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Crash at 13,000 feet

Discussion in 'Phantom 2 Vision + Discussion' started by RealDeal, Aug 9, 2014.

  1. RealDeal

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    I've had a dozen successful flights and then it suddenly happened to me. I was up in the mountains near the continental divide. It was calm and everything seemed fine then suddenly only about 2 minutes into flight it quit responding and the screen showed returning home while it flew away from me and into the mountain. I was only about 100 feet away and all batteries were fully charged. I was running 3.0.2. Luckily it crashed into the only mountain top nearby, maybe 100 feet away. What was strange is the motors never turned off, even after it crashed. Does this help to explain what may have happened? Luckily everything appears to be ok other than 2 shredded props. The props were very hard to get off on the side that hit the ground.

    Here's the video. You'll see me take off, fly away to check home lock, then make one pass overhead. Any ideas what may have happened? If it was really trying to return to home, it should have flown upward, then towards me, instead it flew to my left and into the mountain.

    https://www.youtube.com/watch?v=WM-imZLsIeI

    Dave
     
  2. fastsmiles

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    Did you have a good satellite lock before you started?
     
  3. RealDeal

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    I'm sorry for the delay on the video. It is now uploaded and playable.

    I had 11 satellites when I took off and a good home lock. I double checked the home lock by flying away, turning 90 degrees, flipping the switch to home lock, then pulling back on the stick. It flew back towards it's home position (as you can probably see in the video at the beginning).
     
  4. locoworks

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    only a guess, but the motors may have turned off because it sensed it had stopped moving and assumed it had reached home and landed?????????
     
  5. RealDeal

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    The strange thing is the motors never turned off, even after it had crashed...2 of them were still turning and 2 of them couldn't turn because they were smashed into the ground. I watched it start flying to the left and I looked at the screen and it said return home or something like that. Then when I looked up I couldn't see it but it was only about 100 feet away. I clicked on find my phantom and it led me right to it.
     
  6. DBS

    DBS

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    Just guessing here... On the one pass you did over head you showed that killer jeep ... then in the remainder of the video it would seem you flew out and around and in front of that jeep (if you and the kid were still standing in the same place as the flyover)... OR ... The kid walking around got between your controller and the Phantom

    If you let the Jeep or the kid get between you and the Phantom... then that's all it takes... at 5.8Ghz control signal it doesn't take much at all in the way to break the link.

    Then it says RTH on your screen... and flies the wrong way... but lands fairly close by ... that could just be GPS problems sir... GPS is a fickle beast and it doesn't always work properly 100% percent of the time... at the very least you are lucky it was only off by a hundred feet or so and not 2 miles... GPS latency can be effected by large flat reflective surfaces (like the entire side of that huge slope as you flew out over the edge) and it's called the canyon effect by hikers and technicians who experience it deep in the downtown city streets surrounded by tall buildings.

    He said the motors "never" turned off... and you can see that in the video as the props keep chopping the ground.
     
  7. gunslinger

    gunslinger Moderator
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    Could it be that the mountain top was between you and the Phantom? It looks like you had just gone over the peak and had descended a bit...

    -slinger
     
  8. DownunderPhantom

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    Looking at the video it seems as though when you turned 90deg and checked home lock the bird was flying away from you, not towards you (or home position) because it moved far more away from you than towards you.
    After you flew overhead, stopped, turned right, the bird flew towards the ridge line, if it was doing a return to home it would have flown into the side of the mountain before it reached the ridge line.
    looking at the video it seems that there had to be input from you for it to clear the ridge line. just before it reached the side of the mountain it ascended and small amounts of right yaw were given to change its direction slightly, once it cleared the ridge line, it propped, turned (yawed) right then descended, made contact, hopped a few times then ended up on its side.

    One reason why the props were still spinning may have been your bird was waiting for input from yourself. This has happened numerous times with me when I crashed my FC40.

    Was the popup "Returning Home" on your screen the whole time.

    Just my observations from the video
     
  9. JWarren

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    Altitude was too high in my opinion. Seems as though whenever I read about our pilots flying in the mountains I read about crashes. Didn't look to bad and I hope your damage wasn't bad. If you were in the U.S., and there was snow where you were at in August, I don't think I'd be flying that high in the thin air.
     
  10. RealDeal

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    Has anyone else had any problems flying at a high altitude? I'm wondering if the thin air had something to do with it? And maybe I had a bad compass calibration since it turned the wrong way when it tried to return home.
     
  11. cahutch

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    From the video it doesn't look like you lost line of sight.
    But if you did fly behind the jeep or dip down into the canyon enough to lose line of sight, here are a few thoughts.

    When in GPS mode, if the control signal is lost there is no momentum. So it you fly behind an obstacle and lose control, it won't coast through to the other side. It stops immediately and hovers. Three seconds later if you didn't move to regain control it will initiate RTH.

    Could it have hit an updraft or downdraft near the side of that slope?
    If the wind was blowing over that ridge, there could have been a significant downdraft on the downwind side.

    Also, I don't see the 3 second pause on the video before RTH. The phantom should pause and hover for 3 seconds on loss of signal before initiating RTH.
     
  12. cahutch

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    Compass calibration near the jeep might have been a problem.
    And yeah, I've read several stories of high altitude flights ending badly due to loss of lift.
    You also need to worry about updrafts and downdrafts near cliffs and slopes.

    GPS reception could be a problem too near steep slopes, when you descend you lose half the sky and could drop a lot of satellites quickly.
    Most of the GPS satellites you receive are closer to the horizon, not directly overhead. When you drop down over a slope like that, you block half of your horizon. Dropping into a canyon is twice as bad.
     
  13. John Shaw

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    It is a fact that high altitude has an adverse effect on performance. The air is much thinner - at 13000 feet it is only about 60% of the density at sea level. At some altitude you wouldn't have been able to fly at all. Obviously you were able to fly but it would take a much larger percentage of your available power than at sea level. You would have had much less performance left for maneuvering. A quad uses that remaining power to control stability and to maneuver. You may have just run out of maneuver margin. A slight down slope wind could easily be greater than you could over come.
     
  14. flyNfrank

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    After watching two times it looks exactly as if you did not calibrate the compass before flight. If the altitude reads anything above 2.5ft while sitting on the ground, I always reboot the quad which generally only takes one time to get a good number. We are taught in the manual to calibrate the compass each time when going to a new location. Btw, it appeared to even start to dance right before the crash.
     
  15. XL-Studios

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    Spectacular landscape!

    I am not sure exactly when the RTH kicked in but this is what I see.
    She flies over the cool jeep, then she turned and fly (controlled?) over the mountain ridge.There seem to be stick inputs and she is definitely gaining a lot of altitude to get over the ridge at a point much higher up then where you started.
    On the other side of the ridge I assume you lost control? Anyway she turns actually to your direction but looses a bit of altitude ad is on the ground already. You should have set an elevated home point for this scenario.
     
  16. Jstic

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    That looked more like an auto land than a real crash. Any chance you reset home point by accident?
     
  17. slothead

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    Hey Real! Great story and video! I knew as soon as I saw the video that you were in CO. I was there in July and only decided not to take my P2V+ because of the NPS letter that was published June 20, 2014. I really wanted to fly in RMNP while driving from Granby to Estes Park. Thanks for the report. Sorry I can't help with your anomaly.
     
  18. FalconPix

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    My 2 cents.....

    You think you were in Home Lock mode but you weren't... You were in Course Lock mode.

    Home lock only works when you are about 20 meters out I believe. Within that radius, it auto changes to Course Lock no matter what position S2 is in.

    My theory? You assumed a GPS home lock position but it never got one prior to takeoff. It only got a course lock (direction). You accidentally reset your GPS home position while in the air or most likely the Phantom acquired one near the crash spot on its own. Looked to be landing to me.

    I ALWAYS get down on my belly and manually flip S2 until I can visually see fast blinking green lights before all takeoffs
    VISUAL on the lights. Always

    To properly test GPS home position. Fly out at least 30 meters and 90 degrees to the direction you were facing on takeoff.
    Otherwise.... You'd never be able to distinguish between HL and CL
     
  19. John Shaw

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    A little twist on your suggestion...
    Even if you got a home lock as intended as soon as you came back through the 10m HL min limit it would have switched to CL. You wouldn't have noticed since in that maneuver "back" was the same in HL and CL. As far as I know it doesn't automatically switch back. There as some good demos of that on youtube by Zbip57. I really doubt it set a false home position. If it is in CL and you are thinking HL it is not going to be doing what you think. You should have had great GPS coverage, certainly nothing was blocking the view of the sky.
     
  20. BlackHawk388

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    Dave,

    As a crew member with over 4,000 flight hours on various models of the UH-60/MH-60K Blackhawk, I can diagnose your crash with complete confidence because I was in a real life Blackhawk crash that looked just like this although, without a stabilized camera recording the event. It was quite violent when viewed through my own eyes.

    On high mountain ranges and ridge lines like where you were flying when this crash occurred, there is a phenomena we called "Mountain and Ridge Line Wind Sheer" when I was doing HATS training in Colorado in our MH-60K model Blackhawks.

    What happened to your drone is what's known as "Mountain Wave Turbulence". Your drone was quite stable and, likely "dropped" a bit when you flew off the ridge line, looks like to the East, initially. Then you flew what appears to be West and encountered the windward side of the Mline which likely "lofted" your drone a bit. However, soon after flying to the leeward side of the ridge line, you got caught in the "washing machine" effect of winds being projected over the windward side of the Ridge Line and then, forced immediately down on the leeward side.

    Please read this information, you can scroll down to Fig. 80, Mountain Wave, for a thorough explanation of what caused this crash.

    http://pilotoutlook.com/aviation_weather/turbulence

    Saying it was pilot error would be correct. More direct, it was a case of pilot ignorance. I've crashed one of my R/C gliders in this very situation and I do not have ignorance of the situation to salve my wounds. I knew better and still thought I could out-fly the turbulence. I didn't and a $250 glider was lost due to the terrain off of Pikes Peak in Colorado Springs.

    An expensive lesson my friend. Hopefully, you'll see your drone back into flying condition with a minimum of expense! Good luck to you!

    Edit: I should mention the easiest way to prevent this. Altitude is your friend along these ridge lines. The more you have, the more time the drone and the pilot have to react to the downward force of winds aloft at a 13,000' mountain range. Also, the higher over the ridge line, the less the winds forces will affect your aircraft.
     
    #20 BlackHawk388, Jun 11, 2015
    Last edited: Jun 11, 2015
    mad in nc likes this.