Primarily for general aviation discussion, but other aviation topics are also welcome.
By thegasguy
#1852554
On the way to Popham today , just in the tight bit south of Biggin Hill, my Skyecho 2 suddenly showed red on the gps light and Skydemon flagged up gps failure.
A bit inconvenient but not too much, switched to 'location services' instead of the wifi from the SE2 when conditions allowed, and all good with Skydemon

However, all attempts to re-boot the SE2 have failed.
I've tried holding down the button as well as the classic turning it off and on again, and the gps light just stays red.

Any ideas out there?

It's worked perfectly up to now, and the failure was in flight with a reasonably cool cockpit and a good battery light - although not fully charged.
Ive just completed a full re-charge at home , and no change.

Is the internal gps toast ?
By thegasguy
#1852561
Further info on SE2 failure is;
Ive downloaded and applied a software update - no change, and also noticed that the status page, accessible via wifi, unsurprisingly says ' no satellites '

Also, the barometric altitude says 'minus 296 feet' which definitely is a surprise in mid- kent.

I'm pretty sure that it's packed up, but any ideas are very welcome.
By thegasguy
#1852581
Boxkite; that makes sense in that it’s high pressure at the moment.

I had noticed that when it sees other aircraft, it reports their relative height as being somewhat lower than reality.
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By ls8pilot
#1852584
If the GPS has lost the almanac it could take some time to find satellite info... If you've not tried it already I would leave it with a clear view o f the sky for an hour or two. However does sound like a n internal failure, so maybe a warranty return?
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By GrahamB
FLYER Club Member  FLYER Club Member
#1852585
thegasguy wrote:I had noticed that when it sees other aircraft, it reports their relative height as being somewhat lower than reality.

How do you know that?

If all the other ADSB-out units that you are detecting are emitting pressure alitude, i.e. to the same same datum, then the separation between you and them is the separation, irrespective of the QNH on the day*.

*I'm aware that there could be small differences between actual and reported separation due to temperature and ambient pressure effects but these would not be detectable to the human eye.
By riverrock
FLYER Club Member  FLYER Club Member
#1852592
Each cockpit will have a different internal pressure compared to others & outside ambient, depending on venturi effect (reduce cabin pressure), RAM air (from vents, heater which will increase pressure dynamically with airspeed) and how well sealed it is.
If your aircraft had an alternate static source, try and see the effects.
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By gaznav
#1852616
As @ls8pilot states. Try turning it on putting it in clear view of the sky for 45 mins to see if it’s a GPS Almanac issue (it should download every 12.5 minutes, but give it chance over 2 downloads). Don’t dabble with it during that time - you may find your attempted resets have caused the issue of a GPS ‘cold start’ to be reset each time. If that works, then that is the only issue I can think of, otherwise it’s broken and would need to be a warranty return.

The GPS Almanac is normally uploaded daily with up to 60 days of data that stays valid for 90 days before it needs to fully download again. The GPS Control Segment update it at least every 6 days. So it may have got it’s knickers in a twist on a changeover, then if you were attempting reset inside the 12.5 minute download cycle, then you could easily get stuck inside the loop. The only other thing is if the GPS took a “bum” fix for a few minutes and it’s position is more than 60 miles away than where the last downloaded almanac thinks it is - that can cause a ‘cold start’ that takes that time to resolve itself.

On the Sentry, I used to carry a flash-card of the latest GPS Almanac in my flying suit pocket to force the aircraft GPS back into a faster start mode (warm start about 30 seconds and a hot start less than 15 seconds) should the Almanac get corrupted through unintentional or deliberate jamming. It is one of those things we have to live with, but normally bigger aircraft will have Laser Inertial Navigation Systems (LINS) to back up the GPS, should it fail for short periods. In GA we don’t have that luxury :thumright:
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By GrahamB
FLYER Club Member  FLYER Club Member
#1852622
riverrock wrote:Each cockpit will have a different internal pressure compared to others & outside ambient, depending on venturi effect (reduce cabin pressure), RAM air (from vents, heater which will increase pressure dynamically with airspeed) and how well sealed it is.
If your aircraft had an alternate static source, try and see the effects.

That’s a good point, but it would reduce apparent separation in one direction and increase it in the other.
By johnm
FLYER Club Member  FLYER Club Member
#1852640
I haven't used my SE2 for a couple of weeks, so I charged it up then switched it on and put it on a table at the top of the garden. Just over 10 mins later GPS went from Red to Green. Moral, repeat the exercise if there's a gap of more than a week between flights.
By BoeingBoy
#1852908
I also had a GPS failure of my SE2 on Saturday, just as I took off on my Instrument Rating Renewal. Just what I wanted! :roll:

A recent update to SkyDemon included an automatic fall back to internal location reference but this didn't happen. I found myself tapping furiously to get the GPS back through the tablet whilst also negotiating a zone entry. Speaking to someone else they also confirmed that they've not seen the fall back working. Has anyone else found it a problem?
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By Miscellaneous
#1852936
Interesting thread. Why so many drop outs all of a sudden?

I had one myself when leaving Glenforsa. I put it down to the SE2 battery being discharged. Although I believe it was charged and I recall switching it off I can't be 100% sure it was charged or that I didn't inadvertently leave it on overnight at Glenforsa. So certainly not enough evidence to be pointing fingers at the device.

That aside I am curious at the log for the flight. It makes sense the for the blocks time to stop when the GPS was lost and it makes sense the engine time is simply based on the clock, however I'm a bit confused as to why the flight time is recorded as 1.09? My understanding was the flight time is based on speed? It seems the end flight time coincides with engine off time? :?

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By thegasguy
#1853227
Big thanks and respect to Uavionix for immediately sending me a replacement unit.
It arrived today, 2 days or so after asking for help in diagnosing the fault. I didn't ask for another unit as it happens.

I shall be very interested to see if the height displayed of other aircraft is more accurate, or if it's a quirk of the very draughty Jodel cockpit environment throwing the Baro out of whack.

Answering a previous enquiry: I know it's wrong because of flying in company through controlled airspace on a specific altitude clearance - and then checking again with other aircraft and my own two, pretty good, altimeters.

Anyway, thanks again Uavionix- very good customer service.
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