IFD 5 Series & IFD 4 Series Touch Screen GPS/NAV/COM

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IFD540 LPV Vertical Alert Limit

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=2331
Printed Date: 16 Apr 2025 at 1:19pm
Software Version: Web Wiz Forums 12.01 - http://www.webwizforums.com

Topic: IFD540 LPV Vertical Alert Limit

Posted By: by9468840
Subject: IFD540 LPV Vertical Alert Limit
Date Posted: 24 Feb 2022 at 8:08am

I was on course to intercept LPV final aproach last night and suddenly I saw LNAV/VNAV on the screen and Alerts flashing amber. It said "LPV VAL alert" can't remember exactly what it was and it had a counter that looked like about 1min. Approach was degraded to LNAV/VNAV but GP never became available. I had to abort and come back resequenced for an ILS approach instead.

There is no information on the manual about such LPV Val alert and I have never seen it before.

does anyone know what that was?
Baris

Replies:

Posted By: AviSteve
Date Posted: 24 Feb 2022 at 10:26am

Maybe the alert said "LPV Unavailable Use L/VNAV DA"? That alert is generated when the GPS doesn't have sufficient integrity to to the LPV approach. The IFD compares the Horizonal Protection Limit (HPL) from the GPS to the Horizontal Alert Limit (HAL) associated with the approach. If HPL exceeds HAL, you'll get the alert and the LPV approach is unavailable.

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Steve Lindsley
Avidyne Engineering

Posted By: by9468840
Date Posted: 11 Mar 2022 at 8:54am

Hi Steve

this is what I have in the logs

Select approach VTF.RNAV 6

vDev failed - couldn't compute it (actLegNOTonFinal hat=2890 notPaQual Integ OK)

Lev:0 Cmd:2 Pri:008/000 Rpt:01 Own:00 Sent:00 IssueTm:65544 Dur:0 AD:0 ID: TermMode sMsg:<> lMsg:<>

Lev:3 Cmd:0 Pri:008/000 Rpt:01 Own:00 Sent:00 IssueTm:65544 Dur:0 AD:0 ID: Approach sMsg:<> lMsg:<>

Lev:1 Cmd:0 Pri:008/000 Rpt:01 Own:00 Sent:00 IssueTm:65544 Dur:0 AD:0 ID: UseLV2 sMsg:<LPV Unavailable Use L/VNAV DA> lMsg:<Exceeded LPV VAL>