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P3P Way Point End of Mission RTH Tested and Verified

Discussion in 'Pro/Adv Discussion' started by Albert D, Jan 27, 2016.

  1. Albert D

    Aug 22, 2015
    Likes Received:
    Winter Springs, Florida
    I actually posted this info in a different forum and was asked to post it here also.

    After reading much discussion and speculation, I decided to do some real time testing with Way point and Orbit missions to verify exactly what happens at the end of missions when battery gets low.

    I conducted the first tests on 1/24/2016. The simple summary is that, with Return To Home set as the Failsafe action, at low battery the P3P will initiate RTH.

    I set up two way point missions and also ran some orbit missions. (These were planned for all of the final portions to occur in an open field at 30-40 feet altitude, 200' to 500' from my observation point, with no obstructions.)

    For the first mission, I set up and ran a 14 minute mission on Litchi with the end of mission Finish Action specified as None. I ran this mission once normally to verify the flight paths, then flew back and landed. I ran the mission again with a fresh battery. About 10 minutes into the mission, I physically powered off my remote controller, to create a Loss of Signal condition. The mission continued to the end of the full 14 minute mission, then the P3P immediately initiated and successfully executed Return to Home, climbing to the 150 ft RTH altitude I had set, then returned and landed safely, about 5 feet from the take off position.

    For the second mission, I added numerous circuits at the far end of the field, creating a mission on Litchi that would take almost 25 minutes to complete (7-8 minutes past the expected battery endurance). I ran the mission with a fresh battery and again physically powered off my remote controller after about 10 minutes, to create a Loss of Signal condition. The mission continued until about 18 minutes, then the P3P executed RTH, returned to home point and landed safely. (Checking later, I had about 7% battery left.)

    My third test mission was to run an orbit mission to end of battery. When battery power got low enough, the P3P initiated RTH (message: aircraft requesting return to home, will go home in 8-7-6... seconds). At the end of the countdown, the orbit stopped, the P3P climbed to RTH altitude, came to home point and landed safely (8% battery left). I was going to test orbit with loss of signal next, but I decided to do the following test to verify the RTH was happening based on when the vehicle calculated how much battery needed to go home, instead of low or critical battery warnings..

    My final test mission was to send my P3P out, run a 3-row panorama (pano mode, mostly for fun and to run the battery down some), then start an orbit about 5000' from home point. Again, when the vehicle calculated it needed the remaining battery to come home, it initiated RTH (without any intervention from me). This time, RTH was initiated with almost 30 % battery (well above my low battery warning) and the P3P came to home point and landed safely. (I thought it said 8% when it landed, but when I re-checked the batteries after I got inside, it showed 6% left.)

    From previous reports and discussion, I had expected the vehicle to operate each mission or orbit until critical battery, then land wherever it was. I was pleasantly surprised to see that, with the Failsafe mode set, the P3P safely brought itself home when it reached the RTH battery level, regardless of RC signal or Loss of Signal.

    I am flying Phantom 3 Pro with latest firmware v1.6.0040 on aircraft and RC. Running the latest DJI Go 2.5.1 and Litchi 2.7.1 on a Samsung Tab S2 9.7 32 GB LTE with Android 5.1.1

    Round 2 of testing completed on 1/26/2016. These were based on additional discussions about how critical battery levels would affect Failsafe operations.

    CONCLUSION: The Phantom 3 Pro firmware calculated Failsafe Return To Home margins are based on the remaining power in the battery, independent of the Low Battery and/or Critical Battery settings.

    This means that, with a low (I use 10%) Critical Battery Level set, the Failsafe Return To Home will kick in, based on how far away it is from home point (initiated by firmware) and bring the P3P home. This is even in a waypoint mission or Orbit mission modes and happens even if there is Loss of Signal.

    IF you use a high Critical Battery Level, critical battery settings will override any Failsafe actions that are set and cause the P3P to land immediately.

    The Low Battery Setting seems to have no effect on any of this and only tells the P3P and RC when to start sounding the Low Battery warnings.

    Three tests today (last two done with orbit mode, but previous tests indicate this applies to waypoint mode also):

    Test 1 (done with DJI Go to allow better monitoring of low and critical levels, as well as fast resetting of battery settings):
    Set Critical Battery Level to 30% and Low Battery Warning to 40%. Flying 200 yards away. No aircraft reaction when low battery warning started at 40% except for indicator lights. When battery level hit 30%, P3P immediately landed where it was.

    Test 2 (done with Litchi for better Orbit mode):
    Critical Battery Level set to 25%. Ran random flight until battery got to about 40%, then initiated an orbit (at 25 feet altitude, about 200 yards away). Orbit continued until battery hit 25%, then P3P landed immediately. (Remember that previous test with similar configuration and critical battery setting at 10% caused RTH to be initiated and successfully completed.) [Just for fun, after this landing, I reset the critical battery setting back to 10%, then restarted the motors and flew it back to my original home point base at about 5 feet altitude instead of carrying it.]

    Test 3:
    With Critical Battery Level set to 10%. Ran random flight until battery got to about 40%, then initiated an orbit (at 25 feet altitude, about 200 yards away). When battery got to about 25% (3:30 remaining flight time indicated), turned off RC to create Loss of Signal. Orbit continued for about 3 more minutes, then RTH was automatically initiated and completed successfully. (This is similar the previous testing, but this time had the actually loss of signal.)

    The test I will not do, because I do not have a big enough field to do this safely, is to set Critical Battery level about 25% and run far enough out so that RTH is initiated before critical battery (at 30-40% battery) but the battery would drop below critical well before it got back to home point. I suspect that the aircraft will abort the RTH and land immediately under these conditions.

    After all of these tests, I have these final thoughts:
    - Always have Return To Home and an appropriate RTH altitude set before flying.
    - I will continue to keep my Low Battery Setting between 20% and 25%. I am always watching my battery level anyhow when I am flying, so I don't need to listen to the repeated Low Battery Warning announcements.
    - I will continue to keep my Critical Battery Setting at 10%. 10% is enough to land from 400' and way more than enough to land from 160' which is the highest RTH altitude I typically use. If I do loose signal and RTH initiates, I just wait and the signal usually reacquires during the automatic RTH trip. If that rare RTH situation ever happens that I did not reacquire signal, I don't want my P3P landing somewhere random if there is enough battery to get it closer to home or closer to reacquiring signal.
    Brock123, stoneyb245, joeruby and 2 others like this.
  2. joeruby

    Jan 25, 2016
    Likes Received:
    Glendale, Arizona
    Very well thought out series of tests, and a well documented report. I took the trouble to print it out and add it to my flight book. Thank you so much for taking the trouble to post your findings.
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