Stupid & Lucky - A Beginners Tale

[kgmf]

Hello,

I'm just sharing this in case it helps someone not make the same mistakes I did. I've had my spark about a week. Its my first drone, and I'm super excited. I live in Ireland and its winter time so its dark, cold and windy. Terrible time to take up such a hobby but I dove in anyway.

Took it out a few times in a park, with great success, despite a wee bit of wind. It works a little to stay stable but it sucdeeds well. Only impact is slightly reduced battery time.

In all thoase times I've just popped it on the ground and taken off, nothing more complex than that. This led me to a false sense of confidence in carelessness.

Brought it to my friends house. His kids were home and he didn't want to leave them alone for us to go to a park or something, so we went to his backyard. I was so excited to show him the drone i ignored many many common sense issues. His backyard is very small. Bad decisions made that day:

• Took off with no GPS
• Took off too close to the house (had to swerve to avoid hitting the lip of the roof)
• Took off too close to the house (compass interference)
• Took off too close to the house (IMU interference)
• Took off in the dark
• Took off in wind
  
• Took off with limited visibility of the surrounding area (fences, other houses etc in the way)

Completely unsurprisingly, the Spark lifted off and then just drifted away very quickly. I tried to bring it back and land it in a panic but it didn't respond as I expected it to and it collided with my friends house but was still flying somewhere above a halfway-up ledge. I now couldn't see it anymore but i could hear it. I tried to bring it back over the grass but instead it collided with his neighbours house, then his neighbours satelite dish and then finally - the ground.

Damage report:

• My ego
• 1 destroyed rotor blade, 2 damaged rotor blades.
  
• 1 LED light fell off (but was put back on and works)
• Scratches
• Possibly the neighbours satelite signal (I have contacted them, I will pay for a service if their dish needs to be aligned)

Powered it back up and it reports no issues but its now super windy and not safe to fly so I can't test it in flight. Assuming it takes flight again I am incredibly lucky in terms of the damage. I was really stupid with what I did.

Assuming you've read this far and aren't saying "you muppet you deserve this mess" I do have some follow up questions. I tried to look at the flight/sensor data but I don't understand it too well. I THINK I see it get the altitude completely wrong (presumably due to interference from the house/electrics). At the point of takeoff, the altitide goes DOWN instead of up. I'm sure this led to confusion and panic and why it moved off to correct this supposed problem.

So my questions are:

• Is it more likely that the wind took the drone away and the lack of sensors meant it could not recover, or is it more likely the wonky sensors caused it to move away and the wind just made it worse
  
• In the event that the drone is making the decision to move, will it adhere to the speed limit in the control settings (ie will the drone move away faster than i can attempt to bring it back if i've set the speed limit super low)
• Any advice for the first flight after the crash (asside from the "obvious" ie everything i did wrong the last time)

If anyone is interested i'll upload the .dat from the "flight".


Thanks for reading guys. It's been educational for me

K

 

[Virtual1]

• Is it more likely that the wind took the drone away and the lack of sensors meant it could not recover, or is it more likely the wonky sensors caused it to move away and the wind just made it worse
  
• In the event that the drone is making the decision to move, will it adhere to the speed limit in the control settings (ie will the drone move away faster than i can attempt to bring it back if i've set the speed limit super low)
• Any advice for the first flight after the crash (asside from the "obvious" ie everything i did wrong the last time)

No GPS means its using the cameras and proximity sensors only. Low light means the front and down cameras aren't going to work well either. So you're flying with the front and bottom IR sensors and gyro/compass only. Basically only bottom and front collision avoidance will be working, no position holding at all. Orientation should still work (turn/pitch/roll should be very minimal) but drift is your problem because position cannot be detected, particularly backward and sideways. So to recap, dark + no GPS + wind = dangerous drifting.

The speed limits (like if you are in beginner mode) are relative to ground speed, and so a sudden gust should be fully compensated for even if the correction requires a large reaction that would otherwise exceed the speed limit it is following.

As you have already noticed in your post-event analysis, you made several bad decisions that compounded with each other and resulted in a high risk.
- night flying is always higher risk, although this risk is lower if you are very familiar with your environment. being over at a friend's house doesn't count. Your own back yard maaaybe. Overhead wires and thin leafless branches this time of year can be hard to see or notice during the daytime, and are extremely hazardous and difficult or impossible to see at night.
- wind, especially gusty, is a bad thing to have in combination with a restricted area, because you have less time to react to a gust to prevent being pushed into an obstacle even if you are aware of it being there. throwing in low light and loss of GPS disables most of the Spark's protective features, and leaves you on your own for the most part. It's not impossible, but there's a lot heavier burden on the pilot to maintain control.
- I've found IMU interference to sometimes be annoying but not a serious problem. In severe cases it can be trouble, but most of the time it goes away after the aircraft has moved a short distance, getting it away from the interference. Trying to take off from a picnic table for example, you might find the metal bars below the wooden deck mess with your compass, but the problems go away immediately after takeoff. Metal only affects the compass (which keeps you pointed in the right direction) - the accelerometer (which keeps your aircraft level) and gyroscope (which buffer the gyro and accel and improve their response time) are unaffected by nearby metals.
- IMU interference is actually more of a hazard when you have GPS. Without GPS (and specifically when you are close to the ground) it relies heavily on the cameras for orientation and the corrections it makes to the motors will always be in the correct relation to the direction you are facing, because it's just trying not to move, rather than trying to get to / stay in a specific coordinate. But when the GPS is up, the flight computer will try to keep your Spark parked in a specific coordinate, and if it feels it needs to adjust it will make a correction relative to the direction it thinks your aircraft is facing, (and no, GPS does not tell you which direction you are facing, only which direction you are traveling) so if the compass is wrong it will correct in the wrong direction. The cameras may still be consulted, but if you are very far off the ground the camera can't get enough precision to be useful. For example, if your compass is 90 degrees off right and it thinks you need to move West, it may move you North instead. Now the GPS realizes you are both East and North of where you ought to be, and so it corrects SouthWest, which takes it NorthWest. As you might imagine this results in your aircraft slowly curving away from where it wants to be, hopefully leaving the area of interference in the process... but it's likely to then head right back to the interference once it regains its bearings.

The details are a lot to learn, you may just be better off adhering to "best practices" which are easier to remember and respond to.

 

[kgmf]

Thanks for the reply - I didn't even realise the bottom camera & sensors helped with position and I didn't really understand the decision making process the spark uses to stay steady in the air. As you say, any one of the issues might have been recoverable, but all together was a high risk and a crash waiting to happen.

 

[DesertWindAero]

1) Beginner Mode (allows only 30 meters distance from home point and 30 meters altitude
2) Tripod Mode (takes more stick than normal to move the aircraft)