Anwar .
I can add from my first electric conversion of the Tiger 60   which was incidentally flown at Sholavaram that you  are seriously underestimating the need for cooling in a plane .
On my first electric conversion I did not realize the importance of cooling  and also did not know that special electric Props had to be used

Hence I nearly lost 2 nos 11.1V 4300 mah batteries only on the cooling count .

The current draw by a normal regular 13 x 8 JXF prop was  high  and the LIPOS  got over drawn within  a couple of minutes of flying  to a point  where you could not hold them by hand . I then created a large Air Ram at the front end of the  battery compartment  and  two out lets at the rear  end of the compartment and  the entire heating problem just vanished .

I have seen the funstar and  can say such an arrnagement was not there .

Sai

This is the first time I heard about lipos needing cooling. I know ESCs enjoy cooling (and airflow around them). See this thread from the other forum :

http://rcqatar.com/helicopters/scorpion-commander-45a-esc-heat-problem-solved/

And your explanation does not relate to this discussion at all (I feel uneasy saying this, but it has to be said ), as yours is a clear case of high amp draw, which causes the lipos to heat up, puff up and in general get seriously damaged.  The "amp draw" is the root cause, not heat or "lack of cooling".

The airflow may have helped your ESC, which may in turn had some effect on the batteries.

Anwar

In any case, a heating device requires proper heat dissipation, otherwise it is prone to overheat. The amount of temperature rise required for shutdown to occur is only a matter of time. That I think is accepted. Now www.rcmodelreviews.com is a website owned by an individual who is devoted to testing most RC systems independantly. His credentials are pretty amazing and his reviews and articles are both authoritative and informative. If he says 120 deg F as the point at which shut down occurs, I would tend to believe just that, whatever Futaba says. Now adding fuel to the fire, it seems JR /Spectrum has gone in on the kill by launching an advertising compaign saying that their receivers work even till 300deg F. Clearly Futaba is on the defensive here, as witnessed by their receiver tips mentioning about the cooling necessity.

If you are still not convinced... Well you have your own viewpoint and I respect that..



I forgot to add ... It could also be that some other device close to the heating  device could also be the cause for the shutdown... not necessarily the main device which may be rated for 60degC.. This reminds me once again about my work related related problem and investigation, wherein,  a resistor over heated under particular operating conditions related to the operation of the machine causing shutdown, not the main power device.
   

Tally Ho


Saju

Yes Futaba has a heating problem, you can search this forum, and you can see how many times I have said this myself.  JR/Spektrum using this as an advertisement item is also dated news. JR/Spektrum will need to do some advertising, since they seem to be alarmed by people's acceptance of Futaba's version of 2.4 as being superior to theirs, and Futaba asking questions like "why did you have to come up with more and more satellite receivers, and why did you go from DSM1 to DSM2" and so on.  But if I continue down that path, this thread would end up being another Futaba versus Spektrum thread.

So far I am under the impression that we are not having a discussion on whether Futaba FASST has heat related issues (it clearly has!) or whether Spektrum is superior, it is a discussion purely about whether heat was a factor in the recent crash.  If we want to have a Futaba versus Spektrum discussion, let us open another fun thread   Your last response is what we typically see from Futaba bashing folks, mostly at others who defend Futaba at all cost (which I clearly am not) !

On the other hand, I have posted videos of people trusting their prized equipment to Futaba FASST also.

Now regarding the temperature itself, I guess I would trust the manufacturer and the research I have done myself, instead of one guy who makes a living reviewing stuff, and his take on this issue is the line quoted below.

QuoteIndependent tests (conducted by FASST owners) indicate that once these receivers reach or exceed a temperature as low as 120 deg F, they simply shut down and stop working.

For one, he himself did no testing, and is quoting unnamed sources.  I tend to question such "review only" folks, who put Google Adsense ads on their websites. But I do leave the possibility still open that this guy is genuine.

That said, the general information I see on this issue is that the shutdowns happen around 138F or higher (about 59C).

http://www.rcgroups.com/forums/showpost.php?p=10506281&postcount=21 is the kind of stuff I tend to trust. While devices that heat up (while working) do fail as the temperature increases (like you said), the point at which they fail is clearly determined by the tolerances of the components inside, and the component with the tolerance problem is rated at 60C.  If something failed at a lower point, that should be treated as a manufacturing defect affecting a minority of the devices, and is not representative of the design/technology/implementation (and manufacturers including Futaba and JR/Spektrum will both replace the affected units).  If the number of such failures is noticed in large numbers in repeated tests, then it is a design/implementation problem, typically leading to a recall by the manufacturer, or a law suit against them.  What we have seen in this case is that the failure can be reproduced around 138F or higher (typically around the 150F mark).

In any case, such lockouts are supposed to put the receiver in failsafe, which did not happen in this case.  Yet another reason why heat is not a primary suspect.

Anwar ,
Lets see what you think is the estimated temp when :

Ambient is around 40 Deg C +  heat radiated  from tarmac +  device heating  inside a closed box  area without air circulation + Engine heat  due to repeated sorties  .

I am sorry  to say this but I guess like Anwar put it it has to be said :

The tragedy is this discussion does not rely in any way on our knowledge and experience  in our conditions  most Indian's are prone to quoting the experience and reviews of some guys of whose competency we have no clue about  and who have all had their experiences in far cooler climes than us .

This is a typical Indian syndrome that I have seen during my long stay and experience abroad. I have experienced this in my Professional experience when I took over as Director  of Sales and Marketing in Saudi of a major Steel Mill from a Britisher .

Further Anwar  you are right the Lipo's heat due to Amp Draw  every one knows it I have been flying electrics for the past 2.5 years hence am well aware of it what you have stated is  not something new .  
From my experience with electrics in our climates  requirement of  circulation for LIPO's as well  is essential to ensure cells don't damage , I have been using the same cells for the past 2.5 years without any loss major loss of power precisely due to this . In our climates Lipo's also need Heat to be dissipated . BTW I have achieved 15 + Mins of flying time on my Tiger 60 on a single charge using improved cooling . I know this experience will not be accepted  as it is not Validated by some "" Expert "" from abroad  , but thought I would share it all the same for the benefit of Indian Aero Modelers as a few might use it to their benefit  .  
The Normal operating range of LIPO's in terms of temperature at  is Discharge:
32 to 140 degrees F  which  is max 60 Deg C   when you have an ambient of  around 35 to 40 deg  cooling is a must  for any system  as in an eneclosed place with hig amp draw  you would be approaching the max operating temp in  any case .
This is why cooling of Lipo's is also essential .

It is common sense that heat generated has to be dissipated to ensure a system functions .

As much as you seem convinced that heat is not the problem , in my opinion it is the cause as I am sure being the only plane he had that day  Chan is most likely to have flown quite few sorties  prior to this crash , hence heat build up on the devise and in the fuse is  the most likely reason .
You have not experienced the  heat at Sholavaram , we have    you are starting the system of around 38 + on the tarmac at around 10 am .

Sai

Quote from: anwar on July 21, 2009, 09:38:27 PM
This is the first time I heard about lipos needing cooling.

Anwar ,
manufacturers deliberately create air  gaps  between individual cell precisely for cooling and the fact that Lipos heat up .
This fact proves that Lipos do need heat management as well.
This is all the more essential in the case of High Voltage/Discharge applications like the ones used in large planes like the 50 and 60 size .
sai

That is "natural" cooling, which is not a burden on the user.  Except for saying don't keep lipos in the direct sunlight, I never came across manufacturers recommendations saying you should create airflow around lipos, or you should cut slots or put small fans on lipos 

I agree that airflow is a good thing, but I never saw it being quoted/mentioned as a "requirement". In fact, not even as a "nice to have" in general. 

Quote from: rcforall on July 22, 2009, 07:00:05 AM
The tragedy is this discussion does not rely in any way on our knowledge and experience  in our conditions  most Indian's are prone to quoting the experience and reviews of some guys of whose competency we have no clue about  and who have all had their experiences in far cooler climes than us .

My experiences are from places that are much hotter than Sholavaram (welcome to Qatar!).  And people who are interested in these discussions are people from places like Arizona. Others don't care, it does not affect them. People think India is unique, well yes and no.  And a huge NO in this case.

And everyone seems to ignore the fact that failsafe did not kick in, which was supposed to happen if this is a temperature related shutdown of the receiver.

Quote from: rcforall on July 22, 2009, 07:00:05 AM
Further Anwar  you are right the Lipo's heat due to Amp Draw  every one knows it I have been flying electrics for the past 2.5 years hence am well aware of it what you have stated is  not something new . 

Of course. Then you are also well aware that amp draw over the limits can cause a lipo to overheat in seconds (versus probably many minutes in other cases like exposure to heat from direct sunlight or other issues), and no amount of cooling can save your lipo from overheating and getting damaged if you draw too many amps.

BTW this is the 3rd case I know of a 2.4  lockout in Chennai .
I have spent 2 decades all over the Gulf  so  also know what it is like there .
I think a lot has been said from my side on this , you for your point of view and me for mine all the best

Quote from: anwar on July 22, 2009, 09:14:37 AM

Of course. Then you are also well aware that amp draw over the limits can cause a lipo to overheat in seconds (versus probably many minutes in other cases like exposure to heat from direct sunlight or other issues), and no amount of cooling can save your lipo from overheating and getting damaged if you draw too many amps.

Anwar ,
I have been flying only electrics from 200 gms till 60 size  for the past 2.5 years so the last thing I need is a tutorial on amps draw .
I once again state I am an only electric flier so know all that you are talking about .
I have stated my experience with it that is all .
BTW I am possibly one of the few in India who flies large electrics.

sai

Sai - Everything me, you and Saju have written here will help someone At least it will give them ideas about "options" to consider in various situations. That is the only reason I am not giving up yet !  Every post adds more useful information.  Now people even know not to trust everything they see in the first Google search result on any subject !

So I would request that we continue the discussion.  There is nothing personal about this. If I highlighted something, that is because it is relevant to the discussion, and you did not mention it yourself.  That does not mean you don't know it (and the same works for me).

I felt it may have started turning a little bit personal when you mentioned [1] Indian conditions which I am not aware of and [2] You know everything about amps draw and do not need a tutorial.  You did not mention that amps draw is a significant cause of overheating, and cooling alone cannot overcome it.  I am sure you did not mean it that way (personal), it may just be my take on it

These discussions are not about what (or how much) we know; instead they are mostly about [1] "what we remember" and [2] "what we think is relevant" ! And all of us can go wrong in these departments easily, so we help each other with the finer details.

Hi everyone,

To clear up certain things about the crash, let me put across the following points,

1. The time of crash was about 8 am and I had only one sortie prior to the crash!!
2. The crash happened 2 mins after takeoff
3. The Lipo was fully charged
4. Was not able to check the BEC becuase the wires were all torn and ripped IN THE CRASH since the model went skidding on its belly and side across the runway!!
5. I did not provide any cooling vent for the Rx because I did not feel that ir required cooling like in ESCs.. Just made sure enough surface area of the Rx is exposed for dissipation!!
6. Being a covered model, heat build up inside the model is minimal and I park it in the shade.
7. Weather on Sunday was cloudy and not hot
8. Antenna orientation was correctly setup
9. In addition to the Pitts and my Funstar going down, there were serious glitches in the air at the same spot and one other spot for 2 of Capt. Manish's planes flying on conventional radios!
10. Othere flyers on conventional and 2.4Ghz did not experience any glitches!

Hope this helps in clearing the scenario of the crash!! Even though heat reset is a possibility, I dont think it must be the culprit here taking into consideration the time and scenario of the crash!!

- Chan

Anwar ,
The way an electrical system is chosen is that the battery can normally handle higher amps than the max of the Motor , hence amp draw beyond the capability of the battery would in variably result in a motor or ESC  failure  before it hits the battery.
Despite that in the case of high discharge applications like in the case of large electrics the batteries need air circulation  , you will see that this is quite a standard practice  followed in the case of glow to electric conversions .
Sai

Anwar and Sai

I have had a word with Chan on the subject and he has accepted that the rx was in a completely enclosed environment with the LIPO powering it sitting beside it with no possibility of air-flow dissipating the heat generated.

Elsewhere from the internet (http://www.carolinaskydancers.com/reviews/FutabaFasstSystem.html) I have authenticated reports of possibility of rise in temperature in an enclosed space with the rx sitting inside, to as high as 135 deg F (57 deg C) with the ambient outside at 85 deg F (29.4 degC). That is almost an increase in temperature of 27 deg C!!. So if the ambient in Sholavaram is even 33 deg C, it would go over the 60 deg C limit. So the possibilities  I think are all pointing to this.

I am not intending this as bashing any manufacturer. All manufacturers have reached where they are with a lot of sweat  and I respect that. I entered this discussion in the first place with the idea of helping to reach some firm conclusions with lessons for all. I am not willing to turn any part of my country into a "Bermuda Triangle" for RC. Because if it can happen in Sholavaram, there is all the likely hood that it may happen in any other place close by. I like to do my flying with piece of mind, knowing fully well what I am getting myself into.

It has to be understood though that we have a lot of ministers and other govt. officials going around with "Z" category security status which entails that they have radio frequency scramblers running around. Can the FASST or DSSS system be upset by these scramblers ? It stands to reason that they do not get effected ... or  do they get effected ? This could spell the death knell for these systems in India if they do!!

Saju

Please see the pdf file linked here:

http://www.aaccmac.org/documents/2.4FutabaCautionNotice.pdf

It shows actual measurement of temp and a definite point of learning

Saju

Quote from: mpsaju on July 22, 2009, 10:04:32 AM
It has to be understood though that we have a lot of ministers and other govt. officials going around with "Z" category security status which entails that they have radio frequency scramblers running around. Can the FASST or DSSS system be upset by these scramblers ? It stands to reason that they do not get effected ... or  do they get effected ? This could spell the death knell for these systems in India if they do!!

Saju

From what little i may know, if their is radio scramblers switched on by security forces then all types of freq will be scrambled(locked out) whether kHz, Mhz, Ghz. Therefore they are called scramblers.

Quote from: rcforall on July 22, 2009, 09:56:52 AM
Anwar ,
The way an electrical system is chosen is that the battery can normally handle higher amps than the max of the Motor , hence amp draw beyond the capability of the battery would in variably result in a motor or ESC  failure  before it hits the battery.
Sai

While this may be true in general, I can give you at least two cases that I can think of where this is opposite of what we see in practice.

1. For some of us in the electric heli world trying to do "pitch pumping" 3D (it would make a nice thread what that means ) a common choice we have to make is what "pinion" to use.  The number of pinion teeth determines the maximum head-speed. So we can go for a higher teeth pinion and try to get mad head-speeds, which can be used to do very impressive tic-tocs etc.  But one thing we see in practise is that if we choose a pinion with large number of teeth, your battery overheats and puffs due to the amps draw, but nothing happens to the ESC or motor  (unless you are careful and try progressively higher throttle curve settings, in which case you can run almost any pinion you want as long as you adjust the throttle curve to it).

2. The second case is your own experience, where the wrong prop increases the amp draw, and you can totally overheat and kill a battery without doing any sort of permanent damage to the ESC or motor.

Increased amps draw will also cause faster discharge than usual, and if the pilot is not careful, your battery alone gets damaged, without affecting ESCs or motors.  In summary, we see that in practice it is much easier to kill a battery than to kill ESCs or motors.

Saju ,
That is a great  article  what hits you is the para on the first page that clearly mentions Chan's funstar's symptoms of the plane  going into full throttle and the fail safe not working.

The astounding rise in temperature shows exactly what you said that the heat generated on account of electrical activity by the chip  is amplified to a huge extent in the absence of proper cooling.

The thermal images more or less seal the case  of heat being  most likely  culprit  in Chan's as well as the earlier reported  cases .

Quote from: mpsaju on July 22, 2009, 10:04:32 AM
Elsewhere from the internet (http://www.carolinaskydancers.com/reviews/FutabaFasstSystem.html) I have authenticated reports of possibility of rise in temperature in an enclosed space with the rx sitting inside, to as high as 135 deg F (57 deg C) with the ambient outside at 85 deg F (29.4 degC). That is almost an increase in temperature of 27 deg C!!. So if the ambient in Sholavaram is even 33 deg C, it would go over the 60 deg C limit. So the possibilities  I think are all pointing to this.
Saju

Saju - I never said heat is not the problem.  My point is that based on the evidence and circumstances (time of day, cloudy day, no failsafe activated etc), it seems unlikely.

If Futaba is not reliable at 85F, they will be talking to their lawyers now (which might really be, I don't know !).

But the link you posted does not help your argument a whole lot.  

In one case, he put the ambient temperature at 85C, simulated a servo failure that caused an amp draw of 3.9A (that is the root cause!), and had the receiver temperature noted at 135F !  What kind of test is that ?  He concludes by saying just mount your receivers as recommended by Futaba, and keep planes in the shade; and everything will be fine.

In the second case, he says he was able to achieve internal temperatures of 125F with ambient temperature of 85F (does not say how!); but he noticed NO failures ! At the bottom of the page, he says he flew very well all summer without any problems, and gives Futaba a full thumbs up !

I think this thread needs a failsafe... I am sensing a raise in temperature..

Anwar ,
 
I give up Futaba 2.4 G is not affected by heat at all   .
If you just don't want to accept clear pointers   .
All you seem to be stuck on is the fail safe did not work , this report clearly states that the problem of fail safe not working has been reported earlier .
He seems to be a die hard futaba fan as well he has highlighted the problem and taken precautions like using a fan to cool the receiver  to ensure  he had a happy summer of flying   .

Anwar there is nothing personal or against futaba from my point of view , I sell Futaba .

Sai

Maybe there was a stuck servo (throttle servo perhaps) which caused excess current draw in the rx leading to a rise in temperature. This could also have happened.

Chan, if you are in on this, could any of the servos you had on the model got stuck temporarily, leading to the crash and later after the crash, righted itself in the ensuing vibration ?

I rest my case... Chan to answer

Saju

Quote from: izmile on July 22, 2009, 02:25:59 PM
I think this thread needs a failsafe... I am sensing a raise in temperature..

More than a fail safe a fan or a blower  with cooling air rams would be better  

I have locked my self out of this thread  no more signals here  

Sai

Quote from: izmile on July 22, 2009, 02:25:59 PM
I think this thread needs a failsafe... I am sensing a raise in temperature..

You just ruined my party  I was just beginning to have fun by getting on the nerves of Sai and Saju (and in the process helping others understand how to take everything you see online with a grain of salt etc etc). And now you come and spill the beans     Not cool, dude ! I hate you 

You barged in just when Saju and Sai were about to give up on me  Talk about bad timing !

Quote from: rcforall on July 22, 2009, 02:28:51 PM
Anwar ,
 
I give up Futaba 2.4 G is not affected by heat at all   .
If you just don't want to accept clear pointers   .
All you seem to be stuck on is the fail safe did not work , this report clearly states that the problem of fail safe not working has been reported earlier .
He seems to be a die hard futaba fan as well he has highlighted the problem and taken precautions like using a fan to cool the receiver  to ensure  he had a happy summer of flying   .
Sai

Sai, per Futaba failsafe is activated when there temperature issue kicks in.  Even the document quoted by Saju says throttle going to full etc is likely to be be caused by people not setting failsafe correctly. Ignore failsafe for arguments sake, even then the temperature at Sholavaram at 8am and the cloudy day with a plane kept in the shade on purpose etc does not warrant enough temperature to trigger this issue.  That is my point   Of course a stuck servo etc is another valid possibility.

Here we go round the mulberry bush... the mulberry bush... the mulberry bush...

Yes, I love Futaba    Thinking of getting my youngest daughter married to Futaba owner's handsome son

 hey guys i am conducting some tests on my 2.4 to see the failsafe problem right now and possible bec problem too. will try to post a video too. not over heating the rx but everything other than that