approche ILS ( instrument landing system) en anglais

Today we'll be talking about the most common precision approach, the Instrument Landing System (ILS) approach. It uses both a localizer and a glideslope for guidance. Our nav radios can only tune the localizer frequency and we then receive the glideslope as well. So, when preparing to fly an ILS, we tune the localizer frequency in the nav radio. The ILS is located at the airport and they are runway-dependant, so large airports may have several ILS frequencies. So, now that we know what ILS approaches are, let's brief our chart and then go flying. Since we've already gone over chart symbology, I'll just touch lightly on most of these things.
"A" tells us that we're going to be doing the ILS Rwy 9R approach at Melbourne, FLA. Because the ILS is going to take us directly to a particular runway, we will always see the runway number in the approach identifier. We also see that the primary navaid is the localizer (IMLB), it's frequency being 108.3. "B" points to a chart notification, telling us that we must have DME or radar (ATC, not onboard) in order to fly this approach. It also tells us that there is pilot-controlled lighting for this runway. The first question I always ask myself is "Why do I need DME or radar?". The most common reason deals with being able to reach the IAF. If you look at "C" you'll see that the IAF is at MERCS, the outer marker. Well, since a marker just puts out a signal to our marker lights and aural system, we have no way to navigate to it directly. "D" shows us a feeder route from the VOR, which we CAN navigate to directly, which will take us to MERCS if we fly the 268 radial at 2100ft MSL until 7.8DME. So, you can see that we'll have to have DME to reach MERCS via the feeder route or get radar vectors from ATC. Otherwise, we have no way to start the procedure.
The next question I ask myself is "Why don't they just make the VOR the IAF then?" Well, there's no good answer. You'll have to call the FAA and get their reason if you really want it. "E" shows us our localizer frequency and front course heading.You'll notice this ILS does NOT have DME (otherwise it would say "ILS DME"), so if you use it in X-Plane (like I will for this example), you're cheating. "F" shows us our procedure turn. "G" tells us a few things. One, you see the maltese cross which represents the FAF. However, this is only if you were doing this approach as localizer-only. For an ILS approach, the FAF is wherever glideslope intercept occurs. You can see that at "G" it says "GS 2025". That means that if we are on glideslope, we should be at 2025ft MSL when we pass MERCS. You can see that glideslope intercept actually occurs a bit before MERCS. The line with the "090 degrees " through it represents the glideslope, the dashed line indicated the localizer-only approach procedure, the MAP being at 1.4DME from the VOR. "H" shows us our approach minimums.
Our Decision Height (DH) for the ILS is 233ft MSL, the MDA is 480ft MSL for localizer-only. Our visibility minimums are RVR of 2400ft or 1/2 SM visibility. "I" shows us our times for the localizer-only MAP. It also shows us our proper descent rate to maintain the glideslope for several groundspeeds. So, if we're doing 90kts, we should descend at 455ft/min in order to maintain the glideslope. OK, now that we've briefed our plate, let's do this...

Today's weather is ceiling 350ft overcast, visibility 1 mile. We'll be doing the full procedure, starting at the VOR. So, what we're going to do is take off from Melbourne, climbing to 2100ft, and request the full ILS 9R approach. At that point, Center will say "9246F proceed direct Melbourne VOR, cleared full ILS 9R approach, maintain 2100 until established, contact tower 118.2 when procedure turn inbound". So, now we've tuned in MLB and turned the needle until it center TO the VOR. We're level at 2100ft and proceeding to the VOR. I'll use NAV1 to fly the feeder route and set NAV2 to the localizer. After the procedure turn, I'll tune NAV1 to the localizer as well so you can see the procedure on both instruments. Normally, I would leave it set to the VOR frequency so I could use its DME. We see that our course for the feeder route is 268 degrees FROM MLB, so as we pass over the VOR, we will turn the OBS to set 268 on top and turn to intercept the course. We'll continue on this course until we get to 7.8DME. This may not take us directly over the beacon since it is designed to be aligned with the localizer, not the VOR radial, so when we reach 7.8DME, hopefully we'll hear the beacon as well, but we might not. Also, let's get those flaps out.