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.
