ILS Approach

[JP Dice]

This may be an absolute silly question, but I'll ask anyway. I know how to do an ILS approach, but I'd like the AP to fly the approach. I have an Aspen Evolution setup (actually 3 screens), STEC 30 AP, and 430W and KX155 for avionics.

I will give you the scenario. ATC says maintain 3,000 until established clear for the ILS "xyz" approach. I would like the AP to intercept the final approach course using GPSS and once established on the final approach course I would track inbound on the localizer.  I know I can do this using the HDG bug, but will GPSS fly the intercept once I activate the approach. Keep in mind, I don't want GPSS steering to fly the approach - just intercept the localizer. Once I turn inbound, I would switch to VLOC and fly the ILS with STEC 30 in High Track mode.

Is this possible? I know how to do with G1000 setup, but not exactly sure with my configuration.

Thanks!

JP Dice

 

 

 

 

[PTK]

20 hours ago, JP Dice said:

This may be an absolute silly question, but I'll ask anyway. I know how to do an ILS approach, but I'd like the AP to fly the approach. I have an Aspen Evolution setup (actually 3 screens), STEC 30 AP, and 430W and KX155 for avionics.

I will give you the scenario. ATC says maintain 3,000 until established clear for the ILS "xyz" approach. I would like the AP to intercept the final approach course using GPSS and once established on the final approach course I would track inbound on the localizer.  I know I can do this using the HDG bug, but will GPSS fly the intercept once I activate the approach. Keep in mind, I don't want GPSS steering to fly the approach - just intercept the localizer. Once I turn inbound, I would switch to VLOC and fly the ILS with STEC 30 in High Track mode.

Is this possible? I know how to do with G1000 setup, but not exactly sure with my configuration.

Thanks!

JP Dice

GPSS as the name implies is a gps function. Unless your AP has an approach mode that you can “arm” (for autointercept localizer/gs sense and the 30 does not) you should probably use heading mode to intercept the localizer as you indicated. You can load the full approach on the 430 and use gpss to fly the initial segment and any pt. But intercept the localizer in heading mode as vectored by ATC and then have the ap track in high gain. You can use the loaded approach as reference. But I don't think the 30 has an actual approach mode to intercept localizer or gs.

[Cris]

The Stec 30 is a great autopilot but it is basic. It is relatively bulletproof proof and thus very low cost to maintain. Like most autopilots 90% of the time you will use heading, alt hold & GPSS. However It will not intercept and track a course unless it is within 10 degrees of the lateral course. Thus you can not “arm” it with Heading/Nav. When on the localizer or following the magenta line use “TRK HI”. Bear in mind that It will hold altitude but will not intercept/track a GS. Same is true for an LPV. Verticle mode on an approach must be handled by the pilot which is no big deal. The use of GPSS will work to intercept the final approach course but then you must change over to “TRK HI” to legally fly the localizer. (Note: TRK LO is used when tracking a VOR to allow it to pass over the VOR without a lot of undulations. You will rarely use TRK Lo.) If you have a 2nd Nav you could set it to the localizer and monitor the approach while continuing to fly with GPSS. One hint to help with sensitivity is to set the CDI course width to less than the standard 5nm enroute on your GPS. You can download both the Stec 30 POH and GPSS from the Genysis site for details. 

Edited June 5, 2018 by Cris

[Marauder]

I have a STEC 60-2. Like Cris mentioned, the 30 is a great basic AP. On the 60-2 you can set defined intercept angles with an automatic conversion to approach mode. As well, it can track the vertical guidance.

To answer your question, since the 30 can track GPSS I think the best you could hope for is to fly the GPSS overlay to the ILS and then do the VLOC conversion (on my GTN, ILS approaches automatically go to VLOC, VOR approaches however require me to do the VLOC manually) when you are within parameters needed for the autopilot to couple. My airport is served by a VOR approach. I typically will fly the GPS overlay for the procedure turn and then when I am inbound to the FAF, do the VLOC change.

[Cruiser]

On the S-tec System 30 the LO TRK is basically the same as NAV on other A/Ps and HI TRK is the same as APR. 

GPSS on the Aspen is a HDG function. It will follow the heading bug.

If ATC is giving you vectors follow the heading indicated but watch the CDI for intercept of the approach course. You will have to turn the heading bug manually to intercept the final course. When turned on the final approach course switch to HI TRK on the autopilot and VLOC on the GPS. 

[Marauder]

3 minutes ago, Cruiser said:

On the S-tec System 30 the LO TRK is basically the same as NAV on other A/Ps and HI TRK is the same as APR. 

GPSS on the Aspen is a HDG function. It will follow the heading bug.

If ATC is giving you vectors follow the heading indicated but watch the CDI for intercept of the approach course. You will have to turn the heading bug manually to intercept the final course. When turned on the final approach course switch to HI TRK on the autopilot and VLOC on the GPS. 

Tom -- I think we are spoiled with the autocourse on the Aspens...  (Don't let Peter Garmin hear this).

 

[Cruiser]

Yes, but I didn't want to cloud issue with the OPs question. 

GPSS needs a waypoint for autocourse. IF the OP loads the approach and then activates it, he can then fly direct to the IAF and the autocourse (with GPSS on the Aspen) will intercept, turn on the final approach course and fly the heading all the way to the airport but he said he didn't want to do this.

Hence my comment above. I think it is correct. He will need to fly the heading (without a waypoint) intercept manually then go to VLOC for the approach?

[PTK]

On 6/5/2018 at 4:09 PM, Cruiser said:

Yes, but I didn't want to cloud issue with the OPs question. 

GPSS needs a waypoint for autocourse. IF the OP loads the approach and then activates it, he can then fly direct to the IAF and the autocourse (with GPSS on the Aspen) will intercept, turn on the final approach course and fly the heading all the way to the airport but he said he didn't want to do this.

Hence my comment above. I think it is correct. He will need to fly the heading (without a waypoint) intercept manually then go to VLOC for the approach?

I don’t think an ILS should be flown in heading mode. That’s nuts! I hope there's zero wind when you’re in hdg mode trying to get on the localizer! That’s what approach mode is for. And I don’t see how you can fly an ILS on GPS legally.

All this technology and you’re going to have him fly an ILS in heading mode and/or on gps?Granted the Aspens are ancient but still!

Look. Load the full approach on the 430, use GPSS to fly around the initial and intermediate segments PTs etc. but get on the final course in heading mode when vectored to intercept final. Why? Because more often than not the vector will not be to a fix, i.e. IAF, IF OR FAF. If it is to a fix and are cleared for the approach from there use gpss. Then put the STEC 30 to track on hi gain. Make sense?

[DXB]

I also have an STEC30 with GPSS through an Aspen and appreciate the discussion, as I am new to the IFR world.  If flying a full ILS/LOC approach from an IAF, certainly you can fly onto the final course in GPSS mode, then switch to VLOC to start displaying the localizer signal on the Aspen HSI before the FAF.  One would normally turn GPSS off and switch the STEC30 to Trk hi mode at the same time.   Alternately, I think one could leave GPSS on, in which case the autopilot would fly the same course based on the GPS signal, which is still available in the background to the Aspen in VLOC mode.  As long as you display and monitor the localizer signal on the Aspen HSI, I suspect doing it this way is perfectly legal.  

However if getting vectored to final, intercepting the localizer course using GPSS may be problematic because you cannot specify an intercept angle - I think it generally uses a default of 45 degrees beyond a certain distance?  Also I'm not sure GPSS will work at all if the GPS navigator is in vectors to final mode, which suspends waypoint sequencing until established (at least on my GTN650).  I think this problem with vectors to final may be the same whether flying an LPV or an ILS.   Does anyone know for certain?  I've never actually tried to intercept this way.  

[kortopates]

Its critical for the OP to understand the basic concepts before getting into buttonology. Vectors and heading are synonymous period. You aren't flying a heading in GPSS mode ( you are flying a GPS course). Failing to turn to the assigned heading can and will get you a pilot deviation if you end up getting to close to other IFR traffic causing a TA. Best to go practice this with an instructor till you fully understand your equipment.

GPSS is entirely appropriate if the controller clears you direct to
some IAF and clears you for the approach. But on a vector in heading mode you are setting up the AP to intercept final.


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[Marauder]

I also have an STEC30 with GPSS through an Aspen and appreciate the discussion, as I am new to the IFR world.  If flying a full ILS/LOC approach from an IAF, certainly you can fly onto the final course in GPSS mode, then switch to VLOC to start displaying the localizer signal on the Aspen HSI before the FAF.  One would normally turn GPSS off and switch the STEC30 to Trk hi mode at the same time.   Alternately, I think one could leave GPSS on, in which case the autopilot would fly the same course based on the GPS signal, which is still available in the background to the Aspen in VLOC mode.  As long as you display and monitor the localizer signal on the Aspen HSI, I suspect doing it this way is perfectly legal.  

However if getting vectored to final, intercepting the localizer course using GPSS may be problematic because you cannot specify an intercept angle - I think it generally uses a default of 45 degrees beyond a certain distance?  Also I'm not sure GPSS will work at all if the GPS navigator is in vectors to final mode, which suspends waypoint sequencing until established (at least on my GTN650).  I think this problem with vectors to final may be the same whether flying an LPV or an ILS.   Does anyone know for certain?  I've never actually tried to intercept this way.  

Unfortunately the STEC manual leaves a lot to be desired when it comes to the newer technologies like GPSS. I think though the concept of what he wants to do is not possible because of what Tom described above. It is a GPS waypoint driven course and selecting headings in GPSS is not possible.

I am not sure why he would be trying to combined the technologies anyways. If he is being radar vectored to the FAF course, he needs to follow the vectors. And when he is on the FAF he will need to switch to VLOC fairly shortly afterwards if not before the final intercept.

As for the legality of flying an ILS or VOR overlay, well, some pilots feel that the GPS overlay is more accurate. Not sure how they would handle the glideslope flying an ILS this way. I have a lot of experience flying the VOR approach into my airport and I agree that the GPS may give the appearance as being more accurate. The reality is that it was never flown as an approach and probably doesn't meet the TERPs requirements -- let alone being illegal to fly. I even have heard pilots even comment that they believe flying the georeferenced iPad app is okay as well. 

I don't think there is anything fundamentally wrong with monitoring an overlay, just as long as it doesn't become your primary navigation. On this practice RNAV approach, I had the ILS as the backup on the second HSI. Belts and suspenders man.

 

[jaylw314]

19 hours ago, JP Dice said:

This may be an absolute silly question, but I'll ask anyway. I know how to do an ILS approach, but I'd like the AP to fly the approach. I have an Aspen Evolution setup (actually 3 screens), STEC 30 AP, and 430W and KX155 for avionics.

I will give you the scenario. ATC says maintain 3,000 until established clear for the ILS "xyz" approach. I would like the AP to intercept the final approach course using GPSS and once established on the final approach course I would track inbound on the localizer.  I know I can do this using the HDG bug, but will GPSS fly the intercept once I activate the approach. Keep in mind, I don't want GPSS steering to fly the approach - just intercept the localizer. Once I turn inbound, I would switch to VLOC and fly the ILS with STEC 30 in High Track mode.

If the 430 is anything like the 530, it should automatically switch you to VLOC when you intercept the ILS approach course some distance outside the FA.  Before that, GPS will still provide steering, but as @kortopates and @DXB pointed out, if you're on a VTF approach, there's no GPS course to steer.  The intercept heading MUST be dialed in on the AP.

 

[PTK]

On 6/5/2018 at 1:01 AM, JP Dice said:

....I will give you the scenario. ATC says maintain 3,000 until established clear for the ILS "xyz" approach. I would like the AP to intercept the final approach course using GPSS and once established on the final approach course I would track inbound on the localizer.  I know I can do this using the HDG bug, but will GPSS fly the intercept once I activate the approach...

With that approach clearance ATC also gave you a vector to fly to intercept and get established on the final course. If that vector was to a specific fix and cleared you for the approach from there you can use gpss to that fix. However more often than not that vector instruction is not to a specific fix but somewhere on the final course outside the faf.  Then you are expected to fly that heading and get established.

[flyboy0681]

14 hours ago, Marauder said:

As for the legality of flying an ILS or VOR overlay, well, some pilots feel that the GPS overlay is more accurate. Not sure how they would handle the glideslope flying an ILS this way. I have a lot of experience flying the VOR approach into my airport and I agree that the GPS may give the appearance as being more accurate. The reality is that it was never flown as an approach and probably doesn't meet the TERPs requirements -- let alone being illegal to fly. I even have heard pilots even comment that they believe flying the georeferenced iPad app is okay as well. 

IFR Magazine talked about this maybe a year or two ago. The one takeaway that I got from it is was that while the controller may not necessarily know which one you are flying (ILS or GPS), you will certainly be called on the carpet should you execute a missed approach since the ILS and GPS missed approach procedures are more than likely different.

Can you say Brasher?

[Cruiser]

The AIM makes it clear that you cannot use GPS on an ILS approach unless the approach specifically includes GPS overlay. Then you would be flying the GPS approach and not the ILS. Following the GPS heading inside the FAF is forbidden.

[Andy95W]

2 hours ago, Cruiser said:

The AIM makes it clear that you cannot use GPS on an ILS approach unless the approach specifically includes GPS overlay. Then you would be flying the GPS approach and not the ILS. Following the GPS heading inside the FAF is forbidden.

Yes, but...

It is probably safer than flying a poor ILS approach where the localizer needle is swinging back and forth like a metronome.  

This to me is where a GPS (not an iPad) provides excellent situational awareness- primarily as it regards wind correction/crab angle.

[kortopates]

The AIM makes it clear that you cannot use GPS on an ILS approach unless the approach specifically includes GPS overlay. Then you would be flying the GPS approach and not the ILS. Following the GPS heading inside the FAF is forbidden.

Actually the AIM was updated in 2016 to clarify that you can navigate by GPS provided you are still able to monitor the raw navaid signal, such as with a second CDI or EFIS that allows you to use both. This is really meant for NPA procedures since you need the glideslope with an ILS.

Otherwise you've been spot on above.

 

Check it out.

 

 

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