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Another "dropping from the sky" event

Discussion in 'Phantom 2 Vision + Discussion' started by Silverminer, Jul 26, 2014.

  1. Silverminer

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    I know there are many discussions regarding sudden descents on the discussion board and I've looked for something that matches my situation but haven't found anything. If there is, I apologize and please redirect me to the correct discussion.

    The low-down: P2V+. Current software updates on both RC and P2V+. Flown probably 50 times or so with no issues other than those created by me.

    Event 1: Flying at about 14,000 ft. (top of Pikes Peak after confirming it was okay with the Ranger), everything is going fine, >60% battery, moving laterally at maybe 10 kts, no significant wind, flew for about 6.5 minutes and then sudden descent. Lucky crash onto just about the only flat spot in the area. No damage, prop had spun off which seemed unusual and I thought that what caused the crash. No vibration or jarring, just slow drop while moving laterally followed by pretty quick vertical descent.

    Event 2: Fresh battery. Same altitude, same general area. Flew for about 2 minutes, flying laterally, same slow drop while moving laterally followed by quick descent. Flipped, 2 props broken but that was it.

    Event 3: Down at about 13,000 ft., about 1 mile away from original crash sites. Same battery as Event 2 but well over 80% to start, over 50% at eventual impact. Flying great for about 5 minutes, moving laterally and notice it's not gaining altitude even though I've got the left stick fully up. I was over a crater (a cirque to be accurate) and pushed the pitch full forward to deliberately crash at the lip of the cirque (before the P2V+ plummeted to the crater below.)

    I've flow at about 12,000 ft. before with no problems and I've heard of others that have flown at greater altitude with no issues. I am familiar (first hand) with VRS and this was not VRS (I was not descending and was moving laterally.) P2V+ was within probably 300 ft. of the RC, in direct line-of-sight. Battery was still on and the camera filming after each crash.

    I'm at a loss. The oddest thing is that I was flying just fine for a long time before it happened. And it happened 3 times in a row! My plan is to go to a safe area at lower altitude (6,000 ft.) and see if it happens again. I would be surprised if I did though. Any suggestions?
     
  2. Silverminer

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    I did a test flight down lower with no issues. It's a mystery and another reason not to fly too close to people or objects you don't want to pay to fix.
     
  3. wattage

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    Can the electronics overheat at higher altitude?
     
  4. Paul K

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    Go to local wether station and have them explain to you differences in wind force at the ground - 6.000 ft and 13.000 ft then calculate how hard the machine must work to fight the wind force .
     
  5. sixx

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    i would think the motors might be getting hotter than normal since they need air to keep them cool but at a higher altitude of course the air is thinner.
     
  6. Silverminer

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    The elevation/motor overheating explanation sounds good, but I'm suspicious as the temperature at the top was probably only 55 F and I've flown with no problem in 90 F+ weather. The density decreases with altitude (pressure) but also increases as the air cools. I'll have to do a little research to see which affects it more: altitude or temperature.
     
  7. Codacious

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    I agree with you, the less dense air could cause cooling problems. It could also be that the Phantom has to work harder to keep at the same altitude. Since the air is less dense, it has to work harder to get more lift. It is hard to say really, its such a small machine. There could be so many small variables that change flight significantly. There are also a ton of weather affects on mts. increasing turbulence. On the side of the mt. that the winds are being forced up, the air is forced to its dew point, creating an abundance of moisture and strong winds. On the leeward side of the mt. strong dry winds are sinking. All of these conditions create serious problems for real aircraft, so I am guessing it could cause a million problems for something the size of a cat.
     
  8. Silverminer

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    The air density at 80F @ 6,000 ft., 20% RH = 0.0584 pcf.
    The air density at 55F @ 14,000 ft., 20% RH = 0.0449 pcf.
    It sounds like the air density/motor overheating explanation might be the correct one. I agree that wind could contribute but the winds were unusually settled this morning on Pikes Peak and the fact that I had flown for several minutes repeatedly over the same areas before losing control leads me to believe the winds might not have been a contributing factor. I've also flown a considerable amount at around 12,000 ft. (but not at 14,000 ft.) in 15-20 kt winds with no issues. But I think you put it well; something the size of a cat could be affected pretty easily by a number of things. Thanks to all for your help.
     
  9. Codacious

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    well the really cool thing is that even though its so small, people manage to put it through it's paces quite often with no issues. I am very impressed by that alone!
     
  10. Silverminer

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    Yes, they are very impressive machines. I did a little calculating last night and got a sense for what affects air density more: temperature or elevation? I discovered that to get the same air density decrease as moving from 6,000 ft. to 14,000 ft., the temperature would have to increase from 50 F to 235 F! This alone seems to substantiate the theory that the motors were overheating as they were working extra hard to keep the P2V+ flying and there was less air available to cool the motors. I have a lot more high altitude flying in my future and I'll add to this post if I find anything of note to add. Thanks to everyone for the help!
     
  11. paulsluxmd

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  12. Fplvert

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    Interesting problem Silverminer. Have you noticed any difference in temperature between motors? I had one on a p2v that got a couple of micro magnetic particles in it. It didn't feel any different when hand turning, but that motor definitely got warmer than the others. (It did come down 330' in 10 seconds) just like your description. I got some of that silly putty cleaner and it easily captured the particles. No problem since, but I am a lot more careful staying out of the dirt. As far as elevation, yes definitely less lift in thinner air. Since you plan on more high elevation flights, it might be worthwhile to get some of the new dji 9450 props. I've seen VRS, and there is a big difference when one motor shuts down! :lol:
     
  13. Silverminer

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    paulsluxmd - As mentioned at the start, I don't believe it was VRS which I cover here:

    https://www.youtube.com/watch?v=Nm_5a4xwdP4

    Did it contribute? Perhaps. The actual crashes are shown here:

    https://www.youtube.com/watch?v=WrWDCaBG4xk

    Fplvert - I was thinking of getting a temperature gun and checking the temperatures on each motor. It was really strange that one propeller had spun completely off during the first crash. You make a very good point that dirt could be contributing to the problem. I've wrecked many, many times and have forced a lot of dirt into everything so it's a definite possibility. I blow everything out with compressed air but that will only go so far. I was not aware of the other 9450 props but will check into that. Thanks!
     
  14. Mal_PV2_Ireland

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    One propeller spinning off, I'm wondering if a motor suddenly stopped and jammed would it cause this?
     
  15. Silverminer

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    That only happened on the first of 3 crashes and all were very similar in nature so I don't think that was the cause.
     
  16. rgsinsc

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    Prop guards or no prop guards, if you bring the copter down vertically and too rapidly you will/can have an issue.

    Normal rule is to descend with simultaneous forward/backward/side motion to avoid the prop wash.......the addition of the prop guards changes the aerodynamics very little.

    The 4 arms of the Phantom itself create more turbulence based on the sq in of obstruction under each prop than any prop guard.

    Another red herring by those who think their addition is a detriment to flying. IMHO
     
  17. Fplvert

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    Pretty obvious from the vid. Not VRS, just a lack of lift. Altitude is a real factor. :roll:
     
  18. Silverminer

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    Exactly. The video is clear: I was not descending into the rotor propwash which, by definition, is a necessary component of VRS. I was moving laterally on all 3 occasions.

    https://www.youtube.com/watch?v=WrWDCaBG4xk
     
  19. Silverminer

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    As a side note, what do prop guards have to do with this discussion thread?
     
  20. WyattEarp

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    Prop guards contribute to VRS.