IFR Alternate Airport Requirements | 1-2-3 Rule | Standard Alternate Minimums

here at flight insight we always like to think of our plan b so let's plan an ifr flight here in the mid-atlantic to talk about alternates we're going to depart college park airport in maryland and head for ocean city on the south jersey shore with the direct route it's 110 nautical miles and our cessna doing 100 knots should make that distance in 66 minutes how much fuel do we legally need to have on board you might remember vfr fuel minimums from private training and ifr fuel requirements aren't too much different far 91.167 a is what we're looking for to know this it says that we have to have enough fuel to go to our destination airport then our alternate airport then an additional 45 minutes of flight at cruise speed it's very similar to the nighttime vfr minimums except for this addition of an alternate which we don't see in vfr cross-country fuel planning so what is an alternate it's a plan b if for whatever reason we can't land at our intended destination it could very likely be because the weather is too poor to even make an instrument landing there there's a much bigger chance of this happening under ifr so we have this added requirement for an alternate so we're able to add an alternate airport into our flight plan we don't always have to go to our alternate once we're up in the air the decision of where to divert is up to us and we're not held to going to whatever airport we listed on our flight plan do we even need to file an alternate if our destination airport doesn't have an instrument approach we do but what about if like at ocean city there are usable instrument approaches then it depends on the weather forecast at our destination the same far we referenced before says that no alternate is needed if either one hour before or after our estimated time of arrival at the destination the weather forecast there shows a ceiling of at least thousand feet agl and a forecast visibility of three statute miles or more you'll hear this referred to as the one two three rule and this is a great way to remember the requirement so we check a taft near ocean city and see this report let's say our planned arrival time is 0-200 zulu so this taff is valid at our exact eta that satisfies the 1 in our 1-2-3 rule it's showing visibility better than six statute miles which satisfies the three in the one two three rule also the ceiling is forecast to be broken at four thousand feet a bit low but it satisfies the two in the one two three rule all three conditions being met we are okay to skip filing an alternate if we don't want to so now let's figure out our fuel requirements without the alternate the time to our destination at ocean city is 66 minutes as shown on the map we also need a 45-minute reserve per the regulation there's no alternate so we add just these two up to get our total time of 111 minutes or 1.85 hours to make it simple let's say we burn 10 gallons an hour at that rate we'll burn 18.5 gallons in this time so this is the legal minimum for this ifr flight now let's say we check the weather and see this this is a temporary change to the issued forecast its period is from 0-0 zulu to 0-100 zulu so it applies to 1 hour before our intended arrival this satisfies the 1 in the 1-2-3 rule next the 5 statute miles is more than the required 3 so it satisfies the 3 in the 1-2-3 rule the ceilings are low though broken 900 feet well below the required 2000 feet so we fail the two in the one two three rule all it takes is one ding and the whole test has failed so we do require an alternate given these forecast conditions and for good reason with ceilings this low at the destination it makes very good sense to have a plan b airport so where to divert to as an alternate remember we won't be held to going to this airport in flight but because our alternate is going to be a factor in our fuel requirements it can have an effect on our planning let's see how let's first choose atlantic city as our alternate it's not a terrible choice it's a big classy airport with a lot of different instrument approaches to rely on plus it's very close to ocean city only 12 miles or seven minutes in our cessna if we add those seven minutes to our total calculation we get a 118 minutes or 1.97 hours which is 19.7 gallons at our burn rate compared to our plan with no alternate will now be carrying just over one additional gallon it might not be wise to choose atlantic city as our alternate though if the weather is too poor to land at ocean city the odds are decent that this weather might also be present at our alternate making landing there tricky too another thing to keep in mind is that coastal areas tend to experience their own weather patterns that's the atlantic ocean there to the east and fog rolling in there can affect aerodromes up and down the coast it might not be a bad idea to find an alternate more inland so let's use philadelphia international another solid choice big airport lots of air traffic control to help plenty of approaches it's a bit further though 47 miles or an extra 30 minutes of flying so let's see what that does to our fuel requirements adding this extra 30 minutes of flight gets us a total time of 141 minutes or 2.35 hours we'll need 23.5 gallons of fuel with philly as our alternate so now we can compare all these scenarios and see how fuel factors into the decision on where to file our alternate if needed now the decision process we talked about can be mapped out like this to start building a complete picture of the part 91 ifr alternate requirements the first thing we did was determine if our destination had an instrument approach we said yes so we moved on to the one two three rule if we pass the one two three rule we don't need an alternate if we fail the 123 test or our destination doesn't have an approach we're required to file an alternate but we're far from done here we have to figure out if and under what conditions we can use our intended airport as an alternate the first question we have to ask is if the alternate itself has an instrument approach not all airports have instrument approaches here nema colon and brown doesn't have one while cumberland in green does if the alternate doesn't have an approach like nemacolin we can only use it if the forecast weather will allow us to descend in vfr conditions from our filed in root altitude and land makes sense if there's no instrument approach the only way you can land there is in visual conditions if the airport does have an approach like cumberland does we need to look at those approaches starting with the one we're most likely to use if we divert there so let's pull up an approach played at cumberland this is the localizer dme approach to runway two three in the notes we see the reverse a symbol this means that the minimum weather conditions required to use this as our alternate are non-standard and we'd need to look them up in the terminal procedures publication so we grab that document for this region and look in the section with the reverse a at the top of the page see in cumberland and the loc23 approach we have two tick marks one and four which say first of all that for our category a cessna the weather minimums have to be at least one thousand foot ceilings and two miles of visibility or we can't use this approach in our alternate planning we could still use the airport but we'd have to look at another approach plate there to see if one qualified secondly it says that the approach is n a not allowed to be used as an alternate if the fbo is closed at the airport that's kind of weird right the fbo staff aren't air traffic control they're not even faa or anything so what does that have to do with our choice of alternate remember that the margins get stricter when you're talking about alternates the rules are set up so that nothing should stop you from shooting that approach into your alternate because you're close to the end of your legal fuel requirement ground-based navaid approaches like the localizer require monitoring to ensure they're still working big airports with round-the-clock personnel the faa typically handles this but at smaller airports like cumberland there's usually just a signal to alert fbo staff that something is wrong with the equipment they won't be able to fix it but they can tell the faa there's a problem and put in a call to the cable repair guy to come out and fix it when the fbo is closed for the night there's no one monitoring the equipment unmonitored nav8 approaches are not allowed to be used for the purpose of alternate planning so back to our decision boxes if we look at the approach plate and see that reverse a we then need to ask ourselves if the approach is even allowed to be used as an alternate we'd either see that note in the tpp like we saw for cumberland or we'd see this symbol on the approach plate itself a-n-a if the approach plate says a-n-a it means alternate not allowed we see that here on the plate for the ils at winchester regional this is another smaller airport with a navaid based approach but this time no one's monitoring any time a day so it's a a again doesn't mean we couldn't use winchester as the alternate we just have to find another approach that was suitable for the conditions in our airplane's equipment it used to be that no gps approaches were allowed to be used as alternates the faa changed that in 2013 and started allowing some gps approaches and more being added all the time there are some gps approaches that won't be allowed anytime soon though as the aim says in chapter 1-1-8 gps approaches to airports without weather reporting capabilities will still be classified as a a here at clearview the gps to 1-4 is listed as a-n-a because the local weather isn't at the field it's a dmw nearby carroll county airport to be able to use a gps approach in your alternate planning there has to be local weather on that field available so now we know that if we see that ana we can't use it as an alternate if we don't see the a a next to that reverse a we're good to use the alternate as long as the weather meets the minimums in the tpp like the ones we found for cumberland okay now we've gotten rid of all the non-standard stuff let's talk about the standard rules you need to know when selecting an alternate if the approach plate doesn't have that reverse a in the notes at all then we first need to ask if it's a precision or non-precision approach remember the definitions here a precision approach is anything with horizontal and vertical guidance typically an ils the faa doesn't consider gps approaches to be precision even if you're flying an lpv which has vertical guidance if our approach is precision we can use it as our alternate if the weather is at least 600 foot ceilings and two miles of visibility if it's a non-precision approach like any gps approach a localizer approach a vor approach or anything the minimums are higher 800 foot ceilings and 2 miles so this is a lot of detail and in typical flight insight style we've over explained what could be a simple topic for the sake of getting a deeper understanding but here's the bulk of what you need to know when we're planning an ifr flight under part 91 we only need an alternate if the weather fails the 123 rule and then we can only use our alternate if the weather is better than 602 with a precision approach or 802 with a non-precision approach if you can remember these figures you should be able to fill in the rest of the details one last thing all of this really only applies to our plan so once we're in the air things are more fluid if we filed an alternate with an ils but fine once we're about to actually shoot the approach that the weather is lower than 602 it doesn't mean we can't fly the approach the same requirements apply as they would for any approach as long as the weather minimums listed on the plate are met we're good to go if this was helpful please click subscribe so that you could 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Channel: FlightInsight

Views: 18,801

Keywords: IFR Alternate Requirements, IFR Alternate, 1-2-3 rule, 600-2, 800-2, unmonitored navaid, alternate not allowed, part 91 minimums, non standard alternate minimums, standard alternate minimums, alternate minimums na, alternate minimums ifr, alternate minimums faa

Id: IOrKSSq-OBE

Length: 12min 17sec (737 seconds)

Published: Tue Oct 12 2021