I know its nearly impossible as most turn turtle when you loose power and the pitch of the props are fixed but.........Today my Spark auto rotated from 500 feet. How is this possible you ask? You have to meet two very important criteria.


1st - you have to have a forward CG


2nd - you must be facing into the wind


How did I attain these two critically important factors? I can tell you that it is a nearly impossible feat but what you need is for your battery to eject itself after nine minutes of flight. This event satisfies the CG condition needed for the proper forward speed from a dead hover. Secondly you must be lucky enough to be facing into the wind.


Having said all this you may have guessed that this was not a controlled decent. The left side of the battery retention system failed which I still wouldn't think would cause the battery to eject from the Spark but it did. With no prior warning I lost signal and immediately heard the blades speed up. My initial thought was that it was returning to home, so I looked up to watch it decend and land. Well as I did so the first thing I saw was the battery whip past my head and bounce in the parking lot. Signal loss explained, the spark blades were still screaming and I watched it make a shallow arc from over head to six or seven spots over and bounce across the lot as well.

Spark status, battery = toast. The Spark itself has some road rash on the bottom and I had to snap the top right corner of the top plate back into position. Did a flight test and it flys perfect (for now) video quality excellent, gimble good, gps system good, l.e.d.s good and blink appropriately, responds to all commands, blades good and locked into position.

A+ for crash survivability.......F   for battery retention

That must have been an awful sight.

To be honest, I'm having trouble converting the description into a mental picture of what happened.  It sounds interesting (if devastating), but I'm not converting the text to cognitive understanding.  What happened?

Impressing. I would certainly expect the propellers to collapse before starting to run backwards.
What made the battery pop off?

heliman Posted at 2017-10-6 09:59
Impressing. I would certainly expect the propellers to collapse before starting to run backwards.
What made the battery pop off?

I don't think the props turn backwards in an autorotation.

Surprising

Autorotation is probably not the right term... with folding blades.

Didiko Posted at 2017-10-6 12:13
Surprising

Autorotation is probably not the right term... with folding blades.

Thinking about it.. I don't thing the blades would fold.. the forward motion of the craft would keep the proper pressure on the spinning blade to keep it turning... I guess someone could test it with a leaf blower and a spark :-)

The pressure will force them to stop or run backwards. Unless the spark is upside down.

When the big choppers start auto-rotating the prop doesn't change direction.  The pilot will use the collective to maintain the right pitch to maintain forward speed and lift until they get close to the ground and then increase the pitch to trade blade momentum for lift to reduce the impact speed.   

When you properly remove a battery from Spark, you pull the 2 dark tab on the battery towards the indicator end to unlock the battery. Some people pull the battery out without properly releasing the locking  tabs. Eventually the tabs may become worn or broken and the battery is NOT locked onto Spark and can cause the battery to fall off the Spark. This may be what happened to the battery flying off.

heliman Posted at 2017-10-6 14:32
The pressure will force them to stop or run backwards. Unless the spark is upside down.

That is not what happens when a helicopter  autorotates..why would a quad copter be any different.

I cant call it a true auto rotation but all 4 sets of blades were spinning loudly as it hit the ground. I was a bit shocked to see the battery bounce and know that I had no power yet the Spark continued to sound as if it were under power. I'm sure the blades were spinning in the opposite direction of lift. But it was enough to slow it down and give some forward momentum. The battery bounced several seconds before the Spark made it back to earth. I actually found the left side battery tab closer to where the Spark landed than where the battery did. The locking tabs on the battery were in nearly perfect condition as it was the newest battery. I've been in RC for close to 10 years now and because I can't afford to run out and buy new stuff constantly I take great care to ensure my aircraft are as safe and flight ready as possible. I am amazed that the battery didn't hit me in the head, it was very close.

Quite amazing incident indeed!

birddawgg Posted at 2017-10-6 17:55
I cant call it a true auto rotation but all 4 sets of blades were spinning loudly as it hit the ground. I was a bit shocked to see the battery bounce and know that I had no power yet the Spark continued to sound as if it were under power. I'm sure the blades were spinning in the opposite direction of lift. But it was enough to slow it down and give some forward momentum. The battery bounced several seconds before the Spark made it back to earth. I actually found the left side battery tab closer to where the Spark landed than where the battery did. The locking tabs on the battery were in nearly perfect condition as it was the newest battery. I've been in RC for close to 10 years now and because I can't afford to run out and buy new stuff constantly I take great care to ensure my aircraft are as safe and flight ready as possible. I am amazed that the battery didn't hit me in the head, it was very close.

Did you update firmware for your new battery ?

Sorry to hear about this case, so in this flight, the battery just physically ejected from the slot, but it still worked and providing the power, right? If the data still reserves on the drone, please help to export them out and upload them to Dropbox, or you can contact support.us@dji.com for a further help. If there is any damage on the drone, please send it back.