Course Radial in DED or the HSI
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The Falcon4 manual page 3-8 explained to input the course radial with the HSI Course Knob. Red Dog’s Chart Tutorial on page 9 recommends that TACAN data be done in the UFC via the ICP and DED. When I input the course radial in the DED through the UFC, the HSI course arrow and the HSI course window do not change to match what I keyed into the UFC. Is this a bug? Or am I always supposed to enter the course radial with the HSI course knob and don’t bother to enter the course radial in the DED through the UFC?
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You need to do both to have the course/HSI synchronized AND have the ILS/TACAN frequencies active.
(technical/aeronautical language might not be ‘right’, but the bottom line is for precision/IFR approach you need both.)
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In BMS the only azimuth data input thing that has anything to do with displays is the CRS setting on the T-ILS page. And the only only only only (did I mention only?) thing it does the little “V” caret on the heading tape to help you with crosswind corrected heading when in the ILS-HUD Mode. Funny enough the “V” caret moves (wrong) but is correct once you align with the mark. The crosshairs and steering cue work without regard to any other setting than the proper ILS freq is plugged in and power is on.
The CDI deflection on the HSI (and ADI which are just repeaters for LOC/GS raw data) is correct no matter what the CRS knob setting. It’s only a “nice to have” to set the CRS knob so the HSI picture is right side up. You notice that given a certain deflection you can spin the HSI picture in circles with the CRS knob and the deflection never changes. In fact if you followed a published procedure (or good vectors) that delivered you into the ILS inception area it would be practical (maybe not legal) to never look at your HSI and just follow the ADI repeater bars and HUD cues all the way in.
There is a small aside that in the real airplane I’ve read (which I can’t find now) that the HUD steering cues depend on a manually entered course value (DED or CRS knob I don’t know, I think it was CRS knob). If you think about it this makes sense. There is a feature of the HUD steering cue that will give 45 degree intercept guidance laterally onto the center of the LOC. How does it know the intercept course if it doesn’t know the course? By trusting the pilot input value.
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The “V” could center when the a/c tracks on the CRS heading regardless of compass heading.
I can’t see using the “V” when the CMD STR Cue mode is on. When would you not use the CMC STR Cue mode?
It’s very hard to perform an interment landing with just the LOC an GS bars in a crosswind. I tried to bring it up in another thread. -
IRL you can set the HSI course via the DED but only with the EHSI.
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The “V” could center when the a/c tracks on the CRS heading regardless of compass heading.
I can’t see using the “V” when the CMD STR Cue mode is on. When would you not use the CMC STR Cue mode?
It’s very hard to perform an interment landing with just the LOC an GS bars in a crosswind. I tried to bring it up in another thread.Correct the “V” is equal to the selected course +/- any calculated crosswind correction. The correction should be simple vector addition with INS calculated vs current GS & selected course. The fact that the “V” moves around so much is screwy.
“V” caret is good for if the FPM or CMD STR cue is off the HUD due to crosswind. It’s also a good reminder and helps you roll out on a good heading as you see the heading tape move. As for why use it shrug it’s always there so it’s worth a look. The cue and caret are both part of the “flight director.”
Establishing a wind correction for any “on course” indication (TACAN, NAV, ILS LOC, etc) is an interesting skill. The lesson I was taught was to pick a heading and wait to see what happens. Notice if it’s too much or too little, pick a new heading, and try that. It was also said to pick your heading shifts at least as large as you need. It’s faster and safer to “bracket” than to “sneak up from one side.” So if I’m drifting off course with too little correction I am more likely to give it 10 degrees more correction than 5. Interpolation is better than extrapolation.
IRL you can set the HSI course via the DED but only with the EHSI.
I found the text and it’s definitely for a non-EHSI model:
The reference caret indicates the heading required to maintain the course selected on the DED (magnetic heading scale displayed) or ground track error relative to the course selected (magnetic ground track scale displayed). The course value may be changed only by entering the new value through the DED.
The ILS presentation on the HSI and ADI is controlled by the CRS set knob (HSI) and INSTR MODE knob. All other control functions are selected by the upfront controls.
The ILS page is selected by verifying the CNI page is displayed on the DED and then depressing the T-ILS function button. Commanded (OFF or ON) ILS status and three changeable items appear: the ILS frequency, the localizer course for the ILS flight director cues on the HUD, and the selection of the flight director (CMD STRG).
Three steps are required before the ILS flight director (command steering) HUD cues are usable: the localizer course is displayed on the DED, the flight director is mode selected on the upfront controls, and an ILS mode is selected with the INSTR MODE knob.
The course setting on the HSI is not connected to the flight director in the HUD. For consistent ILS displays, the inbound localizer course should be set on both the DED and the HSI.
So the HUD presentation (caret and cue aka director) are based on UFC data entry only.
The reference caret indicates the heading required to maintain the course selected on the DED
I notice this says to maintain instead of to establish and maintain so I believe the reference tick (“V”) is a static display on DED-input CRS (±WC) and won’t display lateral guidance to fly to LOC center when off center. In fact the later diagrams confirms this as the V is out of view while following the lateral steering cue.
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Three steps are required before the ILS flight director (command steering) HUD cues are usable: the localizer course is displayed on the DED, the flight director is mode selected on the upfront controls, and an ILS mode is selected with the INSTR MODE knob.
The course setting on the HSI is not connected to the flight director in the HUD. For consistent ILS displays, the inbound localizer course should be set on both the DED and the HSI.
So the HUD presentation (caret and cue aka director) are based on UFC data entry only.
The INSTR MODE knob is not UFC. Leads me to believe the DED CRS “V” caret is a backup for the CMD STRG cue. I’m guessing the HSI provides DME for the CMD STRG cue. <plausible shrug=“”>To be crosswind proficient on ILS approach both position and track heading information is needed. (deviation bars centered and track on runway radial)
Maybe on a slow a/c you can poke and hope with a heading compass.</plausible> -
Read it again carefully. The three steps required are:
1. LOC CRS input on DED
2. Flight director selected on DED
3. Nav mode set to NAV/ILS or TCN/ILS
Step #3 is basically “it’s turned on.” This step is required for any ILS use at all and not unique to using the HUD director.It’s not a backup. CMD STRG is the flight director which is both items, steering cue and reference mark. They are a system of symbols that work (and are enabled/disabled) together.
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I found the text and it’s definitely for a non-EHSI model:
So the HUD presentation (caret and cue aka director) are based on UFC data entry only.
well, that seems to mesh well with what Amraam said about the HSI.
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I have no knowledge of the eHSI functionality. I wouldn’t be surprised if in that case the two course settings were unified into one and that either the knob or DED would adjust the same value. That would be good design.
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It’s the case ;).