erroneous terrain and too low warnings

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erroneous terrain and too low warnings

4/14/2020 9:17 AM

Robert Laird

Joined: 9/26/2017

Posts: 61

Re: erroneous terrain and too low warnings

Walter --

Interesting information!

In my particular case:

1) Bad reception: I use the SkyFX-EXT external GPS puck with my EchoUAT, so this should not be an issue.

2) Cockpit interference: all my avionics are < 4 years old, and I have no other interference issues. So this should also not be an issue.

3) This is the interesting one, to me. I wasn't aware that the "transponder only sends altitude data when it gets a radar ping " What about the altitude encoder? I thought that is what was providing the altitude data... in between radar pings, anyway. At some point in the recent past I did disable the " Pressure Altitude Support ", but my disabling the Terrain Alerts preceded that.

So, it's clear to me that, now that I have disabled " Pressure Altitude Support ", I definitely need to give Terrain Alerts another try..

If all I ever did was fly in the local area, I wouldn't worry about it and just leave it off. But I have flown over mountains, and will do so in the future, so Terrain Alerts are not a bad thing to have. (And, yes, at my nominal flight speed, it's unlikely I'd ever really *need* a terrain alert, but one never knows!)

Thanks, Walter!

----------------- AutoGyro Cavalon N535RL ||| uAvionix echoUAT w/ SkyFX-Ext ||| iFly 740b / iPad / Android ||| http://www.texas-flyer.com

4/14/2020 9:39 AM

Alasdair

Joined: 10/12/2011

Posts: 411

Re: erroneous terrain and too low warnings Modified By Alasdair on 4/14/2020 12:32:49 PM

Hmm. I have been having some spurious alerts recently on my 740b. I am in Vermont and also have an Echo UAT. I think the Pressure altiitude issue Walter mentioned may be the issue. I can absoutely fly different areas/levels/terrain that result in Pressure altitude errors (i.e. missing) on PAPR reports (resulting from areas of no radar interogation). Interesting.

I will try turing off the pressure altitiude support on the iFly for now report and report back also. Next condition inspection when I have things pulled apart I think I'll be hard-wiring my encoder to the Echo (rather than just letting it "sniff" as it does now) so that it has pressure altitude at all times, with any luck that will clean up my PAPR reports too.

Thanks for the insight. Interesting.

4/14/2020 11:41 AM

Walter

Joined: 7/8/2009

Posts: 2778

Re: erroneous terrain and too low warnings

Robert Laird wrote:

3) This is the interesting one, to me. I wasn't aware that the "transponder only sends altitude data when it gets a radar ping " What about the altitude encoder?

The altitude encoder always knows the altitude, but your transponder is not always transmitting that information. As Robert noted, I think you can hard-wire your Echo to your altitude enocder if it's supported, but most folks just have it passively listening for the transponder. This can cause some big swings in pressure altitude that can appear to be an extreme descent, resulting in a terrain alert.

Walter Boyd
President, Adventure Pilot