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  1. David Cooke

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    I've seen people complain about not stopping level but losing 8-10 feet in altitude when braking. . . . but I cannot find where I commented on this topic before.

    I've got a few hours in low level heli flight Bell206 Kiowa Twin Huey. This reaction seems normal to me given all the aerodynamics, autopilot inputs and human controlling going on, so I decided to experiment with my new P4 and see what it does naturally. It does indeed lose a few feet if you brake quickly and use no other inputs just like a real helicopter. The autopilot/GPS/Sonar does actually compensate to maintain altitude . . so it really depends on how aggressive you are on the controls and how close you are to the ground. The sonar sensors underneath are only effective below about 30ft. I was able to brake slowly and smoothly at about 3ft altitude and it was pretty rock steady with virtually no loss in height.,. . . moving in any direction. If I race in at full speed and brake by just letting go, either forward or sideways it can and does lose up to 6ft or more . . and it can lose even more if I actively reverse direction and brake aggressively.

    If you want to brake aggressively, with no height loss, all you need to do is anticipate the brake and add a little touch of left forward "collective" input just before it stops . . and it reacts quite predictably by stopping quickly with no dip. I suppose dji could program a small control move that would match the rate of deceleration . . but its really a natural control move if you are actually "flying" the machine rather than just "controlling" it.

    I only have about 10-12hrs on the P4 and it has behaved exactly as expected . . very responsive . . and quite predictably. It's auto modes are nothing short of amazing if you can appreciate all of the aerodynamics, gyroscopic forces, response times (latency), processor/firmware behavior, GPS/IMU/Compass calculations, radio frequency and camera performance . . . all going on in the midst of you shoving controls around expecting it to do what you want rather than what you just told it to do. . . . really amazing. I built my own drone 2 years ago so I got a feel for what it takes to assemble and tune a quadcopter with an autopilot and a camera so nice job on this Phantom 4. I love it. . . some last advice too . . keep your "braking sensitivity" under 100 (under Advanced Settings) until you have 10-15 hrs just flying around. Have fun. . . and what are some of your experiences?
     
    Chopstix Kid, thunderbird and sar104 like this.
  2. John Locke

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    I've accepted the small 6-8' yoyo stop effect as standard operating procedure for my P4, even though my P3P has never exhibited that behavior.
     
    Kman likes this.
  3. aaronrivera

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    Just wondering why my p3p never had this problem...only my p4
     
    John Locke likes this.
  4. Intrepid97

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    Well. It is a different machine. Maybe there is something yet to be discovered we don't know about?
     
  5. David Cooke

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    my guess is likely some differences in firmware and to how or in what order the autopilot invokes braking commands while maintaining GPS updates on position . . . there's a lot going on under the hood
     
  6. sar104

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    That's true, but these are fundamentally similar aircraft, presumably with similar FCs, so one might think that a flight maneuver that they had basically perfected on the P3 would be implemented in a similar manner on the P4.
     
    David Cooke likes this.
  7. David Cooke

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    True if the same software team has made it a point to do so . . however . . the P4 has some significant hardware and software improvements so it would not be unusual to adjust certain portions of the code to allow for the new functions to be integrated properly.
     
    sar104 likes this.
  8. snowghost

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    Flying in P-Mode toward my garage, it auto braked with no loss of altitude. Any speed runs would be above treetop level anyway, so I'm not too concerned. I think my brake setting is 80 on both the P3 and P4.
     
  9. John Locke

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    I think the P4 yoyo effect only occurs above 30' AGL when VPS is out of range to work.
     
  10. snowghost

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    Makes sense now that you mention that.
     
  11. Dirby

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    mine doesn't do that.
    I have checked it several times
     
  12. John Williams

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    It's the barometer.
     
  13. John Locke

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    There's a ton of bad barometers out there. Everyone seems to have a yoyo P4.
     
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