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Problem with Rescue - caused by insufficient BEC

Posted: Thu 28. Aug 2014 17:11:10
by Mikej
I will leave this thread here in case anyone else has the same issue - it looks extremely likely that my issue was caused by insufficient BEC power causing the Rx / Spirit resetting when I flicked the rescue switch. Hopefully no-one else will have this problem.

Apologies for the duplication - but I posted this on Helifreak and was wondering if anyone here has any ideas ....

I was out yesterday flying a couple of packs, and at the end of the second pack (with about a minute left) it was just starting to get a bit dusky so I had been taking it easy and came in to a hover about 20 feet up, and I thought I would just play around for the last minute. I was in an upright hover, flicked the switch to enable Rescue and the heli flipped upside down and plowed into the ground - I managed to hit TH on the way down to minimise damage.

I went over to the heli to survey the mess - bent boom, stripped main gear, bent mainshaft and feathering shaft, lost rudder rod, broken servo arm. Before I unplugged, I flipped out of rescue and tried doing pitch pumps to see how the servos were moving - the elevator servo was moving "reversed" - down for positive pitch and up for negative (though the other two were moving fine). I flipped into / out of rescue a few times and tried again and the servos were all moving properly.

I'm pretty certain that it initialised properly, and it was flying very nicely before I flipped the rescue switch.

It's a T450 Pro, Savox 0257 cyclic servos and a DS520 on the tail, running a DX7 with an AR6115 Rx.

It Piro-ed perfectly - very flat and stationary actually (very impressed) - so I am confident that Piro-comp is correct.

I always power my helis up as flat as possible (it is on a field so might be slightly off), and never touch them during intialisation (been flying FBL for 4 years). In fact if they wobble during intialisation I will unplug it, move it to somewhere more stable and re-power.

I've done about 20 - 25 flights with the Spirit on, and flipped into Rescue about 15 times (not in anger, just testing) from both upright and inverted and it had been perfect every other time.

original post http://www.helifreak.com/showthread.php?t=645599&

If it would help I will happily send the Spirit back so that you can check the settings / logs etc. - just hoping to understand what went wrong so that I can rebuild my confidence in it or change my usage if I am doing something wrong...

Thanks,
Mike.

Re: Failure with Rescue

Posted: Thu 28. Aug 2014 18:04:30
by error414
Can you upload your settings?

Re: Failure with Rescue

Posted: Thu 28. Aug 2014 18:22:41
by Mikej
error414 wrote:Can you upload your settings?

How do I do that ?

Apologies this unit is still new to me ..

Re: Failure with Rescue

Posted: Thu 28. Aug 2014 18:44:30
by error414
In pc software.
Backup tab - > profile section - > save button.
And upload that file on this forum.

Section 5.5.9 in pdf manual.

Re: Failure with Rescue

Posted: Thu 28. Aug 2014 19:00:30
by ritchieicu
Think i will wait on the results from this before installing on my bigger helis

Re: Failure with Rescue

Posted: Thu 28. Aug 2014 19:07:39
by Mikej
error414 wrote:In pc software.
Backup tab - > profile section - > save button.
And upload that file on this forum.

Section 5.5.9 in pdf manual.

Here you go - I was struggling to find them

Re: Failure with Rescue

Posted: Thu 28. Aug 2014 20:58:32
by ZeXx86
Hello

Sorry to hear your troubles.

For me it seems that servo wasn't reversed. Technically it is not possible during the flight if there is no bluetooth attached.

One possibility is, that BEC voltage dropped so drasticly so the unit can't operate correctly and was resetted in the flight so it flipped somewhere without any control. After few seconds it was in the ground and you observed geometry correction behavior which could confuse you.
In this case it could look like the servo is working in the opposite direction.

Unfortunately we can't guarantee that it will work in all circumstances and it is not so easy to tell you at this point what was the reason.
But because you are flying rather acro I am very sure it was not direct fault of the unit.

If the rescue is activated then it could generate the biggest load you can ever achieve on the BEC, because all servos changing its position rapidly. So there is very important to have BEC which can handle it. Moreover Savox 257 are not quite good for flybarless helicopters so it can generate very high spikes.
I am afraid but probably half of the helicopters are flying with insufficient BEC and the rescue is very intensive test for it. This is not first time that BEC was not able to handle this situation.

This is one possibility, but I am afraid, there are more. For instance if helicopter was initialized on the flat ground.

Also, are you sure that collective pitch for the rescue was configured properly?

Re: Failure with Rescue

Posted: Thu 28. Aug 2014 21:34:22
by Jman841
I posted this in the other thread, however, Always check the correct operation of the rescue before flight! Hopefully this can be added to the manual and software as well as a warning.

If it is not initilized properly it can be reversed as I have seen this issue with mine as well. After I started checking before every flight it has been flawless.

I suspect this could have been avoided if it was checked before flight. I could be wrong though, if it was a under powered BEC then it would be more difficult to prevent.

Re: Failure with Rescue

Posted: Thu 28. Aug 2014 22:00:09
by Mikej
ZeXx86 wrote:Hello

Sorry to hear your troubles.

For me it seems that servo wasn't reversed. Technically it is not possible during the flight if there is no bluetooth attached.

One possibility is, that BEC voltage dropped so drasticly so the unit can't operate correctly and was resetted in the flight so it flipped somewhere without any control. After few seconds it was in the ground and you observed geometry correction behavior which could confuse you.
In this case it could look like the servo is working in the opposite direction.

Unfortunately we can't guarantee that it will work in all circumstances and it is not so easy to tell you at this point what was the reason.
But because you are flying rather acro I am very sure it was not direct fault of the unit.

If the rescue is activated then it could generate the biggest load you can ever achieve on the BEC, because all servos changing its position rapidly. So there is very important to have BEC which can handle it. Moreover Savox 257 are not quite good for flybarless helicopters so it can generate very high spikes.
I am afraid but probably half of the helicopters are flying with insufficient BEC and the rescue is very intensive test for it. This is not first time that BEC was not able to handle this situation.

This is one possibility, but I am afraid, there are more. For instance if helicopter was initialized on the flat ground.

Also, are you sure that collective pitch for the rescue was configured properly?


Thanks Tomas,

I must admit I hadn't thought of the BEC - it is a fairly old Castle Creations Phoenix 45 - and only has a 3 amp (max) BEC. It has been in this heli for the past 3 years running FBL with a Tarot ZYX - but I don't fly very hard, only sports. I also have a capacitor that I can try which will give a little extra capacity.

I have a YEP 45 with a 6 amp BEC that I can try.

Thanks for the suggestion.

Mike.

Re: Failure with Rescue

Posted: Thu 28. Aug 2014 22:46:51
by ZeXx86
OK, no problem.

Also did you checked the log from the unit? In case it was power issue there should be saved log in the unit, so you should see a message about log from the previous flight when you opened Log viewer in the software.