ILS Needles

[Johnpilot]

I finally figured out that I had the needles in the STOW position on the Nav panel which was driving me crazy. I took a flight from Kobuleti to Batumi. I set up a nice glide on about a 90 angle to fly through runway 13. I flew through the localizer and the yellow needle never appeared. I then made a hard bank to the left and then it suddenly showed up. I had the morse tone the whole time and once the needles appeared it seemed to work fine.

 

Q: Can you have TACAN and ILS selected at the same time? I realize the sim will let both buttons show the green triangle, but I am not sure what you actually register with the needles on the CDI?

 

I am an actual IFR rated pilot, so it seems like the needles should have come alive when I flew through the localizer and "slid" across the CDI as I went through it.

 

Any thoughts on what I am missing and my question? thanks!

 

John

[PFunk1606688187]

As I understand it the yellow bars in the A-10's ADI are meant to function as Command Steering bars, much like the flight director on commercial airliner, but are borked and only function as deviation indicators for both lateral and vertical flight path.

 

You can't use the TACAN and ILS simultaneously because one of them has to be the thing which the CDI and the ADI bars are using for information.

 

I'm not sure exactly what the issue could be without seeing the flight, so if you have a track posting it should be helpful.

 

 

As I said at the top, unless something has changed, the steering bars are pretty useless so I usually leave them stowed for precision approaches and rely on the CDI and GS indicator.

[aaron886]

So you flew through the course from left to right, and then the needles appeared off the left wall once you reversed your turn?

 

If properly modeled, a localizer does not care what your HSI's OBS setting is... it broadcasts in two VHF lobes just like the glideslope of an ILS. (90/150MHz) If you were expecting it to work on a specific course you set in, it will not... it will only work on the final approach course with which it is aligned. (And sometimes on the back-course of that approach course.) Try it in the airplane... get the CDI within scale and spin the OBS around. You should get no change.

 

I can explain in more depth if you need. I'm a II, at yer service.

[Johnpilot]

aaron;

 

Yes sir, I flew through it. I agree; if I am on the runway centerline, the localizer should be straight up regardless of my heading for that brief moment. I came in on a heading of about 235 for Rwy 13 and when I went through 130 degrees I never saw a steering bar for the localizer. I flew the ILS training mission again last night and I saw that the yellow steering bars kind of "jumped" alive in that one as well. I think if you have "pegged" them they do not always slide back but seem to jump back onto the AH. I need to focus on the CDI and the glideslope indicator on the far left of the artificial horizon and run it again. I am used to the needles moving more smoothly through the travel I guess.

 

I appreciate the feedback, and at least you can pause this guy and sort it all out as opposed to those days doing real IFR down to 800 feet. Never mind 200 and 1/2 in the real world for CAT I. Never had to do one in that poor of conditions.

 

John

[roadrabbit]

 

If properly modeled, a localizer does not care what your HSI's OBS setting is... .

 

:thumbup: Correct as far as it goes - but it is not the complete picture. Put the aircraft on the ground halfway down an ILS equipped runway but on the edge of the runway, say the left side. Set the OBS on the HSI to the runway course.

 

Displacement from the ILS course deviation indicator (CDI) appears as you would expect - localiser CDI to left means turn left to intercept, CDI to the right turn to the right. If you set the reciprocal to the runway track direction the whole instrument presentation becomes reversed. Try setting it correctly, then change the OBS selector to the reciprocal course. Notice the whole display of the course arrow and the CDI rotate around. Because the aircraft hasn't moved the CDI will not move, but will now show on the other side of the instrument.

 

Thus what you set on the OBS is important - for an ILS you set the course published for the runway.

 

Two pictures of the HSI here would show exactly what I mean. I still don't know how to take a screen shot - any help would be appreciated :music_whistling:

Edited August 5, 2013 by roadrabbit
Clarification

[Nealius]

I'm interested in the logic behind why the A-10 designers chose to make ILS and TACAN mutually exclusive. AFAIK in the F-16 they are not; you actually have a choice of TACAN/ILS and NAV/ILS. It makes things in the sim a bit difficult when flying an arc and turning to final, as I have to take my hand off the stick and hope I'm trimmed well enough to not crash while I switch from TACAN to ILS. In the F-16 in BMS all I have to do is set to TACAN/ILS and I can keep my hands on the stick the whole time.

 

Two pictures of the HSI here would show exactly what I mean. I still don't know how to take a screen shot - any help would be appreciated

 

Print Screen key. Automatically saved to C:/Users/<username>/Saved Games/DCS/ScreenShots in Windows 7.

Edited August 5, 2013 by Nealius

[Eddie]

I'm interested in the logic behind why the A-10 designers chose to make ILS and TACAN mutually exclusive..

 

They didn't, and nor are they in DCS.

[Nealius]

Page 453 of the manual says that TISL, TACAN, and ILS are all mutually exclusive. This has also been my experience in the sim.

[Eddie]

Have you ever tried selecting both TACAN and ILS on the NMSP? Because you can.

 

Obviously a single instrument can only display from one source at a time, but you can indeed have a nav data from both TCN and ILS selected together, and doing so gives exactly the same information as selecting ILS/TCN in the Viper.

[aaron886]

I flew the ILS training mission again last night and I saw that the yellow steering bars kind of "jumped" alive in that one as well.

Hm! Hard to visualize what you're seeing, but maybe they're just extremely sensitive? I've heard something on these forums about there being a sensitivity setting for the HSI in the Hog.

 

200 and 1/2

It definitely gets the blood going. :)

 

:thumbup: Correct as far as it goes - but it is not the complete picture.

Oh yes, you're absolutely right... my phrasing could have been misinterpreted. I was not making comment on "reverse sensing," only the fact that the LOC broadcasts the VOR-equivalent of one "radial." If you want a fun exercise in chair-flying, try working through the correct OBS settings to fly the missed approach of the VOR DME-E at KASE:

 

http://155.178.201.160/d-tpp/1308/05889LDE.PDF

 

If you work through it, you'll see why it's my go-to example. Cheers.

[whartsell]

Another fun exercise is flying a DME Arc

[roadrabbit]

If you want a fun exercise in chair-flying, try working through the correct OBS settings to fly the missed approach of the VOR DME-E at KASE:

Cheers.

 

:lol: Yes - I see what you mean! I had to fly similar in a past life, but never at 14,000 ft altitude. It does say you need two nav receivers working, but it is still a 'fun' missed approach.

 

Interesting note back in DCSW: I did my set-up at Nalchik on runway 24. The published ILS inbound is 235 degs, but when lined up on the runway itself it is 228 degs. :doh:

 

No wonder some of the noobies struggle.

 

I've just this moment done some research and discovered that over Georgia the magnetic declination is 6.1 degs East. If the runway ILS had been given in degs True then the magnetic reading would be 228 degs Magnetic. The charts say that all bearings are in degs magnetic, but is this really so? Or is this just an odd coincidence?

Edited August 5, 2013 by roadrabbit
Possible 'eureka' moment!

[Nealius]

Have you ever tried selecting both TACAN and ILS on the NMSP? Because you can.

 

Obviously a single instrument can only display from one source at a time, but you can indeed have a nav data from both TCN and ILS selected together, and doing so gives exactly the same information as selecting ILS/TCN in the Viper.

 

No need to get so snappy. It has been my experience that what you say is not completely true. I haven't flown with the latest update, but a few months ago when I tried flying improv instrument approaches with an 11nm arc at Batumi, I planned to begin my turn to final after crossing R-310 for an ILS landing. I had both TCN and ILS selected, and I was receiving bearing/distance to station however I was not receiving any course information, so when I crossed R-310 the CDI gave no indications that I had indeed crossed it.

 

I will fly again tonight with the latest update, perhaps something has changed.

[PFunk1606688187]

I'm not an expert on how the navigational instruments function, but from what I recall, having both TCN and ILS selected in the NMSP leads to the ILS controlling the CDI. I'm not sure if this can be changed, but that seems to be my recollection.

[Nealius]

Confirmed:

 

TCN selected, showing present position as being SW of R-310 Batumi TACAN (correct position)

TCN and ILS selected, showing present position as crossing R-310 Batumi TACAN (incorrect position)

 

Unless my memory is super fuzzy, in the Viper you should be able to use both TACAN and ILS at the same time, but in DCS you cannot because the CDI gives erroneous information.

 

EDIT I think I found out why. I don't think it's mentioned anywhere in the DCS manual, but the TO 1A-10C-1 says that "ILS localizer deviation signals are supplied to the course deviation indicator (CDI) on the HSI.

 

So I guess if you have TCN and ILS selected, the CDI is giving your position relative to the ILS and not the TACAN? Time to throw out the DCS manual and use the real thing, since the DCS one is apparently just plain wrong and any attempt to ask here results in "RTFM"...which ironically doesn't have the info in the first place.

Edited August 5, 2013 by Nealius

[-Pv-]

I have had both TCN and ILS modes selected at the same time and they behaved as expected being able to track TACAN with the HSI and ILS with the HSI AND ADI at the same time.

-Pv-

[Nealius]

If you take a look at these screenshots, it supports what the real TO-1A-10C-1 manual says about the CDI with ILS:

 

-First picture, inbound R-299* Batumi TACAN with TCN selected puts me left of the runway.

 

-Second picture, same course setting (299*) this time with TCN and ILS active, puts me more or less on runway centerline, as well as on the localizer in the ADI. The CDI also moves opposite to what it would with only TCN selected, and only receives data within range of ILS.

 

Therefore, with TCN and ILS both active, the CDI gives localizer info, not TACAN info. Just as the -1 states. It probably behaves the same way without TCN selected.

 

So, in a sense, the "mutually exclusive" bit is partially correct, because if you have TCN and ILS active at the same time, you will not be able to intercept TACAN radials. This is the point that I was trying to make.

[PFunk1606688187]

So I guess if you have TCN and ILS selected, the CDI is giving your position relative to the ILS and not the TACAN? Time to throw out the DCS manual and use the real thing, since the DCS one is apparently just plain wrong and any attempt to ask here results in "RTFM"...which ironically doesn't have the info in the first place.

 

Yea thats what I meant when I posted. There's only one instrument that can be used for course deviation and since ILS is a precision instrument mode you need that CDI to be displaying Localizer deviation since by the time you're flying on the ILS the TCN will be useless for any kind of RWY line up.

 

Using the TCN can still provide a DME read out which is why you can have both I guess.

 

So, in a sense, the "mutually exclusive" bit is partially correct, because if you have TCN and ILS active at the same time, you will not be able to intercept TACAN radials. This is the point that I was trying to make.

 

Generally speaking you don't need to use TCN radials when on the ILS localizer. I'm sure there are cases where you could need one for an instrument approach plate, but the military defies so much of the normal safety considerations of civilian flight in many cases.

Edited August 6, 2013 by P*Funk

[Nealius]

All of this goes back to my original curiosity of why they designed it like that. I don't know how accurate it is, but the F-16 as modeled in BMS (IIRC, been awhile since I did instrument work) does not give localizer info via the CDI but instead maintains TACAN info when both ILS and TCN are active. This makes it much easier to turn to final after crossing a certain radial in an arc because I don't have to take my hand off the stick and switch over to ILS mid-turn. Although the real Block 50/52 manual seems to state that the HSI/CDI should function in the same manner as the A-10's....I will have to double-check how it is in BMS.

 

I don't really understand the purpose of putting localizer info through the HSI/CDI, except maybe as a backup, but without glideslope info wouldn't that be pointless?

Edited August 6, 2013 by Nealius

[PFunk1606688187]

What does the F-16 display Localizer info with then?

 

Also, localizer only approaches exist in real life. The glideslope is a separate signal emanating from an entirely different source.

 

This makes it much easier to turn to final after crossing a certain radial in an arc because I don't have to take my hand off the stick and switch over to ILS mid-turn.

 

I would think that in real life a pilot would release the throttle rather than the stick to do this because he doesn't need to use the mouse. :P

Edited August 6, 2013 by P*Funk

[Nealius]

What does the F-16 display Localizer info with then?

 

HUD and ADI. With those both displaying localizer and glideslope info I don't see the point in repeating it on the HSI.

 

I would think that in real life a pilot would release the throttle rather than the stick to do this because he doesn't need to use the mouse.

 

Obviously...

 

The main problem for me is that my mouse is to the right of my stick...and it's a right-hand only trackball.

[PFunk1606688187]

HUD and ADI. With those both displaying localizer and glideslope info I don't see the point in repeating it on the HSI.

 

Except that I'm fairly certain that those don't count as actual primary instruments in their own right, ie. they don't provide the means to cross check or have a redundancy or serve as primary in this particular function (the ADI is clearly the primary instrument for Attitude, not necessarily for Localizer navigation).

 

First of all the HUD is not a primary instrument so its immediately off the table. Secondly, the ADI is its own instrument, but if that breaks you have nothing. Even so, I assume you're referring to some sort of Flight Director steering bars that tell you how to steer, or is there an actual localizer deviation indicator like the glideslope indicator on the A-10s ADI which is included in the F-16 ADI?

 

If its the former I'm pretty sure that doesn't count as an instrument in its own right, but a representation of information derived from information that would be on an instrument, like the CDI. If its the latter, thats a snazzy ADI. Last point, the ADI serves Attitude awareness, so Localizer alignment is not its primary purpose, so any overlay which serves this purpose is acting as a secondary to the primary purpose of the instrument.

 

Fact is that while we can use instruments one way that seems more convenient, in reality there are safer better more professional ways to do these things, which is why they're designed a certain way. I'm pretty sure having the localizer on a Course Deviation Indicator is significant for flying any manual approach with a localizer. I know that in a commercial airliners you wouldn't have only Flight Director steering bars without a localizer alignment indicator of some kind to cross check the sanity of the Flight Director. I've used Autoland on the PMDG 737NGX and had Localizer deviation while on full autopilot, and without that cross check I wouldn't have been able to correct manually and finish the approach without a go around.

 

 

The main problem for me is that my mouse is to the right of my stick...and it's a right-hand only trackball.

Right, but the sim represents systems designed for someone who doesn't have that issue, so any work arounds that function to avoid using the mouse, likely end up bypassing the intended, often safe, normal procedures.

 

**Advisory** My analysis of the validity of navigational instruments is based on nothing at all professional or credible except my own knowledge. More knowledgeable people are welcome to call me a liar. :smilewink:

Edited August 6, 2013 by P*Funk

[Nealius]

I know nothing of instrument procedures beyond what little is represented in these sims, so bear with me for a moment.

 

I have heard that the HUD in the Block 50/52 is rated as a "primary instrument" and they can use it for ILS, however I believe lower Block numbers are not rated as such and the pilot has to use the instruments down on the instrument stack. No clue how true that is, but it's what I have heard. If that's the case, then the HUD isn't necessarily off the table. Unlike the A-10, the F-16's ADI is a good distance away from the HUD and is quite small.

 

I'm not sure about the Flight Director steering bars versus localizer/glideslope indicator. The real 50/52 manual states that they are "localizer and glideslope deviation bars" that are displayed in the HUD. In addition to the localizer/glideslope bars, there is a Command Steering cue, which is basically a floating circle that moves around the HUD and tells the pilot where to fly in order to intercept the localizer. I've attached a screenshot of the ILS HUD/ADI page in the manual.

 

Last point, the ADI serves Attitude awareness, so Localizer alignment is not its primary purpose, so any overlay which serves this purpose is acting as a secondary to the primary purpose of the instrument.

 

I'm a little confused on that point. Is the CDI considered a separate instrument from the HSI? Because the HSI's primary purpose is also not for localizer alignment. It just seems a bit odd to me to have primary localizer info on one instrument and glideslope info on another instrument when having both on the same instrument reduces pilot workload.

Edited August 6, 2013 by Nealius

[roadrabbit]

I know nothing of instrument procedures beyond what little is represented in these sims, so bear with me for a moment.

 

I'm a little confused on that point. Is the CDI considered a separate instrument from the HSI? Because the HSI's primary purpose is also not for localizer alignment. It just seems a bit odd to me to have primary localizer info on one instrument and glideslope info on another instrument when having both on the same instrument reduces pilot workload.

 

:smartass: Forgive me if I am saying what you already know, but historically primary flight instruments are Artificial Horizon, ASI, VSI, altimeter, compass and Turn & Slip indicator. All else is overlay or addition.

 

Thus the compass now can have VOR and ADF needle additions to it, and often will have a CDI display as well. It may have DME readout(s) incorporated, too. It is then called an HSI. The Artificial Horizon can have 'command bars' added to it, as well as ILS information, and it then becomes an ADI.

 

The ILS presentation in the DCS A-10c is halfway between a raw ILS display (one without a course setting facility) and a full 'flight director' display. As has been said elsewhere the yellow bars on the A-10c ADI do not appear to be flight dirctor bars, but are just repeat course and glideslope deviation bars. As has also been said, it is usual to find an aircraft that has a flight director to also be equipped with some sort of basic ILS as a cross reference to check the flight director is not giving erroneous information. On the A-10c this is essentially what you have got, despite the flight director not being modelled as an FD.

 

Finally, to give some kind of answer to your question :D:

the CDI is part of the HSI, but not essential to the HSI definition above.

 

Some may disagree with what I have said, but it is what I was taught.

Edited August 6, 2013 by roadrabbit

[PFunk1606688187]

Yea for all I know the F-16 late block HUD is usable as a primary instrument. I know that recent Boeing airliners are being equipped with their own HUD's that can be used to fly fully eyes-out with no need to cross check instruments.

 

The fact that the F-16's ADI is so small apparently suggests that this is the case. In either case, the F-16 is a far more sophisticated aircraft than the A-10. Fly by wire aircraft operate under very different constraints. If you lose the fly by wire you're dead pretty much, and if you lose that you're not likely going to have many of the other instruments I suppose.

 

Meanwhile, in the A-10 you can lose everything including hydraulic power, both batteries, and every computer onboard and still fly it home, drop the gear, and pump the brakes. With the A-10 being so old school the CDI is probably a far more significant instrument than on an F-16 I guess.