# Key Takeaways - You are always required to file an IFR alternate (except when not required by the [[1-2-3 Rule]]) - A filed alternate must be a legal alternate choice - Alternate planning is to force a reasonable Plan B airport and [[FAR 91.167 IFR Fuel Reqs|sufficient fuel]], but when actually flying you can go to any airport that makes sense # Details ## When is an Alternate Required > [!tip] > [[DPE]]s love when you answer this with "An alternate is always required, except when...", instead of something like "An alternate is only required when...".^[It's a nod to how [[FAR 91.169 IFR Flight Plan Info Reqd|FAR 91.169]] is written.] An alternate is always required, except if there's an [[IAP]] and the [[1-2-3 Rule]] applies. ![[1-2-3 Rule]] ## Which Alternates Are Legal to Choose > [!caution] Alternate minimums ≠ approach minimums > Alternate minimums are used to determine if it is legal to file this airport as an alternate, while approach minimums are used while actually flying the approach. ### Minimum Weather At Alternate Arrival Time According to [[FAR 91.169 IFR Flight Plan Info Reqd|FAR 91.169]], **at the ETA at the alternate airport**, forecasts must indicate weather will meet at least: - **If there is an [[IAP]] at the alternate**, one of three situations may apply - *Non-Standard Minimums* (<svg xmlns="http://www.w3.org/2000/svg" width="13" height="13" viewBox="0 0 100 100" style="vertical-align:-2px"> <polygon points="50,6 94,94 6,94" fill="currentColor"/> <text x="50" y="88" font-size="58" font-weight="bold" text-anchor="middle" fill="var(--background-primary,#fff)" font-family="sans-serif">A</text> </svg>) shown on the approach plate means required minimums are published in the [[TPP]] - *Alternate NA* (<svg xmlns="http://www.w3.org/2000/svg" width="13" height="13" viewBox="0 0 100 100" style="vertical-align:-2px"><polygon points="50,6 94,94 6,94" fill="currentColor"/><text x="50" y="88" font-size="58" font-weight="bold" text-anchor="middle" fill="var(--background-primary,#fff)" font-family="sans-serif">A</text></svg> NA) shown on the approach plate means this airport cannot be used as an alternate - Otherwise, *Standard Minimums* - 600-2 for a precision approach^[Note: An LPV is not a precision approach] - 800-2 for a non-precision approach - **If there is no IAP at the alternate**, must be able to descend from [[MEA]] to the airport, approach, and land under basic [[VFR]] ### Weather Forecasts 1. How to get the weather forecasts at airports without a TAF #todo :: Expand on this ### Equipment Limitations When using a non-[[WAAS]] GPS, either your destination or your alternate can plan to use the GPS approach, **not both**. > [!quote] From [[AIM 1]]-1-17 > For flight planning purposes, TSO-C129() and TSO-C196()-equipped users (GPS users) whose navigation systems have fault detection and exclusion ([[FDE]]) capability, who perform a preflight [[RAIM]] prediction for the approach integrity at the airport where the RNAV (GPS) approach will be flown, and have proper knowledge and any required training and/or approval to conduct a GPS-based [[IAP]], may file based on a GPS-based IAP at either the destination or the alternate airport, but not at both locations. When using a WAAS GPS, your alternate plan must be for [[LNAV]] or circling minimums. > [!quote] From [[AIM 1]]-1-18 > Pilots with [[WAAS]] receivers may flight plan to use any instrument approach procedure authorized for use with their WAAS avionics as the planned approach at a required alternate, with the following restrictions. When using WAAS at an alternate airport, flight planning must be based on flying the [[RNAV]] (GPS) [[LNAV]] or circling minima line, or minima on a [[GPS]] approach procedure, or conventional approach procedure with “or GPS” in the title. ## Difference Between Planning and Actual Flight Alternate selection is meant to ensure you've considered a Plan B and have sufficient fuel to execute it. However, when you're actually out flying, you do not necessarily need to divert to your planned alternate. And if you do go to your planned alternate, you can use your non-WAAS GPS for the approach even if you've used it already once. > [!summary] In short, you need to make the best decision based on the actual situation when flying. Any filed alternate is for planning purposes only. > [!note] > ATC cannot see your filed alternate anyway ## Practical Tips The best alternatives: 1. Are in a different microclimate than your destination 2. Have an [[ILS]], which gives you the best chance of landing in IMC^[[The Advantage Of Landing On Runways With An ILS](https://www.boldmethod.com/shorts/shorts.ifr.0103/)] 3. Have a [[TAF]], making it easier to forecast the weather specifically at the airport # Additional Resources - [[FAR 91.169 IFR Flight Plan Info Reqd]] - [[FAR 91.167 IFR Fuel Reqs]] - [[AIM 1]]‑1‑17/18 (GPS/WAAS alternate flight planning) - [[TPP]] #concept