DME Arcs…..because they just had to build the airport right inside of all the mountains.
A DME arc is a ROUTE, that is part of the PUBLISHED portion of an APPROACH. It could be on an ILS, RNAV, VOR, or any approach really. The key ingredient here is there is something that is going to give you DME, and you will need something to receive that DME signal (either GPS or a DME receiver in the airplane). In our case below, the DME is coming from the SJT VOR, and we know this because we see “SJT 15 Arc” written alongside the Arc.
How to Fly It
The idea here is you would:
- Fly over the SJT VOR
- Fly outbound on the 309 degree radial or 135 degree radial
- The IAF (initial approach fix, or in simple terms, where the PUBLISHED portion of the approach begins) is when you hit 15 DME from SJT VOR
- (let’s say you flew outbound on the 135 degree radial), you would then make a 90 degree right turn to fly a heading of 225 degrees.
- You then twist your OBS knob from 135 degree FROM indication, to a 145 FROM indication, as the CDI needle begins to center, turn another 10 degrees right (heading 235 now) and twist another 10 degrees on the OBS knob (now 155 degrees)
- You keep repeating this process, of turning 10 degrees “inbound” or closer to the airport, while twisting 10 degrees at a time towards the final approach course for the actual approach.
- As you get to the final 10 degrees (in this case an OBS setting of 205), you’ll use your judgement based on winds aloft of when you want to start that 90 degree right turn inbound, but don’t delay, overshooting is never fun, and it does take some distance to make a 90 degree turn at “standard rate” (remember we’re always making those turns standard rate now!
Taking the High Road
Hi THERE! Time to Fly the HI-ILS (I hear its highly rated and way better than a regular ILS!). Although the chart may look a little different, I’m going to explain this to you very quickly here, because, well, it really is just a regular old ILS.
A “HI-ILS” or high ils, is different from the regular ILS approach going into an airport as it has a few different fixes on it. These fixes go further out from the airport and help an airplane (a high-performance airplane) get set up to fly a nice long 3 degree descent usually from up above 10,000′ (Airplanes are efficient at high altitude, thus the longer they can stay high, and then just make an idle power descent down the glideslope, the more fuel they’ll save). Typically only jets and turboprops will use these approaches, but nothing is stopping you from trying one out (except gravity and physics of your airplane probably not getting that high). Note: a Hi-ILS is its own plate, and although it’s an ILS to the same runway as the regular ILS plate, they are TWO SEPARATE APPROACHES and you are only going to be cleared for ONE of THEM! So don’t go getting any ideas about mixing and matching fixes or altitudes between the plates!