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Motor Cut-Off in Flight

Discussion in 'Phantom 2 Discussion' started by ussvertigo, Nov 21, 2014.

  1. ussvertigo

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    Just got my second P2 with 3D gimbal with first fpv system and my last flight almost ended up in nearby trees. I had flown up to approx. 200m to video at night and at 38% battery started to descend, and as expected with new updates it was very slow coming down. I refrain from holding down the throttle more that 2-3 seconds since the manual is not clear to me if in GPS or ATTi holding the throttle down all the way will not shut down motors as long as it is in flight. So still a ways up it got to the first battery warning (which was at the time set for Go Home), but it started flying off over trees next to my driveway and began descending (probably 30-40' from take off point). Just before hitting the tree tops I gave full throttle and struggled to get it away from the trees. Only until I switched to ATTi could I get some control and get back over head to land, but it still acted like it wanted to go somewhere else and almost broke my neck to catch it. I have switched off the "Go Home" under battery options and plan on higher battery levels to start heading back home.

    My reason for this post is to get response on the throttle issue. What is the fastest way to descend, can the throttle stick be held all the way down until a safe altitude (GPS or ATTi), or will this shut off motors. The manual at one point seems to indicate this will not shut motors off, but later states under no circumstance hold the throttle down while in flight in any mode. I notice if I catch it which is approx. 7 feet higher than it took off and hold throttle down it shuts motors off after about 3 seconds. Hence why I don't hold throttle down more than a couple of seconds, but sure needed to come down faster that night. The home point being off so much didn't bother me as much as the close call with the trees, at least I would have know where it was at
     
  2. Damon

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    I have held down throttle to bottom for well over 9 seconds straight with no motor kill. The CSC commands are the only way to shut off motors in flight.

    That being said, if you had a perfect updraft that happened to hold the phantom in one place (altitude) then it would think it has landed and shut off.
    The odds of that happening are quite rare.

    The Phantom will only descend 2 m/s regardless if in ATTI or GPS mode. The only way to come down faster is programming S1 bottom level to manual. (Not recommended unless you have mad flying skills)
     
  3. ussvertigo

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    Thanks for reply, I needed that for confidence. And the comment on an updraft, I agree. It must sense no movement and throttle down for X amount of seconds before shutting down motors. But when I hold P2 by hand while observing the IMU readings in Phantom software, its hard to hold still enough to keep values from changing. But hopefully I won't let myself get caught again that low on battery that far out.
     
  4. malibusteve70

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    I hand catch land most of the time and use the throttle down stick to kill the motors once I have it in my hand, is there some fail safe where the phantom knows that it is in the air and wont shut the motors down? I know I've seen videos of guys holding the sticks down for 8 seconds plus with no issue, just really trying to figure it out. Thanks.
     
  5. ussvertigo

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    That's what I'm thinking. It detects maybe no longer descending before shutting down. I think I have confirmed to some degree just awhile ago by catching and throttle down, while moving the P2 about aggressively and motors keep going until I stop moving it. That's as scientific as I can get.
     
  6. N017RW

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    Yes, you got it.

    When there is no longer any measured barometer pressure change it 'assumes' it is no longer airborne.
     
  7. wkf94025

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    I don't post online videos that are clearly in violation of FAA recommendations or common sense. However, last week outside the US over our private golf course and with no commercial or GA traffic around, I hit 1,500 meters AGL, then descended safely in Manual mode. This was not for fun or PR, but the altitude necessary to capture the entirety of the golf course with my 5.4mm lens. Very fun flying that high and descending at 10m/sec after bagging the shot. Battery was at about 60% at turnaround point. FWIW, I believe 2,000 meters is quite achievable. Manual mode was scary at first, but is now an essential capability for my video/still missions. I cannot imagine choosing to CSC kill the motors, when idling the motors in Manual mode achieves rapid descent with immediate ability to revert to ATTI and regain stable flight.

    Kelly
     
  8. ussvertigo

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    What are you calling manual mode? I only have GPS-ATTi-Fail Safe choice on Sw. You using a different TX? Does it give more options than Phantom Assit Software?
     
  9. wkf94025

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    See screen shot below of Assistant page where you can set third option on Basic / RC screen. This shot was taken without my P2 attached, so value here different somewhat with those with P2 attached. In the bottom right corner, control mode switch has pull down menu in right-most switch setting. One of those options is Manual, when P2 is attached and powered on.

    If you have an iOSD, you will see Manual in place of GPS or ATTI when manual mode is enable. Suggest testing it VERY briefly at sufficient altitude for recovery in ATTI mode after brief flirtation with Manual mode. In absence of left stick forward/up, quad will drop at 10 meters per second or better as motors and props idle with no commands from FC to maintain altitude.

    Kelly
     

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