N205S Posted April 9, 2020 Report Share Posted April 9, 2020 Good morning, all. I am working through my instrument rating in my M20J, which is equipped with an Aspen 1000 PFD, Avidyne 540, and KAP 150 Autopilot. This morning, I was hand flying a few different RNAV approaches and during one approach the Aspen's glideslope indication was intermittently coming on and off. My Avidyne showed "LPV" and I was planning to fly the approach to LPV minimums. However, once I saw the intermittent glideslope I was prepared to fly LNAV minimums. The glideslope came back on and everything was fine until LPV Minimums. Still, I don't want this distraction to happen in actual IMC. Has this happened to anyone else? This was the first time it's happened to me. Any way to correct/troubleshoot this issue? Quote Link to comment Share on other sites More sharing options...
LANCECASPER Posted April 9, 2020 Report Share Posted April 9, 2020 I would check glideslope antenna connections first. Quote Link to comment Share on other sites More sharing options...
David Medders Posted April 9, 2020 Report Share Posted April 9, 2020 33 minutes ago, LANCECASPER said: I would check glideslope antenna connections first. Glideslope antennas are not used for an LPV glidepath. 1 Quote Link to comment Share on other sites More sharing options...
LANCECASPER Posted April 9, 2020 Report Share Posted April 9, 2020 3 hours ago, David Medders said: Glideslope antennas are not used for an LPV glidepath. Sorry I didn't read through your post carefully,. just went off of your title. Quote Link to comment Share on other sites More sharing options...
PTK Posted April 9, 2020 Report Share Posted April 9, 2020 5 hours ago, N205S said: My Avidyne showed "LPV" and I was planning to fly the approach to LPV minimums. However, once I saw the intermittent glideslope I was prepared to fly LNAV minimums. A very important question to answer in order to differentially diagnose is did the Avidyne downgrade the approach? When there is loss of vertical guidance during an LPV or LNAV/VNAV the navigator should downgrade to LNAV and properly annunciate. Did this happen? Quote Link to comment Share on other sites More sharing options...
N205S Posted April 9, 2020 Author Report Share Posted April 9, 2020 1 hour ago, PTK said: A very important question to answer in order to differentially diagnose is did the Avidyne downgrade the approach? When there is loss of vertical guidance during an LPV or LNAV/VNAV the navigator should downgrade to LNAV and properly annunciate. Did this happen? The Glideslope on the Aspen only vanished for roughly +/- 1 second - and it only did it 3-4 times. When I did look over at the Avidyne Unit, it still showed LPV (but the GS indication may have been back up). It could have possibly downgraded the approach but I did not confirm since the Glide slope came back online so quickly. I suppose my concern is more if this happened and (1) the glide slope indication didn't reappear and (2) if I were already under LNAV minimums. Hopefully this was a one time occurrence but wanted to understand/troubleshoot the problem, if this happens periodically. Quote Link to comment Share on other sites More sharing options...
Cruiser Posted April 9, 2020 Report Share Posted April 9, 2020 what part of the approach were you having problems? Outside the FAF or inside of it ? LPV glideslope is a calculated value based on GPS position, there is no "real" signal to follow. It might be that the GS indicator does not display if it is outside predetermined values. Quote Link to comment Share on other sites More sharing options...
N205S Posted April 10, 2020 Author Report Share Posted April 10, 2020 16 hours ago, Cruiser said: what part of the approach were you having problems? Outside the FAF or inside of it ? LPV glideslope is a calculated value based on GPS position, there is no "real" signal to follow. It might be that the GS indicator does not display if it is outside predetermined values. I had already passed the FAF and started my descent. Hopefully I can get back in the air this weekend and see if it happens again. I've got 30-40 approaches without an issue until this. I would just like to understand why this happened, troubleshoot it if possible, and have a plan incase this happens in actual IMC. Quote Link to comment Share on other sites More sharing options...
Lake Aero Posted April 22, 2020 Report Share Posted April 22, 2020 On 4/9/2020 at 7:43 AM, N205S said: Good morning, all. I am working through my instrument rating in my M20J, which is equipped with an Aspen 1000 PFD, Avidyne 540, and KAP 150 Autopilot. This morning, I was hand flying a few different RNAV approaches and during one approach the Aspen's glideslope indication was intermittently coming on and off. My Avidyne showed "LPV" and I was planning to fly the approach to LPV minimums. However, once I saw the intermittent glideslope I was prepared to fly LNAV minimums. The glideslope came back on and everything was fine until LPV Minimums. Still, I don't want this distraction to happen in actual IMC. Has this happened to anyone else? This was the first time it's happened to me. Any way to correct/troubleshoot this issue? Ring out wiring connections for Up/Down and check the configuration on Diagnostic page for both Avidyne and Aspen. Quote Link to comment Share on other sites More sharing options...
carusoam Posted April 23, 2020 Report Share Posted April 23, 2020 Welcome aboard LA Avionics Lead! Saw you signed in for the first time today? Does Lasar allow you to use your name? Nice to have you here. Its always nice to have Lasar people here... Best regards, -a- 1 Quote Link to comment Share on other sites More sharing options...
Ragsf15e Posted April 23, 2020 Report Share Posted April 23, 2020 On 4/10/2020 at 6:52 AM, N205S said: I had already passed the FAF and started my descent. Hopefully I can get back in the air this weekend and see if it happens again. I've got 30-40 approaches without an issue until this. I would just like to understand why this happened, troubleshoot it if possible, and have a plan incase this happens in actual IMC. If the 440 were to downgrade after the faf due to loss of waas for example, it won’t come back to lpv during the same approach. It shouldn’t cycle quickly between lpv/lnav at all. Sounds like the 440 was happy with the lpv solution the whole time. Communication or display problem? If this happened above LNAV mins you could use those and transition to a non precision approach, or go missed. Below LNAV mins you’d need to execute your missed approach (or land if visual with the runway). I’d be pretty careful continuing to LNAV mins if my display was suddenly questionable after the faf and I didn’t know why. 2 Quote Link to comment Share on other sites More sharing options...
Marauder Posted April 23, 2020 Report Share Posted April 23, 2020 On 4/9/2020 at 4:57 PM, N205S said: The Glideslope on the Aspen only vanished for roughly +/- 1 second - and it only did it 3-4 times. When I did look over at the Avidyne Unit, it still showed LPV (but the GS indication may have been back up). It could have possibly downgraded the approach but I did not confirm since the Glide slope came back online so quickly. I suppose my concern is more if this happened and (1) the glide slope indication didn't reappear and (2) if I were already under LNAV minimums. Hopefully this was a one time occurrence but wanted to understand/troubleshoot the problem, if this happens periodically. I have been flying behind an Aspen setup for the past 8 years with a GTN navigator. Never encountered what you are seeing. If your navigator is not indicating a LOI (Loss of Integrity) status and you are seeing LPV throughout the process, it may be some anomaly with that approach itself (unlikely) or more likely a glitch either in communication between the IFD and the Aspen or possibly the current IFD data has an error. Another thing to check. A lot of people don't check the error summary for a current database download. Instead of sending out a new database download, the error summary may indicate if a particular approach has a change or other anomaly that wasn't caught when they dispatched the database download. I would check that along with the NOTAM for the airport to make sure it isn't one of these corner cases where the glide slope may be affected in some fashion. Once I did have a legitimate LOI on an RNAV (LPV) approach after passing the FAF. I lost all GPS signal and was greeted with the LOI and a message to use another nav source. Fortunately I had the ILS running on the second HSI. 2 Quote Link to comment Share on other sites More sharing options...
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