We're moving into the flight director's role in instrument approaches now — Page 348, Lesson 406

We're moving into the flight director's role in instrument approaches now. Let's pick this up with the wind velocity point, because it's a subtle one. The excerpt opens by noting that the flight director does not display wind velocity information, even though the INS could provide it. What you're seeing on the display is purely the effect of the flight director giving commands to fly the desired course or track that you've selected. So if you think you're seeing wind data, you're not — you're seeing the result of the flight director trying to hold your selected course against the wind. Now, the main topic: Flight Director Approaches, abbreviated FDA. This is the procedure for flying an ILS approach using the flight director system. Here's the sequence. First, you tune the ILS frequency into the VHF nav radios and identify it. Then you set up the QDM — that's the magnetic bearing to the station, the inbound course — in the course window. The mode selector should be set to AUTO/APP. The annunciator will show that the FDS — the flight director system — is looking to capture the LOC, the localizer. After beam capture, in a similar manner to VOR tracking, the FDS will — given enough distance — arrange the intercept to establish you on the localizer with a turn demand. The annunciator panel will then indicate LOC capture. At that point, the FDS is looking for the glide slope signal, so the annunciator GS light or magnetic indicator will indicate that. As soon as the glide slope is captured, the annunciator changes again, and the FDS will indicate a pitch nose down demand to fly the ILS glide slope. Now here's an important operational consideration. If you've misjudged the interception of the localizer, it's possible to end up established on the localizer past the point of GS intercept — meaning you're above the glideslope. Modern systems may automatically adjust and capture from above by increasing the rate of descent. But on older aircraft, it was sometimes possible to temporarily switch the FDS mode to MAN/GS. This forces the FDS into accepting a capture from above. That MAN/GS mode has two other uses. It can be used to establish a fixed intercept angle of the LOC beam, and it can force a LOC or GS capture condition if you know that the beam-sensing circuits of the computer are inoperative. Let me show you what the annunciators look like on the PFD — the flight mode annunciators, or FMA. And here's the altitude acquire and altitude hold behavior. So the key takeaway: the flight director doesn't give you wind velocity — it gives you commands to fly your selected course. And in an FDA, you're watching the annunciator sequence — LOC capture, then GS capture — and responding to the pitch and turn demands, with MAN/GS as the older-aircraft tool for capturing from above or forcing a capture when the beam-sensing circuits are inoperative.