Where's the Missed Approach Point? | Visual Descent Point Explained

instrument approach chart training continues with a question that comes up a lot in ifr flying where is the missed approach point well like every question in aviation the answer is it depends let's start with a simple case here's the ils approach at runway 4 at easton kind of just a plain vanilla ils approach let's look at the minimums for the ils 273 feet and remember that this is a precision approach so this is a decision altitude what does this mean that it's a decision altitude when you're on the approach you're descending with vertical guidance by following the glide slope so when you reach 273 feet the decision altitude you have to decide if you can continue the approach or go missed and if you go missed you'll execute the missed approach at that point so simply put the missed approach on an ils or any precision approach is the point you're at when you're on the glide slope at the decision altitude it's a defined spot now let's look at the localizer approach there's no glide slope for vertical guidance this is a non-precision approach how is this flown we start outside of the initial approach fix rikmi in this case at say 2000 feet after crossing rick me we could drop down to 1 600 feet by some time before the next fix we grow then once we cross we grow the final approach fix we descend again down to 540 feet but unlike on the ils we don't immediately decide what to do and execute a missed approach because this isn't a decision altitude but a minimum descent altitude we stay at this minimum altitude until we gain sight of the runway to make a landing approach if we don't gain sight we can execute the missed approach notice the solid black line turns into a thin hash marked line with directional arrow indicating the missed approach but also notice that there's no defined point where this occurs it's kind of left open-ended so where is the missed approach point and why isn't it precisely defined on the profile view well the point we're looking at where the solid black line meets the thin hash marked one indicates the point on the precision approach where we reach the decision altitude on the glideslope it doesn't apply for us on the non-precision approach but there is still a missed approach point indicated on here it's the one dme point from the localizer of this approach identifier ifgh if you don't believe me you can have a look at the amendment document for this approach in the navigation database review on the faa website admittedly this is a bit wonky but it shows clearly here that the missed approach point is the one dme off the localizer for the approach so why not have this more clear on the approach plate well for more contacts let's look at the same approach play profile on the jefferson approach plate a commercial vendor providing approach plates to operators as a subscription service jeppesen as opposed to the faa has made the decision to depict both the precision and non-precision missed approach points on their chart the precision point is shown with the arrow pointing in the direction of the missed procedure coming from the glide slope at decision altitude while the non-precision missed approach point is noted with the letter m again at the one dme point from the localizer so the faa chart doesn't have that detail and instead falls back on the convention of having that last point on the approach be the miss point let's have an even closer look at the profile view of the approach for this localizer notice the upside down black triangle at 2.5 dme this is called the visual descent point what this point represents is where you can make a normal descent from your minimum altitude to the runway so if you're past the visual descent point and still haven't gotten sight of the runway and you're still at that minimum descent altitude you won't be able to make a normal approach to land this would be a time when you might think about doing a missed approach again though because the missed approach point is the one dme from the localizer essentially the approach end of the runway it's at that point that you would execute the missed procedure but the visual descent point itself does not represent the defined missed approach point on these non-precision approaches the point where you decide to go missed and the point you actually execute the missed approach could be different points this is as opposed to the ils where the decision point and execution point are one and the same now not all faa approach plates have this ambiguity about where the missed approach point is on the profile view why is this one special have a look at the missed approach procedure we might get a clue the first step is to start a climb straight out on a zero four one heading up to two thousand so we'll be flying runway heading initially then let's look at the plan view to see what this looks like from the top down as we're coming in on the approach we're following the localizer down which protects us from obstructions and as we fly the mist we're flying the same course on the way back up so we're still protected so as long as the approach doesn't have a maximum altitude which is rare and we don't see one here we can start the climb prior to the missed approach point and stay on the chorus and still be assured protection let's contrast that with a different approach here's the rnav gps alpha at college park go terps we see on the profile view that once again the solid line meets the thin hash marked line indicating the missed approach but notice that there's a defined point where this happens in this case it's the gps waypoint for runway 1.5 let's compare this to the localizer approach we just looked at no defined missed approach point why is this different you might say that maybe it's because with the gps we can identify where the runway is when with the localizer we maybe couldn't but what if we look at the climb out instructions on this missed approach this one has us doing a climbing left turn to 2100 feet remember the localized approach to easton involved a straight-out climb on runway heading if you look at the plan view here you'll see that it's crucial we start the climbing left turn precisely at the runway if we did it too early or too late we couldn't be assured clearance from any of these obstructions here's another way that chart makers will define a missed approach point here's the ils approach into frederick runway 2-3 unlike the ils at easton the points along the approach are not defined as dme distances and crucially the non-precision missed approach point is not even given a waypoint on the profile view instead we need to look at the timetable underneath the airport diagram to see where the mist is it says that the distance from the final approach fix to the missed approach point is 4.3 miles the only way to discern this distance with the minimum equipment required for the approach in other words no gps is to time our course from the final approach fix and execute the mist after the time indicated for our ground speed so for example if we had a ground speed on the approach of 90 knots our time from the faf to map would be 2 minutes and 52 seconds so on these non-precision approaches we might decide to go missed at one point but make sure before you actually execute the missed approach that you check where the defined missed approach point is this is an added challenge you don't need to deal with on a precision approach where there's no confusion about where the decision and execution point are

Channel: FlightInsight

Views: 16,201

Keywords: missed approach, missed approach point, decision altitude, decision height, minimum descent altitude, visual descent point

Id: KGctqYBDKUw

Length: 7min 20sec (440 seconds)

Published: Tue Jan 11 2022