david.p.mann
Captain
Flight distance : 18669501 ft
United States
Offline
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Justin,
First - I'm very sorry that you had such a bad first flight experience. I feel for you. I crashed my very expensive DJI Inspire 1 on my first day of flying it a year ago. So, I can honestly say, I know how you feel.
COMMENTS: First, here's what you did RIGHT! You had Beginner Mode turned ON for your first flight (smart!). You made no wild stick moves - in fact, just the opposite. You made very reasonable and controlled movements consisting of small incremental increases in elevation to 9.8 feet and then 13-16 feet, and then to 36 feet and two partial turns with less than 50% stick. And - you knew about (and at least attempted) to execute a Return to Home (RTH) by pressing the RTH button when the P4 started drifting away from you in a spiral. (NOTE: you have to PRESS and HOLD the RTH button on the remote controller for several seconds until it remains illuminated and starts BEEPING continuously.) Finally, you are reaching out to other forum members for input and analysis and respectfully acknowledging that input instead of lashing out at DJI. You want to know what might have happened and what you might have done better/differently -- I commend you for that.
Here's what you could have done better/smarter: You picked a particularly bad location for a first flight - on top of a xx-story building in a very urban, busy area near other multi-story buildings and an elevated freeway. It would have been much safer and a much more controlled environment if you had chosen a clear, open field with no trees or other nearby obstructions or people for your first dozen or so flights. I can honestly say that I would hesitate to launch any of my aircraft from the location you chose - even with a year of flying experience on multiple DJI aircraft.
My Non-Expert (and possibly incorrect) Analysis:
I have reviewed your flight log and the partial video you recovered. Based on only that information, I don't think this was a compass calibration error. I don't claim to be an expert, but I have been flying multiple DJI quadcopters for over a year and I have dealt with failed compass calibrations, which you clearly did not experience (calibration succeeded), and I have experienced "compass calibration errors" caused by calibrating and then taking off from rebar-reinforced concrete structures (driveways, parking lots, even an 8-foot-diameter concrete helipad at my local model airplane park).
Although calibrating your P4 on top of a concrete and/or steel-reinforced building certainly COULD have caused a compass calibration error - as noted by several other forum members, I don't think that's what happened in your case. WHY? In my experience a compass calibration error presents itself as an almost immediate drifting after take-off and is often accompanied (though not always) with a "Compass Error" warning message on the DJI GO app. That did NOT occur in your case.
In your documented flight, you rose to 9.8 feet, executed a 180-degree turn, then rose to 16 feet, made a second 240-degree turn - all with less than 1 foot of drift from Home point as recorded on the flight log. It was only when you started ascending a third time and reached ~36 feet above the rooftop that you launched from that the P4 started spiraling away from you. And again, the P4 had essentially zero drift from home point as you were ascending UNTIL you reached 36 or so feet (above the rooftop).
Based on the satellite image in your flight and the partial video you were able to salvage - you were in a very urban area with possibly other apartment buildings and commercial structures surrounding your launch location. Many of these buildings (including your own) often have satellite dishes, microwave transmitters, cellular phone repeaters and other high-power radio frequency transmitters/receivers. My best guess is that when you reached 36 feet elevation above the roof of the already elevated structure you launched from - your P4 was hit with very strong radio-frequency interference from one or more nearby sources. Another possibility is that a nearby taller concrete and steel building or the freeway interfered with / reflected one or more of the GPS satellite signals that your P4 was currently locked onto.
ADVICE: Since you recovered your crashed P4 you can extract the detailed flight log .DAT file from the internal memory (not the micro SD car) inside the P4 aircraft using a USB cable and a laptop PC (search for instructions on this forum on how to do this) and then send this .DAT file to DJI for analysis. They can examine this .DAT file in detail and possibly identify exactly what one or more things likely caused the spiral drift behavior.
Finally, please take this a very painful, but valuable, lesson learned (like I did with my Inspire crash a year ago). My guess is that DJI will at least offer you a discount on a replacement aircraft. And, your damaged aircraft may be repairable for much less than the cost of the new P4. At the very least, you still have a perfectly good $400 transmitter.
My best wishes for a much more positive experience on your second flight with a new or repaired aircraft, whenever that might be.
Kind regards,
- Dave |
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