SALT in DED not adjustable by ICP

[Rongor]

During NORM INS alignment on the ground, we have to verify LAT LON and the SALT, acknowledging present values for these shown in the DED. If necessary, we can edit the numbers with the ICP.

 

1. I am unable to edit the SALT. Whenever I enter numbers on the ICP, pressing ENTR simply returns the SALT value to the number shown before in the DED. Therefore I can only acknowledge but not edit the SALT number.

2. SALT value seems to be affected by the Altimeter setting. Turning the QNH knob on your Altimeter not only adjusts the Altimeter readout but also the SALT value in the DED.

3. SALT number is shown higher than the Altimeter. There is a mismatch of around 50-60 ft. You can't bring them both to the same value, ideally this would be the current ground elevations as shown in the F10 map

All three described items: Why? and: Bug?

4. SALT value is showing correctly only after completing alignment by turning the INS knob to NAV.

 

Edited December 21, 2021 by Rongor

[Kilo]

If you rotate the altimeter knob you will also adjust the SALT value at the same time. The difference between the altimeter and the DED value is likely bacause your altimeter is in PNEU mode instead of ELEC.

[Rongor]

3 hours ago, Kilo said:

If you rotate the altimeter knob you will also adjust the SALT value at the same time.

This is exactly what I wrote in point 2.

 

3 hours ago, Kilo said:

The difference between the altimeter and the DED value is likely bacause your altimeter is in PNEU mode instead of ELEC.

It is, PNEU is the initial mode when starting up the F-16. Following the Cold start checklist beginning on page 103, there is no item telling me to switch it to ELEC.

in ELEC mode, the values match, but still it's not possible to edit the DED SALT value by the ICP keypad as demanded on page 79

[Tholozor]

According to the -1, the altimeter's barometric setting is directly sent to the CADC for the altitude display.

[Frederf]

The Kohlsman setting is sent to CADC for calculation purposes. CADC does its calcs and sends back a value for the servo instrument to display in elec mode.

Naturally in pneu the system is entirely mechanical and doesn't benefit from CADC calcs.

Notice in A-10C the altimeter auto changes from pneu to elec. I don't know if the same thing happens on F-16 but it doesn't in DCS. I can check the CL as it might be subtle like "altimeter set" or if it should auto that would explain.

SALT or system altitude is different from CADC altitude. They are related but not interchangeable.

You should be able to set Sys alt at least during alignment. Adjusting it after that would normally be through ACAL which isn't modelled. I don't know if you should be able to direct edit sys alt outside of align.

[Rongor]

3 hours ago, Frederf said:

You should be able to set Sys alt at least during alignment. Adjusting it after that would normally be through ACAL which isn't modelled. I don't know if you should be able to direct edit sys alt outside of align.

Currently it can't be edited, regardless of within or outside aligning.

Also opposite to the manual, the values don't have to be entered/acknowledged, regardless if STOR HDG or NORM alignment. Even Wags doesn't do it in the Cold start training mission.

This is what the manual says:

 

If anybody managed to edit the SALT, please tell us how.

Also if you bother to ENTR all the three data lines in the DED, you can simply stop doing so. Alignment will complete to 10 just normal.

[TEOMOOSE]

3 hours ago, Rongor said:

Currently it can't be edited, regardless of within or outside aligning.

Also opposite to the manual, the values don't have to be entered/acknowledged, regardless if STOR HDG or NORM alignment. Even Wags doesn't do it in the Cold start training mission.

This is what the manual says:

 

If anybody managed to edit the SALT, please tell us how.

Also if you bother to ENTR all the three data lines in the DED, you can simply stop doing so. Alignment will complete to 10 just normal.

Well, currently INS 6 has been "disabled" because of lack of information, so INS 10 in either modes.
 

 

[Frederf]

I have a lot of info on EIA requirements and process and I assume they do too. There is plenty of info available to make a very passable modeling of status <10.

7 hours ago, Rongor said:

If anybody managed to edit the SALT, please tell us how.

Also if you bother to ENTR all the three data lines in the DED, you can simply stop doing so. Alignment will complete to 10 just normal.

I think that's true of the real airplane (degraded flag prevents RER, CEP but otherwise fully functional). However, If you do an alignment without any coordinate confirms the airplane does not work normally in DCS. Try it without confirm and notice how the HSI distance to steerpoint has a flag over it. With confirm the HSI flag is not present on NAV.

The sys alt in DCS seems solely controlled by the Kollsman knob and is always the servo CADC baro altitude value. Typing it in is a no go. The real documentation is quite clear that S ALT is entered via ICP/DED at least at the alignment stage. Interestingly there is a warning to not enter sys alt during FLCS BIT (makes sense, BIT is tricking airplane to think it's flying in test conditions). However MMC sys alt is directly stated as a CADC output mixed with INS vertical rate data. It can be calibrated (read: offset) from that but it is essentially that. From what I gather it's a semi-complicated filter (probably Kalman type) that takes its data from several sources with weighting biases based on confidences, rejection thresholds, and the like. The ACAL page ALT DELTA value I think represents the total delta between the CADC alt and the SYS ALT. Aligning with a huge difference would cement in a large delta at least until the nav filter had some data and time to whittle it back down to reasonable. With GPS HIGH it should be under 300' from truth in a few minutes.

Notably the DED NAV page has SYS ACCUR blank even after a full INS alignment without GPS. The values for SYS and GPS fill in HIGH after several seconds post flipping on the GPS switch. It should be possible to have SYS HIGH with GPS off. One is able to set the master nav filter mode from AUTO to INS. I ran the master nav filter for 20 minutes (in AUTO) with GPS HIGH and it never fixed the 2700' alignment error I had aligned to which it should have. The filter should adjust position when EHE/EVE exceed 300' if everything is running normally. Interestingly I ran the simulation at 1x0 for 4 hours and the 2700' error was filtered down to 2600' and then 2500'. So the filter is there, it's just acting very, very slowly.

All in all F-16 altimetery is a bit complicated and just like the A-10C it has a simple but arguably sufficient implementation at least right now. To fully recreate these machines down to the rivet it would take a billion dollar development budget probably.

[Rongor]

On 12/22/2021 at 7:54 AM, Frederf said:

 However, If you do an alignment without any coordinate confirms the airplane does not work normally in DCS. Try it without confirm and notice how the HSI distance to steerpoint has a flag over it. With confirm the HSI flag is not present on NAV.

Tried that, you are right.

It would be nice to see that corrected and added in the manual then.

The reader needs to know, that not acknowledging the LATLON will still countdown to 10 and yet this mustn't be interpreted as "well done alignment" and that the SALT in fact isn't edited by ICP input...

 

[Frederf]

I'd rather the simulation be remedied.