Queenstown Winter Approach and Alternate
You are planning a Part 91 IFR flight from Christchurch (NZCH) to Queenstown (NZQN) in a Piper PA-46, arriving at 1600 NZDT. The Queenstown TAF valid 1200–1800 forecasts wind 220/12, visibility 9999, cloud SCT030 BKN050, TEMPO 1400–1700 3000 m, light snow, BKN012. You are endorsed and current only for the RNP AR RWY 05 approach, with published DA 1,100 ft and visibility 3,200 m. Your alternate is Invercargill (NZNV), TAF: wind 240/15, visibility 9999, BKN025, TEMPO 1400–1800 4000 m, light rain showers, BKN008. A SIGMET is current for severe turbulence between FL080 and FL140 over the Southern Alps. The aircraft has weather radar. You must decide whether to depart and what alternate and fuel requirements apply.
1. Is Invercargill a valid alternate? Apply the forecast TEMPO and alternate minima.
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Invercargill is not a valid alternate on the forecast shown.
Alternate planning requires the alternate to be at or above the published alternate minima for the expected time of use, and forecast TEMPO conditions must be considered. The TEMPO from 1400–1800 forecasts BKN008 and 4,000 m. That is below the usual alternate minima and is likely below the minima published for the NZNV approach.
Because your arrival and alternate-use period overlap the TEMPO, you cannot treat Invercargill as a valid alternate. You need another alternate, a later arrival, or enough fuel to hold until conditions improve.
2. How should the SIGMET and the Queenstown TEMPO affect your go/no-go decision?
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Queenstown’s TEMPO gives 3,000 m visibility, below the RNP AR visibility of 3,200 m. The destination forecast therefore contains a period below approach minima. You must plan for a missed approach and diversion, not assume you will get in.
The SIGMET for severe turbulence over the Southern Alps affects ride quality, aircraft handling and possibly your route or altitude. Combined with a below-minima TEMPO at the destination, the sensible decision is to delay, replan, or choose a destination/alternate with more robust weather.
3. What fuel and replanning considerations apply?
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Under the Part 91 fuel rules, carry enough fuel to fly to the destination, then to the alternate, then the required IFR reserve, plus holding for the TEMPO. If the alternate is invalid, the flight cannot be dispatched as planned.
Replan with a valid alternate, such as Dunedin or Christchurch, recalculate fuel, and include the possibility of a missed approach at Queenstown. Do not rely on the destination weather improving inside the TEMPO period.