#LOCALIZER BACK COURSE AIRPORTS HOW TO#

When flying inbound to a runway served by a back course approach, you'll see reverse sensing of the localizer needle. This point typically puts you at a point in space 200 feet agl and one-half mile from the approach end of the runway.īut for every localizer front course there's a mirror-image back course. Keep both the localizer and glideslope needles centered, and you'll descend at a constant rate toward the decision height (DH). The glideslope needle gives fly-up (needle rising from the central 'bull's eye') or fly-down (needle descending) commands. To stay on course, you'd fly toward the deflected needle: needle left, fly left needle right, fly right. When flying an ILS front course, lateral course deviations from the localizer show up as standard left-needle, right-needle deflections. The localizer antenna is situated some 1,000 feet or so from the departure end of the runway served by the ILS front course glideslope antennas are close to the approach end of an ILS runway. These VHF and UHF frequencies are paired and transmitted from two different antenna sites. Glideslope information is broadcast over a UHF frequency. Some older VOR navigation heads depict these two colors on the instrument face. (Older texts often call the 150-Hz half of the localizer beam the blue sector. The localizer component of the ILS uses VHF signals, modulating them at 150 Hz for one side of the inbound final approach course and 90 Hz for the other. It's the very precise localizer (about four times more sensitive than a VOR) and glideslope guidance that let you fly precision (i.e., having vertical guidance) approaches on an ILS front course.

The front course provides very precise lateral and vertical guidance to published decision heights-using localizer (for lateral) and glideslope (for vertical) needle steering indications. Think of the signals that make up an ILS as having two parts: the front course and the back course.

#LOCALIZER BACK COURSE AIRPORTS HOW TO#

Trouble is, most autopilot manuals and supplements to pilot operating handbooks do a poor job of explaining how to program for a back course approach. However, if you have a horizontal situation indicator (HSI) and know how your autopilot handles a back course approach, you can make more precise, safer approaches. So, needles that give wrong-way steering information-and a lack of practice-combine to make back course approaches avoided. Everybody hates a back course (BC) instrument approach because it can be such a confusing, demanding experience, and because many instrument landing system (ILS)-equipped airports don't use back course approaches.

Localizer back course airports