I swooped to " - 70 ft " today... and survived! ;)

[aaroncosbey]

Maybe it was me and i did something wrong but...

On the 3rd jump of the day (about 40 mins after the 2nd), i hopped and popped at 5K as usual... Setup as usual, and turned in for a quick 90º @ my usual 300ft marker.

Only i quickly noticed i recovered i bit higher off the ground than normal :rolleyes:
I looked down to find my alti reading "0" Ft!! :eek:

After landing my alti read "-70ft" :shake:

Nothing changed from the 2nd to the 3rd jump of the day, and on the 4th i pressed "im on the GROUND" before getting into the plane. I continued to jump another 7 times with no problems & checked everyones altis for reference on the climb and exit.
It worked fine before and after the 3rd jump.

im baffled... have you any ideas why this happened :confused:

[Roger Allen]

Maybe it was me and i did something wrong but...

On the 3rd jump of the day (about 40 mins after the 2nd), i hopped and popped at 5K as usual... Setup as usual, and turned in for a quick 90º @ my usual 300ft marker.

Only i quickly noticed i recovered i bit higher off the ground than normal :rolleyes:
I looked down to find my alti reading "0" Ft!! :eek:

After landing my alti read "-70ft" :shake:

Nothing changed from the 2nd to the 3rd jump of the day, and on the 4th i pressed "im on the GROUND" before getting into the plane. I continued to jump another 7 times with no problems & checked everyones altis for reference on the climb and exit.
It worked fine before and after the 3rd jump.

im baffled... have you any ideas why this happened :confused:

Hi

Based on the information provided, there are two possible explanations:

1 The N3 doesn't measure altitude, it measures barometric pressure and converts the reading to altitude based on the barometric profile of International Standard Atmosphere. The N3 monitors the barometric pressure at the DZ and when it detects takeoff it locks the current pressure (altitude) as the DZ. If the barometric pressure at the DZ changes between the time you took off, and the time you land then this will show up as an altitude change and that results in + or - altitude reading when you land.

2 Was there anything odd about the takeoff for that jump? If the takeoff is hard to detect this can cause inaccuracies.

If you have any doubts about your N3, please send it back to us and we will chamber test it for you.

Roger

[aaroncosbey]

THats what i figured. I reckoned the alti, took base readings everyonce in a while 'on the ground' and as soon as the acent rate increased it 'locked the' ground pressure reading in for reference.

There was nothing unusual about the jump or the take off. Nothing was pressed and nothing out of the ordinary happened. I jump from a caravan and the pilots ascent rate is fairly steep (we have a short tarmac runway).

I'd be happy to send it back for testing, but i need to use an N3 for reference for an event next month. So unless you send me a replacement (hastle) i'll hold onto my one and keep testing it :D

I wouldnt want it to start reading higher than lower, but wouldnt that be unlikely?

[luisasbilys]

There was nothing unusual about the jump or the take off.
happens quite often to me! ;) Both on my old Neptune and new N3. In general, I don't mind, as the difference is easily compensated with minor corrections in the turn.

But I also have seen a more significant drift in altitude display - like 150meters+. There must be some general problem in air pressure calculation algorithm for some specific conditions. At the same time ALL Neptunes and N3s on the same aircraft were "wrong" in the same way. That happened couple of times already - different Neptunes, different firmwares, so that must exclude a "normal" hardware fault.