Localiser Tracking
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In 2024, whenever I fly an ILS approach, I noticed that no matter the Localiser intercept angle or speed I fly, the plane makes the turn to final and captures the localiser but kinda flies at a shallow angle, almost parallel and never getting centred on the localiser until only a couple miles from the runway. Is anyone else seeing this and if it's an issue is it possible to tighten up the localiser tracking a bit?
@Sunake said in Localiser Tracking:
In 2024, whenever I fly an ILS approach, I noticed that no matter the Localiser intercept angle or speed I fly, the plane makes the turn to final and captures the localiser but kinda flies at a shallow angle, almost parallel and never getting centred on the localiser until only a couple miles from the runway. Is anyone else seeing this and if it's an issue is it possible to tighten up the localiser tracking a bit?
Yelp, can confirm that.
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Here is the response I gave a beta tester about this behavior:
"You led me down a path of discovery, which is always appreciated. I saw the same behavior in some default aircraft, and not others. As it turns out, the native autopilot uses a fundamentally different control loop for intercepting a localizer signal (auto detected) than a VOR or FMS course. It will make a 40 degree intercept angle for a VOR, but it makes an asymptotic intercept for a LOC. So, the aircraft wasn't really turning towards the threshold, it was just making an increasingly shallow intercept angle. The reason we don't see this in all aircraft is because the ones with Working Title GPS units have their own, more advanced autopilot. I've actually seen the code that generates these intercept angles in their library, which is what made me realize what was going on. Unfortunately, I don't think there is anything I can do about this without writing my own autopilot, which is something I promised myself I would not undertake... yet."
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I flew an ILS earlier today and I basically shoved the airplane towards the ILS path while on autopilot until it was on it…
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TIP: Ensure you know the exact Final Apch Crs from the ILS approach chart and set your VOR1 needled precisely to it so that it does track the right heading to the threshold. What Nick said, it is retro tech and yes it does act a lot like a police dog following the scent from the pair of gloves.
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Here is the response I gave a beta tester about this behavior:
"You led me down a path of discovery, which is always appreciated. I saw the same behavior in some default aircraft, and not others. As it turns out, the native autopilot uses a fundamentally different control loop for intercepting a localizer signal (auto detected) than a VOR or FMS course. It will make a 40 degree intercept angle for a VOR, but it makes an asymptotic intercept for a LOC. So, the aircraft wasn't really turning towards the threshold, it was just making an increasingly shallow intercept angle. The reason we don't see this in all aircraft is because the ones with Working Title GPS units have their own, more advanced autopilot. I've actually seen the code that generates these intercept angles in their library, which is what made me realize what was going on. Unfortunately, I don't think there is anything I can do about this without writing my own autopilot, which is something I promised myself I would not undertake... yet."
@Black-Square said in Localiser Tracking:
Here is the response I gave a beta tester about this behavior:
"You led me down a path of discovery, which is always appreciated. I saw the same behavior in some default aircraft, and not others. As it turns out, the native autopilot uses a fundamentally different control loop for intercepting a localizer signal (auto detected) than a VOR or FMS course. It will make a 40 degree intercept angle for a VOR, but it makes an asymptotic intercept for a LOC. So, the aircraft wasn't really turning towards the threshold, it was just making an increasingly shallow intercept angle. The reason we don't see this in all aircraft is because the ones with Working Title GPS units have their own, more advanced autopilot. I've actually seen the code that generates these intercept angles in their library, which is what made me realize what was going on. Unfortunately, I don't think there is anything I can do about this without writing my own autopilot, which is something I promised myself I would not undertake... yet."
Okay thanks for the explanation.
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I flew an ILS earlier today and I basically shoved the airplane towards the ILS path while on autopilot until it was on it…
@Marionettework said in Localiser Tracking:
I flew an ILS earlier today and I basically shoved the airplane towards the ILS path while on autopilot until it was on it…
Okay I'll try to do this next time, maybe even wait a bit longer before arming LOC
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Fun fact: The CRJ has trouble following a LOC in real world. Not all aircraft are perfect, real or not.
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TIP: Ensure you know the exact Final Apch Crs from the ILS approach chart and set your VOR1 needled precisely to it so that it does track the right heading to the threshold. What Nick said, it is retro tech and yes it does act a lot like a police dog following the scent from the pair of gloves.
@CoolGunS said in Localiser Tracking:
TIP: Ensure you know the exact Final Apch Crs from the ILS approach chart and set your VOR1 needled precisely to it so that it does track the right heading to the threshold. What Nick said, it is retro tech and yes it does act a lot like a police dog following the scent from the pair of gloves.
Lol I like that analogy. I thought though that for Localiser, you don't actually have to set the final approach course because of how the localiser antenna work. You should be able to even set the course to something like 90 degrees off from final course and airplanes will still capture and follow the localiser just fine. Of course it's still recommended to set the course properly for situational awareness.
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TIP: Ensure you know the exact Final Apch Crs from the ILS approach chart and set your VOR1 needled precisely to it so that it does track the right heading to the threshold. What Nick said, it is retro tech and yes it does act a lot like a police dog following the scent from the pair of gloves.
@CoolGunS said in Localiser Tracking:
TIP: Ensure you know the exact Final Apch Crs from the ILS approach chart and set your VOR1 needled precisely to it so that it does track the right heading to the threshold. What Nick said, it is retro tech and yes it does act a lot like a police dog following the scent from the pair of gloves.
Or if you’re lazy or you forgot or don’t have the chart, you can fly using FMS until the last turn and then click CRS 1 to set the current course.
