Sign in to follow this  
Guest lemonadedrinker

ILS approach using the autopilot

Recommended Posts

Hi to all!I am a quite new pilot, and I have a question regarding the use of theAPP option of the autopilot to help me land an aircraft. I am referringto large commercial aircraft (I find these the most fun :)) but I guessit has little to do with my problem. Also, please excuse me if this hasalready been asked, because I have searched the web extensively andcouldn't find anything that could help me.Basically, I am simply not able to get the autopilot follow the ILSsignal correctly. For example, when I try to land the 737 in the Lessonssection of FS2004 (the landing lesson in the Airline Transport Pilotsection), I can clearly see that the localizer is captured, becauseI get a reading. However, when I flip on the autopilot and then turnon the approach (APP) switch the plane makes a sharp turn to the right,even though I'm flying almost straight toward the runway. I haven't hadmuch luck with the glide slope either, but firstly I'm very interestedwhy the AP behaves like it does in that example. Of course, that happensto me in pretty much all flights - even though I'm using the ATC, whichautomatically tunes all of my radios.What am I doing wrong? I would really appreciate any help from moreexperienced simmers.Thanks a lot!

Share this post


Link to post
Share on other sites
Help AVSIM continue to serve you!
Please donate today!

Sounds like you don't have your course selector set to the heading of the runway. Note this is not the Heading selector on the Autopiot. With that set to approach heading you should be able to intercept the ILS properly.

Share this post


Link to post
Share on other sites

<>I'm not a big iron guy but if by "course selector" you mean the equivalent of the course needle on an HSI then that has no bearing on flying a coupled approach. You can have that needle pointed in any direction and the AP will ignore it and rather, will track the electronic beams generated by the ILS.Without seeing exactly the problem you are encountering, all I can say is for you to know that the ILS signals make it appear as though you are flying through a cone with the pointed end toward the end of the runway. Therefore, since the cone gets smaller as you come closer to the runway, the AP will become significantly more sensitive to being "off course" than when you are farther away.Even a few yards off the centerline will generate a full scale deflection of the HSI course needle when you are near the touchdown zone. Therefore, if you have not engaged the APP mode until you are fairly close to the runway, then the AP will, in fact, lurch the airplane back to the EXACT centerline.That is why it is not a good idea to wait too long to engage the APP mode. You should do so no later than the Glideslope Intercept Point....where the Glideslope Indicator begins to move below center.In addition, due to the technology of the ILS system, the AP does not fully CAPTURE the Localizer instantaneously. It needs some time to "crunch the numbers" so to speak in order to figure out where the exact centerline is.Just try to engage APP at Glideslope Intercept and see if that fixes the problem for you. (and always approach the Marker from BELOW the Glideslope...with the glideslope indicator ABOVE center)Regards,Jim

Share this post


Link to post
Share on other sites

Hi,From my limited understanding of these systems:this is my procedure for an ILS approach1.Work out descent distance- you want to be about 3500 ft above the runway and just above flap1 speed about 20 miles from runway. As this is going on you will be in contact with ATC and your radios will be tuned to the relevant frequencies for the ILS approach.The autopilot is on.Once at the correct height and at a reasonable angle to collect the ILS beam I would turn on the approach switch as you won't descend and you will collect the beam gradually and turn onto the approach.I generally lower the wheels, more flaps, and hope for the best from now on.You should see the marker arrowheads for height descend to the midpoint as you collect the glide slope and the plane should start to descend.Remember to slow down!to your landing speed.Autopilot off just above the runway.Andy.ps<<>>ATC won't tune your radios to the ILS I don't think- that is your Nav1 set-up and ATC deals with the Comm side of things.A.

Share this post


Link to post
Share on other sites

Be sure your Nav / GPS switch is in the Nav mode and you've tuned the ILS freq to Nav 1.

Share this post


Link to post
Share on other sites

Hi Jim,On some large aircraft the autopilot uses the "Course" selected to identify what the runway heading is, then uses that in the initial calcs for intercepting the LOC. This is a bit different to the small planes that I fly (and maybe you?) where the OBS selected has not bearing (pun not intended :) ) on the operation of the unit where a LOC is concerned.Bruce.

Share this post


Link to post
Share on other sites

What Daryll said and be careful of this statement that you made:"Of course, that happens to me in pretty much all flights - even though I'm using the ATC, which automatically tunes all of my radios."Only the COM radios are tuned automatically, you must set the ILS frequency manually on the NAV1 radio. R-

Share this post


Link to post
Share on other sites

Thanks a lot to everyone!I'll try your suggestions and see what happens :)I just have two more questions, if you don't mind:1. Some of you said that the ATC doesn't tune the NAV radios, but in that case, how do I know the ILS frequency? And also, I noticed that I'm getting the correct localizer reading in most of my approaches without manually tuning the NAV radio.2. This is slightly unrelated. Whenever I create a direct flight plan (using the GPS, not IFR), I get a guiding line on the GPS to my destination. However, very often, of course, I have to land at some other angle, sometimes in fact I have to land on the runway from the opposite direction to the one I'm coming from (e.g. flying straight north toward the runway, but have to land from the north). My question is, when is the most appropriate time to stray off course and turn to the landing position? Because after the turn I find myself too close to the runway and have to rotate the nose down at extreme angles (even though I've had some successful landings like that :D).Thanks a lot!

Share this post


Link to post
Share on other sites

>>2. This is slightly unrelated. Whenever I create a direct>flight plan> (using the GPS, not IFR), I get a guiding line on the GPS>to my> destination. However, very often, of course, I have to land>at some> other angle, sometimes in fact I have to land on the runway>from> the opposite direction to the one I'm coming from (e.g.>flying> straight north toward the runway, but have to land from the>north).> My question is, when is the most appropriate time to stray>off course> and turn to the landing position? Because after the turn I>find> myself too close to the runway and have to rotate the nose>down at> extreme angles (even though I've had some successful>landings like> that :D).>>Thanks a lot!It sounds like you're not fying the traffic pattern. Flying VFR the tower at a controlled runway will give something like, "Fly left downwind for runway 36" when giving you landing clearance. Pattern altitude is usually 1,000 feet above runway height. You should be at pattern altitude when you enter the traffic pattern. If you are flying IFR/ILS they will usually have you lined up for the approach and at the glideslope intercept altitude. I would suggest doing the lessons on landing and the traffic pattern. Diving for the end of the runway is not recommended.

Share this post


Link to post
Share on other sites

Hi again, <<>>In map view you could locate the airport you want to land at,zoom in to check there is an ILS at that airport (green feathers) and then get the Nav1 frequency for that runway by clicking on the airport and scrolling down to the runway bit.If you fly in crowded areas you may well be picking up the ILS for another airport- there aren't really that many numbers used for the ILS:D).>>>>The GPS takes you right in and you have to sort yourself out for the actual landing! It's great fun to use but doesn't really help you when you need it most- coming in to land.When you are about 25-30 miles from your selected airport it will come up in the ATC window and you can then contact it and get permission to land there. At the same time ATC will direct you to the landing runway. Once you know that you will be able to change course to enter the circuit, or if you prefer to land straight in, to take your plane far enough away so that you can turn to 'capture' the ILS beam. You will need to be at the right height to do this. There are a lot of things to be done before the landing and these will keep you busy;-GPS off and Autopilot(Nav) Approach on. Nav1 tuned to ILS frequency-always allow yourself enough time to capture the beam-right height to catch the beam- right speed-flaps deployed as necessary-wheels down.Andy.

Share this post


Link to post
Share on other sites

The GPS (at least the 500 version of it -- I don't normally use the other one) has a button on the bottom row "PROC". When you select that function, you can then select the runway and procedure you want, and the transition (if any). When the FS9 ATC tells you it is vectoring for ILS to runway X, select your chosen runway and procedure in the response menu and request it. If you have selected a transition point, the ATC will clear you direct to the transition. I find it helpful with the GPS to request the GPS approach (if avail) rather than the ILS approach. That doesn't stop you from using the ILS (though it might not be exactly legal IRL) and using a coupled approach.The GPS also has all the freqs for the airport in it.scott s..

Share this post


Link to post
Share on other sites

In an attempt to summarise all the above info, and make it more simple to follow, here's what will happen, and what to watch for:On approach to your destination, still at Cruise altitude, between 70-100nm out, ATC will contact you and tell you to descend to a given altitude, and to expect vectors to Runway 'X'. you will confirm, and begin your descent. At this point it's a good idea to go to the full-screen map, locate your destination airport, and double-click on it. Scroll down through all the information until you find the entry for your chosen runway; make a note of the quoted ILS frequency. Return to your cockpit view, and enter the ILS frequency you've just noted, into Nav 1 radio. This gets that out of the way early, giving you time to concentrate later on your approach!As you continue your descent, ATC will give further altitudes and hand-offs. ATC will also start to give new headings to follow. Switch back to HDG select and return the NAV/GPS selector switch to NAV. Follow all the new headings, and any further descent instructions from ATC. At this point, ATC are taking you away from the GPS 'direct' course (which just basically takes you to the airport, but not to any specific runway; you have to enter that info into the GPS as you approach, if you choose to fly using ONLY the GPS!), and are lining you up for a 'proper' ILS landing at the correct active runway.It may seem that ATC are taking you miles out of your way, but if you follow your progress on either the map screen, or on the GPS display, you'll see that you are taking a wide path to the correct runway.ATC will normally have you descend to between 2000-3000ft, and give you a heading which will then intercept the ILS beam (green pointy 'feather' on map, or GPS display on your chosen runway) at aprox. 30 degrees. This will of course vary depending upon the airport in question, but I've found that the above is a good average across Europe!Once you cross, or intercept, the path of the beam, you'll see the arrow-head marker on the scale shown on your ADI start to move left/right towards the center of the scale. At this point, engage the APP/LOC mode on your autopilot (dependant on your aircraft). Your aircraft will now lock-on to the ILS beam and will begin to turn to head into the beam. If you also engaged the audio option of the Nav 1 radio, you'll be hearing the morse beeping of the ILS beam too.Whillst your destination airport is clearing you to land, you'll need to be reducing speed, engaging flaps/landing gear, etc. At some point you'll also see the vertical ILS scale (normally shown on the HSI) start to move down. The aircraft is now on the glideslope and will follow it down to the threshold. It's up to you now to monitor the airspeed and ensure that you don't vary too much above or below the marker point on this scale, or you'll land before, or too far down, the runway!I find that a good average speed to hold for most 'heavies' is around the 150-160 knots point.Once ssafely down make sure that all autopilot functions are off, if you haven't already done so, or you'll never get the plane to stop!!Oh boy! This turned out longer than I thought, but, I hope it makes sense and gets the basic proceedure across clearly!Have fun...... :)

Share this post


Link to post
Share on other sites

Hi,<<>>Always interesting to read about the procedures involved and even though the end result- getting the plane on the ground- is always the same, I'm sure each of us create our own unique way of approaching this desired end!!Andy.

Share this post


Link to post
Share on other sites

HII have successfully used the APPR function on FS9 autopilot a lot on most of my heavies but am struggling with this function on the Eric Marciano panel used with the Kirk Ollsen F-16's. Essentially I can capture the localiser but the aircraft fails to adhere to the glideslope.Has anyone any ideas or experience on this?ThanksFerg

Share this post


Link to post
Share on other sites

HII have successfully used the APPR function on FS9 autopilot a lot on most of my heavies but am struggling with this function on the Eric Marciano panel used with the Kirk Ollsen F-16's. Essentially I can capture the localiser but the aircraft fails to adhere to the glideslope.Has anyone any ideas or experience on this?ThanksFerg

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this