ILS gauge question

[PRB]

Perhaps a question for the real pilots out there.

Some planes, such as this beautiful Beechcraft 18 (Milton Shupe's, adapted for FSX by Vladimir Gonchar), have an ILS gauge which requires that the correct ILS heading be dialed in, or it will give your erroneous ILS commands. This airport is a good example. Snohomish County airport (KPAE) has an ILS on runway 16R, the bearing for which is 179 degrees, which is the runway true heading.

But, some ILS gauges don't have a bearing setting. They just receive the ILS signals and place the needles accordingly. So is this a matter of gauge technology? The older gauges were the ones you had to set to the correct heading? If not, what is the point of having a “have to set” gauge? What advantage does it provide?

 

[JamesChams]

Perhaps a question for the real pilots out there. ...

Mr. Paul "PRB",
In the real world, the ILS transmitter (on the field) only broadcasts for a single degree radial (i.e. the magnetic heading of the Runway). So, in a real aircraft, even if you put a bogus degree heading for the course, the needle with line up with the transmitter's broadcasted course of the ILS ONLY. For VOR's, this is NOT the case, you get to chose which radial you want to navigate on to/from.

However, in FS, the Gauges or FS Engine seem to work like they should for a real VOR; i.e. they require you dial things correctly for everything. Some *smarter* dev.'s may have their gauges working correctly to mimic reality, but for the most part they are not accurate with respect to an actual ILS' functionality. Also, with glass technology, like the real G1000, if you load an approach using the GPS PROC function, the entire NAV stack is setup, ID'ed, and all that's left to do is tune your COMM's Radios and select which mode you want from the CDI (eg. NAV1, NAV2 or GPS), which will kick-in correctly when the approach phase of your setdown's commences anyway without you manually changing it.

Does that answer your question(s)?

Hebrews 11:6 "But without faith it is impossible to please Him, for he who comes to God must believe that He is, and that He is a rewarder of those who diligently seek Him."

Thank you very much.
Sincerely,
From,
James F. Chams

 

[PRB]

Well that's very interesting. I didn't know that. Thanks, James!

 

[Ken Stallings]

Perhaps a question for the real pilots out there.

Some planes, such as this beautiful Beechcraft 18 (Milton Shupe's, adapted for FSX by Vladimir Gonchar), have an ILS gauge which requires that the correct ILS heading be dialed in, or it will give your erroneous ILS commands. This airport is a good example. Snohomish County airport (KPAE) has an ILS on runway 16R, the bearing for which is 179 degrees, which is the runway true heading.

But, some ILS gauges don't have a bearing setting. They just receive the ILS signals and place the needles accordingly. So is this a matter of gauge technology? The older gauges were the ones you had to set to the correct heading? If not, what is the point of having a “have to set” gauge? What advantage does it provide?

Actually, the ILS needs two things, the NAV/COM radio and the course indicator (either a CDI or an HSI). A CDI is the more common instrument that shows how far off course (the localizer) and how far off glideslope you are when flying an ILS. The HSI is a more advanced instrument.

In reality, for an ILS you do not need to actually dial in the desired course. The ILS localizer course reports right and left deviations equally well regardless of what course is dialed in. For the CDI, it makes little difference other than not seeing the desired course at the top of the instrument circle. For an HSI it is a bit more distracting as your yellow desired course bar will not be oriented straight up and down unless you set the final approach course in the instrument.

So, when you fly either an ILS or a LOC approach (LOC = localizer) you do not have to set the final approach course in the CDI or HSI instrument.

It is totally different when flying a VOR approach, or when navigating off a VOR enroute. In navigation and approaches flown off a VOR, you must set the course in the CDI and HSI in order to ensure you are flying the correct radial to or from the station. In fact, pilot have killed themselves by making a simple mistake forgetting to set the proper VOR final approach course or route course and mistakenly flew the wrong course into terrain.

For a VOR and LOC approach, all you get is the course deviation (the course bar) showing you either right, left, or on course. You have to reference a distance to make your descents. On an ILS or a WAAS augmented GPS approach, you get both a course indicator bar and a glideslope indicator. The glideslope indicator shows how far above or below altitude you are. A VOR or LOC approach is termed a non-precision approach. A glideslope enabled ILS approach or a WAAS enabled GPS approach with LPV accuracy are called precision approaches because they provide constant course and elevation references.

The COM/NAV radio is also required because you have to set the required station frequency for a localizer, ILS, or VOR station. Then you use the NAV listen button on your audio panel to listen for the proper Morse code identifier for the station to ensure it is operational. If a navaid is being serviced, then the FAA requires the repair team to take the Morse signal offline so a pilot cannot hear it. So, if you tune a station in the COM/NAV radio and do not hear the Morse code signal (dots and dashes) you are to consider the navaid unreliable and avoid using it.

Cheers,

Ken

 

[PRB]

Well, it seems I've been confused. Not the first time! After reading the posts in this thread, I went up and tried it again, with the Beech 18, and with the default Cessna 208. As you can see, in both cases, the “fly to” heading selector is way off the runway heading (and the published ILS heading), but still I'm getting correct course deviation indications. In the case of the Cessna, the yellow line is referenced to the selected course, but it's still providing correct data, so it's isn't working like the VOR stations, like I thought. I could have swore I have some airplanes in the FS hanger that do behave this way, and James's answer seems to confirm that, but now I can't find any!

But this leads to another question. See the pick that shows the ILS freq and bearing for runway 16R at KPAE? It says the bearing is 179.14 degrees, with is 20 degrees off the runway heading. I always thought this info is required because you had to dial that value into your ILS gauge, but you don't. So what's that 20 degree offset all about?

 

[Ken Stallings]

I did an inadequate job of trying to explain this my first attempt. Let me try again.

The systems in your pictures above are both functioning exactly as they are supposed to and do in reality.

You have to understand there are four basic types of instrument approaches. VOR, LOC, ILS, and GPS. I will try to explain how each work.

1. VOR: This is an omnidirection transmitter that is capable of providing navigation signals on all 360 degrees of possible approach to and from the station. This is why it can be used for both enroute navigation as well as for an instrument approach. For an instrument approach, you normally see the VOR navaid closest to the runway chosen to contruct an approach, but sometimes you have to use the one a bit further away but oriented closer to runway orientation (meaning you can use it to head to the approach end of the runway or a radial that is reasonably close to runway orientation).

It is a non-precision approach that only can provide only course guidance, which in the case of a VOR is done by dialing in the closest radial setting to match runway orientation. However, among the many factors that make VOR approaches the least accurate of them all, is that fact often the runway is located and oriented in a way that cannot precisely match even the closest available radial. So, you sometimes see a VOR approach where the desired radial is up to four degrees off the runway orientation. So, you come in at an angle and need to reorient your aircraft when you break out of the clouds and see the runway. If you fail to set the proper radial as depicted on the approach plate (sheet of paper) for the given approach, you will be trying to center up on a totally inaccurate courseline. Remember, on a VOR approach, the course you center up is for the radial you dial in on your CDI or HSI.

2. LOC: For a localizer approach you are not using a VOR station. Instead, you are using a station located in close proximity to the given runway. This station is not like a VOR since it does not provide omnidirection beacon signals, the station is pre-set with just one course setting. In other words it transmits its course bearing on just one line of radial, and therefore you can orient yourself either toward that radial or away from it. If you use the reverse radial, then you are flying what is called a "back course localizer."

This is why you can spin the CDI's compass rose (the circular band of headings) or the HSI's course line (the yellow line) to any heading you care and it doesn't make any difference to the accuracy of the course deviation indicator. As in your example pictures above, you have the HSI course line clearly oriented about 30 degrees off the runway orientation, but since you are actually on a straight line orientation from the runway heading, your course deviation bar shows you pegged on extended runway centerline.

3. ILS: Instrument Landing System: This is similar to a localizer (LOC) approach except it features an additional glideslope indication. So, not only does it reference a fixed course radial, it also is tailored with a fixed glideslope beacon, essentially a signal oriented from the normal runway touchdown location on about a three degree azimuth above level ground.

Again, the course line on the HSI and the compass rose on the CDI can be set to any value possible and it doesn't make any difference because the associated fixed degree radial of the ILS is set for the runway orientation. The glideslope is also fixed.

For all three of these approaches, the dots related to a known deviation in course and glideslope (in the case of the ILS only). So, when you are a dot off to the right, it doesn't mean you are a certain distance off ideal alignment to the right, it means you are a certain number of degrees in error.

4. GPS: Global Positioning System: In this case, your aircraft's GPS location is mathematically computed relative to the ideal location for the given GPS approach. Further, with Wide Area Augmentation System (WAAS) your GPS approach uses an additional ground station to suppliment and rate the accuracy of your raw GPS satellite position interrogation. With WAAS, you now have the ability to rate the vertical deviation accurately enough so that the GPS approach can add a glideslope input to your instrument approach. Of course, this can only be safely done if the WAAS and GPS signals are sufficiently strong and clean enough.

Here is a link to discuss more details:

http://en.wikipedia.org/wiki/Wide_Area_Augmentation_System

So, when these required qualities are met, your GPS receiver indicates Localizer Performance with Vertical Guidance (LPV), which is the highest quality of signal strength allows you to accurately fly a localizer and glideslope referenced instrument approach. Just like with the LOC and ILS approaches, it doesn't really matter what course you dial into your CDI or HSI if you are using an advanced GPS Steering computer. I have an STEC System 30 autopilot on my Skyhawk that is this way. So, for a GPS approach to runway 31 (310) I could if I wanted to dial in 270 into my CDI and the autopilot will still fly the course just as accurately as she pleases.

Ironically, my 310R has an older Cessna 400 autopilot and it is tied directly into my Bendix King HSI and so I do have to dial in the desired courseline for the autopilot to work properly when flying GPS inputs, either for an approach or for enroute navigation.

However, if I manually fly the approach, which I do as habit, it doesn't matter what course I dial in to my HSI. The course deviation bar shows how far left or right or course I am and that course reference will be extended runway centerline.

OK, so to review ...

VOR approach, you have to dial in the proper course into your CDI or HSI or else your approach will be off course of the runway, and in the real world is life threatening.

For a LOC, ILS, or GPS approach it doesn't matter what course you dial into your CDI or HSI, the course deviation bar will remain fully accurate. You'll simply have to look at a course line that isn't pointed up and down on your HSI. And on a CDI, you won't notice anything abnormal at all.

Hope that helps to explain it.

Cheers,

Ken

 

[Ken Stallings]

No matter how long winded you are, there is always more to say! LOL!!!

In your middle of three pictures, I seriously doubt FSX got it right. I have never seen an ILS approach where the runway orientation was that different from the so-called bearing set into the station. Frankly, I think FSX screwed it up!

Ken

 

[PRB]

Thanks Ken! I always thought the localizer only existed as part of an ILS system, and not as a separate stand alone nav aid. Interesting.

 

[Lionheart]

From what I have gathered, with Glass panel systems such as the Garmin G900 and G1000, they have a combined Glide Slope and Localizer built into their panel system.

Also, its well known that many airports in FS9 and FSX have mis-aligned ILS coordinates on a few airports.

:d


Bill

 

[azflyboy]

From what I have gathered, with Glass panel systems such as the Garmin G900 and G1000, they have a combined Glide Slope and Localizer built into their panel system.



Bill

Pretty much every glass cockpit system puts the localizer and glideslope indicators onto the Primary Flight display, since the entire point of a glass panel is to move instruments into a location that's easier to read for the flight crew.

Normally, the localizer is simply displayed on the HSI, but when there's any kind of vertical guidance (either ILS or GPS) signal present, the system adds an indicator for vertical guidance as well.

Some glass cockpit systems (as well as high-end six pack airplanes) can use what's known as a flight director, which is a set of markings that appears on the attitude indicator. When coupled to an ILS receiver, the flight director moves to indicate exactly what pitch and roll movements the pilot needs to make to remain on course, which makes ILS approaches amazingly easy.

 

[expat]

This is fascinating and informative. Have done some work IRL in a Avidyne/S-tec glass cockpit equipped Warrior. Lined up on final using a GPS approach - at this stage using the backup Garmin 530. After that my instructor disengaged it all to let me handfly the nicely set up longish approach into KVRB (Vero Beach FL), where they do not have (by choice) ILS.

As I have only about 16 hours in real life, only some of which is IFR, most of my experimentation and learning about this subject is in FS. In FS its fun to use the default 530 to program an ILS approach hooked to the autopilot. Almost all the time - once you get the ILS freq entered correctly into the Nav1 channel and get the morse bleeps - it will engage the runway localizer beam, but I find grabbing the glide slope to be a hit or miss affair.

I have read and practiced getting the right alt, speed, set up, right point to press the APP button etc and find the GS works well a certain airports but often not at others. You are entitled to think it still may be the virtual pilot that is the problem! Actually, I think that may be partly right as I have pitch trim set on a rotary on a Saitek x-45 and too often I realize too late that it is out of the detent and not "neutral" when hitting the APP button which can screw up your chances of grabbing the GS in AP and letting the AP fly you down nicely to 500' above the threshhold.

Sorry to be so long winded! My question is whether you can do an GPS approach using the default G530 in FS that will give you both a GS beam to follow as well as the localiser? I see using the default 530 that some airports when you press PROG give you ILS and GPS (and other) approach options. Will selecting "GPS" give you just a localizer or will it also give you a glide slope to hook the AP to? Or do you need e.g. Reality XP with WAAS or one of the Garmin G1000 units to do that?

Thanks

expat

 

[Snave]

This is fascinating and informative. Have done some work IRL in a Avidyne/S-tec glass cockpit equipped Warrior. Lined up on final using a GPS approach - at this stage using the backup Garmin 530. After that my instructor disengaged it all to let me handfly the nicely set up longish approach into KVRB (Vero Beach FL), where they do not have (by choice) ILS.

As I have only about 16 hours in real life, only some of which is IFR, most of my experimentation and learning about this subject is in FS. In FS its fun to use the default 530 to program an ILS approach hooked to the autopilot. Almost all the time - once you get the ILS freq entered correctly into the Nav1 channel and get the morse bleeps - it will engage the runway localizer beam, but I find grabbing the glide slope to be a hit or miss affair.

I have read and practiced getting the right alt, speed, set up, right point to press the APP button etc and find the GS works well a certain airports but often not at others. You are entitled to think it still may be the virtual pilot that is the problem! Actually, I think that may be partly right as I have pitch trim set on a rotary on a Saitek x-45 and too often I realize too late that it is out of the detent and not "neutral" when hitting the APP button which can screw up your chances of grabbing the GS in AP and letting the AP fly you down nicely to 500' above the threshhold.

Sorry to be so long winded! My question is whether you can do an GPS approach using the default G530 in FS that will give you both a GS beam to follow as well as the localiser? I see using the default 530 that some airports when you press PROG give you ILS and GPS (and other) approach options. Will selecting "GPS" give you just a localizer or will it also give you a glide slope to hook the AP to? Or do you need e.g. Reality XP with WAAS or one of the Garmin G1000 units to do that?

Thanks

expat

There is no Precision Approach feature in any default GPS representation in FS. So localizer only, I'm afraid. In fact it only came in the aftermarket quite recently, you'd need the Reality XP WAAS Gps addon, as you said.

There may be others, but I'm not aware of them!

 

[Brett_Henderson]

A quick check at AirNav shows that 16R at KPAE has a magnetic bearing of 159, and a true bearing of 179.

We know that runways, VORs, and ILS are all referencing magnetic.. so the only FSX error here, is listing the ILS as 179.. and it's a meaningless error, because the FSX (and FSX ILS/LOC gauges) all function realistically.. as in, once you've tuned an ILS/LOC, the OBS(course) function is rendered useless to the CDI. Now of course, it doesn't hurt to have the inbound course dialed in. With ILS capable VOR gauge, at least it's a reference.. and with an HSI it's best to fly an ILS with that big, yellow CDI in proper orientaion

I've yet to find a third-party ILS that doesn't function realistically .. as in none of them require an ILS/LOC course to be dialed in..
(pssst.. Ken.. you left out NDB approaches )

 

[jetstreamsky]

You can play around with this simulator to see the effect of various conditions http://www.luizmonteiro.com/Learning_VOR_Sim.aspx

 

[srgalahad]

As I have only about 16 hours in real life, only some of which is IFR, most of my experimentation and learning about this subject is in FS. In FS its fun to use the default 530 to program an ILS approach hooked to the autopilot. Almost all the time - once you get the ILS freq entered correctly into the Nav1 channel and get the morse bleeps - it will engage the runway localizer beam, but I find grabbing the glide slope to be a hit or miss affair.

I have read and practiced getting the right alt, speed, set up, right point to press the APP button etc and find the GS works well a certain airports but often not at others. You are entitled to think it still may be the virtual pilot that is the problem! Actually, I think that may be partly right as I have pitch trim set on a rotary on a Saitek x-45 and too often I realize too late that it is out of the detent and not "neutral" when hitting the APP button which can screw up your chances of grabbing the GS in AP and letting the AP fly you down nicely to 500' above the threshhold.

Sorry to be so long winded! My question is whether you can do an GPS approach using the default G530 in FS that will give you both a GS beam to follow as well as the localiser? I see using the default 530 that some airports when you press PROG give you ILS and GPS (and other) approach options. Will selecting "GPS" give you just a localizer or will it also give you a glide slope to hook the AP to? Or do you need e.g. Reality XP with WAAS or one of the Garmin G1000 units to do that?

Last thing first... the GPS approach isn't giving you a "localizer" it is giving 'lateral track guidance' based on the GPS displaying/providing a track programmed into the database. ( gotta watch the technical terms). As was said, the vertical component requires WAAS enabled AND a vertical component to be approved ( each approach must be checked and certified), published and included in the GPS database.

As for intercepting the GS on an ILS approach, altitude is critical. IRL it is difficult and in FS almost impossible to capture from above. Therefore, you need to be stablized at a decent (30* - 40*) intercept angle and (near) level at an altitude that allows flying into the GS from 'below'. The basic formula is 3000 ft AGL for each 10nm from the runway (most ILS glideslopes are 3*).

I like to use the autopilot to teach people the idea and perception for the first couple of approaches, but then it should be learned to be flown 'by hand'. That way, should the autopilot fail, you are able to continue manually without much confusion - and can fly one in an a/c without a coupled autopilot.

Brett_Henderson
A quick check at AirNav shows that 16R at KPAE has a magnetic bearing of 159, and a true bearing of 179.

We know that runways, VORs, and ILS are all referencing magnetic.. so the only FSX error here, is listing the ILS as 179.. and it's a meaningless error, because the FSX (and FSX ILS/LOC gauges) all function realistically.. as in, once you've tuned an ILS/LOC, the OBS(course) function is rendered useless to the CDI.

Looking at Paul's middle(data) screenshot it looks like a view of Super Flight Planner. Entirely possible that the author wrote the database to pick up the True Bearing but this is data for the FP software only and is therefore not an "FSX error". A quick check of a couple of other airports should confirm that.

Rob

 

[PRB]

... Looking at Paul's middle(data) screenshot it looks like a view of Super Flight Planner. Entirely possible that the author wrote the database to pick up the True Bearing but this is data for the FP software only and is therefore not an "FSX error". A quick check of a couple of other airports should confirm that. ...

It is Super Flight Planner, and the database for that application is created using the FS database, so the data comes from FS.

 

[fliger747]

The 737-200/400 and 747-200 required you to dial in the localizer course if you wanted to actually fly the intended approach. The 747-400 auto tunes the approach and sets the localizer.

I have flown RNAV (more or less) precision approaches into Chicago for instance and the comparison to ILS is interesting as it is somewhat easier to fly at the bottom as the sensitivity does not increase to an almost unuseable degree.

The data base for FSX is somewhat out of date as some of the actual runway headings and ILS designators changed just a b it before the introduction of FSX. An example is PANC where 6 L & R became 7 L & R and PAFA where 01-18 became 2-20, somewhat to everyone's confusion.

Cheers: T

 

[Brett_Henderson]

As for intercepting the GS on an ILS approach, altitude is critical. IRL it is difficult and in FS almost impossible to capture from above. Therefore, you need to be stablized at a decent (30* - 40*) intercept angle and (near) level at an altitude that allows flying into the GS from 'below'. The basic formula is 3000 ft AGL for each 10nm from the runway (most ILS glideslopes are 3*).

This opens the door for discussion about how realistically you're simming.. The 3000/10 rule is good for visualizing it when you're still way out.. but in the real-world you'd be vectored to an altitude/intercecpt.. and even if you're "cleared for the approach" well out (i.e. ATC will either lose you as you descend, or you've asked to be allowed to fly the whole approach on your own, while practicing in VFR conditions), you've got the approach plate on your knee, and know to get to the proper altitude before you reach the IAF.

In other words.. there isn't a realistic scenario that would have you above the GS by the time you're flying the approach.

 

[expat]

As for intercepting the GS on an ILS approach, altitude is critical. IRL it is difficult and in FS almost impossible to capture from above. Therefore, you need to be stablized at a decent (30* - 40*) intercept angle and (near) level at an altitude that allows flying into the GS from 'below'. The basic formula is 3000 ft AGL for each 10nm from the runway (most ILS glideslopes are 3*).

Very grateful to all of you for your wisdom and guidance here.

Re ILS altittude, I have found as a rough guide that being around 2,500' - actually 2,300-2,400' may be even better - at the time when you see your a/c icon enter the green ILS beam symbol on the Garmin map is about right. Is this correct? Also, is this when you should press APPROACH button or should that be earlier or later?

Re intercept angle, I have always understood this to mean you should not fly straight at the LOC/GS beam - i.e. which would be roughly in line with the runway and a lined up, straight in VFR approach, but at a significant (and horizontal) angle to that line, i.e. a 30-40 degree angle, apparently to capture the GS more effectively. However, in practice I find with many aircraft that after LOC capture (and hopefully GS too) the plane then will yaw/meander/windvane on and off the localiser and often will not strighten/settle (particularly a heavy) in time to do a stable AP/ILS landing.

 

[Brett_Henderson]

Very grateful to all of you for your wisdom and guidance here.

Re ILS altittude, I have found as a rough guide that being around 2,500' - actually 2,300-2,400' may be even better - at the time when you see your a/c icon enter the green ILS beam symbol on the Garmin map is about right. Is this correct? Also, is this when you should press APPROACH button or should that be earlier or later?

Re intercept angle, I have always understood this to mean you should not fly straight at the LOC/GS beam - i.e. which would be roughly in line with the runway and a lined up, straight in VFR approach, but at a significant (and horizontal) angle to that line, i.e. a 30-40 degree angle, apparently to capture the GS more effectively. However, in practice I find with many aircraft that after LOC capture (and hopefully GS too) the plane then will yaw/meander/windvane on and off the localiser and often will not strighten/settle (particularly a heavy) in time to do a stable AP/ILS landing.

This gets further into how realistically you're simming. Using the GPS (while learning), is counter-productive. This is the time when you need to be reinforcing subconsious instincts, and situation awareness.. not looking at a moving map. An ILS reciever, and an additional reference like a VOR or NDB (ideally an NDB at the outer-marker), and an approach plate are all you need. The plate has fixes and corresponding altitudes.. And no autopilot allowed either ...

... Make the turn to final yourself.. and then finish up configuring (flaps, gear, airspeed), while working the needles. It's best to have a full visualization and understang all the nuances involved in an approach, before turning it over to an autopilot and end up being a spectator