Flipping during landing :(

[DenisDespair]

Hi
I have quite a wrong choice for beginner, but nevertheless.. Recently built tarot T810 for aerial photo, AUW 5.6-6.0 kg, this building log http://multirotorforums.com/threads/tarot-t810-build-log.24116/

Common problem that upon landing it tend to fall on the side or even flip, which can lead (or leads) to the props damage. I'm landing at slowest available speed in GPS or ATTI mode.
-Can balance of the copter affect the following flipping?
-Should I move batteries down under the frame, so that center of gravity will be lower?
-Should I land in manual mode, so that it can be slower? (or will it make only worse?)
-Should I immediately turn down throttle after touching the ground or a bit before?
-Tried to google "how to land a copter", not much info. I would be very grateful for any advice

Thanks

 

[eskil23]

-Can balance of the copter affect the following flipping?

If so, it would flip alredy at takeoff. That's what happend to me on my first flight. The gimbal was not mounted, so the mr was backheavy. Fortunatly, the prop guards saved the day.

-Should I move batteries down under the frame, so that center of gravity will be lower?

Should probably help stability both while landing and flying. Mounting your landinggear wider should also help stability while landing.

-Should I land in manual mode, so that it can be slower? (or will it make only worse?)

Worse I believe.

-Should I immediately turn down throttle after touching the ground or a bit before?

I turn down throttle immediatly.

 

[DenisDespair]

Regarding the throttle. While it is still on, even under 50% in Atti/GPS mode, copter still maintains its levelled position.
So, can my flipping be caused by too fast throttle cutting down after touching the ground? (So, there is nothing to compensate any momentum flipping the machine)

 

[Motopreserve]

If the machine is balanced, you should still be able to have a bit of a rough landing and not flip. It takes a little practice to lower it to the ground nice and smooth, and even then sometimes wind and ground effect can make it a challenge.

The batteries below should definitely help with steady landing.

The only way the fast throttle cut would hurt the landing is if it's unbalanced or on unlevel ground. If the MR seems to be rocking a bit from wind/ground effect when I'm landing, I get down close to the ground as possible and then cut the throttle. It should land and stay upright from its own balance from a few inches off the ground.

As Eskil mentions, the landing gear being wider (left/right) and the LG "feet" being longer would help with stability.

 

[Vojec]

Upon inserting data to e-calc first look: you are on the fence to over limit your bird motor .
Do you remember time of flip (you did it twice, right) if this hapend in same time must be related motor or esc. Have same problem 3 years ago with overloaded bird and esc just switch off...

hope it helps..

 

[DenisDespair]

It takes a little practice to lower it to the ground nice and smooth, and even then sometimes wind and ground effect can make it a challenge.

I'm landing it with a minimum speed I can get in GPS or ATTI mode. Throttle moves usually in a little steps due to a ratchet on the joystick. I use just one step down from howering mode, so I couldn't do it slower.

The batteries below should definitely help with steady landing.

Yep, ordering now rails and mounts, will re-build the MR

I get down close to the ground as possible and then cut the throttle. It should land and stay upright from its own balance from a few inches off the ground.

I've tried it as well. It lands and stays upright but rocking in a very scary fashion

As Eskil mentions, the landing gear being wider (left/right) and the LG "feet" being longer would help with stability.

[/QUOTE]

Can't do it, landing gear is already mounted wider, then intended by manufacturer

 

[DenisDespair]

Upon inserting data to e-calc first look: you are on the fence to over limit your bird motor .
Do you remember time of flip (you did it twice, right) if this hapend in same time must be related motor or esc. Have same problem 3 years ago with overloaded bird and esc just switch off...

hope it helps..

Well, so far I assume that the biggest problem is the pilot.
First flip happened when I was landing with some horizontal speed due to wind gust. Second one - when one leg went on the trail and one on the grass. But even during successful landings MR stability doesn't look so great, it rocks and it is scary. I'm going to rebuild it and put batteries under it.

Regarding e-calc calculations. Do I understand correctly, that increase weight over 50% thrust only decreases flight time? Or can it lead to the catastrophic consequences?

 

[Vojec]

increase weight over 50% thrust only decreases flight time? Or can it lead to the catastrophic consequences?

it can lead to hard land, if you have near 80%... with combination of other thinks like temp, height, etc...

 

[DenisDespair]

it can lead to hard land, if you have near 80%... with combination of other thinks like temp, height, etc...

Am I missing something? Ecalc gives value about 60% only, not 80

 

[Vojec]

this is ok lower the value better, but to low is a same as too high... sweet spot 45%-65%

 

[Motopreserve]

Doesn't the ecalc show hover at 62%??? If so, I don't think that should cause the issue. 50% is ideal - but 62% is not beyond capability of landing, no?

Not sure I understand the throttle explanation about 1 notch down from hover. While that should be the slowest, smoothest landing - when you get right down to ground, lower it more to get it planted and the weight holding it down.

The battery underneath I suspect will cure a lot of these ills.

 

[DenisDespair]

Not sure I understand the throttle explanation about 1 notch down from hover.

The battery underneath I suspect will cure a lot of these ills.

Well, on Futaba 8J throttle joystick moves in tiny steps, compared to continiuos movements of 3 others. There is a kind of ratchet mechanism inside. So, I'm landing it by moving just one tiny step down from hovering throttle.

Let's see, trying to find now any shops in Europe who sell those rails for tarot. Thanks for help

 

[Vojec]

There is a kind of ratchet mechanism inside

Open your Futaba8J and remove it for smooth movement ;-)

 

[Motopreserve]

I still think that the stick having "steps" shouldn't effect your ability to gently bring it toward the ground.

 

[DenisDespair]

Open your Futaba8J and remove it for smooth movement ;-)

Opened it. Removing the ratchet turns throttle into the same kind of centered sticks, like 3 others. And removing the spring just make it freely floating - certainly something I don't want to experience.

I think I'll wait a week for rails and batteries mounts and check again

 

[sledge57]

Opened it. Removing the ratchet turns throttle into the same kind of centered sticks, like 3 others. And removing the spring just make it freely floating - certainly something I don't want to experience.

I think I'll wait a week for rails and batteries mounts and check again

Can you take a pic inside the radio? Should be easy to get rid of ratchet action.

 

[DenisDespair]

Can you take a pic inside the radio? Should be easy to get rid of ratchet action.

I've assembled it already. Well, there is a plastic part with tiny teeth and metal spring over it. I could remove those teeth by using a file, but would like to avoid irreversible actions

 

[eskil23]

I've assembled it already. Well, there is a plastic part with tiny teeth and metal spring over it. I could remove those teeth by using a file, but would like to avoid irreversible actions

Try to put some tape over it.

 

[jhardway]

I posted this on Denis's build thread but thought I would put it up here also.

Hey Guys I am just getting caught up on this feed and looking through it I can throw in a few things. I have built a few 810 and for what I have had with the copter I can say this. Over all its a very good design, if flies great, and to me its a work horse, I have had it up in winds over 25mph, I have had it carry about 3lbs of payload and have not had any issues.

Currently I have 15 inch collapsible props, and with 2 x 5300mah I am getting 16min of safe flight time before needing to land. When it comes to voltages on the batteries, for my T810 the voltage is not an issue if I fly my copter right down to 21 volts under load, its a perfect result for 80% used.

With that said I also have bigger copter, a Tarot x8, and that one is 21 lbs loading at takeoff, when flying if I fly it down to 21 volt under load, when I recharge the battery its only takes in 60% of capacity, I did contact a few battery companies and asked about flying the voltage down to below the 21 volts (or 3.5volts per cell), they told me that if you fly to 3.4 volts that is fine, 3.3 is OK but not advise able, and 3.2 will cause the battery damage. In my case if I fly it down to 3.4 I obtain my 3.7 per cell not under load and it take about 80% of capacity to recharge the battery. All good stuff.

About the flipping two things first is on the first flight video, in a way to me the copter looks like its a little to light for the situation, if that is true unstable landing will happen, and you will see in flight, rock just like it did when you give it an input and let off the sticks, it will get in an over compensating teetering. My guess is if you tie a 3lbs weight on the bottom you will have a different result.

Also the landing gear is long so the higher off the ground it is the more prone to tip some. if you have it a little unstable and you land at a bad angel (it will not take much) then you could have it tip. I also bet if you add weight to it you will have much better landings

Here is a clip of one of my copters and it was to light, I could not figure out what was going other then it may be to light, so after tying a 5lb weight to the bottom the issues went away. The clip show what it look like when its to light.

At the end of the day for my 810 here is a clip of it working when you get it dialed in.

and this is a clip of the copter in flight how nice it will fly.

I know there is a lot here but I hope some may help in the questions .

over all I think its a great design and for a build I find it a very versatile craft.

best Jack

 

[jhardway]

Also when it come to batteries make sure the lipo chemical rating is in the SP1 rate, this is a better quality compound and will allow you to run them down a little better, if not you will end up puffing after 25 - 30 cycles, example for this is Turnigy Nano-Tech, I have not used a ton of differnt batteries but when it comes to cost i like to drop in the middle range, I feel Max Amps are to expensive but decent. Same with Thunder Power, so along the way I found I had good luck with Gens-Ace. I have four of them, they are over 2yrs old, 100+ flights, and still are working very well.

cheers