Fatal Barometer/Altitude Issue Documented. Please Comment.


Jan 1, 2014
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Albany NY Area
By way of background. I am a very serious pilot. I am a video professional and I have been flying DJI platforms for more than 3 years accident free. I am currently in pilot school, because I believe in doing it right and that knowledge is safety. Lastly I calibrated my IMU and compass early that afternoon and had 2 epic flights without incident.

Fast forward 2 hours:
Right at dusk I wanted to do a quick bay flight. Shortly into the flight I got a warning that said: “Warning:]data exception (In Flight) (Using)”

Shortly there after on an attempt to get back the Phantom became erratic, losing and gaining large altitudes and alternating between being sluggish and then hypersensitive to stick input. Altitude and vertical speed telemetry became unreliable. After a long series of dramatic assents and descents I got the bird back within 1500 ft of me before it went down. I have heard a lot about these unexplained altitude issues and (hopefully for the common good) decided to spend the afternoon putting together a video of the visual flight data and the fpv to show the forum in detail what I experienced. I would sure appreciate it if a few of you would put your eyes on it and give me your feedback. Ultimately I would like the group’s opinion on if this was truly un avoidable due to mechanical failure and if I will have a leg to stand on with DJI.

PS so as to be accurate I did not compress time on this 3min 8 sec flight so you can watch it all or the action begins a 1 minute 24 secs if you just want to cut to the chase.

Vimeo Link:
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Password: djip4
My experience with a barometer error was that I was flying towards a storm front comming in, I decided to go out befor the storm got close to me, the sky was overcast but no rain and the wind was around 15mph. Flying into the wind towards the front and quite a ways out I got a barometer error in GO, the message was a big red square top center of GO stating the error and to land with caution. I was unexperienced at that time and I think I had to cancel the auto land at this point too. Even with the error the AC remained at the same altitude of about 350 feet, flew back home without a glitch as if the AC new the error was erroneous because my max altitude recorded was over 5000 feet and the AC stayed at the same altitude. The speed comming back was awsome Go shows 76mph, this is probably high but it came back quick. Landed the craft did a off and back on and all was good, since then flew 1.5 million feet and it never happend again. About 5 minutes after my landing and back in the house the wind became really high ( I got back just in time). I did some pressure calculations and you need a presure differential of 2 psi to get those numbers. I think the wind speed in flight plus a drastic pressure drop because of a storm comming in would cause a barometer error but I would have never expected that big of altitude difference, 2 psi in a tire is not much but 2 psi atmospheric is huge.(possible but not probable)
Doesn.t the gps allow the bird to determine its height also? So if only the barometer fails shouldn.t it still be able to know its height?

What i learnt from the video is to maintain lots of height if the drone starts bobbing up and down
Many say only the barometer is the only altitude instrument in the craft, after flying 3 miles in the wind with no baromete (error stayed on for the rest of the flight) and maintaining altitude with no stick input, I tend to think that the P4 can use gps for altitude, tracking 16 satelites can give a pretty good altitude reading, I use my hand held GPS that has no barometer and can walk in the bush and track my elevation, it's not precise but it a darn good tool. Would be nice if dji would eleborate on this.
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