The ILS approach
Localizer, glideslope, markers, and categories -- read on the real ILS or LOC RWY 4R chart into Boston Logan.
16 min read · Instrument approach systems
After this lesson you can
- Explain what the localizer and the glideslope each guide, and their approximate frequencies and sensitivities.
- Identify a false glideslope and state the technique that avoids flying one.
- Read the S-ILS and S-LOC minimums lines on the same chart and explain why they differ.
- Locate the localizer frequency, final approach course, glideslope angle, and missed approach instructions on a real ILS chart.
The Instrument Landing System is the oldest precision approach still in widespread use, and the standard every other approach in this module gets compared against. It gives you two independent, continuous signals: one that tells you whether you are left or right of the extended runway centerline, and one that tells you whether you are above or below a 3-degree descent path to the touchdown zone. Fly both needles to center and the airplane arrives at the runway.
That precision comes from sensitivity, and sensitivity punishes sloppiness. A pilot who flies the ILS with VOR-sized corrections finds the needle already pinned by the time they notice a deviation. This lesson works through the localizer, the glideslope, the markers, and the categories of ILS service, all on the real ILS or LOC RWY 4R chart into Boston Logan (KBOS).
The rest of this lesson
- 1.The localizer: lateral guidance
- 2.The glideslope and its false courses
- 3.Markers and compass locators
- 4.Approach lighting and ILS categories
- 5.Reading it on the chart: ILS or LOC RWY 4R, Boston Logan
- 6.One chart, two philosophies: S-ILS versus S-LOC
- 7.Flying the ILS: technique that matches the sensitivity
These 7 sections, their figures, the checks along the way and the end-of-lesson quiz come with the IFR track. Paid once, yours for good.
Key terms
Try to recall each definition before turning the card.