HSI just doesn't make sense. Help!

[Joe Larussa]

So here is the deal. I have been trying to understand whats going on with my HSI for a while now. I have a KIng

Hsi with an Stec 60 autopilot and Garmin 530 non Wass. All this equipment is new to me. So when I intercept the ILS

inbound and set the Hsi to the inbound course with autopilot on it steers me right of course. If I set the course selector

roughly 5 degrees to the left it's almost dead on. Looks like the course selector will steer the plane. On my old plane 

with a normal indicator with localizer and glide slope no matter what you set the OBS at if you flew the needles it would

plant you on centerline. If I hand fly with Hsi same applies only with autopilot does it steer off course. Ideas?

[M20F]

Did you hit the OBS button on the 530 to switch from GPS to localizer?

[Joe Larussa]

3 minutes ago, M20F said:

Did you hit the OBS button on the 530 to switch from GPS to localizer?

Please excuse my ignorance but do mean the CDI button?

[rbridges]

it may be your STEC turn coordinator needing adjustment.  When you have your heading bug on 360, for example, what heading does the AP fly?  I don't have an HSI, but I had a similar issue with my STEC/DG

[N601RX]

If you dial in some heading say 20 deg, does the gps show it as being 15, 20 or 25? I'm not familiar witht he 530, but I think you will find a maintenance screen where you can make the HSI and 530 headings match by adding an offset.  At least older GPS's have this ability.

[M20F]

Just now, Joe Larussa said:

Please excuse my ignorance but do mean the CDI button?

Yes, sorry :-)

[Joe Larussa]

Just now, M20F said:

Yes, sorry :-)

Yep switch to Vloc

[Joe Larussa]

1 minute ago, rbridges said:

it may be your STEC turn coordinator needing adjustment.  When you have your heading bug on 360, for example, what heading does the AP fly?  I don't have an HSI, but I had a similar issue with my STEC/DG

Hmm... Didn't think my turn coordinator was part of the system on the Stec 60 but you may be right!

[Marauder]

Just now, Joe Larussa said:

Hmm... Didn't think my turn coordinator was part of the system on the Stec 60 but you may be right!

I have an STEC 60-2 in my plane. If you are experiencing a slight off course while you are in the approach mode, it is probably not the turn coordinator. The STEC goes into soft mode when you are in the approach mode which should eliminate any chasing of the needle and if you are off course, you may need to adjust the roll computer or there may be an offset caused by the HSI. This should not be a factor if you have the GPS set in parallel mode since you are flying VLOC.

I will say that if the winds are a factor, flying an ILS is different than an LPV. I flew a coupled ILS last weekend with winds at 35 to 40 knot crosswind. The STEC was struggling to maintain the centerline due to the high winds. Flying to the same runway but using the LPV, it was on rails.

[Marauder]

Just a comment on the turn coordinator and the rest of the hardware. The TC is the heart of the STEC and it is used to establish the rate of turn. Bendix King autopilots use the attitude indicator for this function. Once a Nav signal is present, the left/right guidance is driven by the Nav signal. If it is off course, it could be driven by the data source (GPS or ILS), by a parallel track being entered (called the offset) or a problem with the HSI CDI (Course Deviation Indicator) or the autopilot roll being off.

[Joe Larussa]

2 minutes ago, Marauder said:

I have an STEC 60-2 in my plane. If you are experiencing a slight off course while you are in the approach mode, it is probably not the turn coordinator. The STEC goes into soft mode when you are in the approach mode which should eliminate any chasing of the needle and if you are off course, you may need to adjust the roll computer or there may be an offset caused by the HSI. This should not be a factor if you have the GPS set in parallel mode since you are flying VLOC.

I will say that if the winds are a factor, flying an ILS is different than an LPV. I flew a coupled ILS last weekend with winds at 35 to 40 knot crosswind. The STEC was struggling to maintain the centerline due to the high winds. Flying to the same runway but using the LPV, it was on rails.

Ok you got me. What is parallel mode? The thing I don't get is why if you move the course selector on the Hsi the plane turns

with it?

[carusoam]

Take some notes while you fly.  

What works, what doesn't, and what the failure is...

Auto pilot and HSI functions.

- holds altitude

- follows a heading properly...

- tracks a VOR properly.  Nav1 and nav2

- tracks a GPS magenta line properly. Nav3?

- tracks an ILS properly. Horizontal and vertical guidance.  Intercepts auomatically?

- HSI maintains magnetic heading matching the compass.

Essentially, these require several different sources of information to be delivered between the HSI, AP and the source.

often a dirty connector can cause some of these challenges.  Eliminating what works from what doesn't work narrows the problems significantly.

I had the electronic flux gate compass in the wing miscommunicate with the system causing some funny issues.  The local instrument shop was able to find the issue and take care of it. Turn it off and adjust by hand.

for more details on the complexity of the BK system, you can go to their website and read about all of the things that are interconnected.  It easy surprisingly simple to read.  You may get a feeling of what is not working just by reviewing it...

hope that helps...

Best regards,

-a-

[Marauder]

 

Just now, Joe Larussa said:

Ok you got me. What is parallel mode? The thing I don't get is why if you move the course selector on the Hsi the plane turns

with it?

Parallel mode is a feature on the GPS to allow you to offset a track. Let's say you want to fly VFR and use the Victor airway. Rather than flying the actual airway, you can tell the GPS to parallel the airway. On the 430/530, this function may not exist or if it does exist, it may be limited to the two waypoints making up the airway since these units don't have victor airways in their database like the 650/750.

If your AP is turning when you turning the course selector and you are tuned to an ILS, are you actually in approach mode? I have been fortunate with the Aspen HSI since the course selection is done automatically but I think on an ILS shouldn't turn.

 

What are the button sequence you are using on the ILS for the STEC?

[Marauder]

Parallel Track:

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[Joe Larussa]

1 minute ago, Marauder said:

 

Parallel mode is a feature on the GPS to allow you to offset a track. Let's say you want to fly VFR and use the Victor airway. Rather than flying the actual airway, you can tell the GPS to parallel the airway. On the 430/530, this function may not exist or if it does exist, it may be limited to the two waypoints making up the airway since these units don't have victor airways in their database like the 650/750.

If your AP is turning when you turning the course selector and you are tuned to an ILS, are you actually in approach mode? I have been fortunate with the Aspen HSI since the course selection is done automatically but I think on an ILS shouldn't turn.

 

What are the button sequence you are using on the ILS for the STEC?

I use the GPS to fly the approach in GPSS mode. After it makes the turn to intercept the localizer I switch to Vloc and

Nav mode on the autopilot.

[carusoam]

https://www.bendixking.com/HWL/media/Pilot-Guides/006-08256-0004_4.pdf

This document shows the devices that are being used by the system for this particular HSI...

Of course you need to know the model number of your HSI.

This one comes from the 525A.  Oddly, all BK systems are not the same.

 

Best regards,

-a-

[Marauder]

1 minute ago, Marauder said:  

Parallel mode is a feature on the GPS to allow you to offset a track. Let's say you want to fly VFR and use the Victor airway. Rather than flying the actual airway, you can tell the GPS to parallel the airway. On the 430/530, this function may not exist or if it does exist, it may be limited to the two waypoints making up the airway since these units don't have victor airways in their database like the 650/750.

If your AP is turning when you turning the course selector and you are tuned to an ILS, are you actually in approach mode? I have been fortunate with the Aspen HSI since the course selection is done automatically but I think on an ILS shouldn't turn.

 

What are the button sequence you are using on the ILS for the STEC?

I use the GPS to fly the approach in GPSS mode. After it makes the turn to intercept the localizer I switch to Vloc and

Nav mode on the autopilot.

Sounds like the right sequence. The STEC should be going through the capture phase and end up in soft mode. Once it does all that, it should be close to dead on.

With GPSS, as long as you switch to VLOC, it should ignore any GPS signal. Sounds like something needs calibrated.

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[Marauder]

Near the end no of this video (around 9:20) it shows the STEC in soft mode. Does your unit end up there?

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[PaulM]

You should first read this:  http://www.csobeech.com/files/S-TecServiceManual.pdf

The roll-centering adjustment needs to be correct or you get odd capture/turn/offset issues. 

It can be adjusted in either HDG or NAV mode.. Just tweak the adjustment until you track correctly.

When I bought my bravo the 55X was about 5° off and NAV mode would eventually integrate onto the NAV line, but at every GPSS waypoint transition the integral factor would be reset to zero and the turn would be off until the "I" in PID could factor back in.

About 5 mins in cruise with NAV mode will allow you to adjust this. I couldn't believe that the previous pilots flew with that offset, I noticed the issue right away. 

[Joe Larussa]

3 hours ago, Marauder said:

Near the end no of this video (around 9:20) it shows the STEC in soft mode. Does your unit end up there?

 

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Yep I do get the capture and soft indications. Just don't understand why when I turn the course selector

it turns the plane as well. If the selector is set off of the final approach course by 10 degrees then it will

be off for sure. I must be setting something wrong.

[carusoam]

Some things are not coming together from the discussion.  At least the way I used to understand them...

1) Often the GPSS is an addition to the system. GPSS usually works with old APs in Heading mode.  This way the the GPSS continues to keep track of what is the next WPT and continuously makes adjustments for heading changes through multiple WPTs.

2) In Nav mode the AP uses the GPS to navigate between multiple WPTs but requires the pilot to change the heading bug on the HSI In a timely fashion.  A warning from the GPS can be programmed to start the turn slightly early to cut the corner using a standard rate turn.  Limitations of the computer box made GPSS an update to a simpler system.  Just not easy to understand.

3) in approach mode... Switching over to the approach requires a whole set of procedures to select the proper buttons for proper accuracy.  This needs to be done at a particular space and time prior to the FAF

4) The GTN blends GPS and other Nav functions VOR and ILS nicely in one box.

I have a KLN90B, KAP150 and no GPSS yet.... Mid 90s technology.

Just wondering if you are seeing the same thing,

-a-

[Joe Larussa]

5 minutes ago, carusoam said:

Some things are not coming together from the discussion.  At least the way I used to understand them...

1) GPSS usually works with old APs in Heading mode.  This way the the GPSS continues to keep track of what is the next WPT and continuously makes adjustments for heading changes.

2) In Nav mode the AP uses the GPS to navigate between two points but requires the pilot to change the heading bug on the HSI to go to the next WPT.  A warning from the GPS can be programmed to start the turn slightly early to cut the corner using a standard rate turn.

3) in approach mode... Switching over to the approach requires a whole set of procedures to select the proper buttons for proper accuracy.  This needs to be done at a particular space and time prior to the FAF

4) The GTN blends GPS and other Nav functions VOR and ILS nicely in one box.

I have a KLN90B, KAP150 and no GPSS yet....

Just wondering if you are seeing the same thing,

-a-

When intercepting the localizer I switch from GPS to Vloc on the 530 then go from heading to Nav on the autopilot.

Then it goes to approach mode.

[rbridges]

3 hours ago, PaulM said:

You should first read this: http://www.csobeech.com/files/S-TecServiceManual.pdf

The roll-centering adjustment needs to be correct or you get odd capture/turn/offset issues. 

It can be adjusted in either HDG or NAV mode.. Just tweak the adjustment until you track correctly.

When I bought my bravo the 55X was about 5° off and NAV mode would eventually integrate onto the NAV line, but at every GPSS waypoint transition the integral factor would be reset to zero and the turn would be off until the "I" in PID could factor back in.

About 5 mins in cruise with NAV mode will allow you to adjust this. I couldn't believe that the previous pilots flew with that offset, I noticed the issue right away. 

thanks for that.   I remembered that the AP was linked to the turn coordinator, but I forgot the adjustment was made in the faceplate itself.

[Marauder]

11 minutes ago, Joe Larussa said:

When intercepting the localizer I switch from GPS to Vloc on the 530 then go from heading to Nav on the autopilot.

Then it goes to approach mode.

What is driving your GPSS? I wonder if it is disengaging.

[carusoam]

Add this to the discussion...

The King HSI heading selector is important for the the needle deflection/centering.  But, the system will be trying to fly itself down the centerline generated by the localizer regardless of the heading bugs actual position.   There is no setting for localizer heading (I believe).  The Nav radio knows it's receiving a localizer.  The pilot is responsible to know it is the right localizer using the morse code identifier.  The only other choice on the AP is for flying a back course.  Reverse sensing and no vertical guidance.

Quirkyness of a fully digital system with simple mechanical display and input parts.  Limited by it's minute memory.  Makes the Aspen look ingenious!

Also know: I have more MSFS simulator time than actual flying time.  

I did have a similar offset experience with my O when I first got it.  What ever it was resolved by my local instrument shop...

Let me know if I am off base with this logic.

Best regards,

-a-