Autopilot approach without ILS in B 737?

  • To make an automated landing real world aircraft need an ILS or MLS (never got to replace ILS) or a ground based GPS calibration (still in development and testing) or some military devices I am not familiar with.

    We could easily program any aircraft to autoland with its autopilot but that would not be realistic.

    So you have to land manually like in the real world. But you can also fly an approach (get real close to the ground above the threshold) on autopilot without an ILS at an airport a so called RNAV approach.

  • Thank you for replay.

    I agree that if the real plane i unable to land automatically, it should be impossible in the simulation too. But I am curious if the variant of B 737 recreated in FS 2 (in real life and in the sim) is able to make some type of partly automatic approach (with manual landing in the final part) like B 747, Airbus or Learjet using FMS. Or maybe it is possible to land manually but with ability to use Flight Director to show correct approatch patch, or real pilots in this type of plane are landing fully manually without an help without any instructions from on-board systems?

  • In all of the aircraft in Aerofly that have the advanced autopilot you can fly an approach on ILS or using the FMS and you can fly down to about 50ft above the runway before the autopilot disconnects when it is not able to do an automatic landing. A fully automatic landing is only possible with the A320 and B747, I think some user pointed out that the 737 is not autoland certified and I think I removed it, not sure if that is already changed in the public version. 737 should not be able to do an autoland as far as I know.


    When you disconnect the autopilot to fly manually you still have the flight directors that guide you on the approach path. Real pilots set a decision height at which at the latest they have to see the runway, then they disconnect the autopilot and land manually. Only in very bad weather and only in ILS category 3 certified aircraft (not in LJ45, Q400, 737, C90) would the autopilot do a fully automated landing of a real aircraft. One criteria is the runway visibility, if you can't see the runway when the wheels already touched down, then the landing should better have been performed by autopilot. Autoland is not used on a day to day basis, if the weather allows the pilots to see the runway they usually disconnect the autopilot and land manually.

  • If you set a route, it does display the Green rectangles all the way down final, if you are wanting something like that. If you want to land manually and are using external controllers, you may be able to set up things like To/GA buttons and Autothrottle and Autopilot disconnect buttons...


    The VR version has some restrictions as some of those options are not available.


    I think it is agreed the plane will Autoland with an ILS approach. right now.

  • So if I understand correctly (my English is not very good) it should be possible (both in the sim and in reality) to use FMS and autopilot during the first phase of landing approach in B 737, but the last part of landing must be done manually in similar way that I am doing that when flying Learjet or Bombardier. Am I correct? If yes, what is the right procedure? I can land fully manually or using autopilot when landing on airfield equipped in ILS, but when I am trying to use FMS to aprroach to an airfield without ILS plane does not descend at all after pushing APP button and turning the second autopilot on. Am I doing something wrong?

  • Yes, you understood that correctly.


    The autopilot only descends when it captures the glide slope. In the 737 you need to manually tune the ils frequency and course, which happens automatically in the A320 and also the B747. When the ILS receiver is receiving a signal you should see the glide slope indicator going from a red "G/S" flag on the attitude indicator to a green/blue pointer (if I remember the coloring correctly :D ). That glide slope needle needs to be above the center before you arm the glideslope, then you can maintain the altitude and when the needle comes down the autopilot will follow it and starts descending. When you see the needle below the center the autopilot won't descent on its own but you can press the vertical speed button and select a high rate of decent (e.g. 1000 to 1500ft/min) which should be sufficient to descent fast enough to capture the glide slope from above. But even if there is no glide slope you can do that and the autopilot will fly you into the ground if you're not careful. So the recommended procedure here is: tune the ILS, select and intercept heading, press the approach button, capture the localizer first (without the localizer captured the glide slope capture wont be possible), make sure you have a good glide slope indication (should be above you), maintain the altitude and wait for the needle to move to the center, the autopilot should descent then and you should see a green glide slope light go on above and to the right of the attitude indicator.

  • Yes, you understood that correctly.


    The autopilot only descends when it captures the glide slope. In the 737 you need to manually tune the ils frequency and course, which happens automatically in the A320 and also the B747. When the ILS receiver is receiving a signal you should see the glide slope indicator going from a red "G/S" flag on the attitude indicator to a green/blue pointer (if I remember the coloring correctly :D ). That glide slope needle needs to be above the center before you arm the glideslope, then you can maintain the altitude and when the needle comes down the autopilot will follow it and starts descending. When you see the needle below the center the autopilot won't descent on its own but you can press the vertical speed button and select a high rate of decent (e.g. 1000 to 1500ft/min) which should be sufficient to descent fast enough to capture the glide slope from above. But even if there is no glide slope you can do that and the autopilot will fly you into the ground if you're not careful. So the recommended procedure here is: tune the ILS, select and intercept heading, press the approach button, capture the localizer first (without the localizer captured the glide slope capture wont be possible), make sure you have a good glide slope indication (should be above you), maintain the altitude and wait for the needle to move to the center, the autopilot should descent then and you should see a green glide slope light go on above and to the right of the attitude indicator.

    Thank you for answer. When ILS is present on airfield I am landing exactly the way you described and all works correct, but I am curious if something similar is possible during landing on airfields without ILS, using only FMS (like for instance in Learjet) or in this case only manual landing is possible.

  • Thank you for answer. When ILS is present on airfield I am landing exactly the way you described and all works correct, but I am curious if something similar is possible during landing on airfields without ILS, using only FMS (like for instance in Learjet) or in this case only manual landing is possible.

    Two things we're talking about here: flying an approach to a runway and actually landing on it. For me the approach ends at roughly 50ft above the runway, so the landing itself is pretty much just the flare, touchdown, rollout and vacating.

    The landing has to be made manual for pretty much all aircraft, except when they are certified for an autoland, which the A320 and B747 are.


    So to answer your questions: you can currently approach any runway from any direction in any of the Aerofly aircraft that have the advanced autopilot (e.g. not the C172 or Baron at the moment) using the FMS approach. In the Learjet in particular the navigation source has to be set to the FMS, then just press the approach button and it should intercept the computed descent path just like it would intercept a glideslope. For this to work you only need set up a simple route with the desired destination runway.

  • Two things we're talking about here: flying an approach to a runway and actually landing on it. For me the approach ends at roughly 50ft above the runway, so the landing itself is pretty much just the flare, touchdown, rollout and vacating.

    The landing has to be made manual for pretty much all aircraft, except when they are certified for an autoland, which the A320 and B747 are.


    So to answer your questions: you can currently approach any runway from any direction in any of the Aerofly aircraft that have the advanced autopilot (e.g. not the C172 or Baron at the moment) using the FMS approach. In the Learjet in particular the navigation source has to be set to the FMS, then just press the approach button and it should intercept the computed descent path just like it would intercept a glideslope. For this to work you only need set up a simple route with the desired destination runway.

    That's what I thought and this procedure works perfectly in Learjet or Bombardier, but in case of B 737 it does not seem to work. After pushing APP buton and turning the second autopilot, plane still continues level flight. The white mark on the side of artificial horizon, which should show glide slope does not move at all.

  • You can't turn the second autopilot on with the 737, when you do it should disconnect the first one.


    It looks like you can engage the second autopilot if on an approach. I had mine set up with both radios on the same ILS frequency and course dialed in but I don't know if that is mandatory... The airplane should be able to complete an approach with one autopilot so it should capture the G/S if only one were engaged. And it does if that airport has a G/S on that ILS.


    I haven't done any VNAV approaches.


    The newer airplanes are confusing me.

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    Edited once, last by Saltgrass: NEW INFO ().

  • I just did an RNAV approach and it seemed to work pretty well. I set the altitude to the MDA or around 500 Ft. AGL and let the and let the system fly it down. It stayed in the Green rectangles better than I would have expected it to. The airspeeds reduced with flap movement so the first time I touched the airplane was just before minimums.


    I could not turn on both autopilots in that mode....... I did not hit the approach button because that is for the ILS.. The ILS/Course switch stays in Course and is not switched to ILS.


    I am still trying to get worked out, in VR, how to hit a TO/GA button to engage the FMS. In the A320, just pushing the throttles all the way up seems to do that automatically.

  • 737-500s were a cheaper option offered to fit in well with -200 operators. They might not have had autoland autopilots fitted but the 737 does have autoland capability. The central standby instruments provide the independent third channel of flight data for the autoland autopilot even though the crew only activate the two autopilots selectors and flight directors.

  • The approach button is generally used for both types of approaches: ILS or "FMS", pretty much regardless of the aircraft. From what I've seen or read the second or third autopilot is only used for ILS approaches.


    Some aircraft have the option to manually chose the navigation source, e.g. the Q400, LJ45 and C90. In those aircraft your manual selection of the navigation source dictates weather you fly the ILS (ils tuned and NAV selected as navigation source), or the FMS computed approach (route planned with landing on destination runway, navigation source FMS selected). In the B737, B747 and A320 this manual navigation source selection is not available, they manage the selection for you. If you program the FMS to fly an ILS approach they will indeed arm an ILS approach when you press the APPR button and then you can engage a second or third autopilot. But if no destination runway ILS frequency is available we currently just select the FMS approach for you, so that you can at least fly down to minimums on all runways, even though this might not even be possible in the real world.


    Right now you can't manually select the approach you want to fly in the A320, B747 or B737, you just have one choice to make: the runway you select at an airport. If the runway happens to have an ILS, ILS is selected for you and autoland is available, if it doesn't then a FMS approach is still available. In the future you might be able to select from a variety of different approaches to a specific runway.

  • Thank you for informations. After some tests I have found that automatic approach (with manual only final part) is really possible in B 737 even without ILS (with only first autopilot active) but GS seems to be much more shallow than in ILS approach, so I have to begin on lower altitude. It looks like I was earlier approaching on too high altitude and autopilot was unable to intercept GS.