my first crash: hard, wet!

[GearLoose]

Yesterday our local news was all about a major river event just a few miles from our cabin. A major landslide sent a "bore" of mud, boulders and debris downriver, scouring it from bank to bank. This seemed like a great opportunity to use the Phantom and my Drift action cam for some dramatic footage. (I'm still a noobie but gaining confidence in flying this thing.)

I had to launch from a plastic box set among the rocks but it went smoothly. There was a brisk upriver breeze so I decided to fly in GPS mode, as I was nervous about keeping the Phantom well under control. I also taped a small 100 lumen LED headlamp above the battery door, to help me with orientation.

Based on previous flights with the Drift camera, I set my kitchen timer for 7 minutes.

Long story short... Somewhere just past 6 minutes I was bringing the Phantom in close and low when it began to descend steadily toward the rocks. I tried to bring it to my feet but didn't quite make it. It crashed into the stream very close to me, bashing into a rock (gouged the camera's lens protector).

I fished it out very quickly -- it was still running -- disconnected the battery and drained the water. One motor turns reluctantly, with a distinct grinding sensation. Otherwise, no apparent damage either externally or internally.

Looking back on this I think I underestimated the battery drain while flying in wind, in GPS mode. Also, although the LED headlamp is very light, it did add some weight and drag -- and I forgot to compensate for that.

This leads me to a question: I checked the battery voltage and it shows 11.3v, which I believe is "normal" at the end of a flight. Did a low battery actually cause the Phantom to descend or is it more likely pilot error? At what point does a low voltage actually cause a forced landing? I'm not clear on that....

Awaiting a new motor now as I don't trust the gritty one.

 

[HurricaneProductions]

Good call on ordering the replacement motor.

Not sure what the minimum battery voltage is to maintain normal flight but in my experience, when the battery is low what you described can definitely happen.

Was the built-in LED blinking red rapidly as you were bringing it down?

 

[BruceTS]

look at the videos on how to take apart your motor, should be salvageable. Learn the light patterns on the back, they will give you warning on when battery is getting low. Lastly windy conditions, over water and low flying = disaster waiting to happen, even with a full charge.

Take it apart and make sure all electronics are good and dry before putting any power to it. Good way to extract all moisture is use rice kernels.

 

[GearLoose]

I was definitely getting all red flashing lights, though I have no idea how long they'd been giving the "code red" signal. The time stamp on the flight video shows the Phantom hitting the water at just 6:03 minutes, which is well under the usual time I get with the camera onboard.

Live and learn!

 

[DomKane]

Get yourself one of these: http://www.hobbyking.com/hobbyking/store/uh_viewitem.asp?idproduct=18987

They are LOUD.

 

[GearLoose]

Get yourself one of these: http://www.hobbyking.com/hobbyking/store/uh_viewitem.asp?idproduct=18987

They are LOUD.

Thanks for the tip; I just ordered two -- one for each ear :twisted:

 

[DomKane]

Haha. Also handy for generally checking the voltage levels of batteries on the field.

 

[toolman2a]

yeap and flying against the wind as you stated will drain your battery faster , the motors have to work harder to stay in one spot in gps mode.

 

[GearLoose]

I've just bench tested the Phantom after opening and drying the interior. Other than one motor that probably needs bearings it looks surprisingly good. I ran the Naza Assistant and everything checked out ok, no calibration required. As others have mentioned, the Phantom can definitely survive at least a quick dunking.

 

[Gizmo3000]

additional weight,. even tho it might seem slight, can definitely impact flight time as well.
imagine from now on you'll be setting your timer to 6 minutes

keep the old motor around as a spare, or use it as practice replacing the bearings, and it might be re-useable again later on in case you damage another motor.

 

[GearLoose]

I will actually be setting my timer for 5 minutes! I've found that it is much easier on my nerves to bring the Phantom in close before the timer alerts me to a low battery. But, in this particular instance, I managed to forget that precaution. When the Phantom dove into the water I still had at least a minute left on the timer. So, wind + GPS + a little extra weight wiped out my margin of error. And that left nothing but.... major error.

 

[tvpopta]

Yep.. always stay on the safe side, especially when flying over water. All the different warning levels (led blinking, auto descent, etc) can be set from the naza assistant, or turned off altogether. But it's recommended to not let the voltage drop below 11.2V if I'm correct; this is what the naza maintains by default. Normally you should be able to bring the phantom in for a landing when the auto descent kicks in; about 45 seconds of hovering at 90% throttle should be available with very slow climbing @ 100%; but sufficient winds vs. gps may cause the phantom to bank too much to be able to maintain altitude.