Is there a known problem with the autopilot and ILS approach? I have tried 3 airports, I capture the glide slop. The diamond starts to come down. Then keeps on going down to the bottom. So I believe it captures the glide slop. But just ignores it. Any help would be appreciated.

Airports: KPHL KBOS and KPHX.

Thank You.

Bill McCracken

Well. It would help us to know which aircraft you are flying so we can help you resolve this issue.

Sorry About That. Hopefully this is all you need.

Thank You

Bill McCracken

 

Bonanza G36 Turbo and Non Turbo

PMS50-gtn750-aircraft-g36

KPHX ILS Rwy 26

KBOS ILS Rwy 33L

KPHL ILS Rwy  9R Z

 

3 hours ago, macpilot said:

Is there a known problem with the autopilot and ILS approach? I have tried 3 airports, I capture the glide slop. The diamond starts to come down. Then keeps on going down to the bottom. So I believe it captures the glide slop. But just ignores it. Any help would be appreciated.

Airports: KPHL KBOS and KPHX.

Thank You.

Bill McCracken

Bill,

I am not sure I understand the details of the behavior you are describing. So as a quick review, to fly the ILS you need to have the correct frequency in Nav1, you need to be in VLOC (not GPS) mode, and you must capture the GS from below, that is, the GS diamond should come down "from above" on the display as you approach the FAF (Final Approach Fix). Assuming you have captured the Localizer (are on course laterally), when the GS diamond reaches the 'center', the AP should capture the GS and start the a/c down.  At minimums, typically about 200ft AGL, you should disconnect the AP and hand fly the landing from there.

Al

Edited November 10, 20214 yr by ark

Al,

I assumed that since the GS diamond started to descend I had captured the GS. Is this a wrong assumption? I think that when I select approach Nav1 switches to VLOC, I will have to confirm this.

Thank You.

Bill McCracken 

42 minutes ago, macpilot said:

Bonanza G36 Turbo and Non Turbo

PMS50-gtn750-aircraft-g36

KPHX ILS Rwy 26

1. Since you are using the GTN750 mod, make sure that the WT g1000 NXI is not installed from the Marketplace.  The NXi is excellent but is not compatible with the GTN750.
2. Once you are established on the localizer, make sure that you are on LOC/VLOC. Then press the APR button to follow the glideslope at intercept.  If you do not activate approach mode you will simply fly through the final approach fix.

29 minutes ago, macpilot said:

Al,

I assumed that since the GS diamond started to descend I had captured the GS. Is this a wrong assumption? I think that when I select approach Nav1 switches to VLOC, I will have to confirm this.

Some avionic systems will automatically switch you from GPS mode to VLOC for an ILS approach, but the a/c has to be within a specific area relatively to the FAF for this to happen. With the G1000 you are in VLOC if the Nav display (localizer needle and GS diamond) are Green (vice Magenta). Although it can vary a tiny bit depending on the coding, you essentially capture the GS when the GS diamond reaches the center point.

And you should have the AP in APR mode before reaching the FAF. For that matter, you should have approach mode armed as you near localizer intercept if you want the AP to capture the localizer for you. For example, to intercept the localizer you could have the AP in Heading mode with the APR mode armed. When the localizer is captured, the AP will switch to APR mode.

Al

Edited November 10, 20214 yr by ark

 

WT g1000 NXI is not installed from the Marketplace.

Al,

So what I think you are saying. The the GS is not really captured until the GS diamond reaches the center point. So if the diamond continues to drop past the center point. I have never actually captured the GS. With all the information I have received. I will have to take a closer look at what happens when. I'll get back when I've had time to sort all this out.

Thanks to all who have replied.

Bill McCracken

39 minutes ago, macpilot said:

The the GS is not really captured until the GS diamond reaches the center point. So if the diamond continues to drop past the center point. I have never actually captured the GS

If you have activated the Approach Mode (APR) before you intersect the GS (diamond at center) it will capture and follow.  The NXi may do this automatically, but the GTN750, g3000, etc. require that you activate the approach mode.

Be at the charted intercept altitude, be on LOC as NAV source, activate APR prior to the glideslope and you should be good-to-go.

Edited November 10, 20214 yr by RandallR

35 minutes ago, macpilot said:

So what I think you are saying. The the GS is not really captured until the GS diamond reaches the center point. So if the diamond continues to drop past the center point. I have never actually captured the GS.

If you are in VLOC, and the Localizer freq is in Nav1, and you are on the localizer, and APR mode is on, and the GS diamond is coming down from the top of the display, then when it reaches the center point the AP should capture the GS and start the a/c down.

Al

Bill,

I just tried the ILS 33L approach into KBOS using the G1000NXi and it works as expected, so I don't think there is a problem with the approach itself.

Al

I have experienced exactly the same problem that Macpilot is experiencing.  I have been flying across the country and now up the coast of California.  28 landings in all so far.

I do all the steps as several have outlined above.  Sometimes it works.  Most of the time it doesn't.  Flying the Cessna 172 and Bonanza Turbo. Have latest upgrade on G-1000

Some ILS airports work perfectly. The Phoenix runway 26 he mentions, I tried several different times and never did get it,  I landed today at Redding, CA (KRDD) RW34 and is was perfect. 

The Redding landing for the first time in all of these, automatically turned on the LOC and turned Green,  Then it picked up the GS and took me right down to the runway.

Some approaches have been a mile or so to the right.  Other times, if I've got the ALT set at the GS waypoint, it sails right through it at doesn't change the altitude.

Sacremento I never did see the airport until I was well past it.

Another problem I have sometimes is it will take me right down perfectly aligned with the runway, then I turn off the AP when over the markings, hold everything as steady as I can, and I wind up off the right side of the runway. This may be something I am doing wrong, but all that other stuff happens.

Roy

3 hours ago, Roy Warren said:

Some ILS airports work perfectly. The Phoenix runway 26 he mentions, I tried several different times and never did get it,  I landed today at Redding, CA (KRDD) RW34 and is was perfect. 

....

Another problem I have sometimes is it will take me right down perfectly aligned with the runway, then I turn off the AP when over the markings, hold everything as steady as I can, and I wind up off the right side of the runway. This may be something I am doing wrong, but all that other stuff happens.

Roy

I tried the ILS 26 at KPHX using the G1000NXi and it works, but you do have to be careful because of the step down fixes before you get to the PRUNN FAF at 3000ft. If you haven't captured the GS prior to PRUNN, you don't want to be any higher than 3000ft as you get near to PRUNN, or you won't capture the GS from below as required. You can capture the GS further out than PRUNN, but again you have to do so from below which can be a challenge because of the requirement to be no lower than 5000 at TODRE and no lower than 4000 at JAGAL. If you are at 4000 at JAGAL than you have 3.3NM to get down to 3000 just prior to PRUNN to capture the GS from below. If for example your ground speed is 120Kts (2NM/min), than it will take you 3.3NM / 2NM/Min = 1.65 min to reach  PRUNN, so you will need a Vertical Speed down of 1000ft / 1.65min= 606 ft/min. 

For a quicker calculation, most ILS approaches use a slope of about 3 degrees which is 318ft/NM. Call it 300ft/NM for an easier mental calculation. So at a ground speed of 2NM/Min the required VS is 300ft/NM x 2NM/min = 600ft/min.

Probably safer in this example case to use a VS of -700ft/min because if you get to PRUNN at 3100ft you may not capture the GS.

Now if you are at 5000ft just prior to TODRE,  or at 4000ft just prior to JAGAL, and you have the ILS APR armed in the AP, then you could also capture the GS at these fixes since they are on the 3 deg GS. But again you have to be at those altitudes to capture the GS from "below".

ILS26 at KPHX

As for ending up off to the side of the runway, that could be due to wind, or your feet on the rudder pedals have introduced a little yaw, or you have a bit of aileron applied which the autopilot has been compensating for on the "way down", but these inputs now come into play once the AP is turned off. Once the AP is off (usually the AP is turned off at minimums, about 200ft AGL for a typical ILS) you do have to actively fly the plane down to the runway.

Corrections or clarifications welcome.

Al

Edited November 11, 20214 yr by ark

Thanks Al.  I'm going to try it again using your suggestions.  On missing the runway, I now think was pilot error.  I know in one case, not at KPHX, I had the LOC set up for the other end of the runway, and the sim was trying to take me around to that side, if that makes any since.

I appreciate all you have been doing to help me.  I learn something new every day. The more I learn, the more I enjoy the sim.

Roy

WOW!

Over the years. I have found the AVSIM members have always been very helpful. This is an example.

Thanks to all of you. I have some homework to do. 🙂

Bill McCracken