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This is somewhat common question and occurrence here. So I thought I would make a thread for people to reference on the topic. This describes how to recognize, avoid, and respond to botched landings. If anyone here flies full size aircraft, you'll recognize this is really no different than recognizing when it's time to go around.
Landing Detection: To understand why this happens, you need to understand how it's thinking first. The solo detects it has landed in the same manner regardless of being in Fly, Fly Manual, or Automatic (RTH, RTM, etc). The pixhawk flight controller detects that it has landed when it's vertical speed is nearly zero (within +/- 20cm/s) for one second despite the motors being at minimum throttle. This takes place when it lands itself automatically, or when you land it manually using the sticks. If throttle is at minimum, either by way of the stick being down or the auto landing reducing power, and the solo stops descending, it is obviously on the ground and will shut down. Note that in these cases, you do not need to move the throttle stick to the left also. Just fully down will do it. Fully down and fully left really only applies to stabilize mode now.
Refusal to disarm, copter won't stop: If it balloons back up, tries to takeoff again, or otherwise refuses to stop and disarm, there are a few common reasons. It's easy for new pilot to get flustered here. Don't.
To recover from this situation: First of all, stop fighting it. You're making it worse. If you keep trying to manhandle the controls to force it down, it will just make things worse. if you try to grab it by hand, you'll make it way worse, and probably hurt yourself. Relax.
Flips when landing: If you have a situation as described above, and the copter flipped over, this is likely why. Remember, it thinks it is still flying. The copter tries to adjust it's horizontal position or adjust it's pitch/roll attitude due to unlevel ground, GPS drift, or pilot stick inputs. There is 1 or more legs on the ground that drag and it will tip itself right over. This is why, as I said above, stop trying to fight it.
The other cause of flipping while landing is hitting the ground while still moving horizontally, catching a leg, and over it goes. This can be due to you moving it around, also know as pilot error
. It could be due to gust of wind hitting it. Or it could be from GPS drift while in FLY or RTH modes. So again, land gently and slowly. Fighting and man handling any aircraft to the ground almost always ends badly.
Crash Detection: The flight controller has a number conditions it uses to detect it has crashed, or to detected it is in flight but beyond recovery. This usually works fine. But, if you've tipped over and it doesn't automatically stop, use the A+B+Pause kill switch to stop the motors. What's happening here is just like everything else above. It thinks it is still in flight and is trying to recover itself. If the pitch/roll is still less than a certain point, as in it isn't completely flipped over, it will not comprehend that it has crashed. For example, if it is just nosed over resting on the props, it will think it is in flight and pitched forward. So it's trying to compensate for that.
Landing Detection: To understand why this happens, you need to understand how it's thinking first. The solo detects it has landed in the same manner regardless of being in Fly, Fly Manual, or Automatic (RTH, RTM, etc). The pixhawk flight controller detects that it has landed when it's vertical speed is nearly zero (within +/- 20cm/s) for one second despite the motors being at minimum throttle. This takes place when it lands itself automatically, or when you land it manually using the sticks. If throttle is at minimum, either by way of the stick being down or the auto landing reducing power, and the solo stops descending, it is obviously on the ground and will shut down. Note that in these cases, you do not need to move the throttle stick to the left also. Just fully down will do it. Fully down and fully left really only applies to stabilize mode now.
Refusal to disarm, copter won't stop: If it balloons back up, tries to takeoff again, or otherwise refuses to stop and disarm, there are a few common reasons. It's easy for new pilot to get flustered here. Don't.
- A rough, fast, rocky, or unpleasant approach and landing will throw off the accelarometers in the IMU. Therefore, it will not be able to detect that it has stopped. It will essentially be disoriented and think it's still in the air. Since it isn't suicidal, it will not disarm if it thinks it's still in the air.
- Air pressure from the prop wash feeding back to the barometer will make it think it is changing altitude. This is mostly suppressed while landing, but it will absolutely compound problem #1 above. It can also happen by itself if have a small narrow landing area that forces the prop wash back onto the solo.
To recover from this situation: First of all, stop fighting it. You're making it worse. If you keep trying to manhandle the controls to force it down, it will just make things worse. if you try to grab it by hand, you'll make it way worse, and probably hurt yourself. Relax.
- Climb up to 5-10 feet and hover. Just give it 5-10 seconds at 5-10 feet so the flight controller can clear it's head. Then land gently as normal. In nearly all cases, it will work properly this time around. If for whatever reason it still refuses to disarm...
- Bring it down and hold it down using throttle fully down. Use your free hand if you have one to activate the A+B+Pause kill switch (hold all three buttons for 5 seconds). It will stop. Or another options is....
- Put Stabilize mode on the A or B button. Land manually in stabilize mode. Throttle stick fully down and fully left will disarm. If you're comfortable flying in stab, this is a great mode to keep on your A or B button along with Fly Manual. This is one of the reasons. But for a lot of new consumers used to fly and fly manual modes, you'll probably just crash. So it requires practice.
Flips when landing: If you have a situation as described above, and the copter flipped over, this is likely why. Remember, it thinks it is still flying. The copter tries to adjust it's horizontal position or adjust it's pitch/roll attitude due to unlevel ground, GPS drift, or pilot stick inputs. There is 1 or more legs on the ground that drag and it will tip itself right over. This is why, as I said above, stop trying to fight it.
The other cause of flipping while landing is hitting the ground while still moving horizontally, catching a leg, and over it goes. This can be due to you moving it around, also know as pilot error
. It could be due to gust of wind hitting it. Or it could be from GPS drift while in FLY or RTH modes. So again, land gently and slowly. Fighting and man handling any aircraft to the ground almost always ends badly.Crash Detection: The flight controller has a number conditions it uses to detect it has crashed, or to detected it is in flight but beyond recovery. This usually works fine. But, if you've tipped over and it doesn't automatically stop, use the A+B+Pause kill switch to stop the motors. What's happening here is just like everything else above. It thinks it is still in flight and is trying to recover itself. If the pitch/roll is still less than a certain point, as in it isn't completely flipped over, it will not comprehend that it has crashed. For example, if it is just nosed over resting on the props, it will think it is in flight and pitched forward. So it's trying to compensate for that.
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