F-15c ADI stuck during ILS landing?

Hi all, I have recently began learning the F-15c and I am currently focusing on ILS landings.

I seem to be able to land quite successfully, however it appears the horizontal line on the ADI in my aircraft is stuck. I have attached a track (F-15c Landing.zip) showing my latest landing, and you can see that even when I have the "+" inside the Velocity Vector, the horizontal line on my ADI never levels out, it always remains stuck at the bottom.

Is this a bug? Surely it should line up with my wings in the centre? I have tried pitching up and down dramatically, but the horizontal line never budges!

Thanks all.

PS - Any critique on my landing is also welcome. I am currently going by what the manual says as closely as I can, but this is only approx my 10th or so landing.

F-15c Landing.zip

The airfield you land on doesn't have ILS for starters.

https://forums.eagle.ru/showthread.php?t=120897

Horizontal ADI glideslope deviation bar works for me from about 4.5nm away from the ILS-equipped airfield.

Landing although smooth was below glideslope. Don't chase the cross - make it come to you smoothly. Start the airbraking way earlier to set on-speed before outer markers.

The airfield you land on doesn't have ILS for starters.

https://forums.eagle.ru/showthread.php?t=120897

 

 

Horizontal ADI glideslope deviation bar works for me from about 4.5nm away from the ILS-equipped airfield.

 

 

Landing although smooth was below glideslope. Don't chase the cross - make it come to you smoothly. Start the airbraking way earlier to set on-speed before outer markers.

Thanks for reply. Oh no, really? I was sure it did. If you are going by the list in the link you gave, I think that list needs updated as things have probably changed since 2014. It has Mozdok's runway numbers wrong for example (or one of them at least). I found it before and when I noticed the incorrect number it put me off using it. I also think some airports that didn't have ILS now do, like Krasnodar-Center (Krasnodar). Could be wrong of course, still learning.

In the track I was in ILSN mode and I tripped both outer and inner markers, as well as having the landing steering cross, so wouldnt that mean the runway had ILS? Just to be sure I re-ran the mission on Mineralnye Vody which definitely has ILS, and it was just the same - no additional markers of any kind - HOWEVER the horizontal line on my ADI, DID function as expected, so that's progress!

Now were on the subject, something I was wondering for a while, is the white fan type object in the below map screenshot, a representation of a runway glide slope / ILS? I notice that some runways have this object on both runway approaches, and others just have it on one, and some don't have it at all.

Would you mind telling me what "on-speed" means? Ive read that word a few times now but have been unable to get a satisfactory definition. Also if you have the time, could you tell me what pattern altitude means? I think it means the altitude of the beginning of the glideslope, but I'm not sure. If this is the case, are all pattern altitudes for the runways the same? Or are there a list of them somewhere?

Sorry for all the questions!

Thanks!!

I'm not up to date with the details of different runways in DCS. What's wrong with Mozdok's numbers? Doesn't 27-8=18? ;) It's close enough - just like runway numbers IRL.

Markers are another system and this doesn't mean the runway uses ILS:

https://en.wikipedia.org/wiki/Marker_beacon

The symbol from the image is used to indicate ILS localizer on charts. Some airport are just not bi-directional at all or have ILS only for one approach direction.

On-speed is the airspeed you get (and suppose to hold until flare) when you fly correct glideslope (-3 degrees) in landing configuration (gears, flaps) and with 21 units of angle of attack (see the mark at the gauge).

Pattern altitude is applicable to overhead pattern approach and decided by local ATC. For Caucasus just use 600m (mostly correct IRL) to not overthink it. Since F-15C doesn't have radar altimeter you do the math with the airport elevation :thumbup:

I'm not up to date with the details of different runways in DCS. What's wrong with Mozdok's numbers? Doesn't 27-8=18? ;) It's close enough - just like runway numbers IRL.

Just a bit odd the chart has it wrong. If its not correct, then its wrong IMO, 'close enough' doesnt really cut it for me :smilewink: which made me question the validity of the entire chart. Airports in real life operate a 'close enough' policy? That seems odd. I would have thought that type of thing would be extremely important.

Markers are another system and this doesn't mean the runway uses ILS:

https://en.wikipedia.org/wiki/Marker_beacon

Ok thanks.

The symbol from the image is used to indicate ILS localizer on charts. Some airport are just not bi-directional at all or have ILS only for one approach direction.

Yeah that's what I was asking - so the runways with the symbol that I have arrows pointing to, means the runway has ILS? As you can probably see the runway in the screenshot has the symbol, and that's the same runway I landed at in my track.

On-speed is the airspeed you get (and suppose to hold until flare) when you fly correct glideslope (-3 degrees) in landing configuration (gears, flaps) and with 21 units of angle of attack (see the mark at the gauge).

 

Pattern altitude is applicable to overhead pattern approach and decided by local ATC. For Caucasus just use 600m (mostly correct IRL) to not overthink it. Since F-15C doesn't have radar altimeter you do the math with the airport elevation :thumbup:

Ok great thanks. Il aim to be at 2000ft for the start of the glideslope, however are you aware of any lists that exist containing the exact pattern altitudes for the different runways? I have been searching everywhere but the closest I have found is the kneeboards and they give me a ton of information except what I actually want. Thanks!

...I also think some airports that didn't have ILS now do, like Krasnodar-Center (Krasnodar). Could be wrong of course, still learning.

 

In the track I was in ILSN mode and I tripped both outer and inner markers, as well as having the landing steering cross, so wouldnt that mean the runway had ILS? Just to be sure I re-ran the mission on Mineralnye Vody which definitely has ILS, and it was just the same - no additional markers of any kind - HOWEVER the horizontal line on my ADI, DID function as expected, so that's progress!...

 

 

...

In your image, Krasnodar-Central indicates the "Russian ILS" (PRMG). That's why the informational text is blue (838.00 MHz, channel 38 ). NATO ILS is indicated by white text.

In your image, Krasnodar-Central indicates the "Russian ILS" (PRMG). That's why the informational text is blue (838.00 MHz, channel 38 ). NATO ILS is indicated by white text.

That is seriously useful information man, thanks for sharing! While you're here do you mind if I ask you a quick question?

Im now trying to get my head around 'flaring'. I know that flaring is basically pitching the nose of the aircraft up just before touch down, to make a nice soft landing on the back wheels. I can do this no problem.

But my question is, with the F15c, I understand that approach should be made at about 22 units AoA, however if the bird is coming down at this AoA, how then can I flare? Wouldnt flaring put my AoA even higher and risk tail strike? I could follow 22 all the way down and touch down with my back wheels as 22 already has the nose in the air, I don't understand flaring here.

Thanks.

Yes. Those little bits of information come in handy sometimes.

As far as flaring the F-15 is concerned, it’s been so long since I’ve been in one that I don’t recall. If I was home, I’d jump into the pit and refresh my memory. I’m sure a true-blue F-15 type will come by soon, though, and enlighten us both. :)

EDIT: Senility strikes again. Realized that, yes, you do flare. Here’s a good video. Take note of the flight path marker.

EDIT 2: Here’s the thread that video was posted in: https://forums.eagle.ru/showthread.php?t=195901&highlight=Landing

Yes. Those little bits of information come in handy sometimes.

 

As far as flaring the F-15 is concerned, it’s been so long since I’ve been in one that I don’t recall. If I was home, I’d jump into the pit and refresh my memory. I’m sure a true-blue F-15 type will come by soon, though, and enlighten us both. :)

 

EDIT: Senility strikes again. Realized that, yes, you do flare. Here’s a good video. Take note of the flight path marker.

 

 

EDIT 2: Here’s the thread that video was posted in: https://forums.eagle.ru/showthread.php?t=195901&highlight=Landing

Thanks for the video. It highlights the exact issue I was questioning. The manual states not to exceed 22 units AoA but in the video he reaches 24 during the flare! And if you are coming down at 22 units AoA, why do you even need to flare, if your nose is already pitched up (from being at 22 AoA). I could understand a flare, if you were coming down level (no pitch) or even pitch down, but not coming down already pitched up. The manual then says to finish the flare approx 1m above the runway, Id love to know exactly what it means by 'finish'. In fact, much of what the manual says on this doesnt make much sense, to me anyway. Unless by 'finish' it means to level the plane out, but then how would your back wheels touch the ground first..

I actually found some threads that you had posted in, and I downloaded a track you had posted landing the F-15, however it didnt make a lot of sense to me as you landed beside the runway, not on it, then I think you crashed. So it must have been an earlier version of DCS you recorded it on and the replay wasnt accurate (has happened to me a few times even with replays ive just recorded). There was another replay (track) in the same thread, and in that one, the guy didnt even take off! So definitely bugged tracks there.

On final approach, set on-speed for 20-22 units AOA. At the flare point, smoothly retard the throttles

to IDLE and reduce rate of descent so as to finish the flare at 0.75 - 1.0 meter above ground. At 0.75

- 1.0 meter above ground, take an attitude for a cushioned landing on the two main wheels.

Raising nose too high up to 22 units AOA in the flare may cause a hard landing and engine ground

contact. After touchdown, maintain directional control by pedals. Raise the nose to approximately 13º

pitch attitude to achieve aerodynamic braking.

Also, why does the AoA scale on the left read about 11-12, but the digital readout says 22? Ive noticed that in different videos and just chalked it up to an earlier version of the F-15 build with a bug. Just makes everything that bit more confusing / harder to grasp.

One more thing quickly, the manual states "Approaching the final approach fix, slow to 200-250 knots and extend landing gear and flaps." So it tells you to down flaps and landing gear even before the final approach fix, which is before the start of the glide slope, is this accurate? It seems very early indeed.

First, the purpose of the flare is to reduce your descent rate to within acceptable limits. As you already noticed, it's not needed to make your mains touch first.

Next, the AoA steam gauge (I assume that's what you're referring to) is indicating your actual AoA. The HUD readout is giving you units of AoA. There's a mathematical relationship between the two but they are not the same units. Pay attention to the HUD readout, since that's the number you're using.

As far as the IAF, gear, and flaps are concerned, if you are set up for the landing just prior to hitting it, then it's one less thing to worry about later when there might be other pressing natters, especially in bad weather. The F-15 handles well but the aircraft I tend to fly need retrimming, etc after each action. So I definitely prefer to be set up when I hit that point.

Tracks can become useless after any update that changes something the track is using. Something as simple as the friction coefficient between tires and concrete can render any track with a ground start involving that aircraft useless.

1. The manual states not to exceed 22 units AoA but in the video he reaches 24 during the flare! And if you are coming down at 22 units AoA, why do you even need to flare, if your nose is already pitched up (from being at 22 AoA).

2 .Also, why does the AoA scale on the left read about 11-12, but the digital readout says 22?

1. The 22 units are for the correct approach speed/AoA, not the flare.

That said, 22 units is the lowest speed / highest AoA for approach and as you have noticed, during the flare you are rather close to a tail strike.

1. The RW manual says 20-22 units for approach. The faster you fly, the more energy is left for the flare, pitch control is a bit better at higher speed as well.

No need to fly exactly at 22 units.

2. Just checked and I didn't notice any difference between the HUD digital, HUD scale and gauge AoA values. During the approach all three are e.g. indicating 20 units.

First, the purpose of the flare is to reduce your descent rate to within acceptable limits. As you already noticed, it's not needed to make your mains touch first.

Cool.

Next, the AoA steam gauge (I assume that's what you're referring to) is indicating your actual AoA. The HUD readout is giving you units of AoA. There's a mathematical relationship between the two but they are not the same units. Pay attention to the HUD readout, since that's the number you're using.

No I was talking about the vertical scale that runs parallel to the speed scale on the left of the HUD. I didnt even think to look for a steam gauge to be honest! It gives a scale version of the digital AoA display. These two should be the same, and they are the same in my HUD when I land, but in the video you linked, they aren't. So I'm wondering maybe if something was changed from an earlier version of DCS. I'm aware that the AoA units in the HUD arent actual degrees but have a relationship with them as you said.

As far as the IAF, gear, and flaps are concerned, if you are set up for the landing just prior to hitting it, then it's one less thing to worry about later when there might be other pressing natters, especially in bad weather. The F-15 handles well but the aircraft I tend to fly need retrimming, etc after each action. So I definitely prefer to be set up when I hit that point.

Yeah OK fair enough. I just find it soo slow and a lot more difficult keeping the AoE all the way from the start of the glideslope to the runway threshhold. I prefer to just stay on the glideslope and watch my speed, and only think about AoA when its time to flare.

Tracks can become useless after any update that changes something the track is using. Something as simple as the friction coefficient between tires and concrete can render any track with a ground start involving that aircraft useless.

This is true. It doesn't take much to render a track quite useless!

1. The 22 units are for the correct approach speed/AoA, not the flare.

That said, 22 units is the lowest speed / highest AoA for approach and as you have noticed, during the flare you are rather close to a tail strike.

So its acceptable to go above the 22 during the flare then? I can't see any other way around it to be honest so I hope so lol.

1. The RW manual says 20-22 units for approach. The faster you fly, the more energy is left for the flare, pitch control is a bit better at higher speed as well.

No need to fly exactly at 22 units.

I find I can only really fly at one speed when at 20-22, and remaining on the glideslope. If I fly faster then I begin to gain altitude. This is why I dont like it, its so restrictive. I prefer to just ignore it until time to flare.

2. Just checked and I didn't notice any difference between the HUD digital, HUD scale and gauge AoA values. During the approach all three are e.g. indicating 20 units.

I was referring to the video that Iron shared. If you look at the HUD in that, you will see the AoA HUD scale is showing about half of the digital number AoA readout. My aircraft is the same as yours, all matching in values, so Im thinking something changed along the ways somewhere, or maybe a bug that was fixed etc.

....

 

 

I find I can only really fly at one speed when at 20-22, and remaining on the glideslope. If I fly faster then I begin to gain altitude. This is why I dont like it, its so restrictive. I prefer to just ignore it until time to flare...

There seems to be a difference in approach between western and Russian technique. The West tends to fly the AoA to the landing. So 21-22 units will have you at the right airspeed for landing adjusted for gross weight. Increase or decrease your gross landing weight and the required airspeed will be a different number. And as you’ve noticed, the throttle controls your sink rate. You may have also noticed that the stick then controls your airspeed.

The Russian approach is to leave the ISF at around 380 km/hr, gradually slowing to around 340 as you cross the outer marker, 310 across the inner marker and 290 across the threshold. That gives you good visibility down to the threshold but with a slowing increasing AoA.

I don’t have a clue as to why the video differs from the present. Perhaps a bug that was fixed. Just not in this put enough.

1. So its acceptable to go above the 22 during the flare then? I can't see any other way around it to be honest so I hope so lol.

 

2. I find I can only really fly at one speed when at 20-22, and remaining on the glideslope. If I fly faster then I begin to gain altitude. This is why I dont like it, its so restrictive. I prefer to just ignore it until time to flare.

 

3. I was referring to the video that Iron shared. If you look at the HUD in that, you will see the AoA HUD scale is showing about half of the digital number AoA readout. My aircraft is the same as yours, all matching in values, so Im thinking something changed along the ways somewhere, or maybe a bug that was fixed etc.

1. Sure. 22 is just for the minimum approach speed. Since you have to flare, AoA will increase during the flare, but again, 22 is the highest AoA you should fly.

Any higher AoA will lead to buffeting during the approach and most likely result in a tail strike at touchdown.

2. Why? You can fly the approach e.g. at 15 units as well, but the speed will be higher and the pitch attitude lower.

3. Never seen this weird indication discrepancy except in this video.

The Russian approach is to leave the ISF at around 380 km/hr, gradually slowing to around 340 as you cross the outer marker, 310 across the inner marker and 290 across the threshold. That gives you good visibility down to the threshold but with a slowing increasing AoA.

But even with the 'Russian' (or in the West called 'decelerated') approach you need to arrive at the threshold with the correct speed/AoA corresponding with the actual weight.

But even with the 'Russian' (or in the West called 'decelerated') approach you need to arrive at the threshold with the correct speed/AoA corresponding with the actual weight.

Absolutely!

The video is from 2014 and indeed shows an old bug:

https://forums.eagle.ru/showthread.php?p=1982923

The ADI GS deviation bars need western ILS (white ILS details on the DCS map) to work correctly. (thx Ironhand)

22 units of AoA translates to around 13 degrees nose up. Tail strike is at 16.

Again correct F-15 landing in short: gear down, flaps extended, AoA 22 on GS (on-speed), flare before TD to level flight just above ground, throttle idle... TD, airbrake extend, hold 13 degrees nose up as long as you can, slowly put the nose down, full aft stick... wheel brakes as needed (better not).

One problem in landing the DCS F-15 is the missing ground effect which means you need to flare the DCS F-15 to a higher pitch attitude than you need to flare the real F-15.

Another problem is the wrong ILS GS indication when more the 4NM out and the fact that the GS becomes alive way too late.

Even if you are well below the GS the FD issues a full 'fly down' command when more than 4NM out.

If you are below GS, at 4NM (which is way too late) the FD GS bar suddenly becomes alive and flips to a full 'fly up' command.

Just a bit odd the chart has it wrong. If its not correct, then its wrong IMO, 'close enough' doesnt really cut it for me :smilewink: which made me question the validity of the entire chart. Airports in real life operate a 'close enough' policy? That seems odd. I would have thought that type of thing would be extremely important.

It's not at all that important. Real magnetic heading is, but only for IFR and nav calculations. You just have to know the exact runway you're supposed to land on esp. if there are multiple or parallel.

https://en.wikipedia.org/wiki/Runway#Naming

Yeah, pity about ground effect so rare in DCS.

Thanks for all the replies guys.