My question is this: is the Y6 actually supposed to compensate in cases of motor/prop/esc failure, or is this configuration really no more reliable than "normal" multicopter configurations?
I've been flying my Y6 regularly for nearly a year now. I've upgraded to the 2014 frame, upgraded to Pixhawk, upgraded to 4S batteries... it's been a great machine and I've been very impressed with it. And although other multicopters seemed lighter/faster/more-agile, I thought the Y6 was better because it was "safer".
Yesterday, mid-hover (in Loiter mode) the motors sounded wrong. It looked like the bottom motor on the tail slowed down, then nearly instantly the whole thing flipped upside down and drove itself into the ground. When I tested the motors afterward the back-bottom one didn't respond at all... it appears that it failed mid-flight.
It looks like the damage is limited to the GPS mast, a few stand-offs, several propellers, and at least one prop-adapter that was smashed into a rock during this upside-down dive. It could have been worse, but I truly believed that it was supposed to gracefully recover from a failure like this.
I chose to invest in the Y6 over other configurations with the understanding that the stacked motors/props provide redundant safety in the case of a motor/prop/esc failure. Is this really the case?
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I had another prop disintegrate during flight with my Y6 yesterday. Didn't even notice that half the prop was missing until I flew nearby and heard the Y6 sounding a bit rough. Only saw after landing that half the prop was missing.
It seems that high speed flight is too much stress for the prop roots. Maybe they were ove tightened?
Bottom line, my Y6 is still in one piece after yet another prop failure.
I will be assembling a Tarot FY650 today, and later this month will be upgrading it to an X8.
I am loving my APM and PixHawks ! Thanks 3DR and PX4 ! Great job.
(3DR Y6, Manufactured Oct 3rd, 2014)
I had a similar crash on my 4th flight.
Apparently my right-bottom motor gave up the ghost mid-flight. I was flying low to the ground (6ft) in loiter taking taking video of my family with my gopro (I thought... I actually forgot to turn it on). I experienced unanticipated roll to the right, could not recover, and killed the throttle (not wanting to take my grandmas face off). It landed on its side and sheared the platform mount holes on the right and rear aluminum arms.
When started troubleshooting, the #2 motor(right-bottom) made sparking noises and smelled of burning, only rotating in fits and starts.
Now I'm waiting to see if the motor is covered under warranty... Had to order a replacement frame too...
I've had two ESC issues with a Y6. One ESC fried under high throttle and traveling horizontal at a fair pace at about 20 meters above the ground. After going into a hover it came down but stayed the right way up. Another ESC had an intermittent failure where the motor would spin down on relatively low throttle and then spin up again.
My observations:
1/ When a motor stops the magnitude of the vertical thrust (up) will reduce by (around) 1/6. If in any mode other than altitude hold and with no throttle adjustment it will start coming down, and build up speed. You can compensate by increasing throttle but given how quickly it can accelerate it needs to be applied fast!
2/ If a motor fails and it is not flat (ie: banking etc) the flight controller may not be able to compensate in time. Once I had an ESC stop driving a motor when around 2 meters AGL and it came down quickly, bounced and flipped upside down. (On grass luckily - no major damage).
I feel a bit more comfortably flying the Y6 than a Quad, as there is a level of redundancy, but it won't (and can't) save all possible single motor out issues.
I was just out flying my Y6 and it just happened to me... I lost the top front left prop. The Y6 did a full loop and managed to recover. I was able to bring it back to land in stabilize mode.
Looks like a bad moulding on the prop. I was able to find the prop (or at least half of it) in the field. I do have video footage from onboard camera and you can clearly hear the prop letting go.
I was flying pretty fast too and in a tight bank.
Still flying the Y6A with an APM 2.5.2. Awesome piece of equipment!
The Y6 and X8 will fly with motors failing, but it will depend on a few things. If the aircraft is too heavy, and needs all 6 or 8 motors to fly, losing one will cause it to crash. With a gopro and gimbal, full fpv gear, and autopilot both the Y6 and the X8 will fly with one or more motors not producing thrust. Here is some video of the initial testing I did when trying to prove this thoery last year, before they went into production:
https://www.youtube.com/watch?v=N_GJv_x18dE
https://www.youtube.com/watch?v=cdS6Cy5aOvk
I have a Y6 "A" (2013) model with the APM 2.6. Lost the esc or motor on the top tail mid-flight today while in ALT-HOLD mode. When the esc/motor failed the Y6 tail dipped slightly causing it to drift backwards and started descending slowly. I throttled up and tried to compensate by dipping the nose. The failure happened at about 14 feet and I had about 12 seconds before the legs touched down. In that time I managed to get it to a relatively level area and landed without damage.
I'm just getting into multi-rotors so I reacted late to the tricopter not responding properly to the controls. In hindsight, I should have switched into stabilize mode, popped the throttle to keep altitude. I feel pretty certain I could have kept it flying.
The net is if you react appropriately, throttle up and get into a mode that gives you more control, an experienced pilot can still fly it.
I suspect a lot of cases where a prop unscrews itself began with the prop hitting the ground from tipping over. This often loosen the prop nut due to the direction of rotation. If you don't recheck the tightness again, you could be flying a loose nut.
Wouldn't a prop guard be a practical solution improvement to a lot of things?
I had a propeller pop off flying an X8 with an old model APM (can't remember what version exactly -- before they came with cases!) I definitely lost some power, but I was able to land. Recently I had a similar incident with a large (1m diameter) hexactoper with a pixhawk. Propeller popped off and I lost yaw control but the descent was surprisingly stable -- pitch and roll were ok and it landed flat on the gear. Time for me to invest in 3-hole props, I guess...
As for the ardupilot code, it's probably time to implement something like ETH Zurich's propeller loss compensation algorithm soon.
Why are people losing props? I just swapped out all of the prop nuts with nylon reinforced "lock-nuts" from the hardware store. Sure they're heavier by maybe a gram, but it's a damn sight better trade-off than having your rig fall from the sky.
I switched to the lock nuts after a near failure with the normal cone prop nuts (I was lucky and happened to feel a prop spin weirdly while moving my Y6). The lock nuts are not as pretty as the prop nuts, but they are definitely not going to accidentally fall off... these things are rock solid.
Here's a picture of the ugly-but-safe nuts from the hardware store. If anyone needs to know: the nuts are metric "M6 Lock Nuts with Nylon Inserts".
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