 4 0.5 Visibility and tailwind 1 Visibility 15 3 Tailwind 3 0.6 Total 86 6,024 577.1
reporting conditions above the alternate minima were released for Mildura within 30 minutes of the previous report compared to Adelaide. Figure 107: Distribution and cumulative percentage of type meteorological reports by time since previous release at Mildura Airport 2009 to 2013 Figure 108: Distribution and cumulative percentage of SPECI type meteorological reports by time since previous release at Adelaide Airport 2009 to 2013 Appendix C – Data validation and assumptions supporting data 9: Assumed visibility and ceiling in the absence of explicit values for elements in TAF, TTF, METAR and SPECI weather products of preference Value Category Weather Element Applicable weather products Nominal value Visibility Ceiling 1 Explicit Visibility or cloud data METAR, TAF, TTF As reported Reported cloud layers 2 Weather condition flags SKC METAR, TAF, TTF N/A 9999 NSC METAR, TAF, TTF N/A 4999 NCD METAR N/A 4999 CAVOK TAF, TTF 9999 4999 3 Explicit Vertical visibility As reported As reported 4 and visibility sensor anomaly CLD:SKY MAY BE OBSC METAR As reported or 999 3 degree visibility height 5 Explicit Remarks section data METAR As reported As reported 6 Average Average between reports METAR Average of surrounding reports Average of surrounding reports Table 10: Number of weather reports by type of visibility value used, 2009 to 2013 Visibility Number of METARs and SPECIs Mildura Adelaide Explicitly reported in body text 14,581 51,895 Flags used: CAVOK (Set to 9999) 35,982 40,035 Sky Obscured: Set to 999 36 0 Visibility explicitly extracted from remarks section (VIS: XXXX) 40,603 251 No estimation - exclude record from analysis (Set visibility to NULL) 1 2
Table 11: Number of weather reports by type of ceiling value used, 2009 to 2013 Ceiling value Number of METARs and SPECIs Reported in body text octas >= 5 33,386 Octas sum > 0 but < 5 set ceiling to 4999 4,075 18,286 used: SKC (set to 9999), NSC, NCD, CAVOK (set to 4999) 40,165 CLD: Below XXX, (set to XXX) 155 Explicit cloud groups in remarks 189 Slant Visibility Height where CLD: SKY MAY BE OBSC reported 36 0 Average of prior and after METAR within set time limits 47 2