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Old Aug 01, 2009, 06:36 PM
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stuart warne's Avatar
Hong Kong, Hong Kong Island, Central And Western District
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Plane crash after Spektrum 2.4 signal loss! Was it brown out?

Posted in the radio section but thought I'd give it a goe here too see what you guys make of it.

Ok here's a little summery of what happened to me yesterday, I'm thinking its related to 'brown out' caused by my Rx nimh pack dropping below 3.5Volts. The only thing is having checked the pack afterwards, its showing 80% full I need to sort this before I fix and fly the model again, but I'm stuck as to what could have caused it now that I know the rx pack wasn't flat. Can you get interference on Spektrum 2.4? Here's what happened:

I was on the last turn into my approach last night when I lost all control. The model wouldn't respond to any input I gave via the Tx, all control were just frozen at there last command input. I fear it was a classic 'brown out'. So with no real height to wait out the 5 seconds or so it takes relink she went in with a nose down banking angle.

Its really soured this couple of weeks I've had off work, but it can be rebuilt. I just didn't want to be rebuilding a model that I'd just finished and that flew so well and I liked so much. Plus I had other projects ready to start next week, but they'll have to be pushed back now too.

As mentioned it seemed at first to be a case of brown out as described in the rx instructions. Anything else I wouldn't expect on the Spektrum system. I was lead to believe that Spektrum 2.4 was glitch free etc, after all, thats what we pay for isn't it. Any body else had 'brown out' issues? I'd be interested to know. I thought it may well have been that the Rx pack was going flat. I have flown for so long without the need for a separate Rx pack, that I forgot to charge it recently, so it may have been that except the pack now shows 80% full (5.19v FOR A 4 CELL 2100 NIMH PACK)Is this too low?

One other concern is that I the same thing happened last week for the first time ever with a smaller foam model with no Rx battery (it has BEC). In almost exactly the same place (on approach) and same attitude the exact same happened, but this time I had height to cover by the time it had relinked. So I wonder if there is some local 2.4 noise crossing the field at that particular spot, could this be a possible cause, does this happen with 2.4?

Even if it wasn't brown out, the rx certainly did loose the RF link as the 'Hold' LED on this new AR6250 was flashing afterwards telling me as much. But I'm now stuck as to the cause. Also of note, fail-safesafe didn't seem to kick in. When binding (if I'm understanding the instructions correctly), with all stick in the neutral position fail-safesafe should reset to these neutral positions with the loss of signal. But that didn't happen, the controls simply locked in there last position. If they had have gone back to neutral I'd guess the model would hlevelledeled off and not gone in. So that again brings me back to the Rx pack, becausassumesume if no power is coming from it then the servo can't even return to neutral Oh BTW the system was working again by the time I got to the crash site.

Any help on this no doubt rehashed subject would be greatly received. I had a lot of confidence in Spektrum 2.4, but now with two signal loses in as many weeks and a broken model, my confidence has taken a knock, and I know I need to get to the bottom of it before I fly it again. But for now I'm a little out of my league to figure this one out on my own.

Thanks
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Old Aug 05, 2009, 11:07 AM
turbonut's Avatar
upland CA
Joined Dec 2004
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Hi Stuart, that is a bummer..I hope you can fix it..I dont think it was a reboot..that is less then 1 second on the new receivers.But I also never run 4.8v pack on 2.4.I now only use 6volt packs..its just too close to the low volt. with Rf loss that may just be where the receiver is mounted.if its is too close to the battery or motor or even that metal cowl it can block the signal..
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Old Aug 06, 2009, 10:18 AM
The Hun in the Sun
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Canada, BC, Comox
Joined Nov 2003
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Quote:
Originally Posted by stuart warne
I thought it may well have been that the Rx pack was going flat. I have flown for so long without the need for a separate Rx pack, that I forgot to charge it recently, so it may have been that except the pack now shows 80% full (5.19v FOR A 4 CELL 2100 NIMH PACK)Is this too low?

One other concern is that I the same thing happened last week for the first time ever with a smaller foam model with no Rx battery (it has BEC). In almost exactly the same place (on approach) and same attitude the exact same happened, but this time I had height to cover by the time it had relinked. So I wonder if there is some local 2.4 noise crossing the field at that particular spot, could this be a possible cause, does this happen with 2.4?
Sorry for your loss

Does your volt meter put a load on the battery when testing? If not, 5.19 seems low. As soon as you put the load of the servos on, then that pack may drop below 3.8V, the critical voltage. I would use a 5 cell receiver pack, personally. All but the smallest micro servos can handle the extra voltage, and your receiver will be very happy.

Radio interference can happen to any radio signal. 2.4Ghz is pretty good at rejecting all the dirty info and getting the good info from the transmitter to the reciever. I have had my 2.4Ghz unit now for almost two years, and so far it has been entirely glitch free during lots of flying at some very busy flying fields.
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Last edited by vonJaerschky; Aug 06, 2009 at 01:59 PM. Reason: wrong figures quoted
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Old Aug 06, 2009, 10:56 AM
Registered User
Joined Jan 2007
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i have had glitches on 2.4 what TX are you using
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Old Aug 06, 2009, 01:48 PM
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USA, WA, Edmonds
Joined Aug 2008
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4.8 is plenty safe if you have a voltwatch2 on it. That shows instantaneous voltage and you can load some of the control surfaces to see voltage drop. A fully charged 4 cell battery should not drop below the first few green LED's when its loaded.
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Old Aug 08, 2009, 09:40 PM
Resident giant scale guru
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Picayune, MS
Joined Oct 2007
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dude, me too! ive lost 2 planes within 6 months! a funtana X 100 and a goldberg super chipmunk. i also have 2 ar7000s in a 40% SD yak thats waiting on a maiden, and im contimplating putting futaba gear in it. but, that crash, TOTALLY fixable. if it were me, it would be back at the field the next weekend.
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Old Aug 08, 2009, 09:48 PM
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Newcastle
Joined Oct 2003
581 Posts
I read all the stories of brownout when I first got in to 2.4 and so I use a UBEC set on 6V religiously. Touch wood - but this has never let me down.

On my nito planes I use a small 500 -800 Mah 3S battery connected to a UBEC and this needs chargig once every month or two only. Even then it is a cautionary charge, I think it would still lat on. If you do this, make sure to measure the voltage of the lipo before going flying. It weighs the same as a 4.8V receiver pack but is much, much better.
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Old Aug 08, 2009, 11:14 PM
Gone Flyin!
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WA
Joined Jul 2006
83 Posts
Could it be a dead area on the field seeing as you lost 2 planes in the same spot?
Also are you sure that the batt pack charged correctly? Cos NimH somestimes dont quick charge if under a curtain voltage
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Old Aug 10, 2009, 04:14 AM
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my field has a dead area after heavy rain that affects 27mhz / 35mhz and 2.4ghz
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Old Aug 12, 2009, 03:02 PM
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Hong Kong, Hong Kong Island, Central And Western District
Joined May 2001
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High gents. I got my DX7 back from Horizon this week. Well in fact thats not true, I actually got a brand new replacement! During tests it was shown to have an under performing RF board. So they just did a straight replacement.

Horizon could not say with 100% certainty if this was in fact the source of the problem, but it was certainly not working as it should. I'm glad I've got an entire new unit, so if it happens again, I know its not the TX. I will also however be fitting voltage protectors to all models now, just to be on the safe side. Plus any models that use a separate Rx nimh pack will now all be 5 cell (6v) and not 4 cell (4.8v).

Thanks all for the help and advice. Here's hoping I never have to repeat this story!


Stuart.
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Old Sep 28, 2009, 05:27 PM
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Planet Earth
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A happy ending with the superb Spektrum customer service!
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Old Oct 02, 2009, 08:46 PM
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Joined Mar 2009
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Stuart,
Glad you got an answer from Spektrum. Maybe I should send in my DX-7 Tx too? I recently had a 2.4 crash with a new 2m Poly Pulsar electric sailplane. Still don't know what caused the crash. After a successful maiden in the morning (with my son shooting video "just in case") I did an afternoon flight.
Well, at about 100 feet in the air, it just completely locked up. Nose gradually dropped; no sudden spin, or dive indicative of a locked servo, just gradual lowering of the nose. No response to sticks, flap switch or throttle. It hit the ground vertically, and there was lots of time for a "quick connect". Unfortunately the nose was so mangled, I was worried debris would burn, and thinking Rx was mangled anyway, I quickly disconnected LiPo. I wish I had checked the "lights" on the Rx, like you did.
Later I discovered Spektrum AR 6250 had survived crash, and bench tested A-ok (for me)

Spektrum looked at my AR6250 receiver after the crash. Incidently, the new 3S LiPo still had 12.30 volts, all servos , control surfaces functioned normally, and all servo connections were still tight, to Rx. ESC connection to LiPo was good too.
CC25 ESC was mangled, so couldn't test it.

I salvaged the V-tails, with tail servos which were undamaged, and flap servo, to put them all in a new Pulsar. Hacker motor/gb and even spinner/prop were ok too, and all are flying on the new sailplane. Castle sent me a free CC25 replacement.

Spektum said rx tested ok, but still sent me a new one.

Still don't know what caused the crash, but now if I have room I like a two receiver setup, like the AR6200. Maybe you should get one for your WW I flyer? Looks like you have room. Two separate receivers, with antenna oriented in different planes can't be beat for a rock-solid connection, and peace of mind.

ps. I still have the replacement AR6250 Rx in my "new" 2m Pulsar, with antenna wires in different planes.
I check the "hold" light and brownout light after every flight. No glitches yet I did a VERY thorough range check before the first flight, too.
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Last edited by 320pilot; Oct 02, 2009 at 09:07 PM.
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