Gutted

[Paul Williams]

I fitted a new spektrum receiver (AR6200) to my favorite mustang yesterday, After binding and checking fail safe I range checked it as instructions 30 paces with tx in check mode and confidently let her go. The plane climbed away lovely then at about 300mt the engine cut dead and nothing would respond to stick. I watched my expensive model dive directly into the ground and stood in disbelief at what just happened.

When I reached the crash site the servos where still live showing no loss of power from the battery, I checked the flight battery and it was showing 6.5v. all control rods where still attached and servo testing later showed no faults. The way in which the motor cut then no responce can only mean the rx lost contact. I have removed the rx and range checked again it still passes this test. I flew another model straight after the crash using the same tx and had no problems.

Where did I go wrong? Should I have done a full range check walking away a mile or so? Could some thing else have caused the problem? How can I return the rx when it shows no faults on standard testing. Gutted!

[Brian Lambert]

Paul sorry to hear of your loss.

Drop an email to  (Glenn Doman <[email protected]>)  and explain what happened, I am shure he will be happy to give your receiver a thorough check.

Brian

[Paul Williams]

Thanks, I will mail him to see if he will help.

[winchweight]

Horizon were superb when I had a similar problem with my Sea Fury, they replaced the rx free of charge, even though they found no fault.

Did the model have many servos? What battery did you use and did you have a UBEC fitted?.

Have a read of this thread

Here

[Tim Mackey]

Hi Paul - sorry to hear of your model loss. From your description of events, it does sound like the receiver went into fail safe - I presume when you say it dived straight into the deck, it did so through having lost engine power, rather than the control surfaces deflecting to "down" or whatever. The reason I say that is because the so-called failsafe on these spekkies only actually closes the throttle channel, and all other servos remain at "last known good" EG: hold so the elevator for instance would have held with slight up attitude as you say you were on initial climb out at the time.

A brown out from poor battery is unlikely as it would have recovered again almost immediately due to QC

( I presume you do have QC in all your receivers )

THe only reason for it to enter failsafe is loss of signal - and range checked out - so puzzling. Can I ask what aerial orientation you use on both Rx and Tx ? 

[Paul Williams]

Hi Tim, The aerials where set at 90 deg to each other with as much distance as the leads will allow. The tx straight. I have a tendency to have most of my models slightly nose heavy so I'm not surprised it dived after losing power.

I am even more confused now, I have an old nitro hack which I have a love hate relationship with. I dug it out today and fitted the suspect rx, once again I put it through the normal tests and in addition drove away the best part of a mile phoned up my friend holding the model and all was fine. With a prayer I let it go and for the next 20 minutes it flew impecably. I put it up twice more throwing it around as much as my skills will allow no problems at all.

I hate not finding a fault, I will never have enough confidence to fit that rx to a decent model. I phoned Horizon and they were great offering to inspect the rx even though I bought it else where. I have not sent it I'm thinking they will not find a fault if its working ok.

I have come to the concluson either the rx has a intermittent fault, or it lost power from the battery faulty lead maybe, I cant go with interference I flew straight after using the same tx no problem.

I have just read your thread Shaun, Your system being electric is more complexed so although some things remain you certainly had more to worry about. I think Tim will be thinking oh no here we go again! Thanks for your interest guys I think this one will remain unsolved (unless the rx throws another wobberly) I will console myself thinking about what to replace it with. Just have to keep up the long face so the Mrs will have enough sympathy to allow another purchase!!

Cheers

[Former Member]

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[Paul Williams]

After saying the problem might never be exposed my father rung this afternoon. He was test flying his hawk and the same problem accured. It was within yards of where mine came down and all the symptoms exactly the same. We have flown there often without mishap but I am beginning to wonder if the power sub station could be interfering? Its very strange to have the same fault at the same place with two different set ups on 2.4gh.

Any thoughts?

[Tim Mackey]

I think it highly unlikely that the power sub station per se would cause the crash, but others will doubtless have an opinion.

[Former Member]

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[Paul Williams]

Eric, right next to where both planes came down is a water pumping station, I first thought this was electric. I wonder if its receiving data like you suggested. I have sent my father in his combat suit to investigate. He is 72 they won't lock him up is the theory !!

Can you think of any where I could get information on who is allowed to use 2.4.

[Tim Mackey]

Pretty much anyone I suppose...its used for all sorts of things like wireless networks, some mobile phones, alarm systems and general telecoms etc etc - the whole idea of 2.4Ghz and security was the fact the the GUID ( globally unique i-dentity allows many simultaneous users WITHOUT interfering with each other.

The unique pairing of a Tx and Rx on our RC stuff is supposed to be just that...unique.

[Brian Parker]

The frequency is designated as ISM (Industrial, Scientific and Medical). We are secondary users.

As Timbo says.. ‘open to all’. The way our systems operate, coupled with modern digital filtration should make us immune to interference by other users.

In my opinion, antennae installation is the key.

[Former Member]

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[Brian Parker]

I don’t think I was referring to interference from a receiver!

With regard to swamping the receiver, surely the manufacturers design parameters considered the possible effects of Data communications etc.

Also due to lower ‘noise’ levels, microwave communication can be achieved with signal levels as low as a few nanovolts. Thus damage to the receiver due to overload is probably most unlikely.

Might damage the receiver though if the plane made contact with the Data Coms. Antenna.

[Paul Williams]

the plot thickens! I lost another model today this time the damage was minimal thank god I got it home and had a serious look at things. I think the problem might be my fault. I have noticed when connecting the li-po some times I get a eletric crack at the terminal ( things not quite lined up ) when this happens the rx lights flash some thing I cant see when the wings are on. I have fitted a switch from the esc in line so I dont feed any power to the rx untill the battery is properly connected. This ensures the rx fires up with solid lights every time and passes range check. What exactly do the flashing lights mean? If I fly with the rx lights flashing would this have caused the 3 crashes? Any thoughts?

[Tim Mackey]

flashing lights on the reciver could mean either lost bind  (rapid flashing ) or temporarily lost signal ( slower flash rate ) - if your Rx  are QC enabled, the slow flashing lights indicate a a lost signal.

[Paul Williams]

Thanks Tim, just out of interest, do you use a switch for the rx power or just plug in the lipo? If the lights are flashing and I fly the plane should the rx work as normal ? or does the flashing lights indicate there is a fault.

Peter, 3 different set ups  11.1v - 22.2v. Its happened on 3 different rx's and 2 different tx,

[Tim Mackey]

The sparking as you connect the main battery is quite usual - especially in high voltage setups - the capacitors on the ESC accept a rapid charge up as the battery is first connected - some folk use a resistor to more slowly charge the caps before connecting the main leads. I NEVER usea switch on ESCs - even those that have them fitted to "disconnect" the radio - I cut them off and rely solely on plugging /unplugging the battery to ensure live / dead situation.

If the lights are flashing to indicate a temporary signal loss - then the Rx should reconnect immediately and you would probably not even know you had suffered a loss - hence the QC upgrade involved the flashing leds to indicate this happened. However if your rx is flashing to indicate a bind is in process, and you then try to fly....thats a whole different ball game. You need to establish exactly what is happeneing here - if you are losing bind somehow then something is wrong. I have NEVER suffered a bind loss. You are switching on in the correct manner arent you  - IE Tx on with NOTHING held or pushed etc.... followed by Rx. After switch on, it can take up to 10 seconds to establish a correct mating, as the Tx has to scan for and acquire 2 channels, only then will the Rx display a solid red LED.

[Pete Rieden]

OK, well here's what was in my mind.

When you first connect a battery to an ESC there is an initial current surge to charge the input capacitors of the ESC - this is often seen as a small spark at the connectors are touched together. This kind of arc can do "bad stuff" for unprotected electronics, and is much bigger for higher voltages than lower ones. So on all my setups above 12v (3s/10-cell) I incorporate a "charging lead" in the positive wire. The lead is simply a short piece of wire soldered into the back of the ESC connector, with a 10 ohm resistor on the end (the whole thing being covered in heatshrink to support/protect it). When connecting the battery I connect the negative lead, and then before connecting the positive lead I touch the end of the resistor to the positive battery connector for a couple of seconds before plugging the connectors together. This limits the charge current into the ESC capacitors and eliminates the arc.

I have been doing this for years simply because I regard it as "good practice", and I know of several people operating the larger size electric helis (Trex 600 etc) who have adopted the idea after suffering gyro failures which they assumed were caused by the surge.

I have no experience of 2.4GHz equipment*, but if this surge is causing grief then this kind of approach should reduce or eliminate it.

PDR

 * My personal view is that 2.4GHz will become unusable for model flying in a few years because the band will be swamped with wireless WAN signals, so I'm reluctant to invest in the equipment, especially since there are no decently capable transmitters available at the moment.

[Paul Williams]

Tim, thanks again for your time and effort, just one question more. If I connect the rx after switching on tx  the lights do not go solid every time. Is the rx working full range with the lights blinking? I dont think this is a bind problem. (slow flashing)

Funny enough if I reverse the sequence and switch tx on last, it lights up solid every time. I would not be happy adopting a sequence not recondmended by Spektrum.

I have racked my brains out on this and the one common issue with all incidents is where the models where flying. I have had no issues taking the stuff to another field. coincidence?

Thanks for your views Peter. I will look into the charging lead although I dont think its the key with my problems. If my equipment has suffered in this manner surely the damage would be perminant ?

[Tim Mackey]

The flashing lights indicate nothing related to range. As I say, rapid flashing means the Rx is waiting to be boiund to the Tx and should ONLY occur if the Rx is deliberately set into bind mode, by using the bind plug. It should NEVER flash rapidly in any other scenario. In bind mode there will be no effective transmission oir reception of signal - no attempt should be made to fly with the Rx flashing rapidly in bind mode.

Slower flashing LED is also nothing to do with range - it merely indicates that the signal was interrupted briefly during operation, nothing more nothing less. Following this interruption, normal and FULL range will be restored virtually instantly assuming QC is enabled in the RX.

The ONLY thing which will affect range ( Barring of course a faulty receiver or Tx ) is the deliberate reduction of output power of the Tx and this is accomplished only during a range test procedure. 

You have not stted which tx you are using...or I missed that. I have the DX7 and a DX6i and have necver experienced a single problem with establishing a bind using the DX7. However, using the DX6i I have had found that binding successfully sometimes takes a few attempts - and can also take a LONG time to establish proper locking. 

One final thought.. after a binding operation, you are removing the bind plug before turning off the Rx yes?

Then turn off the Rx, and then the Tx. I always switch on in the normal sequence EG TX ( waiting for around 5 seconds on average ) THEN the rx - a couple of seconds later the system is loked in and ready to go. I cant always see whether the LEDs are solid as the Rx is buried deep away in some models....but I always have a good twiddle of the sticks to see that I have control before launching.

[Lew Weaver]

On Sunday we had similar disasters to Paul's

2 scale models lost within half an hour of each other in roughly the same area. A clubmat lost his Chipmunk the previous week again in the same area.

On Sunday both models were on a gentle downwind turn onto the crossleg landing leg when the turn continued into the deck.

I have flown Spektrum gear for about 18 months at various locations with no problems and had complete faith in the radio link until now

[Paul Williams]

Know how you feel, I just wish I could prove the fault once and for all. I like the spektrum stuff but I wish I knew more about possible interference.

[Former Member]

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