GPS-175 help

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RickC

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RIckC
I just got a GPS-175 installed, paired with a Collins IND-351. When I start the unit, the CDI test works just fine, but when I activate an approach the CDI doesn't seem to be working. The CDI display just seems to be random and not related to the approach course. I am new to GPS navigation, so it's possible (and I'm hoping) that I'm just not doing something that I should be doing as far as setting up the unit for a GPS approach, but I'm unable to find anything in the pilot's guide on the subject. Anyone have a similar issue or suggestion as to why it's not responding as expected?

Thanks
 
Why does it seem random? Can you expand on that? The CDI sensitivity increases in approach mode (+-0.3nm vs +-1 in terminal and +-5nm in enroute) but I'm not sure if that would explain your issue at all.
 
it seems like what is on the CDI is not related whatsoever to the course I am flying. I also have a separate CDI paired with a NAV radio, and the ILS course on the same runway can be totally dialed in, but the GPS indicator is fully deflected.
 
Have you checked the CDI calibration in the setup pages? How does the CDI behave enroute?
 
Are you talking about an external CDI/HSI or the little one in the bottom right corner of the unit?

If the external, the two things which come to mind without seeing it are (1) GPS not manually selected as the NAV source and (2) unless you also have GPS Steering - unless you have an electronic PFD or HSI, you probably don't - the 175 does not turn the CDI or course pointer for you. You have to do it manually. Those would be normal. Not being connected at all is a possibility.

If the little one on the unit, you definitely have a problem,
 
midlifeflyer said:
Are you talking about an external CDI/HSI or the little one in the bottom right corner of the unit?

If the external, the two things which come to mind without seeing it are (1) GPS not manually selected as the NAV source and (2) unless you also have GPS Steering - unless you have an electronic PFD or HSI, you probably don't - the 175 does not turn the CDI or course pointer for you. You have to do it manually. Those would be normal. Not being connected at all is a possibility.

If the little one on the unit, you definitely have a problem,
Click to expand...

Thanks for your response. It is indeed an external CDI, and I know it's connected because the self test when the unit turns on works exactly as expected. It is a dedicated unit for the GPS, it's not connected to anything else so there is no switching the source. And I have been turning the OBS when prompted, but that doesn't seem to change anything. Im just wondering is something got missed on the setup by the avionics shop, or if it's operator error which is highly likely given that I have absolutely no experience using panel mounted GPS units.
 
Chip Sylverne said:
Have you checked the CDI calibration in the setup pages? How does the CDI behave enroute?
Click to expand...
I need to do that, I'm just not sure how. I did watch a video on the Garmin website which may lead me in the right direction. I don't really see any kind of indications while enroute, it just seems like there is no correlation between the CDI display, the unit, and my path of travel.
 
Hit the Direct button, enter the ID for an airport (or any waypoint) and hit enter. If the CDI doesn’t immediately center, you have a problem. Turning the OBS does nothing except stop the annoying messages :cool:
When flying, go to the screen that shows the internal CDI. Your external CDI should match, if not, that is a problem.
 
DGlaeser said:
Hit the Direct button, enter the ID for an airport (or any waypoint) and hit enter. If the CDI doesn’t immediately center, you have a problem. Turning the OBS does nothing except stop the annoying messages :cool:
When flying, go to the screen that shows the internal CDI. Your external CDI should match, if not, that is a problem.
Click to expand...

Excellent idea, thanks!
 
RickC said:
I need to do that, I'm just not sure how. I did watch a video on the Garmin website which may lead me in the right direction. I don't really see any kind of indications while enroute, it just seems like there is no correlation between the CDI display, the unit, and my path of travel.
Click to expand...

Hold the power and home button simultaneously until the unit starts to boot up. Then tap setup, main indicator, calibrate etc.
 
Chip Sylverne said:
Hold the power and home button simultaneously until the unit starts to boot up. Then tap setup, main indicator, calibrate etc.
Click to expand...

thanks, I'll check the settings and see if everything makes sense.
 
This might be a stupid question, but where does it show you in relation to the magenta line on the map? Right on it?
 
Groundpounder said:
This might be a stupid question, but where does it show you in relation to the magenta line on the map? Right on it?
Click to expand...

actually, I'm not sure. I wasn't looking at the map at the time, but it's the same path as the ILS for the same runway and that CDI (tied to my nav radio) was showing right on course
 
RickC said:
actually, I'm not sure. I wasn't looking at the map at the time, but it's the same path as the ILS for the same runway and that CDI (tied to my nav radio) was showing right on course
Click to expand...

You might just want to make sure to have the right portion of the approach sequenced. You probably do, but just double check. An easy way to do that is to bring up the map view and make sure the magenta line is showing where you think it's supposed to be
 
This might be a dumb question, but are you setting the Collins OBS to the course you are flying ? For example, set for 060 degrees to land runway 6 ILS ?
 
Groundpounder said:
You might just want to make sure to have the right portion of the approach sequenced. You probably do, but just double check. An easy way to do that is to bring up the map view and make sure the magenta line is showing where you think it's supposed to be
Click to expand...

great, thanks. I'll check that next time out.
Doug Reid said:
This might be a dumb question, but are you setting the Collins OBS to the course you are flying ? For example, set for 060 degrees to land runway 6 ILS ?
Click to expand...

Yes, I have been when prompted by the GPS to set a course, but it doesn't seem to do anything. Thanks!
 
You are probably setting the heading bug.. you need to press the knob and go over to the course and change it there.. it’s a numerical Value.


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