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"Fail safe" brain teaser

Discussion in 'Pro/Adv Discussion' started by LeonThePeon, Feb 9, 2016.

  1. LeonThePeon

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    Here's a brain teaser for you:
    Facts:
    - Home point was set
    - Flew to about 350m away
    - At 350m away, I tried to land (controlled area with only family in the area)
    - landing site is about (-)75ft AGL from home point (site is 75ft below home point elevation)
    - lost RC and video signals just inches from the ground (I know why - so don't worry about why I lost signal for something that should get 3mi range for this topic)
    - it hovered for about 30 secs (after signal was lost)
    - then it landed, props stopped but battery on the P3P was still on (94% battery life when landing)
    - record shows that my elevation at landing was -24m so it did record negative elevation.

    Variable:
    - after FW update - fail safe altitude setting was set to 30m (I had it at 120m before - Note: always check after updates)
    - Fail safe was set to "return to home"
    - I've only flown from home and at same elevation, just a matter of backyard/front yard (regarding home point sets and compass calibration)

    Question:
    Why did it not initiate fail safe RTH when signal was lost for 30secs?
     
  2. msinger

    Approved Vendor

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    Post your log :)
     
  3. Mark The Droner

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    Okay I'll play.

    I don't have a P3 so I'm at a disadvantage, but I will guess you were on a GS mission and you were using a 3rd party app.

    Disclaimer: I'm on my second craft beer
     
  4. MattM123

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    Loved the disclaimer!
     
  5. LeonThePeon

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    Wasn't much on the app, but I just remembered there are flight logs on the P3P - gotta find an old netbook I can connect it to. Doesn't want to show me .Dat files on Mac
     
  6. jiggyb21

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    If we're playing a game then you need to share why you lost both RC and video inches before the ground. I always lose video WAY before RC.
     
  7. DaGunn

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    The FAA now states that you may not comment on UAV posts while under the influence of alcohol or drugs.
     
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  8. With The Birds

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    Do you know the answer....? If yes i cant be bothered with riddles.
     
  9. With The Birds

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    Joking.... i think you flew straight up and list signal due to antenna orientation.
     
  10. With The Birds

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    Critical battery level....
     
  11. neven

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    It did. Home point was updated when you landed and took off the second time. Since signal was lost within 20m of (new) home point it just landed there.
     
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  12. nick4098

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    That was my first thought, but re-reading the OP it seems like he lost signal BEFORE the Phantom landed, so in theory it should have RTH at that point to the original recored home point. I guess that to record a new home point, it would have had to have landed, and the motors stopped at the landing point.
     
  13. neven

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    Well, only other thing possible is no GPS signal when RC signal was lost.
     
    #13 neven, Feb 10, 2016
    Last edited: Feb 10, 2016
  14. Dome

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    OMG, I'm afraid that if P3 is at <0ft elevation (relative to start home point) and you hoover for sometime at negative altitude (the P3 feels itself steady as on ground) new home point is set !!
     
  15. neven

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    I hope not! Sometimes I take off the deck on 10th floor and go below home point altitude to take pictures. Sometimes that means I'm hoovering for 20 to 30 seconds in minus altitude. If Home point is set to that location and I loose a signal or hit RTH that would be catastrophic!
     
  16. Dome

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    I hope not too !! But I never found myself in such a situation ....
     
  17. Mark The Droner

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    No - it wouldn't do that. It senses the difference between hovering and landing regardless of its altitude. And even if it did actually land, it wouldn't set a new home point on its own.
     
  18. LeonThePeon

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    Well, just an update - the .txt log from the DJI Go app doesn't tell me anything (No third party app used). Healthy Drones plots out the flight - it showed good signal all the way, with a 100 signal strength score; GPS was 15+ at the end. Notifications just shows the standard stuff for assisted takeoff (first 3sec). As if the flight "ended" successfully.

    HealthyDrones.com - Innovative flight data analysis that matters

    Converting what I could on the DAT file doesn't show me much either - using some online parsers. It just gives me the telemetry data - and nothing much as to RC signal or any changes to RTH.

    (I'm guessing DJI has the secret formula for a program to get REAL in depth that I can't seem to find).

    Flight time was less than 2 mins; but I didn't turn the P3P off until about 15 mins later.
     
  19. LeonThePeon

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    Structural interference - was fading when I was landing. I thought I was close enough to the ground to complete the landing and shut down before total signal loss
     
  20. LeonThePeon

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    Haha - on the one hand, I didn't want to add to the myriad of bad news found on this section of the forum. I've enjoyed flying it and to tell you the truth - I'm a "stick and rudder" guy, so I'd rather be flying it home rather than testing RTH out.

    But if you're going skydiving, you'd want to have that assurance that your backup chute is ready to go and prefer to never have to use it.