investigating EHSI

[TEOMOOSE]

Hey @BIGNEWYCould you confirm tacan operation. Currently we are using the backup tacan, and when switched to PLS/TCN nothing works, only if you have a ILS station tuned in which is very weird and it should not work that way.

TACAN Normal Operating Procedures:
1. Turn MIDS on.
2. Depress T-ILS pushbutton on the ICP.
3. SEQ to select the appropriate mode.
4. Enter the desired channel number.
5. Select the desired band.
6. Depress the mode (M) button on the EHSI to select TACAN (TCN) or Precision Landing System / TACAN (PLS/ TCN)

Backup TACAN Operation:
Its pretty much the same thing except you select TCN on the EHSI.

Important to note that the course can be entered via the ICP through the T-ILS page and is stored in the EHSI as well in all PLS modes, but not TCN mode. In TCN mode you have to change it manually on the EHSI.

[BIGNEWY]

Please include a track replay and we will take a closer look. 

thanks

[TEOMOOSE]

11 hours ago, BIGNEWY said:

Please include a track replay and we will take a closer look. 

thanks

PLS/TCN: ( Precision Landing System (PLS)
Setting the course via the ICP will automatically changes the course in the EHSI (as it should) when PLS/TCN selected but the bars are not moving at all. The only way to get the bars working if you tune in to a ILS station. Therefore TCN becomes useless and can be turned off.

PLS/NAV: Using a the waypoint to runway via the selected course in the T-ILS ded page.  Except if you dont have ils tuned in it will not work.

Track included and a video of the same flight.

I have also tried to follow the command steering cues on the HUD which should guide to intercept course to the localizer and when intercepted it will help to stay on it. But it never uncaged from the horizon on the HUD until the flag showed up over the "cicrle" command steering cue. The flag indicates when the aircraft is on glideslope.

 

navtrack.trk command_steering_cue.trk

[Frederf]

There is some confusion here. RWY07 ILS for Kobuleti is on 111.5, not 108.1 as shown on the video. Simply dialing up 67X for KBL TACAN doesn't do anything regarding ILS.

In navtrack.trk you get the right frequency for ILS but you're way too high (CRS should be 064 but this only affects the 45 intercept). The system requires that you intercept the GS from below. It will never "trigger" and give vertical guidance if you're above. The vertical steering will enable +-1 dot GS and be marked invalid (X) until you get into 1 to 0 dot low.

TACAN is independent from ILS. The "PLS/TCN" is an HSI mode which uses the CDI for localizer position and the bearing needle and range readout for TACAN. The alternative is PLS/NAV in which the bearing and range are to INS steerpoint. Unless you care about the HSI bearing pointer and range readout the function of PLS/TCN and PLS/NAV are identical.

There is no B/U control over TACAN. On older non-MIDS airplanes the IFF panel would have the BU TACAN controls but it doesn't look like there is a provision for TACAN operation when C&I is BU. The older planes also called the UFC/BU knob CNI and not C&I. The N stood for Navigation which is missing in the newer airplanes thus the name change.

F16 ILS 07 KBL.trk

[TEOMOOSE]

1 hour ago, Frederf said:

There is some confusion here. RWY07 ILS for Kobuleti is on 111.5, not 108.1 as shown on the video. Simply dialing up 67X for KBL TACAN doesn't do anything regarding ILS.

In navtrack.trk you get the right frequency for ILS but you're way too high (CRS should be 064 but this only affects the 45 intercept). The system requires that you intercept the GS from below. It will never "trigger" and give vertical guidance if you're above. The vertical steering will enable +-1 dot GS and be marked invalid (X) until you get into 1 to 0 dot low.

TACAN is independent from ILS. The "PLS/TCN" is an HSI mode which uses the CDI for localizer position and the bearing needle and range readout for TACAN. The alternative is PLS/NAV in which the bearing and range are to INS steerpoint. Unless you care about the HSI bearing pointer and range readout the function of PLS/TCN and PLS/NAV are identical.

There is no B/U control over TACAN. On older non-MIDS airplanes the IFF panel would have the BU TACAN controls but it doesn't look like there is a provision for TACAN operation when C&I is BU. The older planes also called the UFC/BU knob CNI and not C&I. The N stood for Navigation which is missing in the newer airplanes thus the name change.

F16 ILS 07 KBL.trk 3.01 MB · 1 download

There's no confusion here from my end. If you have watched the video or read the original post.

Im aware of ils frequency's at Kobuleti the question was not how to ils rather the tacan function does not work in pls modes. If I set the ehsi to tcn via the m button it's working as intended.

 

The video is a simple example of the systems that I have questions about. You're missing the point if you start "criticizing" video, it's not a tutorial.

Navtrack.trk is the same flight I have posted in the link above.  The crs might be off but is irrelevant for this conversation, it could be anything for this matter. The point is pls/nav does not care about a tacan station.

CRS cannot be changed via the t-ils DED page in tcn mode but it has to be manually set on the ehsi. Therefore it considered to be as a backup option.

Edited December 23, 2021 by TEOMOOSE
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[Frederf]

That's how the real airplane works. In PLS/TCN the HSI CDI belongs to the ILS and the HSI bearing pointer and HSI range readout belong to the TACAN. The HSI is pulling "split" duty with some parts for ILS and other parts for TACAN.

The CRS field on the T-ILS DED page is for ILS localizer course (HUD) only. The CRS knob on the HSI is for all HSI display purposes. There are two totally different and completely independent CRS values in the airplane. You can type in the CRS field of the T-ILS page at any time even if ILS is not in use. Of course it has no effect on the HSI because it isn't for the HSI.

The "M" HSI button does not have anything to do with backup TACAN. To get backup TACAN you set the C&I knob to backup and it will say "BACKUP" on the T-ILS page regarding TACAN. You can't actually use backup TACAN in this particular F-16 variant so the display is a lie.

If you are specific about what behavior you expect under particular conditions or what you want to accomplish I can explain what actions to do and what to look for.

Edited December 24, 2021 by Frederf