![]() ![]() This gave you at least a fighting chance to fly that NDB approach with a modicum of precision. Instead, you just flew by reference to the heading and bearing as displayed on the RMI. ![]() No longer did you struggle with the mental heading and correction arithmetic. If you were lucky-or wealthy-enough to have an RMI (remote magnetic indicator), which was really nothing more than that bearing pointer on a compass card that, instead of merely being fixed or manually adjustable, was slaved to your heading indicator, life got a whole lot easier. (I’m told it could be done, but I’ve never witnessed it myself.) Consequently, most of us struggled to precisely fly an NDB approach. The bearing pointer was useful for navigation, but that compass card was a challenge because the numbers on it never corresponded to your actual heading on the heading indicator unless you were really diligent at manually adjusting it. The venerable and once-ubiquitous King KR-86-when it worked-provided an ADF bearing pointer on a user-adjustable compass card. Bear with me as we explore a little instrument-flying history.) Perhaps you once learned to fly an NDB approach. We’ll start by wandering at least 20 years back down memory lane. Now, let’s look at how things work with an HSI. But, they were developed with a conventional navigation VOR/LOC indicator. Those rules are the takeaway from the previous article. If you’re inbound on the back course or outbound on the front course, the shaded part of the feather is on your left, so you correct by steering away from the CDI. ![]() If you’re inbound on the front course, or outbound on the back course, the shaded part of the feather is to your right and you correct by chasing the needle. It doesn’t matter where you’re headed or what you’re doing-if you’re on the shaded side of the feather, the CDI is to the left. If you’re off course on a localizer or a localizer back course approach, and you’re on the side of the localizer feather on the chart that has the shading or other differentiation, the course deviation indicator (CDI) will swing to the left. The OBS setting doesn’t matter to the electronics on a localizer, but this is a good rule as we’ll see a bit further down. The Rules Rule #1Īlways (always!) put the localizer inbound front course under the omni-bearing selector (OBS). There’s too much material for a proper review, so let’s just skip right to the good stuff. Boring and repetitive as that is, we needed to start there to get the basis for understanding a localizer and a localizer back course using a conventional dedicated navigation indicator (VOR/LOC) and the need to sometimes chase the CDI to correct, and sometimes to pull it. In last month’s IFR Clinic we discussed how VORs work. ![]()
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