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tatfsn

Falcon 50 and Localizer/ILS Intercept Problems

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Hi,

 

Apologies if this has been covered before.

 

For those of you who are using your Falcon 50s with the RXP GTN 750s, I could greatly use some suggestions. I can't for the life of me get the aircraft to intercept the localizer course, and I'm pulling my hair out. I've tried several combinations of procedures to try and figure it out, but none have worked. In each situation the aircraft will fly past the localizer course, or sluggishly turn as if to intercept it and then fly right past it again.

 

I also have the Flysimware Lear, and have also equipped it with dual RXP GTN 750s. I did some tests with it as well, on more than one ILS approach, and it intercepts the localizer course and the glide slope like a champ.

 

This is the procedure that I followed for the Lear:

 

  1. Master GTN 750 set to the localizer frequency and to CDI mode. HSI set to published LOC course.

  2. Enroute to intercept the ILS course, autopilot in HDG mode and ALT mode. I approach the localizer course at a 45 degree angle. Within a couple of miles of the localizer course I switch the autopilot to NAV mode.

  3. When the plane captures and aligns with the localizer (well before the glide slope intercept point) I select GS on the autopilot.

  4. When the plane intercepts the glide slope the ALT mode on the autopilot automatically extinguishes and the aircraft follows the glide slope down.

 

The Learjet intercepts both the localizer course and then the glide slope beautifully and smoothly, and then holds the horizontal and lateral modes as if it were on rails. The Flysimware Lear again demonstrates that it is a thing of beauty.

 

Now for the Falcon 50:

 

  1. Master GTN 750 set to localizer frequency and CDI mode. HSI set to published LOC course.

  2. Enroute to intercept the ILS course, autopilot in HDG and ALT modes. Again, I took care to approach the localizer at no more than a 45 degree angle. Within a couple of miles of the localizer course that autopilot goes to NAV mode. This is when the trouble begins:

  3. Aircraft turns slightly, as if to intercept the localizer, and then flies right past it.

  4. I try the APP mode on the autopilot, the plane turns a bit more, and sluggishly, to the localizer, but does not intercept it. It flies parallel—kind of--to the localizer course all the way to the GS intercept.

    a) I've also tried activating the approach mode of the autopilot before arriving at the localizer course and get the same result. The plane flies past the localizer course as if it isn't there at all.

    b) at another time, when I used the HDG mode to track the localizer course until the plane reached the GS intercept, then I activated the approach mode a dot below it. The plane pitched up abruptly and then begandiving to the ground to crash.

 

I have another aircraft, by another developer (Lionheart), which I equipped with just one RXP GTN 650 unit. While the 650 doesn't have all of the features of the 750, it is still quite capable. Like the Falcon, the Lionheart

bird has an APPR mode on its autopilot rather than a separate GS mode. I followed the same procedure I attempted on the Falcon and like the Lear, it intercepted the localizer and glideslope without a hitch.

 

In the beginning I was thinking that these issues it might be related to the GTN but my experiences rule that out. It's got to be the Falcon.   I'm aware that the procedures vary from aircraft to aircraft; perhaps there's a 

step unique to the Falcon that I'm missing?

 

I would welcome any and all constructive feedback.

Edited by tatfsn
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Try reducing the 45 degree angle, the Falcon is more sensitive to the degree and distance you intercept. Try flying with the GPS on until reaching your IAP or FAF and make sure you're at the stated altitude with ILS Freq set in NAV1, then hit VLOC, APPR right before reaching either of the two fixes and you should then intercept both the GS and LOC. 

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Try a 30 degree intercept hdg, that's what ATC is generally going to give you if on vectors.

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19 hours ago, tatfsn said:

Hi,

 

Apologies if this has been covered before.

 

For those of you who are using your Falcon 50s with the RXP GTN 750s, I could greatly use some suggestions. I can't for the life of me get the aircraft to intercept the localizer course, and I'm pulling my hair out. I've tried several combinations of procedures to try and figure it out, but none have worked. In each situation the aircraft will fly past the localizer course, or sluggishly turn as if to intercept it and then fly right past it again.

 

 

The advice posted above is all good advice, but I think something is wrong/corrupted with your setup. I just ran an ILS test using a single RXP GTN750 in the Falcon. To push the limits a bit for test purposes, I used a 45 deg LOC intercept angle at 160 knots. I used the AP HDG mode with the APR Armed to set up the LOC intercept. The GTN750 was in VLOC mode. The Falcon initially flew through the LOC just a bit (the needle deflected about 1/2 way to the first dot) and then corrected back nicely. About a 1/2 dot before the GS needle centered, I went to full flaps and gear down. The GS was captured  (at about 140 Knots) and tracked well all the way down. So I conclude something is not working correctly with your sim setup for the Falcon, it does not seem to be just a LOC intercept angle or speed issue.

I think the first thing I would try is using the Falcon50 GPS Management tool again to load a single RXP GTN750 into the Falcon and make sure the GTN is setup correctly (the same way you have it for the Lear35 as far as coupling to the HSI is concerned, etc). Then try another ILS approach. Make sure the AP is on (green AP above the attitude indicator, and yellow lights on the warning panel all OFF, which I find counter intuitive). Try using the AP HDG and APR modes as described above, and intercept the LOC well outside the FAF. As suggested above, use a 30 deg intercept and 130-140 knots.  As the approach progresses, note what the AP lights are doing -- this may provide a clue to what is happening if the approach doesn't work.

If things still don't work, and you are sure the GTN750 is setup as it should, I would uninstall and then reinstall the Falcon 50. If you do this, after uninstalling, make sure no files are left over at the install location. If there are some, delete them.

BTW, my test was in P3Dv4.4.  I don't see above what sim you are using.

Al

 

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160kts is pretty slow assuming you are joining at 7-10 miles final. Good if you are by yourself out there but not with any kind of traffic around.

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5 minutes ago, Dave_YVR said:

160kts is pretty slow assuming you are joining at 7-10 miles final. Good if you are by yourself out there but not with any kind of traffic around.

Yep, but the purpose here was to run an AP LOC capture test at a pretty 'sharp' intercept angle. My experience (although admittedly a bit old) is that ATC would not usually bring you in at a 45 deg intercept.

Thx,

Al

Edited by ark

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Everyone,

I want to thank you all for taking the time to offer your assistance.   I found a solution to the problem, and have been shooting practice

ILS approaches with the Falcon since then.   It has intercepted the localizer perfectly each time.  Now if only a solution could be found

to the RXP GTN 750's rather vigorous manner of intercepting the glide slope...😆

Thanks again, everyone!

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4 hours ago, tatfsn said:

Everyone,

I want to thank you all for taking the time to offer your assistance.   I found a solution to the problem, and have been shooting practice

ILS approaches with the Falcon since then.   It has intercepted the localizer perfectly each time.  Now if only a solution could be found

to the RXP GTN 750's rather vigorous manner of intercepting the glide slope...😆

Thanks again, everyone!

Please post the intercept solution you found as it might help someone else in the future.

I don't know what you mean by "the RXP GTN 750's rather vigorous manner of intercepting the glide slope", but you might get some helpful information through the RXP GTN750 support forum at https://www.avsim.com/forums/forum/823-rxp-gtn-750650-touch/ .

Al

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