Loss of GPSS

[the400kid]

Caution, stupid question ahead..

My GPS Steering module has gotten wonky lately and I'm not sure I'll be able to rely upon it. I have a long trip coming up in my Mooney and have a feeling that I'll have to do without it, and after nearly 20 years of depending on it to get me where I'm going, I'm afraid I forgot how to navigate without it. The autopilot is a KAP 150 and my question is, when approaching a turn (say on an airway), do I place it into heading mode, make the turn and then put it back on NAV or leave it on NAV and have it attempt to intercept after the course changes?

 

[WDD]

Are you flying IFR or VFR? Do you have a tablet, ADSB / Traffic Source, and something like ForeFlight?

 

[the400kid]

Are you flying IFR or VFR? Do you have a tablet, ADSB / Traffic Source, and something like ForeFlight?

Some segments will be IFR. I use Garmin Pilot, which is fed by a GTN 750 using a FlightStream 210.

 

[WDD]

You should be fine hand flying if you have the GTN. Are you concerned because you won’t have an autopilot taking commands from the GTN?

 

[the400kid]

The autopilot will be taking commands from the GTN in NAV mode, but it's turn anticipation that I'm concerned about. In NAV mode I believe it will fly right through the turn and turn sharply to try and intercept the course again.

 

[Martin Pauly]

my question is, when approaching a turn (say on an airway), do I place it into heading mode, make the turn and then put it back on NAV or leave it on NAV and have it attempt to intercept after the course changes?

There is no "cone of confusion" if you use GPS (instead of GPSS), so there should not be a need to go to heading mode temporarily. When you see the turn to the next leg being announced (with the countdown from the GPS for turn anticipation), simply twisting the OBS to the new bearing at that time should be all the autopilot needs to intercept the next leg. Granted, it won't be as smooth and precise as with GPSS, but that's to be expected.

- Martin

 

[midlifeflyer]

In NAV mode I believe it will fly right through the turn and turn sharply to try and intercept the course again.

In shouldn't. As @Martin Pauly mentioned, with a KAP 150, which doesn't natively AutoSlew to the next course, you will have to turn the OBS to the new course. Nice that the GPS reminds us if we're watching for it.* (Yes, one of the airplanes I fly has a KAP 150 with its standard HSI and no GPSS, so BTDT)

(*The main thing lost by pilots who become autopilot-depended is loss of anticipation.)

 

[the400kid]

In shouldn't. As @Martin Pauly mentioned, with a KAP 150, which doesn't natively AutoSlew to the next course, you will have to turn the OBS to the new course. Nice that the GPS reminds us if we're watching for it.* (Yes, one of the airplanes I fly has a KAP 150 with its standard HSI and no GPSS, so BTDT)

(*The main thing lost by pilots who become autopilot-depended is loss of anticipation.)

Great. Like I said, it's been a very long time and that skill has most certainly atrophied.

How would it behave in a hold or procedure turn?

 

[midlifeflyer]

Great. Like I said, it's been a very long time and that skill has most certainly atrophied.

How would it behave in a hold or procedure turn?

Basically, without GPSS telling the AP where to go, the AP is clueless. Left to its own in NAV or APR mode it will wander aimlessly. So, everything other than inbound will be in HDG mode. Make the entry and all turns in HDG mode. Once on the intercept to the extended FAC, you can switch to APR. It will ARM APR and then intercept and engage.

 

[the400kid]

Basically, without GPSS telling the AP where to go, the AP is clueless. Left to its own in NAV or APR mode it will wander aimlessly. So, everything other than inbound will be in HDG mode. Make the entry and all turns in HDG mode. Once on the intercept to the extended FAC, you can switch to APR.

Got it, thanks.

 

[flyingcheesehead]

Caution, stupid question ahead..

My GPS Steering module has gotten wonky lately and I'm not sure I'll be able to rely upon it. I have a long trip coming up in my Mooney and have a feeling that I'll have to do without it, and after nearly 20 years of depending on it to get me where I'm going, I'm afraid I forgot how to navigate without it. The autopilot is a KAP 150 and my question is, when approaching a turn (say on an airway), do I place it into heading mode, make the turn and then put it back on NAV or leave it on NAV and have it attempt to intercept after the course changes?

There is no "cone of confusion" if you use GPS (instead of GPSS), so there should not be a need to go to heading mode temporarily. When you see the turn to the next leg being announced (with the countdown from the GPS for turn anticipation), simply twisting the OBS to the new bearing at that time should be all the autopilot needs to intercept the next leg. Granted, it won't be as smooth and precise as with GPSS, but that's to be expected.

I have a KFC150, which is the KAP150 with a flight director.

Just wait for the "Turn to ### in # seconds" countdown on the GPS, and when it says "Turn to ### now" you twist the course pointer on the HSI to the new course, and the autopilot will mostly make the turn. It'll probably overshoot by a hair and then come back in, but it's as good as you'll get without GPSS.

 

[the400kid]

I have a KFC150, which is the KAP150 with a flight director.

Just wait for the "Turn to ### in # seconds" countdown on the GPS, and when it says "Turn to ### now" you twist the course pointer on the HSI to the new course, and the autopilot will mostly make the turn. It'll probably overshoot by a hair and then come back in, but it's as good as you'll get without GPSS.

I flew yesterday and tried this. Yes it did turn, and yes, it overshot the course, but by slightly more than a hair. I think when I need to make major course change, I'll place it into HDG mode and start the turn sooner.

I now have a new appreciation for GPSS. What a marvelous invention.

 

[Clip4]

Caution, stupid question ahead..

My GPS Steering module has gotten wonky lately and I'm not sure I'll be able to rely upon it. I have a long trip coming up in my Mooney and have a feeling that I'll have to do without it, and after nearly 20 years of depending on it to get me where I'm going, I'm afraid I forgot how to navigate without it. The autopilot is a KAP 150 and my question is, when approaching a turn (say on an airway), do I place it into heading mode, make the turn and then put it back on NAV or leave it on NAV and have it attempt to intercept after the course changes?

You really need to upgrade to a new Cirrus,

 

[flyingcheesehead]

I flew yesterday and tried this. Yes it did turn, and yes, it overshot the course, but by slightly more than a hair. I think when I need to make major course change, I'll place it into HDG mode and start the turn sooner.

Interesting. What did it do right after you turned the course pointer? It should essentially act like it's in HDG mode and you just bugged the new course as your heading. It overshoots because it tops out at 90% of a standard rate turn, so it never turns quite as sharp as the GPS wants, but once it gets around to the course pointer being up it should continue the turn just a little to correct for the now-offset needle and find its way back on course fairly quickly, unless you have a lot of wind from the inside of the turn.

Also, were you on an approach or enroute turn when it did this?

If upon turning the course pointer it just kinda kept wallowing roughly in the same direction, something is wrong.

 

[frfly172]

Use the hdg mode ,

 

[Rick A]

FWIW, I have an S-Tec GPSS panel mounted module (with internal lighting) working when removed, currently sitting on a shelf in the hangar. If you can use it drop me a PM.

 

[Viking1978]

DAC International GDC-31 GPSS

Does anyone have recent experience (or know someone that does) installing a GDC-31 GPSS module? It looks like DAC International does not support these units anymore. I have a bad digital copy of the install manual (Revision Z is the newest that I could find.) I think I have found an error in one of the circuit schematics. I am specifically looking at Figure 13 in the manual. It looks like one of the pins on the transformer is mislabeled. I think the pin labeled 9 should be labeled 15. This makes me nervous that there might be more errors.