The ILS glideslope bar (on ADI) doesn't concide with HUD glideslope

[Maverick Su-35S]

Hi,

 

For some reason, the ADI's ILS horizontal bar (the bank needle is otherwise correctly matching the real localizer) drifts away from the real glideslope as distance decreases to touchdown.

 

Although the VOR/ILS instrument bars on the ADI work as a flight director (thus it tells you to climb or bank in advance to the movement of the HUD's ball indication) similar to a modern airliner, the error / difference in displacement between the ILS glideslope bar (up-down pitching needle) and HUD ball becomes very great as the distance to the ideal touchdown point decreases. At higher distances the indications are quite close although the ADI needles predict when you should climb or turn. There may be nothing wrong with the error between the ADI's horizontal bar indication and the HUD's ball (in pitch) at higher distances, but as you get closer to the touchdown point, the ADI ILS glideslope bar starts to drift more and more away from the real glidelsope path that is correctly measured by the HUD's indication only.

 

In reality, the flight director bars (which our ADI ILS indicator mimics) may be having a great error from the glideslope and localizer indications if the airplane isn't already aligned with them, but as the distance to touchdown decreases, no matter if the plane is more or less aligned with the glideslope and localizer (as directed from the VOR/ILS facility), the difference or error between the flight director bars and the glideslope & localizer indications will also decrease.

 

Here's a shot proving the high drift between ILS and HUD indication and track of a landing trial:

 

 

VOR-ILS instrument and HUD glideslope indications error.trk

 

If our ADI's ILS bars don't work like flight director's bars, let us know. Otherwise there's no reason for the ADI's glideslope bar to start deviating from the real path during the most crucial landing phase.

 

Regards!

[Wrench]

Second. I've been having a hell of a time trying to carrier land IFR. Seems pretty broken TBH.

[Ironhand]

Hi,

 

For some reason, the ADI's ILS horizontal bar (the bank needle is otherwise correctly matching the real localizer) drifts away from the real glideslope as distance decreases to touchdown...

 

That is probably because the ADI in the Su-33 is just an ADI, not an ADI/ILS combination. If you look at the gauge, there are no glideslope/localizer flags to indicate when you have captured the ILS signals.

[wavn]

Second. I've been having a hell of a time trying to carrier land IFR. Seems pretty broken TBH.

 

Therefore, I use the indications on the HUD and the monitor (also for night landings).

[IvanK]

The ADI and HSI ILS bars work just fine for me in LDG mode

[Ironhand]

The ADI and HSI ILS bars work just fine for me in LDG mode

They do. The OP was saying that the ADI's ILS bars weren't functioning properly.

[Wrench]

Therefore, I use the indications on the HUD and the monitor (also for night landings).

 

How do you use the HUD? The 2-Circle Glide-path indication system makes no sense to me.

The way it seems is counter-indicated by forums posts, videos, and even the training missions, but I swear all of that is wrong.

 

The closest I've been able to figure is that the one should place the larger circle on the center of the Roll and Back Indicator, using the throttle to control descent rate. I can fly right down the glideslope until the ILS on the HSI goes live, and then the rate at which the aircraft moves relative to glide-path seems to increase exponentially, and I can never stay "locked" the glide-path like I can in literally every other airframe I've ever flown.

 

Also, What indications do you use on the monitor?

[feefifofum]

Think of it as a three dimensional picture of the glideslope at two distances; the larger circle being your current position and the smaller circle being farther away.

Put the thing on the thing, and use your AoA indexer on the left side of the HUD and you're golden.

[Wrench]

This is what happens if I "put the thing on the thing"

I know this was far from a perfect demonstration, given my airspeed was high, and AOA low, but what I'm really worried about is how the HUD works, for for the scope of this video it makes no difference.

I couldn't keep the circles perfectly concentric, given as my flight path continued to devolve, it was increasingly difficult to fight my natural urge to do literally anything other than what I was doing. However, it does illustrate the point just fine.

Edited March 2, 2018 by Wrench

[Ironhand]

This is what happens if I "put the thing on the thing"

I know this was far from a perfect demonstration, given my airspeed was high, and AOA low, but what I'm really worried about is how the HUD works, for for the scope of this video it makes no difference.

I couldn't keep the circles perfectly concentric, given as my flight path continued to devolve, it was increasingly difficult to fight my natural urge to do literally anything other than what I was doing. However, it does illustrate the point just fine.

Wrench, it's very simple. Ignore the small circle. Just follow the flight path indicator (the big circle on the HUD). Ideally, as you fly either from point-to-point or follow the glideslope and localizer beams down to touchdown, you simply keep it centered in the aircraft datum. In reality, when there are large changes in either course or altitude, you pull it into the aircraft datum center more gradually. Otherwise you end up chasing it all over the sky as you blow through transitions. But your goal is to always have it centered on the datum as you fly.

 

Keep it centered and it'll bring the small ILS deviation index circle there as well and, then, you'll be where you need to be. As the ILS funnel narrows, if you haven't settled your aircraft on the glidepath, things will start to get squirrelly because slight changes have bigger consequences. So be settled in by the time you reach the 2 km mark and you should have far fewer problems.

 

 

EDIT: Here's an example of what I'm saying. I purposely set it up so that there are a few some significant changes in altitude and direction to reach the AIF. So I'm not in any hurry to center the director circle on the aircraft datum prior to the IAF. But take note how, after passing through the IAF, flying to keep the director circle centered on the aircraft datum maneuvers your aircraft into the correct position on the localizer and glideslope and, then, keeps you there. If it start shifting to the left, you shift to the left to recenter it. It is starts moving up, you move up, etc. The one thing you are not doing, is chasing the ILS deviation circle. The system is designed to have the flight director bring it to you. Your only task is to keep the director circle centered on the datum...except, of course, for minor technicalities like managing airspeed, etc. :)

 

 

Edited March 2, 2018 by Ironhand

[Wrench]

you simply keep it centered in the aircraft datum.

 

That was my understanding, but whenever I watched other (much worse) videos, I kept getting the impression you should align the circles, not the Flight Director with the Aircraft Datum.

 

I think I've been getting PIO as the cone narrows, as you mentioned.

[Ironhand]

That was my understanding, but whenever I watched other (much worse) videos, I kept getting the impression you should align the circles, not the Flight Director with the Aircraft Datum.

 

I think I've been getting PIO as the cone narrows, as you mentioned.

Landing mode is no different than either return or enroute mode. The director circle belongs in the center of the datum--actually centered on the crosshairs in the center of the datum. Anyway, you've got it now, I'm sure. Just stay loose. :)

[wavn]

How do you use the HUD? The 2-Circle Glide-path indication system makes no sense to me.

The way it seems is counter-indicated by forums posts, videos, and even the training missions, but I swear all of that is wrong.

 

The closest I've been able to figure is that the one should place the larger circle on the center of the Roll and Back Indicator, using the throttle to control descent rate. I can fly right down the glideslope until the ILS on the HSI goes live, and then the rate at which the aircraft moves relative to glide-path seems to increase exponentially, and I can never stay "locked" the glide-path like I can in literally every other airframe I've ever flown.

 

Also, What indications do you use on the monitor?

 

As good as Ironhand has explained it, I could not have done it :)

 

I also look reguarly to the advised hight and speed on the HUD and the direction on the monitor (don't know if this is a good habit however).

[Baz000]

There is absolutely nothing about landing the SU-33 on the Admiral Kuznetsov or landing in general... Other than description of the AOA brackets and landing mode HUD.

 

Would really like to see this addressed in the future

[Baz000]

After some testing using 1.5.8 stable release, I think on both the SU-27 and SU-33 the ILS needles, ADI director, and ADI bars as well as the HUD are all showing different glide slopes and directions to the pilot for landing.

 

Shouldn't all those instruments be giving the same guidance to the pilot with the exception of the ILS needles on the HSI as they are more sensitive as far as I am aware?

[Flow]

Some indicate pitch and roll inputs (ADI and HUD), others relative glideslope position (HSI).

[Ironhand]

After some testing using 1.5.8 stable release, I think on both the SU-27 and SU-33 the ILS needles, ADI director, and ADI bars as well as the HUD are all showing different glide slopes and directions to the pilot for landing.

 

Shouldn't all those instruments be giving the same guidance to the pilot with the exception of the ILS needles on the HSI as they are more sensitive as far as I am aware?

Neither the Su-27 nor the Su-33 use an ADI with an integrated ILS (or, at least, neither has the flags on the instrument that would suggest they do). So that instrument's altitude, especially, should not necessarily coincide with what you see on the HUD.

 

The HUD and ILS on the HSI coincide perfectly, once the ILS comes online at a certain distance from the runway (8 km in the case of my landing at Mozdok). (If I understand the system correctly, until that point you are following the RSBN beacon. Once the HSI/ILS comes online, you are following the PRMG beacon.) You will notice that the HUD shifts to the HSI reading at that point as well. There will be a flicker and, often, the director circle and ILS deviation mark shift slightly as the HUD shifts to the HSI/ILS for it's data. From that point on, they are identical down to the ground.

 

Here's a video of my landing at Mozdok this morning. You'll see the shift to the HSI/ILS as it occurs on the HUD at the 8 km mark:

 

 

Edited March 9, 2018 by Ironhand

[Baz000]

Can you do the same on the Kuznetsov? With the SU-33?

 

The SU-33 is a more heavy aircraft than the SU-27, maybe do the same Mozdok landing but use SU-33? Just make sure not the flare prior to touchdown with the SU-33

[Ironhand]

Can you do the same on the Kuznetsov? With the SU-33?

 

The SU-33 is a more heavy aircraft than the SU-27, maybe do the same Mozdok landing but use SU-33? Just make sure not the flare prior to touchdown with the SU-33

I elected to repeat the landing at Mozdok rather than the Kuz. Hope you don't mind. Don't have snapviews set up for the Su-33 either. So I just zoom and scroll with the mouse. But the important parts are there:

 

 

 

 

Still don't understand what the required altitude bar on the left side of the ADI gauge is tied to. I have the video of a track from last November that has it exactly where it should be. But currently, to get the correct indication, you have to alter the value in the K window substantially in directions that don't make sense to me.

[Shadow KT]

Are the landing systems on the airfield and the Kuznetsov the same, meaning ILS ?

 

As on western carriers they use MWS for higher precision ? and ILS is for airfields only ?

 

Just curious.

 

And if they are different, does the Su-33 have both systems ?

[Baz000]

I am wondering if the Kuznetsov glide slope indications are even correct on the ILS needles. Maybe that is the problem? I can land at Mozdok right on the money following the glide slope needle in the SU-33... But the carrier is a whole different ball game.

 

What wire are the Russian pilots trying to aim for? I know for the US Navy its the 3rd wire, is is the same for the Russian Navy?

[Ironhand]

I am wondering if the Kuznetsov glide slope indications are even correct on the ILS needles. Maybe that is the problem? I can land at Mozdok right on the money following the glide slope needle in the SU-33... But the carrier is a whole different ball game.

 

What wire are the Russian pilots trying to aim for? I know for the US Navy its the 3rd wire, is is the same for the Russian Navy?

I believe it's the 2-wire (2nd from the stern). And, you're right. There is something I don't understand going on. Following the HUD cues for a carrier landing, leaves you slightly below and to the right of the slope on the HSI/ILS. Which I can live with. But, then, you seem to suddenly intersect a new, slightly steep glide slope at 1 km out. I don't know if this is a "precision slope" similar to what Shadow was wondering about or a bug or what. But whatever is going on, it is most disconcerting, if you care which wire you actually catch.

[LJQCN101]

I just tried with carrier landings. It seems to me that the ADI bars coincide with the big circle (Flight Director), and the HSI bars coincide with the small circle (ILS).

 

I'm catching 3-wire here, and the ILS shows I'm high at touch down. So could be 2-wire for Russians?

 

Edited March 12, 2018 by LJQCN101

[Ironhand]

I just tried with carrier landings. It seems to me that the ADI bars coincide with the big circle (Flight Director), and the HSI bars coincide with the small circle (ILS).

 

I'm catching 3-wire here, and the ILS shows I'm high at touch down. So could be 2-wire for Russians?

 

...

When I followed the slope down solely on the HSI/ILS this morning, the hook slapped the deck just short of the 2-wire and that's the one I snagged. I was also centered according to the OLS. So I think that's the target.

 

I'm going to have to play with it a bit more but, in using the HSI/ILS to stay fairly well centered on the slope, the HUD indications were not what I would expect in landing at an airfield. So I need to experiment a bit more, when I get the chance.

Edited March 12, 2018 by Ironhand