[CHECKING] ILS Glideslope indication, maybe

[Eagle7907]

Another observation I've made involves the ILS glideslope. I noticed if you're above the slope quite a bit (more than full scale), it gives a false indication that you are below the slope. I've experienced false localizer effect IRL, but never with glideslope. Even if there is such a thing, it certainly wouldn't do it if only 2 degrees off the slope. I have a track to show such. It's long from another bug report, but it should show what I'm talking about.

 

 

 

Also the command steering seems to be not as aggressive to get pilot to steer to maintain centered localizer. It seems to act as if there is a tolerance built in to the logic.

 

 

 

https://www.dropbox.com/s/uyqo2n1ddwn83tz/f16cbu97cold.trk?dl=0

Edited October 4, 2019 by Eagle7907

[Sydy]

Eagle,

 

If you are above GS IRL it is possible to get a false GS signal lobe. That’s the reason we never recommend to intercept a GS from above.

 

Good luck,

 

Sydy

[Eagle7907]

Okay. I guess I was much higher than I thought. I’ll revisit this. Just seemed like the distance I was away versus my altitude I can figure my slope angle, and it didn’t seem very high.

 

Thanks for your input though.

 

 

Sent from my iPhone using Tapatalk Pro

[Eagle7907]

test 2

 

I did another ILS, I think I know what happened. The GS wasn't being detected outside 14 miles. Here's my proof.

 

 

I calculated at 6,000ft the GS would be about 20 miles out. I went there, intercepted the localizer, but no GS. Still showed below me, or so I thought. So, I started a 3 degree descent and the GS came alive right at 14 miles out. So either:

 

 

1)Viper is wrong.

2)ILS simulation is flawed.

 

 

Track https://www.dropbox.com/s/9cm1tl9l1dozsas/f16ils.trk?dl=0

Edited October 4, 2019 by Eagle7907

[Bravo]

In RL its very few approaches with GS intercept outside 12 NM to my knowledge. So it theory yes you should be able to intercept it at 20 NM, you would probarly not fly it in RL as it might be unreliable until you are inside where the approach tells you to intercept it. Also note that glide slopes can be more than 3 degrees IRL

[Eagle7907]

In RL its very few approaches with GS intercept outside 12 NM to my knowledge. So it theory yes you should be able to intercept it at 20 NM, you would probarly not fly it in RL as it might be unreliable until you are inside where the approach tells you to intercept it. Also note that glide slopes can be more than 3 degrees IRL

 

 

Uh, no. Thats not true. It happens all the time. Ive seen ILS go out farther than 50 miles. Just the other night, APP in Columbia, SC had me intercept for ILS 11, about 15-20 miles out.

[Bravo]

Uh, no. That's not true. It happens all the time. I've seen ILS go out farther than 50 miles. Just the other night, APP in Columbia, SC had me intercept for ILS 11, about 15-20 miles out.

 

 

Yes 15-20 NM I have seen myself, but for my own curiosity do you by any chance have an AIP reference for that 50 NM or anything beyond 20 NM?

Also, just to be clear when you say intercepting the ILS at 15-20 was that the LOC or GS part?

[Eagle7907]

Yes 15-20 NM I have seen myself, but for my own curiosity do you by any chance have an AIP reference for that 50 NM or anything beyond 20 NM?

Also, just to be clear when you say intercepting the ILS at 15-20 was that the LOC or GS part?

 

 

 

 

Yeah, ORD approach does it all the time for both going east or west. I've seen the indications myself. It all depends on the transmitter, but easily any standard ILS, the beam should go out further than 14 miles, unless blocked by line of sight (obstruction). Let me see if I can find some black and white for you.

[Eagle7907]

From AIM:

The glide path projection angle is normally adjusted to 3 degrees above horizontal so that it intersects the MM at about 200 feet and the OM at about 1,400 feet above the runway elevation. The glide slope is normally usable to the distance of10 NM. However, at some locations, the glide slope has been certified for an extended service volume which exceeds 10 NM.

So, it doesn't indicate how far it actually is certified, but can be higher than 10. Look at approach charts of KORD, KLAX, KDFW. Those ILS approaches are certified for great distances. Now, ATC can tell me to intercept a localizer at 30 miles out, but legally, can't clear me the approach until within the certified distance for that transmitter. That still doesn't mean the indication just stops.

[Bravo]

Thank you for the info :)

[Eagle7907]

Thank you for the info :)

 

 

 

I wish I could get you an example, but that won’t be good for business.

 

 

Sent from my iPhone using Tapatalk Pro

[Terzi]

I have experienced this error as well. I confirm this bug. Especially if you do some rolls during your flight, go around the airfield, it is possible that the ILS/TACAN system shows strange things. When you need to track left it will tell you track right or with up/down (glideslope) its the same issue. I was down on glideslope and it tells me to go down even further, down until so that the ILS signal is lost... Tested airfield was Vaziani RWY 310. I am sure that my ILS freq and TACAN bands were set correctly.

I guess The ILS bug should be fixed ASAP because it is one of those instruments that you MUST rely on.

I am using the latest openbeta as of 28.01.2020, today.

 

Similar thing also existed in F-5E. I filled bug reports, it still is not fixed. Many people at that time reported the same.

[Bear21]

When flying the DCS ILS it starts snacking you around in the last mile before the threshold. You fly the cross centered in a steady 3° descent, well aligned with the runway (you can check it in VFR conditions) and then suddenly both the LOC and GS wanders off on the last mile in, in a way a real ILS doesn't. Strange.

[Bear21]

I have experienced this error as well. I confirm this bug. Especially if you do some rolls during your flight, go around the airfield, it is possible that the ILS/TACAN system shows strange things. When you need to track left it will tell you track right or with up/down (glideslope) its the same issue. I was down on glideslope and it tells me to go down even further, down until so that the ILS signal is lost... Tested airfield was Vaziani RWY 310. I am sure that my ILS freq and TACAN bands were set correctly.

I guess The ILS bug should be fixed ASAP because it is one of those instruments that you MUST rely on.

I am using the latest openbeta as of 28.01.2020, today.

 

Similar thing also existed in F-5E. I filled bug reports, it still is not fixed. Many people at that time reported the same.

 

The Vazani problem is not a roll problem, the RWY31 ILS is confused. Fly it with correct settings and it does what you say. Fly RWY31 with BC LOC setting (108.75 125°) and you have a correct LOC AND a correct GS (which of course in not OK). See discussion here: https://forums.eagle.ru/showthread.php?t=258604&highlight=ILS+vaziani

 

It could also be a result of the weird switching of ILS on airfields with just one ILS frequency, ref https://forums.eagle.ru/showthread.php?t=206555. This must be special for DCS, never hear of it before and it means every pilot who has ever flown approaches will report bugs. It would then be better to introduce BC ILS (Back Course ILS) which is a LOC only approach on the back lobes of the VHF based LOC. (the UHF based glideslope transmitter has too low backlobes for it to give GS, it's a LOC only approach from the other end). The frequency, identifier, etc is the same and by setting the opposite RWY LOC heading you get a correct LOC indication.

 

This is how the real world treats this situation and IMO it's what shall be modeled.

Edited January 28, 2020 by Bear21