ACS Instrument Practice Test

Which statement aligns with determining whether an alternate airport is required?

Use the 1-2-3 rule: 1 hour before and after ETA, 2000 ft ceilings, and 3 miles visibility Alternate airports are always unnecessary An alternate minimums chart is not used Always select your origin airport as an alternate

Correct Answer:

Use the 1-2-3 rule: 1 hour before and after ETA, 2000 ft ceilings, and 3 miles visibility

Explanation:

In IFR flight planning, you determine whether an alternate airport is required by checking the forecast weather at the destination within a specific time window around your planned arrival. The rule used is the 1-2-3 rule: within one hour before to one hour after your ETA, you want ceilings of at least 2000 feet and visibility of at least 3 miles. If that forecast meets these minima, you don’t need an alternate; if it doesn’t, an alternate becomes required. This approach directly guides the decision about needing a backup airport. The other statements aren’t consistent with standard practice: alternates are not always unnecessary; a chart is indeed used to determine alternate minimums; and you don’t always pick the origin as your alternate.

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