GPS Integrity Lost
Printed From: Avidyne
Category: Avidyne General
Forum Name: IFD 5 Series & IFD 4 Series Touch Screen GPS/NAV/COM
Forum Description: Topics on Avidyne's IFD 5 Series and IFD 4 Series Touch Screen GPS/NAV/COM
URL: http://forums.avidyne.com/forum_posts.asp?TID=2398
Printed Date: 16 Apr 2025 at 5:22pm
Software Version: Web Wiz Forums 12.01 - http://www.webwizforums.com
Topic: GPS Integrity Lost
Posted By: Walter5
Subject: GPS Integrity Lost
Date Posted: 08 Sep 2022 at 8:51am
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I received the alert in the subject line on a flight the other day. The GPS seemed to be working fine as I progressed through the way points on my flight plan. When I looked up the alert in the pilots manual the explanation doesn't really offer any additional insight. My question is, what does this alert really mean and is there potentially a systemic issue or is this more related to the IFDs ability to receive satellite data at a certain point in time?  |
Replies:
Posted By: AviSteve
Date Posted: 08 Sep 2022 at 3:11pm
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It just means that the GPS didn't have the integrity that's required for the nav mode you were in. You can go to the GPS Status page to check HPL vs HAL. If HPL exceeds HAL, you'll get the alert. Unless you're constantly getting it, I would blame it on poor reception at that point in time. ------------- Steve Lindsley Avidyne Engineering |
Posted By: Walter5
Date Posted: 08 Sep 2022 at 3:43pm
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Thanks Steve. I appreciate the quick reply. |
Posted By: eallevato
Date Posted: 10 Sep 2022 at 10:37am
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I noticed that the active frequency on the 440 is 132.025. If you multiply it by 12, you will end up with a number that is very close to the GPS frequency of 1575.42. This is called the 12th harmonic. It is very likely that the GPS was clobbered by transmitting on 132.025. The installation manual tells you how to perform a GPS Interference check. It should have been done during the installation of the 440. Basically, you transmit on about a dozen frequencies around the 12 and 13 harmonics and watch the GPS status to see if it loses reception. Gene
------------- Gene |