A mysterious incident

[Martin Harris - Moderator]

I do wonder whether the difference between cheap and mid-range motors is simply their price. It seems that way with LiPos

 

RW - don't forget that it isn't actually the ESC which beeps - it's the excited windings vibrating in the motor that make the noise so if you've turned them into a lump of solid copper/molten insulation it will remain silent...

Edited By Martin Harris on 02/09/2011 16:56:57

[Tim Mackey]

The AR500 passed with flying colours. I flew it way way out - certainly much further than it was when the incident occurred yesterday evening at the flat field site. Not a flicker of any problem at all, full connection and control at all times. Then it was flown in closer and joined in the combat - at least that would also likely show up any dry joints / hidden arial breaks etc...and after a few hits, and some very troubled arrivals - including one so hard that the wing itself broke in two... no problem found at all. Some strapping tape later, and she was thrown out again, and fought on for another hour or so flying. All rock solid.

My faith in the receiver is restored ( and it somewhat rules out any transmitter issue also )

 

So, what was the cause??

 

What evidence I have is that the motor is dead, and appears to have overheated .

 

1) Do people agree with that ?

( Chris, the overheating may well be the reason that solder has sprayed around the windings...that was sort of what I was suggesting myself )

 

2) Did the motor overheat in flight, go dead short and overheat the ESC causing thermal shutdown of the BEC ? Ill take the ESC out of the model, and check for any signs of heat damage.

 

3) Anyone have anything else to suggest?

 

Certainly the quality of the wiring is suspect to say the least, and I shall contact the supplier to see what they have to say. It will be a good test of their service levels.

PS: I have changed the thread title, as it is unfair IMO to blame the radio on the evidence so far.

Edited By Tim Mackey on 02/09/2011 18:13:57

[Dave Bran]

3) Anyone have anything else to suggest?

 

How about a repeat of what happened to my Ripmax Spit, the motor mount joints failed, the motor jammed, but unlike mine because your plane was so far away you could not tell, so it overheated the motor?

[Romeo Whisky]

Re post by Martin Harris ref:

" RW - don't forget that it isn't actually the ESC which beeps - it's the excited windings vibrating in the motor that make the noise so if you've turned them into a lump of solid copper/molten insulation it will remain silent..."

 

OK Martin, but since the issue related above there is no beeping on start up with any motor, yet otherwise the ESC seems to work OK on the bench. But with no beep I cannot verify the program settings even if I program it with a program card, nor can I reprogram it via throttle stick movements. Needless-to-say I don't trust it enough to risk flying a model with it anyway, so it's all a bit academic. I don't really want to strip the heatshrink off it to see what burnt, as I can still use it for bench testing, though at some point I will.

 

The bottom line is I was a bit luckier than Tim, in that my EnErG motor wrote off a ESC, not a model. But the motor and ESC together still amounted to about £55+.

 

It is nice to know that the Spektrum system was almost certainly not to blame for this unfortunate mishap, and I suspect a lot of other crashes blamed on Spektrum are misdirected too. It would take a lot of incontravertible evidence to make me give up the Spektrum Model-Match safety feature. RW

[Wiltshire Flyer]

Posted by Lee Smalley on 02/09/2011 08:40:11:

As for the spekky has more incidents than any other radio, well duh, that because there are more of them out there that any other radio, it's like the old argument that hurricanes shot more enemy aircraft down than the spitfire during the BoB well duh there were more than twice as many of them

 

 

DUH?? just because there may be more of one make of TX being used does not mean that statistically you will hear of more mention of problems when compared with other makes that are not used so much, say Honda produce 100,000 cars and they hit the roads, then Volvo produce 25,000 cars and they too hit the road, Volvo find that there is a common failure of some sort and have to recall x amount of cars, but Honda who have far more on the road do not have any issues with their cars...... hey presto you will here far more about Volvo than Honda and honda have 75,000 more cars in use

 

Look on the homepage and you will find 2 posts regarding TX recall and another mentioning a software bug, what brand is the TX? that is my point, that coupled with the many posts i have read here regarding failures etc are enough for me not to want to purchase Spektrum in the future. anyway drifting too much off topic, sorry Tim

 

 

[Devon Flyer]

There have been several unexplained 'losses' at our club.

The only common factor was Spektrum radio systems.

 

You can draw whatever conclusions you like from that ; but I know where I would spend my money if I was in the market for a new set.

[Lee Smalley]

When incidents like this happen most people do not do the investigation like tim has as a result it generally gets blamed on the radio, whatever brand they are using, therefore the most popular brand will generally get more incidents lodged against it that should be patently obvious, your choice of radio is up to you, but to dismiss one brand based on hearsay and Internet posts is strange, but let's face it futaba is a great reliable radio as well. Unexplained losses, is that not just down to lack of investigation?

Edited By Lee Smalley on 02/09/2011 19:32:55

As for tx recall and bugs, that's one tx only Hitec have had problems as well and futaba had an issue a year or so ago noone makes a perfect product but given the popularity of spekky stuff I think they have an excellent record

Edited By Lee Smalley on 02/09/2011 19:36:46

[James40]

" I had NO CONTROL"

 

Tim, I understand the motor failing will cause a stall but you said you were at altitude and the aircraft was nose down in attitude.

Given the above, she should still have responded to control inputs with enough airspeed in the dive?

Given the damage from the impact, I can only assume it's quite a light weight airframe (I don't know the make well) so even more a case of it should have responded to control input in a dive.

 

 

Do you think the motor shorted dragging the battery voltage down giving the RX a power dip, enough to give it a brown out?

[Biggles' Elder Brother - Moderator]

can we keep on thread please guys

 

Your theory sounds plausable to me Tim.

 

1.Yes the motor is dead and does seem to have suffered some kind of thermal distress - although as Dave points out we can't be certain of the cause of that.

 

2. I would guess "yes" the overheating happened in flight and that led to a thermal shut down.

 

BEB

 

PS Doesn't happen with IC

 

PPS Before anyone gets excited that's a joke at the expense of one of my clubmates - he flies electric and everytime anyone gets a deadstick he always says "Doesn't happen with electric"!

Edited By Biggles' Elder Brother - Moderator on 02/09/2011 20:00:39

[Chris Bott - Moderator]

James I think Tim's theory is that the motor shorted which overheated the ESC so much that the BEC in the ESC shut down on thermal protection, thus removing Rx supply from the Rx.

[Erfolg]

It is interesting that you found your motor burnt out. I am sure that no one will remember that about a year ago I posted a thread, which requested information for a replacement inrunner motor, I am equally certain that no one will remember that it was the result of a similar event.

 

In my case, there was no wind, bags of thermals, I found all the sink. To compensate, in order to get my minimum 20 minutes per flight, I pushed the motor and lipo hard.

 

Whilst climbing with motor full on, the model rolled onto its back, started a shallow spiral dive, the model having rolled out. I did recover, when I thought about what should be my next model.

 

When I landed I found that I had burnt the motor out.

 

I was going to suggest the possibility, of the motor, you got there first.

 

There was a similar event with another modeller in the club, who burnt out his AXI, badly damaging his "Cermart Breeze".

 

[Tim Mackey]

Posted by Lee Smalley on 02/09/2011 19:30:38:
When incidents like this happen most people do not do the investigation like tim has as a result it generally gets blamed on the radio, whatever brand they are using, therefore the most popular brand will generally get more incidents lodged against it that should be patently obvious, your choice of radio is up to you, but to dismiss one brand based on hearsay and Internet posts is strange, but let's face it futaba is a great reliable radio as well. Unexplained losses, is that not just down to lack of investigation?

Edited By Lee Smalley on 02/09/2011 19:32:55

As for tx recall and bugs, that's one tx only Hitec have had problems as well and futaba had an issue a year or so ago noone makes a perfect product but given the popularity of spekky stuff I think they have an excellent record

Edited By Lee Smalley on 02/09/2011 19:36:46

 

Absolutely correct Lee.

[Tim Mackey]

Posted by James40 on 02/09/2011 19:59:42:

" I had NO CONTROL"

 

Tim, I understand the motor failing will cause a stall but you said you were at altitude and the aircraft was nose down in attitude.

Given the above, she should still have responded to control inputs with enough airspeed in the dive?

Given the damage from the impact, I can only assume it's quite a light weight airframe (I don't know the make well) so even more a case of it should have responded to control input in a dive.

 

 

Do you think the motor shorted dragging the battery voltage down giving the RX a power dip, enough to give it a brown out?

 

 

Yes it was high, and simply went into a steep dive - and I definitely had no control over any flying surface.

As I saw the dive start, I closed throttle and slowly pulled up elevator - no response.

I then held the Tx up high and moved all the sticks into the corners ( mode 1) but again ....nothing.

The AUW is 3lb - and very lightly built at the front .

I think its unlikely that the shorted motor would pull the battery low enough to cause a brown out. Extensive testing by me has shown that these receivers continue to operate down to under 3.5V, and a switch mode BEC would have to have a very low input voltage in order to drop its output so much ( drop out voltage). Besides, in my testing I also found that brown outs were so short lived that one can barely notice the effect.

Of course, had I left the Tx switched on, I could have checked the Rx LED - but I was concerned that if something had failed on the radio, the motor may still be live, so I shut it off, knowing that failsafe would then at least stop the motor IYSWIM.

I cant say for sure what the drop out is on the BEC of this unit, but the better ones can be as low as just 1V difference - meaning the battery would need to be shunted out hard to reach that level. Imm pretty sure there would be some evidence of this, yet the battery appears fine, and when measured this morning showed 10.65 V, and very little cell imbalance.

I think the ESC would probably complain and shutdown before that happened.

I am not saying its impossible - and its food for thought - but unlikely.

 

On that note...I have removed the ESC and stripped the heatshrink covering off, but it shows no obvious sign of severe overheat.

[Tim Mackey]

Posted by Dave Bran on 02/09/2011 18:38:46:

3) Anyone have anything else to suggest?

 

How about a repeat of what happened to my Ripmax Spit, the motor mount joints failed, the motor jammed, but unlike mine because your plane was so far away you could not tell, so it overheated the motor?

 

Yup, possible I guess, although knowing its reputation for weak joints in this area, I had gone over all the joints with PU glue when the model was first "built".

Edited By Tim Mackey on 02/09/2011 21:40:20

[Ian Jones]

Wish I could offer something constructive but I'm not really that much of leccy sort of guy. Looks fairly easily repairable though - hope it's not too long before you resolve the issue and get fixed up with a motor you can trust.

[andy watson]

Don't shout at me if this is a stupid suggestion- I am a humble IC flier.............but doesn't the solution stare you in the face here? Using the flight battery to drive both the motor and rx is a weak point in the system. A seperate rx battery would have meant that this incident would have been a "simple" deadstick scenario rather than a full out of control situation.

 

Given that an in control deadstick is much safer than a total loss of any control, is there another reason for adopting a seperate RX as best practise?

[GrahamC]

Being a newbie here.... Apologies if I've missed coments about this, but this sounds like the problem that Spektrum have admitted in a technical bullitin. Basically they admit that there appears to be a hold problem when using a dsmx transmitter (dx8) with a dsm2 rx (a r500).

Horizon Hobby have a technical bulletin and are updating the software on some dsmx transmitters.

Appologies if you have already explored this possibility.

[Chris Bott - Moderator]

Andy it's pros and cons really. The advantages of using a Battery Eliminator Cicuit are:

 

Weight.

A fully charged reliable (usually) receiver supply every time you fit a new flight battery (normally every flight).

No worries whatsoever about whether a separate Rx battery is a good one, or still has a charge.

No Rx batteries to charge between flying sessions.

No problems with receiver switches (you don't have one).

The disadvantage really is the possibility of a BEC failure.

 

An external separate BEC would eliminate the overheating ESC issue. But is overkill in small planes due to how unlikely the overheating issue is.

[Tim Mackey]

Graham...I think thats a relatively old issue, and does not apply to my transmitter which was purchased new only a couple of weeks ago.

[andy watson]

Chris, I'm not convinced I agree with your list there.

 

Weight I understand- especially in a small electric model where weight seems critical, but a 4.8V rx pack is not very heavy and would be easily incorporated in any 40ish size plane (if you don't mind me making an electric/ic comparison!).

 

The worries about the quality of the battery, whether it's good and or charged etc seem very minor compared to the amount of charging electric fliers seems to do. A simple (and cheap) 2600mAh 4.8V NiMH battery will easily last all days flying- and more. The switch is possible to add easily, but if you prefer not to have one then simply connect/disconnect the rx battery at the same time as the main LiPo.

[Chris Bott - Moderator]

I agree 40 sized models are where this debate becomes more down to personal taste.

 

But Tim's model was a small hand launched 3lb Spitfire.

 

I just prefer the fact that I don't have to think about receiver batteries at all. As you say, we have enough charging to do as it is.

 

Some people use a LiPo and a BEC to power their radio. In which case they have the concern about the BEC failing, they have to have a switch, and they have to charge the LiPo..

 

I guess it's all part of the rich array of choice we have in the hobby these days.

[kiwi g]

Nitro ?why doesnt it start?

electric why did it crash?

I read alot of the threads and I fly electric and ic but theres alot of models being crashed due to electrical faults from similiar issues to tims latest.

theres no sure guranteed way of flying electric as if a motor can short and cause electrical problems elsewhere then same can be said about any other part of the electrical system..

Keeping electrics as simple as possible has to be one of the best ways of insuring less carnage does it not. ?

As for spektrum and 2.4g in any form , most issues are usually user and install faults rather than radio. Remember those who have had faults , for evey one fault there must be thousands that dont.

What would be good may be a setup that sets a standard for electric rc aircraft, then add on from there. ?

[James M]

Hi Tim

 

Sorry for your loss, but on the plus side the DX8 and AR500 are a good combination - I have a few AR500 receivers in service!

 

Had something similar on a Seagull Innovator - but this was a build fault on my part!

 

The 50amp ESC i was using has a linear bec 1.5 amp that was in an enclosed space above the battery - no cooling.

 

First flight was ok as i was just trimming and checking the flight characteristics, 2nd flight i was pushing it around the sky and flapping the servos quite hard. The whole plane shut down for a few seconds and started back up!

 

On inspection the ESC was a bit on the warm side! Moving over to a 60amp ESC with a switched BEC which should help with the cooling side of things and stop the issue.

 

The part that worries me is that i have two of those motors on the shelf and was planning to put one into a Seagull Decathlon - any way of checking prior to flight if i have a duffer ??

 

James

[Peter Beeney]

If I might just add a post to this interesting thread and say that we had something vaguely similar at our field very recently. An electric motor stopped suddenly in mid flight, very abruptly, as if it had seized, and the model instantly dived straight in. It was a small lightweight foamy, not very high or far away at the time, and fortunately very little damage was done. The first speculation was of some sort of radio failure, but once the model was recovered it actually took only a few moments to establish that indeed the motor was completely shot and that was the sole reason for the premature termination of the flight. It was a fairly fast revving beastie, quite audible, but I didn’t notice which brand. The owner is not particularly a speed merchant and he said everything was well within spec., and I’m sure it was. The general consensus of opinion was that this was just another ‘failure’, almost to be expected in this age of very expendable items. In the world of model aeroplanes it seems to me that things can sometimes fail on just a whim, they don’t always even have to be grossly overloaded. The radio was working ok, and the ESC also showed no signs of any overheating etc.

With regard to Tim’s motor, with the greatest respect but surely if the motor windings are open circuit this is at least one very good reason for the motor not working? With regard to an overheating regulator, if these on the ESC’s are the same specification as standard regulators it would have to rise to at least 150 degrees C to shut down. I’ve never seriously tried to heat up a regulator from the outside to shut it down, but I have placed a hot soldering iron on one that was working, for some considerable time, but that failed to stop it. I’d consider that the ESC would have to get very hot indeed to shut the regulator down; perhaps almost to an ignition point; and if the motor temperature rose very quickly, sufficiently so to cause the motor windings to go open circuit, broken solder joints maybe, then surely the ESC would quickly cease to carry any current at all? So would it then still then continue to get hot?

My AR500 will continue to operate down to 2.8 volts and at that point it is the servos that are tending to fail, not the rx. That actually shuts down at between 2.7 and 2.6 volts. But at that point the servos would not operate at all, so maybe the whole question of the rx shutting down is somewhat irrelevant anyway. Or, at least, if this happened to me I would consider it so.

Certainly the electric scene is going to keep things interesting for a little while yet…..

PB

[Tim Mackey]

Hi Peter, yes sounds a very similar incident. I am certainly not completely sure that the reason was a shorted motor, and resultant over heated ESC - especially as the ESC upon examination shows no visible signs of "stress". It was just a possibility.

I think the main thing for me is that it almost certainly proves that it was not radio failure....and more particualrly not the AR500 which seems to attract more than its share of criticism. I got raised eyebrows from more than a couple of people after the crash, when they asked what receiver was fitted. As I have said before, provided they are properly installed, and powered, I have found them to an excellent receiver.

So many times we see and read of "mysterious crashes" and the almost inevitable cry of "radio failure". If people only bothered to stand back a little and investigate things properly, Im convinced they would discover in many cases, that other things were actually to blame. We not always find the exact cause, but at east the poor old radio woudnt get blamed without a trial.