Hey guys,
apologies if this has been discussed before.

I'm a fairly experienced professional pilot in the UK. Been flying the s900 for a few years before switching to the Inspire 2 a couple of years ago. The Inspire2 is a very impressive UAV, it, and the s900, are the few aerial platforms I could actually start to *rely* on - always fire up, always launch and fly safely (provided the firmware was up to date on the Inspire!).

However yesterday I was filming in multiple locations (x5s camera gimble). Some in open uncontrolled airspace and some inside Category D airspace (with permission from the ATC of course). After multiple flights both in and out of CatD space, we moved location again returning to Cat D airspace. When I fired the motors up (both sticks down and to the centre) the motors began to spin and idling speed, at this point the DJI cautionary message appeared on the DJIGO4 app which prompted me to remember I had not posted a NOTAM for this particular location, so within a second or so of returning the controller sticks to their centre spot, I pulled the sticks down to the kill position (again both sticks down and to the centre - perhaps this was the mistake?).....the drone immediately powered up the rear props, causing it to pitch up onto it's nose, spin a little and bodily accelerate (as if the throttle stick had been pushed up for more power), it maybe got about 20cm into the air (still nose pointed vertically downward). Approximately 3 or 4 seconds later, with my fingers remaining in the kill position, the props stopped turning, leaving the drone to fall onto its top surface (upside down).

The gimbal op and client standing nearby had already started to run...I stood, mortified....and a little freaked out. Fortunately nothing was damaged except for a single prop blade...after a good 40mins of scrutinising inspection, testing control responses and a few test flights we were back to filming...albeit a little more cautiously.

But now, critically, my confidence in the Inspire2 is shaken. I'm hoping folks here can maybe shed some light on what happened. I tried to attach the .DAT file to this post but it won't let me. Any advice on how I can get that out to folks?

Thanks for any info you guys can provide.

You'll need to upload your .DAT to something like DropBox or GoogleDrive. Then provide the link to the uploaded .DAT

Hello there. We apologize for the inconvenience. What is the error message you saw in the app?

Hi, no error, it was the message confirming I take responsibility for flying in controlled airspace. I didn't get a chance to respond to it ; had my fingers pressing the sticks in the kill position.

BudWalker Posted at 2018-7-16 16:25
You'll need to upload your .DAT to something like DropBox or GoogleDrive. Then provide the link to the uploaded .DAT

Cheers, will do that this evening!

McDroney Posted at 2018-7-17 04:11
Hi, no error, it was the message confirming I take responsibility for flying in controlled airspace. I didn't get a chance to respond to it ; had my fingers pressing the sticks in the kill position.

I see. You can upload the .DAT file through dropbox then provide the link so that we can check this for you.

DJI Wanda Posted at 2018-7-17 06:08
I see. You can upload the .DAT file through dropbox then provide the link so that we can check this for you.

righty, here's the link to the dat file. Any information greatly appreaciated; I'd love to have my confidence restored.

Thanks again for any time you can spend on this.

Cheers,
John

[url=https://drive.google.com/file/d/1RzdiKd3EjdZY_n-owrHRDSWf4tsPHRWa/view?usp=sharing][/url]

I think this is "normal" behavior. The CSC (Aileron, Elevator, throttle full negative and Rudder full positive) is intended to be an emergency motor stop measure. But, there is a builtin delay to avoid a momentary or inadvertent CSC from causing a motor shut down. At the onset of your CSC (3.256 secs) the I2 rolled left (full negative Aileron), pitched up (full negative elevator), and yawed CW (full positive rudder). At 5.5 secs the FC decided the CSC was for real and stopped the motors.

BudWalker Posted at 2018-7-18 05:17
I think this is "normal" behavior. The CSC (Aileron, Elevator, throttle full negative and Rudder full positive) is intended to be an emergency motor stop measure. But, there is a builtin delay to avoid a momentary or inadvertent CSC from causing a motor shut down. At the onset of your CSC (3.256 secs) the I2 rolled left (full negative Aileron), pitched up (full negative elevator), and yawed CW (full positive rudder). At 5.5 secs the FC decided the CSC was for real and stopped the motors.
[view_image]

Wow, cheers for looking at this Bud,

In the control options I have the CSC set to be left stick to bottom right corner and rth button pressed. Though I guess both sticks in to the centre will act as both motor fire up and motor power down. I guess the confusing thing for me is that I've used the "both sticks down and toward each other" to kill idling motors in the past and it hasn't flipped the drone up and over.

If the motors are idling with insufficient rpm to lift the drone why would any cyclic control cause the unit to lift bodily off the ground? Add to that the throttle (albeit fly-by-wire) is simultaneously being told to decrease, so chances of lifting off should be further decreased.  And further, if the motor kill command was enough to lift the drone temporarily surely it would have lifted up onto its rear not it's nose?

My gut still tells me the appearance of an airspace warning at the same time as firing the motors up has potentially caused a temporary instability of the flight control system. Though I'm betting if I simply used throttle-down to kill motors in the future that'll avoid any further issues. It'd be great if anyone from DJI to back this up.

If it wasn't a temporary instability, then I guess I have to assume the combinatin of aeleron-full-left, rudder-full-right and elevator-full-down (regardless of throttle being fully down) is sufficient to lift the drone from idling...a little freaky but easily avoided in future.

Any word from DJI staff? (or are you a DJI rep Bud?)

Thanks again for looking at this, very much appreciated.

McDroney Posted at 2018-7-18 06:05
Wow, cheers for looking at this Bud,

In the control options I have the CSC set to be left stick to bottom right corner and rth button pressed. Though I guess both sticks in to the centre will act as both motor fire up and motor power down. I guess the confusing thing for me is that I've used the "both sticks down and toward each other" to kill idling motors in the past and it hasn't flipped the drone up and over.

And further, if the motor kill command was enough to lift the drone temporarily surely it would have lifted up onto its rear not it's nose?


According to the .DAT it did pitch up.

BudWalker Posted at 2018-7-18 06:17
And further, if the motor kill command was enough to lift the drone temporarily surely it would have lifted up onto its rear not it's nose?

hmmm, that is pretty interesting...I saw it only pitch nose-down, and it was the front right prop that hit the ground, and the nose of the drone that got dented (can attach pic if needed?). Kinda wish someone had been filming at the time.

McDroney Posted at 2018-7-18 06:46
hmmm, that is pretty interesting...I saw it only pitch nose-down, and it was the front right prop that hit the ground, and the nose of the drone that got dented (can attach pic if needed?). Kinda wish someone had been filming at the time.

The data shows that the I2 pitched up to the point it was inverted. Is it possible this looked like it was nose down?

It's a little hard to tell from the data when the impact was. did it hit 2 or 3 times before it was over?

I'd say that because the motors are at idle and you pulled back and left on the right stick the inspire increased power to the front right motor which tallies up with your chart. This then briefly caused the front to get airborne and then it was game over in a matter of milliseconds. Added to that you essentially told it to yaw to the right as well.
I always just hold down the throttle to kill the motors for this reason.
Hope you get it fixed.