Ouch! Weston Obsession A Gonna....

[Adrian Smith 1]

Sadly today my Weston Obsession is no more. Unusually for me I flew this afternoon (I normally like the cool of the morning) in 26 deg C and after my usual range check I took off in very little breeze. On the base leg, going at 3/4 throttle, about one and a half circuits into the flight I felt I was losing control of the working surfaces. Then the engine just coughed and died. Usually it is a straight forward glide in after engine cut but as the plane was going away from me I attempted an inverted roll to bring the plane back to me and generate a bit of nose down speed. However, I managed the roll but I could not pull out of the dive no matter what I did to the sticks. She finally planted her nose in 100 yards or more away in a rape field. Gawd! I am never going to find her there! However, on closer inspection there was a tail sticking upwards in the distance. Have you ever tried walking through a field of rape.......mmmmm you know what mean. After sweating buckets in the heat she was finally retrieved, but damage whilst repairable, was substantial. My gear is all Futaba 2.4g with a 617 RX. I haven't undertaken a full investigation yet as it's all a bit painful, but I wonder if the RX didn't like the heat. This happened once before 3-4 years back with my Flair Edge 540 on a similar hot day, but I may be clutching at straws. I know there have been issues with Futaba Rx in the heat.(mine was unwrapped as per instructions). I know the TX is fine because I just dumped the model in the workshop and took out my Flair Leo as a bit of solice with the same TX without incident until the wind picked up. I did test the working surfaces on the Obsession afterwards with the original RX but all seemed fine, but now I can't trust it. If it had been my fault with a stall issue I could accept that, but until I know what happened I will fidget. Anyway just a thought to be wary of hot hot days if anybody has had such an experience.

[Rick Tee]

I still fly 35mg though i did do some research a few years ago into the then 2 x 2.4g systems with a view to changing over. As there were a number of incidents reported with the Specktrum/JR system and Futaba receivers were ridiculously expensive i opted to stay with 35mg at that time. Currently I have been looking half heartedly at changing over now the technology has settled some, though there does still seem to be some issues occurring with the Specktrum/JR system but the Futaba receivers have come down in price.

I've not come across this issue of temperature with the Futaba gear, do you have any links? Are receivers sold here made solely for the UK and not used anywhere else? Is this problem limited to UK receivers? Are there any reports of heat problems in countries that get hot?

[Martin Harris - Moderator]

The reports I've seen of overheated Futaba receivers were in American "desert" conditions where receivers were "cooked" under canopies in full sunlight. I don't believe that unless you heat the receiver to over 58 degrees C that there should not be any problem.

I know that the (shaded) vario modules with temperature readout in my models don't get any warmer than the ambient air temperature during flight so unless your receiver is being cooked under a canopy with no air flow across it it's unlikely to be getting anywhere near a critical temperature. .

[Adrian Smith 1]

Mmmmm... yes Martin I am with you on that one, I am just clutching at straws. I will test things out later this week although something has occured to me that happened soon after setting the plane up originally. I fitted a South Herts Models glow switch to help with my inverted OS 160 FX and I noticed when I did this there was some radio glitching in flight although I couldn't see why as the unit performed faultlessly. However, I added some, I think they are called ferrule rings, to the servo wires and this seemed to solved the glitching issue, but this was a couple of years ago as nothing untoward has happened since until yesterday. I wonder if this has come back to haunt me.As I say SHM 's unit I have nothing but praise for so may be its the way I put it in originally that caused the glitching thing.

[Adrian Smith 1]

Well I think the problem was with my RX pack. It is a 2700mAh 6v Nimh and I thought as a precaution I would cycle it. It only wants to take just under half capacity charge around 1300mAh so seems like a couple of dead cells there. Lesson learned I guess so to to renew these things every year instead of every 2-3 years.......

[Peter Roberts]

I've heard of ESC's overheating and causing problems on BEC based systems but not heat effecting the RX. However I do remember that ferrite rings wiuth long servo leads wrapped around them helped to prevent gltches in 35 mhz systems. I was also adviced to by 6v Csub cell battery packs for use with the obsession because the demands of the control surfaces could cause unusually high current draws. I use a 3200mah 6v pack with my Obsession and it has always performed flawlessly even with long flight times. My usual flight times are circa 20 mins with an OS 120 pumped and a 750cc tank. My problem experienced today is that I landed short in the long grass and my undercarriage has been put under high strain cracking the main cross member and the side panels. Does anyone have any advice on strengthening the Obsession u/c mount? Do I need to take everyting (including the tunnel out) and replace the core member and carbon tows re enforce it? Any experiences gratefully received. Thanks Peter