# Thread: ILS AP hit and miss.

1. Originally Posted by jeroen79
I agree.

And even without approachcharts, proper preparation is key.
Plan the flight and the approach, write down all the relevant data and you won't find any surprises at the end of the flight.

But I suspect that most people who come here asking "how do I land with ILS?" just generate a flightplan with the builtin flightplanner, load up an airliner, fly the flight on autopilot and GPS, follow the vectors that ATC gives them and then run into trouble when they want to land.
Never missed it flying by IFR,. VFR is a different story. So if I want to capture a 3 degree glideslope at 8000 feet I should be 24 nm out?
Last edited by Double J; 06-04-2013 at 10:22 AM.

2. This is a repeat of a reply to the same topic started 5/22/13 so some of the phrasing references responses of others - And, just to add that if you are trying to learn how to shoot an instrument approach in a 737, Airbus, etc - go back to the Cessna 172 or similar non-complex single engine aircraft and start from there (where many RW pilots started their instrument training).

First, think about all the things below before you take off. Get you charts, approach plates (from the questions you ask it seems that you many not be familiar with reading an approach plate - being able to is a necessity for an instrument approach. This is a pretty good tutorial - http://www.youtube.com/watch?v=fElkNeuKoh0), STARs, etc. ready ahead of time. Plan the approach out (at least in your head) - distances, angles, speeds, altitudes, rate of descent ...

Note that for most airports the glide slope is 3.0 - 3.5 degrees - this translates to ~ 325 ft decent per NM - so if you are approaching at ~ 90 knots (e.g., as in a C 172) your descent rate is a bit under 500 fpm. You can do the math from there.

Get the approach plate from http://skyvector.com/airports or http://www.airnav.com/airports/

Tune your Nav1 to the frequency of the ILS - verify the correct frequency by the Morse code (or ID on the HSI if the aircraft has this capability).

Turn your HSI course needle to the actual magnetic heading of the runway (not the closest '10' number that identifies the runway) - If you are using the standard VOR head for the localizer this does not matter and will not make any difference. The advantage of moving the HSI needle to the actual runway heading is that you will have a clear reference of the center line of the runway / center of the localizer and your relative angle to that. The ILS still works regardless of the HSI cursor setting but it can be a bit confusing if not turned to the actual runway magnetic heading. And, if flying the back course, this can be very helpful since you do not need to think 'backwards' as you do on a back course approach using a standard VOR head (but you should still set the cursor to the front course direction).

If the approach has an NDB on it (somewhere along the extended center line of the runway, generally at the outer marker location but sometimes closer in or farther out - does not matter if it is located directly on the approach line, even if it is on the other side of the runway - on the approach to the opposite end) tune your ADF to that frequency.

Plan your course so you will intercept the localizer at least 10 nm out (I usually shoot for 15 - 20 nm depending on what I am flying).

When you start the localizer intercept portion of the approach (generally 30-60 nm out) verify that the autopilot source is on Nav (not GPS). At this point you can hand fly the course or (as others have said they do, and me too) switch the autopilot to 'Heading' mode once you have turned the heading bug to the desired direction (in FSX, if you have the default key setup, you can hit <Ctrl> 'H' and this will move the heading bug to the current heading and turn on the autopilot heading mode all in one key-combination stroke - no need to turn anything or push any buttons).

Hand fly or turn the heading bug to the headings as desired (or as directed by ATC - that is what a 'vectored approach' is - ATC provides vectors - turns you at the right place and right time. If you are descending via a STAR there is usually a point where it wll state 'expect radar vectors to final approach' but ATC may vector you prior to that point). I control the heading bug through a keyboard via FSUIPC (makes heading changes much easier than trying to change the heading bug with the mouse) so I don't generally hand fly the first part but see my comment below about the final turn to intercept the localizer. The final leg of however it is you get to the localizer should be at a ~ 30 degree angle to the localizer and at a point that will allow you to intercept the localizer about 15 nm out.

Plan your descent based on available information (or as per ATC) - the key altitudes on final will be on the approach plate, profile portion. Other references include STARs, the MSA circle on the approach plate and the MSA published on sectionals. ALWAYS intercept the glide slope from below (glide slopes have false signals above the true glide slope).

If you have an NDB available (as discussed above) and ADF tuned to that frequency, watch the ADF needle and, about three degrees (maybe 4 or 5 degrees, depending on what you are flying) before the actual runway magnetic heading (again, the exact heading, not the nearest '10' number - and beware that FSX data is now ~ 10 years old and actual runway headings may vary a couple degrees if you are using the approach plate value so best to get the actual heading from an FSX-based source) start your turn to intercept the localizer. Remember that the localizer needle swing width is 2.5 degrees (0.5 degree per 'dot') left or right of center, so the ADF will give you an idea of when to start turning before (but wait until just before) the localizer needle would start to move once you are within 2.5 degrees of center.

When you are ready to make your turn to intercept the localizer you can hit the 'Approach' (or 'Back Course') button on the autopilot - BUT - depending on the speed / size / type of aircraft the autopilot may not turn you fast enough so you end up overshooting the localizer (the autopilot will bring you back). So, I usually do the intercept turn by hand using the appropriate (but not exceeding max design or passenger comfort) turn rate to help ensure a smooth intercept, then hit the 'Appr' button - actually I rarely use this - what's the fun in that ??? I generally turn off the heading control and hand fly from just before starting the intercept turn and turn off the altitude hold just before I intercept the glide slope.

If you do use autopilot for the approach you will likely need to manage the throttles (or speed control) along with flaps, gears, arming spoilers, etc. although some aircraft do manage approach speed for you. Once you intercept the glide slope (always from below! Your problem with not capturing the glide slope may be due to being too high) the autopilot should switch off the altitude hold (if on) automatically and begin to descend you along the glide slope. You can let "Otto"pilot fly you down to minimums - or just above - but you should disengage at that point and prepare for a go-around. Remember that if you are using auto-throttle you must disengage this separately - it does not disengage when you disengage the autopilot. (Of course, none of this applies if you are flying a LOC only approach since there is no glide slope).

The rest of the landing is in your hands but should be a piece of cake (the secret to a making great landing is making a great approach).

And of course - Practice, practice, practice -

You might find our web pages on IFR route planning and ATC communication basics helpful so feel free to visit -

http://www.ifrjethops.com/ifr-flight-planning

http://www.ifrjethops.com/air-traffic-control-basics

3. In addition to what has already been said, speed is also critical. Even if you are below the GS, if you are too fast, you will fly right through it. Get at or close to approach speed before you intercept the GS. Once you do, then you have a little bit of cleanup to get configured for the landing.

Flying an instrument approach without charts or knowledge of the requirements doesn't work too well.

Vic

4. "ALWAYS intercept the glide slope from below (glide slopes have false signals above the true glide slope)."

That was the issue.. as for hand flying or using the AP, speed control, autothrottle to land I have no issues, it was just having the appr. control turn off the altitude hold.
However I still swear there are many runways with bugs in FSX. Yesterday I was flying into KPHX using AP and APPR. I had the glideslope indicators (red rectangles) lit up at 8000 ft, the 727 was on the slope but the altitude button wouldn't go off. Suddenly the glideslope indicators disappeared and reappeared about 1000 ft lower. As if the plane was somehow magically supposed to drop 1000ft!.

5. You seem to be trying to catch the glideslope from too high. Normally, you should be no more than 2000-2500ft AGL in order to intercept the ILS signal properly. In the case of KPHX ( +/- 1000 ASL), you should be lfying at 3000ft.

GOod luck!

6. Originally Posted by slarente
You seem to be trying to catch the glideslope from too high. Normally, you should be no more than 2000-2500ft AGL in order to intercept the ILS signal properly. In the case of KPHX ( +/- 1000 ASL), you should be lfying at 3000ft.

GOod luck!
If KPHX has a GS of three degrees shouldn't you be able to hit it at 8000 feet if you are 14 miles out?

7. Originally Posted by Double J
However I still swear there are many runways with bugs in FSX.
We have to remember that FSX is the April 2005 world. It is not the current world and it is not easy to update it completely to current standards. Each airport has to be 'fixed' by hand.

Most of the real runway bugs in FSX have been corrected and fixes posted back within a year of release. There were relatively few - less than a dozen.

There are terrain and water class issues. Those occurred when trying to blend all the different sources of various types of information into a single 'world'. Some of my favorite airports are completely unusable due to such issues.

Originally Posted by Double J
Yesterday I was flying into KPHX using AP and APPR. I had the glideslope indicators (red rectangles) lit up at 8000 ft, the 727 was on the slope but the altitude button wouldn't go off. Suddenly the glideslope indicators disappeared and reappeared about 1000 ft lower. As if the plane was somehow magically supposed to drop 1000ft!.
FS has a 'perfect' radio world. At 8,000ft there is no way you should pick up the glideslope indicators for any of the KPHX runways in the real world. You are almost 7,000 ft above the runway elevation.

The visual glideslope is unreliable that far away from the airport. The useful range of the glideslope in FS is 15nm.

From the chart on the previous page - you should not see a reliable visual glideslope box any higher than 6,000 ft ASL at KPHX. Trying to use it too far away from the airport will make it appear buggy. You should be flying straight and level with the visual glideslope above your aircraft and fly into the 'boxes' - then turn to descend down the visual glideslope.

You should active the AP APPR mode no farther out than 7 or 8 NM from the runway.

8. Originally Posted by ReggieF5421

FS has a 'perfect' radio world. At 8,000ft there is no way you should pick up the glideslope indicators for any of the KPHX runways in the real world. You are almost 7,000 ft above the runway elevation.

The visual glideslope is unreliable that far away from the airport. The useful range of the glideslope in FS is 15nm.

From the chart on the previous page - you should not see a reliable visual glideslope box any higher than 6,000 ft ASL at KPHX. Trying to use it too far away from the airport will make it appear buggy. You should be flying straight and level with the visual glideslope above your aircraft and fly into the 'boxes' - then turn to descend down the visual glideslope.

You should active the AP APPR mode no farther out than 7 or 8 NM from the runway.
Thanks, 7 or 8 I'll try it.

It's just that I read people trying to tap into it at about 15 or 20 miles out. ..that's what I've been doing.

9. Originally Posted by Double J
It's just that I read people trying to tap into it at about 15 or 20 miles out. ..that's what I've been doing.
You should aim to intercept the localizer at 15-20 miles out. Try to intercept it at an angle of around 30 degrees and at an altitude of 2000ft AGL (Above Ground Level). Then your plane will follow the localizer, line up with the runway and you'll be nicely below the glideslope path. Activate APP when you have a glideslope indicator. When you are some 8 miles out give or take you'll intercept the glideslope and you should make a nice ILS landing

Harro

10. Originally Posted by Double J
Thanks, 7 or 8 I'll try it.

It's just that I read people trying to tap into it at about 15 or 20 miles out. ..that's what I've been doing.
I don't know if anyone has been clear to you about how an ILS is really constructed.

There is no such thing as an ILS transmitter, in the real world or in Flight Sim.

There are Localizers which provide laterial guidance to aircraft - pilots use these to align their aircraft with the localizer antenna. Not all localizers are aligned with the runway. Look at the setup for PAJN - Juneau Alaska

http://155.178.201.160/d-tpp/1306/01191LDAX8.PDF

- where the localizer aligns the aircraft up on a heading of 068 degrees (M), but the runway heading is 082 degrees (M). The localizer is to keep the arriving aircraft clear of terrain (granite clouds) until the pilot reaches the minimums point. He should then be able to see the runway and execute the 14 degree right turn to line up and land - or go around.

There are separate Glide Path or Glide Slope transmitters - which provide vertical guidance.

When a Localizer has a Glide Slope transmitter paired together - the combination is called an ILS.

Aligning with a localizer can be done 15-20 miles out, but the glide slope signal will usually not be reliable until 7 or 8 miles from the runway.

FS does not offer any way for us to tell if the feather we see in the GPS and the map views is for a Localizer or a paired Localizer / Glide Slope ILS. There are dozens of ILS systems around the world that do not perfectly align the aircraft with the runway, but the Glide Slope will bring the plane down correctly. MKJP - Norman Manley Intl in Kingston Jamaica - is one. The localizer will align the aircraft to end up 500 feet south of the runway unless the pilot takes the plan off AP and turns to the left to align and land. (This offset is suspected as a contribution to the American Airlines B738 overrun/crash a few years ago.)

There are also a few hundred airports like PAJN with Localizers and NO Glide Slope in the real and FS world.

Again, there is no way to tell without a program such as Airport Design Editor to tell if a Localizer is offset or not, if a Glide Slope is present or not.

The general guideline is that if a localizer feather on a map or GPS view appears directly aligned with the runway - it should be a Localizer/Glide Slope ILS combination. If the feather appears offset - don't expect a Glide Slope.

#### Posting Permissions

• You may not post new threads
• You may not post replies
• You may not post attachments
• You may not edit your posts
•