Loss of power then inverted crash

[cfossa]

I've got a stock Blade 300X with about 30 flights on it. Yesterday it lost power shortly after take off, regained power within about 1 second, then it started rocking forward and backward about 30 degrees in each direction uncontrollably. It flipped inverted and I was able to hit throttle hold before it crashed inverted.

The only visible damage is a stripped servo push rod connector on the front servo Not sure if this was the cause of the rocking and crash, or the result.

Any ideas on what to check for the loss of power? The heli has briefly lost power like this twice before with no resulting crash, and flown without any incidents many times. I'm thinking this is a radio issue, but looking for suggestions.

Also, what else should I be looking for in the way of damage from the crash? Feathering shaft?

Thanks,

Carl

[Birdstrike]

This sounds to me as though the esc has a problem
and potentially reset the 7200bx in flight.

I had a similar issue with the 130x 3in1 a while back which destroyed the board after a severe crash after throttle hold failed to respond.

Smoked the right aileron servo and tore off a few servo connectors with it.

It appeared as though the gyro was reset resulting in horrific instability as you describe.

You could try a full range check with a friend at long range to check for response to rule out any R/Tx problems.

I have however seen a few videos on YT where a simple hover check displayed very brief momentary drop of rpm..The pilot continued to fly it and the issue seemed to go unnoticed as the drop was very very brief.

If it were my heli, i'm sure my ocd wouldn't allow me to risk flying it at all until even this slight problem is completely resolved.

Consider a replacement ESC, and check all electronics including the lipo before you potentially cause more serious damage to yourself or the heli.

[cfossa]

Thanks for the reply. Do you think an ESC problem would be intermittent? I've had the power stop momentarily like this about 3 times in 30 flights with no issues at all in between. The intermittent nature of the problem is what has me thinking it's a radio issue.

[tonys-heli]

this happened to me too, turned out to be bad solder at the ec3 going to the esc. I found it by powering up and wiggling the connections..hope you find it, keep us posted

[cfossa]

Thanks - I'll check that too! Was your problem intermittent too?

Carl

[Birdstrike]

cfossa, you could check the flight log on the Tx to see if there's an issue with the transmission between the Tx and Rx,specifically Holds and Frame loss.

Reading a few older threads here, it had been noted that the stock esc isn't bullet proof in any small part.

Failures regarding weak solder joints,intermittent power loss,even the capacitor going missing have been reported thus far, so this isn't an isolated incident.

If fail-safe has been set correctly, i would expect a Tx/Rx problem to simply cut power without causing these serious stability problems as you describe.

Another thing i would do is bench test the heli thoroughly blades off first.

Let it run and play around with the wiring checking for intermittent connections between the lipo the esc and the BX throttle connection.

Just be careful of the BEC wire going to the BX.
It may be a good idea to unplug the servos before you play with that if there's a problem here.

Check the 7200 for any signs of a reinit the next time you see even the slightest blink of a dropout.

Failing all of the above, I'd let HH know about the fault and perhaps get yourself another esc.

As for a damage checklist, this would depend on how heavy it came down and where.

For any light crash over the grass i'd replace the feathering shaft straight up, followed by a full routine checkup on key components such as the servos.

[thruster]

You can easily check the feathering shaft without removing it. First remove the blades, then remove the push rod links from the grips. Rotate one blade grip while holding the other grip still. Then switch and rotate the other. Even a very slight bend in the feathering shaft will be noticed this way.

[Mikej]

Originally Posted by thruster

You can easily check the feathering shaft without removing it. First remove the blades, then remove the push rod links from the grips. Rotate one blade grip while holding the other grip still. Then switch and rotate the other. Even a very slight bend in the feathering shaft will be noticed this way.

It works even better if you leave the opposite blade in the grip and hold the grip that you are turning the feathering bolt in - as the blade will accentuate the movement of the grip

[DoubleCH]

Yes, that's the best and easiest way to check feathering shaft.

While it's very reasonable to think this is an ESC problem, it could very well be servo problem or problem induced by excessive vibration along the drivetrain. The stock servos aren't the best especially if you've crashed them before. The servo motor may fail due to various reasons and draw a lot of current to brownout the stock ESC/BEC.

[cfossa]

Thanks - this was the first crash of the heli so no previous damage to the servos. The "power loss" had happened twice before, but both times it lasted less than a second and the heli kept flying fine with no incidents for 10 or so more flights.

If I'm having an ESC problem would it likely be intermittent like this? Would it be more likely on really hot days (overheating)?

Another poster indicated he had problems with the motor cutting out and he thought it was due to one of the antennas being zip tied to the tail boom brace. He took it off the brace and problem went away. This was after he tried swapping out ESC and problem remained. Mine came like this stock - anyone else have issues like that?

Not also that the servo push rod on the front servo came off and is stripped/broken. Not clear if this caused the crash (heli was rocking uncontrollably forward and back) or if this happened in the crash.

Thanks for all the replies!

Carl

[terryv83]

I have seen the stock Ds76's strip out mid flight, so it's entirely possible that it stripped before the crash. Has the heli got any vibrations? I've had a similar experience to yours, that was cured by eliminating the resonance.

[cfossa]

Thanks for the reply. The heli did not seems to have any vibration issues. It still had that "new" everything flies straight feeel to it

[thruster]

Originally Posted by Mikej

It works even better if you leave the opposite blade in the grip and hold the grip that you are turning the feathering bolt in - as the blade will accentuate the movement of the grip

Yes, now that you mention it, I agree with that.

[cfossa]

I did a careful inspection of all the wires leading to/from the ESC and found a small nick in the "rubber" covering on one lead coming from the ESC to the motor. It's on the connector where the leasds come together and there is metal exposed. Perhaps this was shorting out causing the temporary loss of power?

I will put some heat shrink on this and see if that helps.

Not a good thing to have even if it's not the cause

Carl

[cfossa]

Hi Guys,

I repaired my 300X and got it back in the air. Although I didn't have any visible damage it turned out I stripped the jesus bolt. I also replaced the feathering shaft while I had the head off.

The heli flies great in "normal" mode - everything is smooth, blades track well, etc. But, when I switch to "stunt mode" I get a lot of vibration. Any suggestions on what to check next? I'm thinking of replacing the blades next - perhaps there's a crack I cant see under the covering that's causing issues at higher RPM (stock wood blades). I'm also thinking of swapping out the main shaft, but I figured if that was bent I'd see vibrations in "normal" mode at lower RPM too.

What do you guys think?

Thanks,

Carl

[Birdstrike]

Blade recommends a maximum of 75% Throttle on a stock/woodie setup.

That being said, i have flown the wood only a few times 100% very lightly without incident. they tend to flex and warp at those speeds and in most cases are not able to maintain form integrity.

Take the main/tail blades off and give it a full power spool up,
Check for vibration sources.

Recheck the main head blade grips tension.
Do not compensate 'notchy' feeling grips by loosening them.
Keep them tight, After a few spools. the rpm will feather the grips apart.

Recheck the fbl follower arms, make sure to give interleaved tension until snug.

Check tail belt tension.
Check motor can/shaft balance

Check that the tail rotor shaft alignment is 90 degrees to the main shaft and the tail hub.

If the main shaft was bent you most likely wouldn't be flying, at the minimum you could expect more damage and snappage after several spool ups, worth checking along with the gear set/hub just to be sure.

[cfossa]

Thanks Birdstrike!

Just to make sure I understand:

By "Recheck the main head blade grips tension" do you mean tightening the bolts on the ends of the feathering shaft/spindle?

Also, I don't know what you mean by "Recheck the fbl follower arms, make sure to give interleaved tension until snug".

I appreciate the advice and will start with removing the blades and spooling up.

[DoubleCH]

Originally Posted by cfossa

Also, I don't know what you mean by "Recheck the fbl follower arms, make sure to give interleaved tension until snug".

The 2 swash follower arm pivot bolts tighten the head to grip the mainshaft tight on the bottom. If you fully tighten one bolt before starting to tighten the other the head will be forced to tilt.

[Ah Clem]

There were multiple reports of 300X's cutting out in flight fairly early on (I was one of them-my first 300X cut out around flight number 70).

There were two remedies discussed at the time: Re-routing the ESC lead away from the AR7200BX and adding a BEC. I did both, and never had another failure.

Your mileage may vary, but it worked for me.

[cfossa]

Update -

My vibrations seem to be solved for the moment Turns out I verified the addendum to the instruction manual which indicates throttle curve settings above 75% can result in vibrations with wood blades. I dropped the throttle curve to flat 75% and so far so good.

I got myself in this situation when I upgraded transmitters. I had 75% in my old transmitter, but must have just looked at the manual an not the addendum when programming the new Tx. Lesson learned - make the changes in the manual!

Thanks for all of the help.

Carl