Confirmed Bug Report (Touch and Go Bug)

[PureSQNut]

I am not sure who has or might have experienced this but I experienced a nasty little bug that in my opinion is easily avoidable and yet if not caught could be a major safety issue when props explode form hitting the ground.

I have received word back from DJI this is a confirmed bug in the current software as I provided them with flight data logs, detailed reproduction instructions and 3rd party video and the fact that it was easily reproduced on more than one I1.

The bug has to do with touch and go landings but with any attempt to slow down the motors (but not stop them) and then taking off.

Here is a detailed step by step of how to reproduce and what happens- (WARNING - IF YOU ATTEMPT TO REPRODUCE THIS AND DO NOT TAKE CAREFUL ATTENTION DURING THE RE-TAKE OFF ATTEMPT YOU WILL CRASH YOUR I1. MY RECOMMENDATION IS DON'T DO IT!)

• land the Inspire 1 from your current flight but do not stop the motors
• After the I1 has landed using the controller attempt to partially slow down the rate of speed of the motors so that it cannot try to take off or drift etc due to having a reasonable level of lift.
• take your hands off the controller and in a very short time the speed of the motors will increase on its own. However it is not all of the motors doing this, sometimes its 1 sometimes its 2, maybe even three.
• At this point on of two things will happen-
  • The I1 will attempt to start to lift on one side which would result in dumping it over on its side
  • The motor speed will increase and the I1 will not go anywhere.
• If you have experienced #2 then VERY SLOWLY attempt to take off using the throttle and only 2 or 3 of the motors will start to increase speed and one side of the I1 will stay pinned to the ground.
  
  Here is a video of what happens -
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  Please listen with audio when watching the video. Note that when you hear the motors slowly increasing in speed my hands are not even touching the controller.
  
  
  I did get a email back confirming that this is an issue however it is EASILY avoidable. Simply if you land and make ANY attempt to stop your motors or slow them down make sure they STOP. Then restart the motors and there is no issues.
  
  this post is not to flame DJI or cause and issues for them and I am posting the permission of the person that I was talking with, so please no flame wars. I simply don't want to see or hear of any more broken I1s heading back to ANY of the DJI repair facilities and most importantly allow a bug that is easily avoidable to be known so that we can all keep our birds in the air.

 

[Ian Fraser]

Thanks

 

[PB30X]

If I'm not mistaken the Phantom also did this.. As for 3 engines firing I can't elaborate, but know for a fact at times it did seem to take back off without touching the controllers.. I have also experienced this with the Inspire also. I'm Not a touch and Go pilot. I have a routine battery drain sequence, and have seen this on my Equiptment several times not thinking it was a bug..

Good Find[emoji6]

 

[NEJO/Wisconsin]

Fair enough. How many people do you think will try it?

 

[PureSQNut]

Hey PB,

Let me clarify on the "Touch and Go".

My circumstance was I was doing some practice shoots for a music video we are shooting this weekend and I landed for a very brief conversation and review with my camera operator / co pilot of the prior 10 second clip we just shot (vs leaving it hovering in the air) and that's when we noticed it starting to accelerate while we were starting to watch the video. Theoretically I cound see this situation happening for other people doing something similiar. But easy enough to simply shut it down all together as well.

 

[PureSQNut]

Fair enough. How many people do you think will try it?

lol... I don't even want to know.... I'm trying to not even think about it.

 

[DCGOO]

I do not think this is a bug at. The Phantom 2's all behave that way. After landing, the bird still thinks it is flying. As GPS and Altitude drift around a little, the motors will adjust to maintain the on-the-ground altitude. The only time the I3 is truly at idle, is immediately after motor starts after being shut completely off. You cannot land, leave the motors on, and take off again, without shutting down in between. IOW, there is no "touch and go" maneuver.

I do not have a lot of experience with non-DJI products, but I would expect just about all to do the same thing. When you land, you must power down.

I am not sure who has or might have experienced this but I experienced a nasty little bug that in my opinion is easily avoidable and yet if not caught could be a major safety issue when props explode form hitting the ground.

I have received word back from DJI this is a confirmed bug in the current software as I provided them with flight data logs, detailed reproduction instructions and 3rd party video and the fact that it was easily reproduced on more than one I1.

The bug has to do with touch and go landings but with any attempt to slow down the motors (but not stop them) and then taking off.

Here is a detailed step by step of how to reproduce and what happens- (WARNING - IF YOU ATTEMPT TO REPRODUCE THIS AND DO NOT TAKE CAREFUL ATTENTION DURING THE RE-TAKE OFF ATTEMPT YOU WILL CRASH YOUR I1. MY RECOMMENDATION IS DON'T DO IT!)

• land the Inspire 1 from your current flight but do not stop the motors
• After the I1 has landed using the controller attempt to partially slow down the rate of speed of the motors so that it cannot try to take off or drift etc due to having a reasonable level of lift.
• take your hands off the controller and in a very short time the speed of the motors will increase on its own. However it is not all of the motors doing this, sometimes its 1 sometimes its 2, maybe even three.
• At this point on of two things will happen-
  • The I1 will attempt to start to lift on one side which would result in dumping it over on its side
  • The motor speed will increase and the I1 will not go anywhere.
• If you have experienced #2 then VERY SLOWLY attempt to take off using the throttle and only 2 or 3 of the motors will start to increase speed and one side of the I1 will stay pinned to the ground.
  
  Here is a video of what happens -
  To view this content we will need your consent to set third party cookies.
  For more detailed information, see our cookies page.

  Accept third party cookies
  
  Please listen with audio when watching the video. Note that when you hear the motors slowly increasing in speed my hands are not even touching the controller.
  
  
  I did get a email back confirming that this is an issue however it is EASILY avoidable. Simply if you land and make ANY attempt to stop your motors or slow them down make sure they STOP. Then restart the motors and there is no issues.
  
  this post is not to flame DJI or cause and issues for them and I am posting the permission of the person that I was talking with, so please no flame wars. I simply don't want to see or hear of any more broken I1s heading back to ANY of the DJI repair facilities and most importantly allow a bug that is easily avoidable to be known so that we can all keep our birds in the air.

 

[Sky High Photography]

Why would you land and keep the motors spinning, especially while you are having a conversation?
I just read your post on the other forum but after hearing how you found this "bug" now I realize that you found it by being unsafe.
I'm sorry, but this bugs me. Turn off your motors when you are not paying 100% attention to the craft. It isn't that difficult to start and stop the aircraft.
There's my vent...

 

[PureSQNut]

Why would you land and keep the motors spinning, especially while you are having a conversation?
I just read your post on the other forum but after hearing how you found this "bug" now I realize that you found it by being unsafe.
I'm sorry, but this bugs me. Turn off your motors when you are not paying 100% attention to the craft. It isn't that difficult to start and stop the aircraft.
There's my vent...

at the time of discovery there was no safety concern at all given the surrounding. And I original called it a quirk, dji called it a Known bug.

next tine ill stop at talking with DJI and let others find out the hard way on their own.

no wonder so many people are afraid to speak out even in good intent. I'll go back to minding my own.

nit sure what you think my intent is but sky high, really. I love my I1 and I would only hope if somebody finds an issue regardless of the circumstances they speak out and le us know.

 

[Sky High Photography]

at the time of discovery there was no safety concern at all given the surrounding. And I original called it a quirk, dji called it a Known bug.

next tine ill stop at talking with DJI and let others find out the hard way on their own.

no wonder so many people are afraid to speak out even in good intent. I'll go back to minding my own.

nit sure what you think my intent is but sky high, really. I love my I1 and I would only hope if somebody finds an issue regardless of the circumstances they speak out and le us know.

What if you, inadvertently, bumped your sticks while having your conversation or your film guy was reaching to touch the screen and hit a stick... Although it is coming across as critical, I would never leave the motors running on the ground.
Don't be afraid to speak unless your are not prepared to hear others opinions. I am simply saying that I find it unsafe to touch and go the machine.

 

[DJeff1]

This happened to me the other day but I thought it was just the wind. I had just landed and was getting ready to take off again and one side of the I1 started to come up and I thought it was a gust of wind so I brought the sticks back and killed the motors. I put the I1 back in the case and said "live to crash another day."

 

[DCGOO]

It IS a known "characteristic," but as I said above I would not call it a "bug." I am surprised that tech support referred to it as a bug. All Quads do the same thing. Think about it for a second, if you are hovering a few feet off the ground, the aircraft moves around a little bit in all directions, up and down. There is no difference between hovering at 10 feet, versus hovering on the ground. If GPS or altimeter varies a little, making the bird think it is descending. Therefore it will push up slightly, with one or more props, likely causing it to tip over. The only way to keep it on the ground, is to pull back the throttle, which of course, shuts it down. If the stick is centered after take off, the assumption is it is flying.

Remember, throttle is not truly the throttle. Rather it is a user request to change altitude. The computer figures out which motors to goose to honor that request.

at the time of discovery there was no safety concern at all given the surrounding. And I original called it a quirk, dji called it a Known bug.

next tine ill stop at talking with DJI and let others find out the hard way on their own.

no wonder so many people are afraid to speak out even in good intent. I'll go back to minding my own.

nit sure what you think my intent is but sky high, really. I love my I1 and I would only hope if somebody finds an issue regardless of the circumstances they speak out and le us know.

 

[PureSQNut]

What if you, inadvertently, bumped your sticks while having your conversation or your film guy was reaching to touch the screen and hit a stick... Although it is coming across as critical, I would never leave the motors running on the ground.
Don't be afraid to speak unless your are not prepared to hear others opinions. I am simply saying that I find it unsafe to touch and go the machine.

touching the screen on the second controller does not merit the safety concern that you speak of as it only controls the gimbal.

yes shut the motors off, I practice this normally but as I intended to land and take off (mainly because my shot startedwhile on the ground) I didnt do it this tine and I almost found out a valuable lesson the expensive way.

simply enough I know I'm not the only one to experience this. I'd rather say, hey this is what happened, how it happened and how to not do it and help at least one person from not having to send in another I1 to get fixed.

call it what you want. I'm gonna keep in flying and enjoying my I1

 

[B Dog]

I for one appreciate knowing about this regardless of what you want to call it! Thanks for reporting on an undocumented feature that helps me to understand the Inspire more.

 

[Kilrah]

All multis will do this (look up integral wind-up). Tiny sensor measurement errors accumulated over time cause the FC to think it has moved and want to compensate to continue matching the stick order. As it's on the ground adding power does nothing to correct the "apparent" angle error, so it keeps trying by gradually adding more and more power. If you now take off that long-term correction is now completely off and will throw it away for a while until the error is "unwinded", which can take several seconds.

Most FCs disable the integral term when you've got the throttle stick fully down (i.e. you're on the ground and waiting to take off) to avoid that, but as DJI multis have a spring-loaded throttle stick that can't happen. I would bet though that just bringing the throttle down fully once just before taking off might reset it in the same way, easy to try as you would hear the motors go back to similar RPMs again.

 

[michaelthewise]

Pure, thank you for reporting this. Don't listen to that guy on his safety high horse. You're the only one that knew his surroundings and if you're saying it was safe, then it was safe.

 

[Navigator53]

Thanks for posting this OP!
I could see landing for a moment, make a quick change in the pilot app then taking off only to have it do an expensive back flip!