P4 with Water Strider' flips into lake on takeoff

Don MacGregor · Dec 10, 2016

Looking for help please. My P4 flipped into a lake on it's first water takeoff using the Water Strider'. (See link below). Has anyone seen this before ? Strider was correctly assembled and attached, bird was in P mode, vps off, fps on, and radio has an Itelite extender. Manufacturer can't explain it, so I'm still trying to figure it out. Good news is after a dry out the bird still flys, although the battery didn't make it. All ideas welcome please.

tml4191 · Dec 10, 2016

do you have any footage from the drone?

Neon Euc · Dec 10, 2016

From what I assume the bird needs air underneath it to rise, the water acted like a magnet and rather then the bird lifting up, it dragged itself down to the water instead. Could be wrong and it shouldn't have happened as it defeated the whole point of the water wings. Another theory is that something from the trees like a thin piece of branch on the water may have got wrapped on the prop causing it to stop and making it drop and flip. Have you got the flight log just to see if their was a motor obstruction

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Mark The Droner · Dec 10, 2016

IMO you need to be more aggressive on the launch.

Welcome to the site!

PixelDoc · Dec 10, 2016

Hi Don:
Looks to me like you possibly did not apply enough power to lift off to break the water surface tension. Three of the pods broke loose of the tension, but the fourth did not --thus the result. Wish your cinematographer was a little more into the shot rather than 'hiding behind the bushes' [emoji87]. Difficult to see from that far back. (I probably just insulted your wife's photographic talents!)

As soon as I saw this water landing set up I had my suspicions, although of course the good old 'retrospectoscope' is a very accurate instrument[emoji57]. I've seen other water landing gear with much less surface area which would be inherently better; i.e.; produce less surface tension. If I find the product I'm thinking of, I'll get back to you. This product does, however, appear to be very suitable for landing almost anywhere; I'd just feel insecure about taking off from water.

It's always surprised me how strong surface tension is. Ever try to lift a lily-pad off the water? Next time, if you're brave enough, I'd apply full throttle for lift off, although that may still not be enough. And of course, all four pads have to break loose of the water virtually simultaneously! -- tricky [emoji15]

Basically, I'd call this design inherently flawed, although I'm not saying it wouldn't work most of the time.

PS: Where are you? Looks nice and warm compared to the sub-zero temps here in southern Ohio. I'm jealous -- Happy flying.

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Hjones62 · Dec 10, 2016

Wowwwwww!!

JohnnyB · Dec 10, 2016

You know, I made these and have only tested in the tub. Very stable as far as the way it's balanced, and has a good center of balance, but after seeing this video, I believe this is going to make good fire starter. Thanks for posting!

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Uptowndisco2 · Dec 10, 2016

From the angle it looks like you were giving some forwards stick while trying to take off , give it full up from a stop with no forwards
motion. sorry for your loss

Foosy · Dec 10, 2016

I have looked at the video a few times and the can tell exactly why it flipped.
You were moving the phantom forward when you attempted liftoff. You can see the phantom gliding forward on the lake before liftoff. When in flight, the normal posture of the phantom when moving forward is more power to the back propellers than to the front which makes it tilt forward.
Then, when you attempted liftoff, the back 'legs' lifted first, center of gravity changed (moved forwards) and the phantom flipped on its front legs.

By the way, same thing would have happened on the ground if you had your right stick pushed forwards, even without a liftoff...
Interestingly, because of the spider legs, you could, up to a certain speed, navigate the phantom on the water, (something you can not do on the ground), as long as you were not attempting to liftoff.

Next time, use the app's liftoff button when on water to make sure your sticks are in neutral.

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Steve_in_DE · Dec 10, 2016

This is the first fine i have seen this particular water landing device, and there are a number of things i don't like about the size of the pontoons.
First is the surface tension issue. Yes it's good practice to "pop up" off the ground rather than rise really slowly. On the ground the issue is getting out of the prop wash; in the water it looks like surface tension is the other issue.
At first glance i would guess that those pontoons are too darn big. They could catch the breeze and alter flight characteristics. And though i have not tested them I think their size might be overkill.

Until today the idea of pontoons seemed like a cool idea to me; now i am a little leery of it. I think most the scenarios that would cause a p4 to go into the drink are probably caused by pilot error; so unless one simply thinks it's a cool thing to do, maybe pontoons sre just an idea to pass on.

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RW-1 · Dec 10, 2016

Basically what you had was a water Dynamic rollover.

Trying to ascend, two floats broke free and two did not, the aircraft then, due to the thrust being generated, rotated on the pivot point, which in this case was the two still "Stuck" to the water by surface tension.

rocketflyer · Dec 10, 2016

Flight Log?

jbrown630 · Dec 10, 2016

Uptowndisco2 said:
From the angle it looks like you were giving some forwards stick while trying to take off , give it full up from a stop with no forwards
motion. sorry for your loss

I'm off this mind. It appears you may have inadvertently applied forward stick before all pads had released the surface. Glad your bird was mostly ok and it was only a battery loss.

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JWH · Dec 10, 2016

I have thought about getting the Water Strider, but not to land or take off on the water. I want them only to keep it from sinking in case something happens to the drone while flying over water. I would be worried about water splashing on it or getting mist sucked in by the cooling fans. I had not thought about the possibility of flipping over on take off. Thanks for posting.

MacCool · Dec 10, 2016

RW-1 said:
Trying to ascend, two floats broke free and two did not, the aircraft then, due to the thrust being generated, rotated on the pivot point, which in this case was the two still "Stuck" to the water by surface tension.

This. The OP has to pop that sucker off the water with authority.

normr · Dec 10, 2016

Don,

I took your video and slowed it down so you can see better how people said you were moving laterally when you touched down and then immediately tried going back up.

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Cookie$Dough · Dec 10, 2016

I wanted to cry seeing it hit the bird bath. [emoji27][emoji25][emoji22][emoji32]

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syotr · Dec 10, 2016

That's sad. A device that was supposed to save your quad from getting wet, actually caused it to. I have played around with lots of flotation designs for the Phantom. In many tests, landing and taking off from water, there was some evidence of one or more pods breaking the surface tension before the others. The shape of the water strider pods contributed to your failure. The large disc has a lot of surface contact and the edge can dig in and catch the water as the pod tilts.
I watched the video several times and it appears to me that it flipped backwards. It's hard to tell since it was so far away. Could it be that the as you increased throttle, the Phantom tried to level itself applying way more thrust to the side that was stuck? As soon as the pods broke free, it flipped the opposite way before it could correct. That's the way it appeared to me but of course I could be wrong.

John1960 · Dec 10, 2016

i cant see for the life of me why you or anyone would want to strap something like that on a perfectly working P4

Don MacGregor · Dec 10, 2016

Wow, tx so much everyone for the great ideas. Re questions ..Unfortunately no flight log or footage on drone sd card. We're in tropical Brisbane Australia. Yes the camera Lady also saw one pod appear to 'stick' to the water, and surface tension issues were my initial thoughts as well, however the manufacturer says no ? Some lateral movement on takeoff is possible, so if I'm ever brave enough to strap the pods on again, I'll try and avoid that. I was wondering about sticking something like the rough side of Velcro strips on the smooth underside of the pods to see if that reduces any surface tension 'stick'. Would be good to hear from anyone else who has used these themselves ?