3250RPM + HW 50A V3 + hard pitch = ...

[madeye]

...forced autorotation.

This was a first time it happened to me, and, having given it a very hard collective, I thought that LVC engaged and I'll just land it with no haste, but alas, looking at the recording, I believe now that there was a complete loss of motor power (but not control power), for a reason I cannot fathom.

Moreover, telemetry (picture below, clickable, Control P4 is pitch) doesn't even show a voltage drop, and no alarm was triggered - though, I don't know exactly what the alarm granularity is and whether a brownout could've fallen through the cracks.

In any case, I've disabled the cutoff completely, I'll rather trust what Jeti tells me.

Funny thing, I didn't even have to disconnect and reconnect the battery, and there was minimal damage (so far, I see just a minor crack in the canopy, and a cracked tail fin), it just flipped over and landed on its feet), it took off without a hitch right afterward, as if nothing happened.

So, two questions -

- Anyone has a better guess to what happened here?
- I know I was unprepared (first time, and wasn't planning on it), and botched the autorotation, but is it possible to take the MiniP down on autorotation from this altitude safely? I remember hearing stories that it autos like a brick...

2015 02 04 Forced Autorotation (0 min 21 sec)

[Aryemis]

umm to be clear, when is the forced autorotation in the log ?
A little after 2min or later ?

Also, this could be an issue with esc settings, as you pushed the motor harder, the esc lost syc and rebooted in flight.

I had this happen with a scorpion 1880kv and a YGE60. With a slight overspeed simply unloading the rotor was enough), the rpm would go too high and the esc would lose sync and reboot in flight.

Needed 24° timing to run well, took me some time to figure it out.

[madeye]

Originally Posted by Aryemis

umm to be clear, when is the forced autorotation in the log ?
A little after 2min or later ?

Jeti says '3 minutes' 7 seconds into the video, motor shuts off at 14.

However, the timer announcement is not related to recording time, it's a countdown starting at 6 minutes and running while TH is disengaged, it's actually announcing "3 minutes left".

The power shuts off at about 3:32.

Originally Posted by Aryemis

Also, this could be an issue with esc settings, as you pushed the motor harder, the esc lost syc and rebooted in flight.

If it did, I wouldn't know, no telemetry on that one

Originally Posted by Aryemis

I had this happen with a scorpion 1880kv and a YGE60. With a slight overspeed simply unloading the rotor was enough), the rpm would go too high and the esc would lose sync and reboot in flight.

Needed 24° timing to run well, took me some time to figure it out.

How do I know whether I need to change timing? Right now it is at default 15°, with the stock motor which I'm not going to change for this helicopter.

Another thing that might help in resolution - ungoverned, this ESC spins the motor (just the motor, with the drivetrain disconnected) to the equivalent of 3700RPM, but with Brain governor enabled, it struggles to get above 3200. Wonder if these two issues are related.

And I don't really think Brain could have anything to do it, could it? Nah.

[Aryemis]

Originally Posted by madeye

How do I know whether I need to change timing? Right now it is at default 15°, with the stock motor which I'm not going to change for this helicopter.

Another thing that might help in resolution - ungoverned, this ESC spins the motor (just the motor, with the drivetrain disconnected) to the equivalent of 3700RPM, but with Brain governor enabled, it struggles to get above 3200. Wonder if these two issues are related.

And I don't really think Brain could have anything to do it, could it? Nah.

Hmm if you have trouble spinning the motor under load, it could indeed mean wrong esc settings.
Not sure what settings you'd want with a hobbywing with the stock 6S motor (it is a 10 pole motor) though, never used one. You could try raising timing a bit perhaps.

My scorp 2520-1360kv, also 10 pole works fine on 18° timing with YGE, but 15 may be too low.

[madeye]

Originally Posted by Aryemis

Hmm if you have trouble spinning the motor under load,

Not quite under load. Still unloaded, but managed by Brain governor.

Looks like I *will* have to build the contraption to hold the helicopter and check how all this behaves under load at high RPM. And learn autorotations

[jmtyndall]

Originally Posted by madeye

Not quite under load. Still unloaded, but managed by Brain governor.

Looks like I *will* have to build the contraption to hold the helicopter and check how all this behaves under load at high RPM. And learn autorotations

Yikes. Another guy had the same problem on a Chase using hobbywing and Ikon governor. Wonder if there's a compatability issue here or an esc issue.

Calling all Ikon developers!!

[JustPlaneChris]

I've been using the Hobbywing + iKon for months with zero issues, so I don't think we're looking at any sort of inherent incompatibility.

What mode do you have the ESC set in? Mine is in "airplane" mode, the iKon is handling all startup and governing.

[madeye]

Originally Posted by JustPlaneChris

I've been using the Hobbywing + iKon for months with zero issues, so I don't think we're looking at any sort of inherent incompatibility.

What mode do you have the ESC set in? Mine is in "airplane" mode, the iKon is handling all startup and governing.

I've started with "Governor off", then, by your advice, changed it to "Airplane" - nice, now ESC soft start doesn't interfere with Brain soft start, and disarming the ESC won't be catastrophic. Other than that, defaults. Except, now the LVC is off, but that was *after* loss of power, and I haven't flown with those settings yet.

Did you have to change timing or anything else? What motor are you using?

[JustPlaneChris]

Mine is installed in my Lynx 450xl, running it on 6S with a cheap HobbyKing motor. My Mini P is using the YGE40 (again with iKon gov).

I believe I'm still at stock timing... my memory is failing me, I'll have to plug it in and check!

[madeye]

I guess I'm up for some experimentation...

YGE default settings: PWM frequency 9 kHz, timing 18°
HW50A default settings: PWM frequency 32 kHz, timing 15°

It's interesting that YGE manual mentions 18° as the lower value for outrunner motors.

[madeye]

Just had the Take Two of this today - this time, though, expecting it, no damage. The only difference between the previous setup and this is that HW timing was increased to 18° in an attempt to match previous YGE setup (see above).

And the current didn't even go high enough to trigger any protection - you can see that the peak current during this flight was somewhere around 28A, but here it was just around 17.5A - granted, of course, that it could've been anything if Jeti MUI sampling is no good. There was no low voltage alarm, either - not even close. The log is attached just in case. P4 is the collective stick.

The most strange thing is - it's difficult to hear it in the video, but I've got a distinct impression that the ESC shut off a moment *after* I got it hard collective - I did it twice to see how it behaves and already thought I was home free when it went down.

Anyone's got a guess about what's going on here? I have a nagging suspicion that it's the new Brain firmware that is causing this by confusing the ESC, but don't have facts to back it up. I guess I'll need more research.

2015 04 19 Mini Protos Loss of Power (0 min 10 sec)

[WI_Hedgehog]

This is a long-shot, but just had it happen this weekend. Battery connector wore out. Plugged/unplugged so often (hundreds of flights) one connector terminal wore thin and couldn't carry the current under heavy load causing a motor shutdown. It appears as if the capacitance of the non-motor circuits was enough to carry them through, no loss of Rx/Telem/control, but complete loss of motor, then recovery (so no brown-out).

I think what happens is without the motor driving the rotor, the "disk" unloads quickly, and the control circuit (DC circuit--the BEC side of things, not the 3-phase motor circuit) has enough residual to hold position and not brown out. A good amount of battery (source) current is always present, so when the motor shuts down the control (BEC side) circuitry is still running on stored energy, and the motor control circuit may immediately recover and spin the motor back up, or it may do a "sanity reset" and spin up slowly, checking for signs of failure. It's kind of a red fox issue, where chickens are going missing but nobody really knows how or why.

Don't know if that is or isn't your heli's issue, but maybe it helps, and glad to hear it's doing okay. That was quite a "plop!"

[madeye]

Originally Posted by bhkrause

This is a long-shot, but just had it happen this weekend. Battery connector wore out.

(read, understood, skipped) Not a case here, all connections are rock solid.

Originally Posted by bhkrause

Don't know if that is or isn't your heli's issue, but maybe it helps, and glad to hear it's doing okay. That was quite a "plop!"

Actually, it wasn't that bad - zero damage. Last time (see the link at the first post), the rotor bled out completely at about 10ft in the air. I was lucky to land straight, all the damage was - bent tail fin, and a small crack in the canopy, Gorilla Gears bent all the way to flat and unbent right back, love them.

[JustPlaneChris]

I know you said all connections are solid, but I'd still be tempted to at least resolder the bullets and verify they're making good solid connections.

I would be surprised (shocked) if the problem is related to the iKon governor in any way. That's a rock solid setup in my experience. I've migrated the HW 50 V3 to my Goblin 380 and it's still working as well as it did in the Lynx 450X stretch.

[madeye]

Originally Posted by JustPlaneChris

I know you said all connections are solid, but I'd still be tempted to at least resolder the bullets and verify they're making good solid connections.

That was done as a part of a rebuild immediately preceding this experience

Originally Posted by JustPlaneChris

I would be surprised (shocked) if the problem is related to the iKon governor in any way.

I just can't say - like I said, it's a nagging suspicion with no facts to back it up. Believe me, I'll get to the bottom of it, it's just all these things take time, and sometimes you just want to fly instead of testing boundary conditions (which this incident, btw, was - I *had* to make sure it's still there after tweaking it).

Originally Posted by JustPlaneChris

That's a rock solid setup in my experience. I've migrated the HW 50 V3 to my Goblin 380 and it's still working as well as it did in the Lynx 450X stretch.

Nice to know. Are you using the Ikon governor there, or HW governor?

[jmtyndall]

So throw a fbl on there and let us know!

[madeye]

Originally Posted by jmtyndall

So throw a fbl on there and let us know!

I think replacing FBL is a bit radical at this point - I haven't done all the things necessary to pinpoint the problem. One of them would be to use the HW governor instead of Brain and see if that does anything.

I posted elsewhere that I was never able to get Brain to sustain the headspeed above around 3200, but the unfortunate timing was that I had to a) replace the ESC and b) upgrade the firmware at the same time (never again if I can help it), so again, not really possible to identify where the problem is.

And, of course, another thing to do - get the *latest* firmware and see if it fixes the problem; the version I'm running now is the one from around February. I was reluctant to upgrade again till I sorted things out, but looks like I have to.

I'll report findings if/when I come across something reproducible and verifiable.

[jmtyndall]

At this point youre in testing mode. I would borrow a fbl. I personally keep a couple spares around, I understand not everyone wants to keep $200 tied up in a FBL sitting around, but it's valuable when testing this stuff.

Mostly I run vbar, so I just export my settings. Import to the spare vbar, install and fly. Quick diagnosis is it's a fbl problem or not.

Best of luck

[JustPlaneChris]

Originally Posted by madeye

Nice to know. Are you using the Ikon governor there, or HW governor?

iKon governor, XNova 890kv motor. Runs like a champ.

[madeye]

Lo and behold, I reproduced it on the bench (pump the collective hard a few times, maybe hold it there for a bit), and found the cause.

Lowering the Ikon governor gain to default value of 50 eliminates the issue.

At 65 it is present.