FAA Instrument Rating Airplane (IRA)Regulations and CurrencyMedium
A pilot's estimated time of arrival (ETA) at the destination is 1800Z. The terminal forecast shows a broken ceiling of 1,800 feet and 4 statute miles visibility for the period 1700Z–1900Z. Applying the 1-2-3 rule found in 14 CFR 91.169, is an alternate airport required for this flight?
- ANo, because the forecast exceeds basic VFR minimums
- BYes, because the source is a TAF rather than a METAR
- CYes, because the forecast ceiling and visibility are below 2,000 feet and 3 statute miles for that period
- DNo, because the forecast covers the entire ETA window
Show answer & explanationAnswer & explanation
Correct answer: C. Yes, because the forecast ceiling and visibility are below 2,000 feet and 3 statute miles for that period
The 1-2-3 rule requires the forecast from 1 hour before to 1 hour after the ETA to show at least a 2,000-foot ceiling and 3 statute miles visibility to avoid needing an alternate. Here the forecast (1,800 ft/4 SM) fails the ceiling requirement, so an alternate must be filed.
Why the other options are wrong
- A. Exceeding basic VFR minimums (1,000-3) is irrelevant; the standard is 2,000-3.
- B. TAF vs METAR format has no bearing on the 1-2-3 rule requirement.
- D. Covering the time window doesn't matter if the values themselves are below minimums.
1-2-3 Rule (91.169)
If, for 1 hour before to 1 hour after ETA, the forecast at the destination is at least 2,000-foot ceiling and 3 SM visibility, no alternate is required.
- Applies only to airports with a published standard instrument approach
- Ceiling AND visibility must both meet or exceed 2,000-3 to skip an alternate
- If either value is below the threshold, an alternate must be filed
Memory trick: '1 hour, 2000 feet, 3 miles — skip the alternate'