So flying around this weekend taking some lovely shots over the coast and countryside. The wind calmed down this evening so I thought I would get some nice shots during sunset.
All was going well, I made a few passes getting the footage I wanted. The plane came back overhead so I uploaded a new mission to make a low pass over a sailing boat moored up about 50m off the coast. I sent it off to WP1 and it duly obliged, gliding down a few metres to attain the new altitude.
I became quickly aware that it had gone under its target altitude and was continuing to sink below the sea wall. I bashed a mode switch which put it into RTL and tried full throttle and some pitch up stick mixing. Didn't work, and plane sunk out of view.
Now my girlfriend's family were watching this from the house and were in touch by walkie talkie. At this point they helpfully shouted over the radio "Its Crashed!"
I sprinted towards the edge of field and vaulted a barbed wire fence into an unseen ditch, shredding my hand in the process. I climbed out and back over the fence and made my way out of the field to find my friends rushing to the slipway to launch a hasty rescue mission in little row boat. All very Hudson River-esque!
The plane was floating nicely so I tried to sail it back in but the motor wouldn't spin, despite the ESC beeping away. So we rowed out, fished it back in and took everything inside to dry it off.
The water damage inside the plane was minor, EasyStars make effective boats. There were signs of moistness though so I cut all the heatshrink off, gave everything a fresh water rinse and then chucked it into a big bowl of rice. Not sure what state the servos are in.
I then got down to looking at the logs. The tlog reveal that the AP was asking for throttle but the motor wasn't spinning when it went down. Hopefully the SD card will have the video of the crash and recorded any strange noises or ESC beeps that were occurring. I'll have a look in the morning. From memory when we fished it out of the river it was double beeping, which the manual says "over or under voltage".
APM reported the voltages as fine, it was a freshly charged battery that hadn't even been through half its flight so its unlikely to have been ESC cutout but I'm not ruling it out. Won't be able to tell much else until I reassemble it all tomorrow/Tuesday and see what still works.
The most gutting casualty was the GoPro which didn't have its fully waterproof back on, it had the lighter skeleton back on. This may turn out to be a costly oversight!
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The balance port of my battery has turned green and disintegrated overnight too, I didn't give this the fresh water rinse for obvious reason. I discharged and charged the battery last night to see if it was toast, this must have caused some some of electrolosys reaction. Salt water is a bloody nightmare!
There is a bit of salt corrosion on the side pins of the APM, I'll have to give it a proper clean up when I get home, its only the very edge of the board so I think I might get away with it. Everything else is looking alright though I haven't repowered anything yet.
The great news is the SD card survived and I have a video of the crash. The problem was a motor failure, it was making a strange sound and clearly not spinning fast. I have had this on the ground on a couple of occasions where the motor spins slowly and makes a nasty noise. Applying more throttle or cutting and repowering usually sorts it right out. Perhaps ESC timing issues? Or maybe some latent damage from a previous landing i'm not sure. If the motor survived I will try and recreate in video form. I'll upload the logs and video when I get home to a real computer.
Sorry for your loss - about 3 weeks ago I had the same misfortune to drop my aircraft with my exposed gopro (even the port flap was removed - thinking it's just going to be lost) into the salty surf on the beach. After some pampering it came to, despite the ports being all green from oxidation.
I'd be surprised if you can't salvage your gopro. If you can't contact gopro - I've done so and they've offered me a large discount on a new one if I send them the busted one, but like I said, it came back to life!
I hope you figure out what went wrong.