Anwar,

You sure passed the jinx on!! Two mishaps in two days..

Saturday :

Landed my Yak and it cleared me and I turned to the right to see my friend waving a car away from the runway... Ran into him and the wing hit him on his leg... Lucky the plane was slow at the time.. Even then, I broke the carbon fiber wing tube and also the fuse part where the wing sits!!

Sunday :

The jinx continued!! Let me say that it was a spectacular crash (and really dangerous as well)!! My Funstar is now resting in pieces.. One of the other flyers (flying a Pitts on PCM) had a lockout and nose dived from more than 50 feet height!! I also had a lockout whien flying my Funstar at full throttle at the same spot!! My plane turned towards the runway and came straight at me at full throttle.. Nothing worked on my radio and I started shouting for the crowd around me to run!! It crashed onto the tarmac on the opposite side of the runway and one part of the wing disintegrated there.. The fuselage came like a torpedo scaled the whole breadth of the runway (must be atleast 20 meters), missed me by a few inches and went under my car, came out through the other side and travelled another 15 to 20 meters before resting!! The fuselage was in almost 3 pieces, one portion of the wing disintegrated, the engine (a brand new ASP .52) had taken quite a beating but would live to see some more flights, the Rx was intact, the Lipo (though hit) survived, the BEC is totally ruined and the servos survived!!  Dumped the plane on the field itself!!

I was real lucky that it did not hit anyone!! Gave me quite a jolt to think of the impact on a person or someone else's car!! The fuse travelled like a torpedo and sailed under my car!! It went so fast that I was not even able to see it!! 

And let me tell you guys.. I fly Futaba 2.4 Ghz.. First time I am having a lockout issue with 2.4Ghz!! And I had taken all the precautions against heating and antenna orientation.. Moreover, the Lipo voltage after the crash was more than 12.5V!!

Time to do some investigation!!

- Chan

Chan,
  Regarding the YAK, how come the CF tube broke? Does this plane have CF tubes as wing joiners? Then it makes sense that it would have broken through the balsa structure.

Reg. the Funstar - that was a great looking plane - in the photos posted on IndiaRC. But isn't that a lot of useful scrap balsa thrown away    Which can be useful for at least repairs of other planes. I've never thrown away balsa - especially when you consider the local price

Anyway, the analysis of this lockout should be pretty intersting. Planning to get a 2.4 system myself, so interested in knowing what fails these systems!!

Sorry to hear that   

Are you sure you had no control over any of the surfaces ?  Did you have failsafe set ?

Most importantly, how much of "plugging in" do you do (for example, if you move receivers around) ?  Loose contacts/connectors is something overlooked easily.

How many people were on the field ?  How many 2.4 systems ?  Did you establish why the 72Mhz guy crashed, was there a true frequency conflict with another flyer ?

I can understand Shabir having a crash  as he was on the good old radio  like mine  .
But  lock out on 2.4G guys its not supposed to happen 
I understand Meenakshi also had a problem of the throttle moving to max when he lost contact with his Futaba twice before , this is scary , I would assume if the receiver were to reset the throttle should not get onto full 

Sai

Throttle position on receiver losing contact with the TX for whatever reason is a function of setting failsafe (or default failsafe). "Failsafe" itself is a topic for another thread.

Unless we know it is a 2.4 lockout, we are speculating. The chances for a 2.4 lockout are pretty rare, but not impossible.

Oww.. sorry for your loss.

Looks like there is too much of RF activity in Sholavaram that even 2.4G is no good!. Its ironic that I have never felt a glitch when I flew in Sholavaram. I was using my good old 72MHz 8UAF (Ch 54).

Ya. the sight of an ariplane ploughing directly to you & your car should be terrifying. I remember when one of the flyer at sholavaram lost orientation flying directly into the sun. The next moment he realized that the model has turned some how and is directly descending on to the run way where the cars were parked. At that moment, I was enjoying my red spitfire and was not looking at this charging missile.  All I heard was a nice engine doppler sound and sound of the aircraft's wing tearing the wind... at that moment i knew something is wrong but have no time to react!... Next second is a loud impact and I could see shards of balsa busting off on impact - just 15 to 20 feet from where I stood.!!.. Man, that was scary!.

-Ismail

Nope, the sight of a 50size (or larger) heli coming towards you with those 600+mm blades going 2100rpm is better  

Ask me how I know ?   

in both cases it is $$$$$$$ in the air I guess Anwar is right the sight in the case of the heli would be more terrifying  or satisfying depends on the way you look at it for obvious reasons 

Its always a delight looking other people's carnage!!..   

Sorry to hear about the crash .. It is a matter for worry for everyone, since this occured with your new 10C .. Now i have the same, and we are planning to use it wit hthe gasser .. So need to really test out the Rx/Radio with cheaper models before installing them into these $$$$$ laden airplanes.
-Gaurav

It will not prevent your model crashing, and will not surely make you less sad if that happens.... but for the record, I fly fully loaded Trex 500 and 600 helis using 2.4 

And couple of months back, I test flew a co-fliers Vario Bell turbine scale heli (1.7meters) on a Futaba 2.4 system.  That is like 12x the cost of what I fly   There was no throttle range control, just pitch to control the ascent/descent.  And my friends were making fun of me saying you should start logging your hours on turbines, like the real pilots do !

The CF Tube is the wing joiner as you have correctly infered.  Yeah.. but I have too much of useless balsa with me and I didnt want to junk up my place any more.. Asked if anyone wanted the scrap, then threw it off!!


It was definitely a 2.4 lockout since I did not have any control over the surfaces.. Failsafe was programmed correctly and it also did not kick in!!  Failsafe was set to 20% of throttle and the crash happened at full throttle.. First thing I did after the lockout was switch on the throttle cut swithc!! Still no cut in engine!! My Rx Lipo was fully charged and was checked even after the crash!! But shoud do a detailed research onto how and why this happened!!

- Chan

To me that seems like there was loss of power. You BEC should be the suspect. If it was loss of signal, then failsafe should have kicked in.

That brings up an interesting point. Do you use a separate BEC, or you use a builtin one in your ESC ?

If you use a separate one, most of them are rated for 2s lipos, and it looks like you were using a 3s pack.  Wonder if that is a factor.

And most importantly, I see every where people not trusting 2.4 because of "rare unexplained crashes", while they conveniently ignore that non-2.4 crashes happen all the time (many times on the same day at the same field) due to a variety of reasons (lock out, frequency clashes etc etc).  Isn't it logical to conclude that even in the worst case 2.4 is at least as safe as non-2.4, and in the best case it is many times safer ?

Maybe yes... but if it happened once I would have accepted your comment!! But 3 times on the same field on 2.4 Ghz cannot be attributed to power loss (there were other incidents too)... And why did it happen at exactly the same place where the PCM locked out?? I have used this BEC with the Lipo for close to 7 months without any problems...I have also found that 2.4Ghz is susceptible to mucrowave interference and this has also happened in Bangalore to 2.4 Ghz flyers too!!




I use a separate BEC.. This is compatible for 2s to 6s!! And moreover I have been using this on 3s for almost 7 months!! I would never say that 2.4 is unsafe!! This is the first time it has happened to me though I had taken all the precautions!! I knew about this technology quite a bit and hence it is not the regular "Voltage was low" / "Heat issues"!! There was something else yesterday which created a mess out of my transmission and I would have to do some research into what that might be!!

That Bermuda triangle in our field has existed for a long time now and mine is the 7th or 8th plane to go down at the same spot!!  Though mine is the only 2.4 plane that went down!!

- Chan

May be it is the temperature affecting the  FASST as mentioned in this article  posted earlier by Saju reposting it for immediate reference .
The article also says it has not been addressed by Futaba.
May be this explains the problems with FASST that have been experienced here .
Sai

Yeah heat is definitely an issue with 2.4 Ghz.  But it is mostly in cases of planes with clear canopies!!  The Rx gets heated up in the sun!! I take care of mounting my Rx in a cool spot in the fuse and I take extra special care not to park my model in the sun because I was aware of the heating probs!!  My bet is still on the microwave transmissions!!

I would also go to the extent of saying the other 2 Futaba 2.4 lockouts might be because of heat issues because the Rx was wrapped up in foam which is a big NO-NO!! That totally cuts off heat dissipation! But mine was free from all that!

But still, if not the microwaves, then my next suspect would be the BEC failing!!

- Chan

Chan

I think Saihe nail has hit the nail on the head. The problem as described in the article occurs at  or near 120deg F i.e 48 deg C. With temperatures here (at Sholavaram ) going close to 38 to 39 deg C, and taking into consideration the heating up of the individual transistor in the receiver by itself when powering servos, it is but anutural feasibility that this is the cause of your problem... This is then inspite of the fact that you have taken due precautions to shield the receiver from the Sun as well as provide a cleared up space around the receiver ( no wrapping in foam!). The article also mentions that some individual users have taken to providing a cooling fan on the receiver to avoid this issue. Maybe, what you have to do is to see that there is sufficient  cool air-flow directly onto the position on the reciever that heats up (where the hot individual transistor is located).

Saju

I find it hard to attribute it to heat.  The chip in question that has the heat tolerance issue is rated for 60C.  I can't imagine Sholavaram temperatures plus the ambient heat due to heated air inside the canopy together going over that, as Chan flies earlier in the day.

Here is Futaba's best practice instructions on this :

http://2.4gigahertz.com/features/receiver-tips.html#air

Anwar

I believe you have mis-understood me... What I am saying is that the power draw by the servos could heat up the power device used in the receiver. Since it is placed in an enclosed space, the heat does not dissipate off easily. In the article (I am attaching a pdf form of the same article for your benefit) under the heading "How to Get the Best Performance from Your 2.4GHz FASST™ Vehicle Receivers", it is mentioned as quoted below:

"  We also recommend that you mount the receiver to the far inner wall of the radio box, opposite of the engine. Mount the receiver on its side. This allows air to flow over the top and bottom of the receiver. Secure the receiver using Velcro® or gel tape.
Tip: To improve the cooling airflow in your radio box, try drilling a few air holes. You must have at least two holes so air can escape as quickly as it enters. Position the holes where they create the maximum air movement over your receiver."


It clearly shows that air flow over the max'm area of the rx is recommended. This may not have been the case with Chan's model and could have resulted in the crash

Saju

Saju -

The same portion you quoted is in the link I posted above too    I did take what you suggested into account, and still feel that heat is most likely not the culprit. 

Waiting for Chan to confirm the time of the day when this happened.  If it is in the morning, I just feel it is highly unlikely a heat issue.

BTW, we are just investigating something together, and this is just a open discussion.  I value your input with the utmost regard/respect.

I think there could be different reasons affecting the 2.4GHz and 72MHz.

Heat: Doesn't explain why the 72MHz rx were hit.

Interference: I don't find the interference theory convincing. It is unlikely that there is wideband interference over the whole range from 72Mhz to 2.4GHz. If the signal is very very strong it is possible (though highly unlikely) that the pcb traces inside the rx is picking up inteference and is affecting baseband directly. If there is such a strong interfering signal, it should be easy to detect it on ground where the glitches occurred. The reason I think it should be observable at ground and not just up in the air is that the 72MHz rx (where there is virtually no reboot time) should have recovered as soon as it was out of the interference region. Since the planes didn't recover all the way to ground, it should be detectable at ground. It'd be more believable that the 72MHz went down because of interference and 2.4 because of other reasons.

BEC: Doesn't explain the glitches on planes without BEC.

And I never heard of 2.4GHz interference in Bangalore. Where did you see that ? I know the corona MHz range receivers and hitec receivers have been hit at specific locations. I have never come across any interference using Futaba PCM and FM receivers.

Anwar

With all due respect... Let me explain my experience in an unrelated topic on similar lines. For this I have to bring my work experience into play:

We manufacture hydraulically operated injection moulding machines. The hydraulics is based on very sophisticated electronically controlled axial piston variable displacement pumps with integral electronics. The pump is driven by an induction motor (size of motors range from 11kw to 74 kw). This induction motor has a fan which also shuffles air over the pump. The electronics is capable of handling 80deg C on the surface of the case. Thereafter it shuts itself down automatically. Suffice to say that in one size of pump (140 cc - 37kw), the temperature in hot climes even with air blowing from the fan of the main motor was not sufficient to cool down the electronics. Investigation showed that the electronics by itself heats up far higher than the oil temperature and the rest of the pump, because of the load of actuation of the swash plate of the pump. We found that we could run the machine if we had air separately channelled to it from the outside by a separate blower. So this is the case which involved a number of experiences of this sort of failure from all over the world, especially during the hottest summer months. We also found that if we enclose the unit separately, the heat generated was too stupendous and failure was almost immediate. If we used cold water, it introduced another element of failure namely condensation of moisture on the electronics which is even more dangerous. Sorry for the digression but this memory is too deeply burnt in me and I couldn't help but relate it here.

Lesson learnt was that enclosing a heating body (in our case the rx) in a separate chamber only builds up the heat. After all this what we learn by the term 'entropy'. So it is not only necessary to enclose the heating body in a separate chamber, but also to see that there is adequate means of removing the heat. In this case it would be by way of convection with sufficient airflow... The airflow could be induced by natural convection or forced. It is accepted that the rx device is heating up on its own, therefore we should see to it that the heat is dissipated.

And another fact is that the temperature at which instability is reported is 48 degC. With Chennai temperatures at about 10.00am in an open space like Sholavaram (with a tarred tarmac radiating heat directly below) and the Sun up and shining, I expect the surrounding ambient temperature to be somewhere near 38 deg C. Only 10 deg C from the unstable value... with a heat source in an enclosed space with no airflow... it is inevitable.

Saju

thanks saju uncle (heard a lot about you from sai uncle) a lot i will ensure i make necessary intakes and exhaust vents in the vtol - osprey.


subbu

The key is that the failure does not happen at 48C, it happens much closer to 60C.  Futaba rates their recievers to 60C (you can look up the manual for the FASST receivers to confirm this).  The 48C (or 50C) number comes from the same explanation you gave earlier. So if the temperature of the day is close to 50 and the heat generated in the enclosed device pushes it up by 10C, the total approaches 60C which may result in failures. Sholavaram ambient temperatures at 50C sounds way overboard for the time of the incident.

I feel you are misled a little bit with the 48C number.  When a company like Futaba says it is safe to use the receiver up to 60C, they have to be pretty close; otherwise class action lawsuits will follow as some really expensive aircraft are trusted to be flown with this 

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.


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

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. 

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.


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

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

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.

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 .

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

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

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 !


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

Thanks Subbu, but there is not much point in doing it on a completely different brand/setup.  Except of course, it will help us realize what will happen with Airtronics.

BTW, since we are having so much fun in this thread, it is time to open another one !  Let us have even more fun over there :

http://www.rcindia.org/chatter-zone/rc-crash-investigations-what-to-look-for/

 

Man!.. this is nice.. I have not given a single useful information in this thread, yet, I am one important guy to spill the beans!!...

Guess, No flying (the real thing) has its effects on me!

hye guys first set of test finished.
results as expected

set failsafe to 20%
and a bit of up elevator

gave it as much interference as i could with 2.4 ghz systems many mhz systems and mobile phones and you name it

then put the radio in range check mode even less signal power

handed over the radio to my sister in the other room about 15m away fail safe kicked in and everything worked as expected now will try it out in a bit of heat out in the sun now the temp was 30-32c and no signs of heating anywhere

in my opinion the two suspects can either be rx or the bec

also was checking out the failsafe of the new radio so no real bigtest done next will try simulating bec failure and then heat test

hey guys one more thing out of context but i got the second prize in English debate competition in my school

i know anwar bhaiya that performing these test on airtronics would not help but we can help in reducing further crashes on airtronics and if some common failure or cause arises it can be looked upon

Hey Folks let us sum up... Atleast I owe it to the readers of this blog to summarise

Cautions to be taken while using FASST rx from Futaba:

a. Clear air flow over the large surface areas of the rx. The rx standing on its shorter narrow edge to provide for large exposed surface area. Did Chan follow this ?
b. Provision for forced air-flow by way of a separate fan in case of large glow-planes and channelled air flow from the prop in case of electrics
c. Rx kept in canopies should be protected from direct sunlight when on the ground
d. Reduce possibilities of high current draw from the rx by the servos. Could be by making the servos reach end of travel in either direction before the actuation reaches its end of travel, thus limiting the current draw by the servo. If this is not possible, connect only the signal line to the rx, the power lines to be drawn directly from the BEC.
e. All other precautions as per Futaba instructions.


Now, when is our friend's daughter marrying the handsome 'beau' ? I may attend it if there is a proper invite!! He has fought really hard to save the damsel's face!!

And Ismail, my friend, you should read the poem "on His Blindness " by Shelley


Saju

Hey Guys ,
Apart from all the arguments and counter arguments I guess this thread should have been most educative for all as  each side trying to prove their theory has got out some fantastic resources that in terms of articles that can be referred to any time .
It has definitely achieved its purpose from the point of view of the aero modeler in being better informed about the pros and cons of 2.4 g .
The BIG PLUS is all now know the precautions to take when using 2.4 G receivers especially Futaba.

As for Chan who got this started in the first place the silver lining is he now knows at the cost of the funstar ( which he was about to retire in any case ) that  he needs to take added precautions with respect to cooling of the receiver in his 50 cc costly gasser .

So all of us have benefited immensely due to this thread and discussion .

A big round of applause to ANWAR and SAJU  for having provided us so much info. on 2.4G in general and FASST in particular  

Sai

PS Chan you owe us a big treat for having analysed your crash in such a way as to save you big time on the BIG BUDGET $$$$ YAK . I might be willing to settle for a Sunday lunch after flying  at an ECR resort with something cooooool to beat the heat ( you know what B__R)

hey sai uncle you forgot your name in the list saju uncle you and anwar bhaiya a loud applause to you
and for the 50 cc gasser chan bhaiya it would be good to make a nice intake and an exhaust as a precaution though i know you will but i will still keep on investigating this matter.




subbu

Oh yes!... I feel like Ozymandias...  No worries... Soon I would be resurrected.

A BIG THANKS TO ALL OF YOU WHO CONTRIBUTED!! And the treat is definitely on!! This was a really really informative thread and this has become the black box of my crash!!


nope !! Not enough space inside the narrom fuselage!! But had made a hole below the RX mounting area hence solving the problem!!

For the 50cc, I would not use an external cooling system but would make use of the prop wash to have better cooling.. Would engineer a neat passage for the air to pass in through the cowl and out of the fuse after passing over the electronics!!  And this would have the new high speed 8 channel Rx!

- Chan

Chan, did the receiver have power after the crash ?  Did you notice the color of the LED on it (green or red) ?

You mentioned the BEC was badly hit, so this may be a mute point, just curious.

I had to pick up the Lipo, the BEC and the remaining bits of the fuse with the Rx in 3 different places !! So no chance of checking Rx binding at the crash site!!

- Chan

Thank you Chan.  That would have been interesting to know.

Let me point out another aspect of Futaba heat issue here.  If the receiver shuts down due to heat issues, then the light would turn from green to red.  But you do NOT have to rebind the receiver by pressing the little button, the light should turn back to green and the receiver should work normally when the temperatures comes down.  So the binding is not really lost, as it happens in the Spektrum world (rarely, due to various issues, not heat though!), rather it is just a shutdown of the signal reception function of the receiver with failsafe activated during that interval.

Hey Chan ,
If I were you I would use a Rs 15/- PC fan rather than complicating life with redesigning the the fuse to  ensure hot exhaust air and residual lube air is not sucked in.
sai

Anwar ,
This thread and the prop thread could also be moved to the RC general section:
http://www.rcindia.org/electric-power/propeller-what-do-we-understand/

http://www.rcindia.org/radios-and-receivers/interesting-article-on-2-4-g-and-the-diff-between-dsss-and-fhss/


sai

Thats news to me!! Never came across this bit of info!! But unluckily I was not able to verify that !!

- Chan

I was just planning on making the plane as light as possible.  So using a PC fan would mean using an additional power source as I would not use the Rx power supply.  Instead, I can just make a vent (a series of gill like slits) for air to exit near the Rx.  That would ensure the air supply coming inside the fuse through the huge cowl would exit throught the vent hence cooling the Rx in the process!!  But I would also give the fan idea a go through!!

The only reason why I am getting paranoid about the weight is that, I would be reinforcing the firewall and also the fuselage and even that would add up weight!! The stock hardware is also pretty heavy and I just dont want it to end up like a sport plane!! Am planning to build a gasser that flies like a foamy !!

- Chan

Moved the prop one.  Since the rest mentioned are radio related, it seemed better to leave them where they are.

See additional information here :

http://www.rcindia.org/radios-and-receivers/are-you-still-skeptical-about-2-4ghz-radio-systems/msg10437/#msg10437

Another interesting post on how one needs to be pretty careful even with soldering of connectors (or cells in A123 battery packs).

http://www.flyinggiants.com/forums/showpost.php?p=791137&postcount=1699

its a dated thread, but the entire thread was on cooling issues. theory apart, is it possible that due to the frequency shifting properties of futaba, with the reckless frequencies floating around including cell phone towers, whether its possible that your 2.4 can have a lock out ? especially if its frequency hopping ? it may be possible with at least a dozen cell towers around you and your radio is switching frequencies ? paper theory may not be always correct and it may be possible even the chances are remote.

Actually the frequency hopping is the reason why FHSS (used by Futaba and Airtronics) is generally considered a better system.  You have to remember that it transmits on a frequency for 2ms, waits for 8ms, and then transmits on another frequency for 2ms and so on.  So even if 2 or 3 cell towers exist in the area, they do not affect the transmission really (it may cause small signal loss with in the 1000/(2+8) = 100 times the information is transmitted per second).

If you investigate forums like RCU and RCG, you can readily see that this "FHSS is superior" argument has broad acceptance.

your argument may be true regarding RC flying when there are 100 flyers flying at the same time. but here the situation is external interference from more powerful transmissions. abroad they have well controlled situations for rc flying but not so in india. may times mobile transmission due to interference is a mess, for example we had to resort of leased line as our GPRS connectivity got affected to a new tower erected by one XYZ (no names) operator.

Nobody is claiming that anything is totally interference proof.  I was stating what is considered the norm, which is easily verifiable by much deeper technical discussions on the international forums.

One thing is sure, the frequency shifting of Futaba is considered an advantage in general (that does not mean it is perfect), as opposed to it being the cause for lockouts.