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2.4 glitching?

Old 06-24-2011, 04:13 AM
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vertical grimmace
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Default 2.4 glitching?

I lost an airplane last weekend and was wondering if anyone else has had a glitch or similar issue with 2.4 that was not a brown out or lock out? I am sure I did something wrong somewhere, but would like to track it down.
The radio is a 9C with a Futaba module added. I was using one of the 6 channel Futaba RXers. This was a 50cc size gasser. A DL 50 with a 42% products opto engine kill. Otherwise a very basic radio install. I did have retracts as well as this was a warbird.
What happened was I rolled out on take off and climbed smoothly. Suddenly I got a hickup in the engine. It sounded like the throttle servo went back to a lower throttle setting. Or maybe just a mis tuned engine. Then instantly, and I mean instantly the plane rolled inverted and I was only about 20' up.
Now I was starteled somewhat and just ended up flying into the ground. I did get the power out of it though before she hit. So I am not fully sure if I had full control or not before it hit.
Old 06-24-2011, 04:23 AM
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JIMF14D
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Default RE: 2.4 glitching?

I know that Hitec had a recent warning notice about using opto engine kill units with their 2.4 systems.

Jim D
Old 06-24-2011, 04:29 AM
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BuschBarber
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Default RE: 2.4 glitching?


ORIGINAL: vertical grimmace

I lost an airplane last weekend and was wondering if anyone else has had a glitch or similar issue with 2.4 that was not a brown out or lock out? I am sure I did something wrong somewhere, but would like to track it down.
The radio is a 9C with a Futaba module added. I was using one of the 6 channel Futaba RXers. This was a 50cc size gasser. A DL 50 with a 42% products opto engine kill. Otherwise a very basic radio install. I did have retracts as well as this was a warbird.
What happened was I rolled out on take off and climbed smoothly. Suddenly I got a hickup in the engine. It sounded like the throttle servo went back to a lower throttle setting. Or maybe just a mis tuned engine. Then instantly, and I mean instantly the plane rolled inverted and I was only about 20' up.
Now I was starteled somewhat and just ended up flying into the ground. I did get the power out of it though before she hit. So I am not fully sure if I had full control or not before it hit.
It sounds like the Receiver lost the signal from the Transmitter and went into Failsafe. For most 2.4 radios, the Default Failsafe Condition is for the Throttle to go to Idle and all other channels to Hold.

I am not familiar with what options you have, with a Futaba Receiver, for Failsafe. An easy way to tell is to turn on the Transmitter and Receiver, and then turn off the Transmitter. The Receiver should go into Failsafe and all channels should move to their Failsafe Settings.

If you model Rolled, then either the Failsafe Setting for Ailerons was to Roll, or one or both of your Ailerons has a Problem.

If you lost power to your Receiver, it would not go into Failsafe, and anything can happen. A Brownout results in loss of power to the Receiver, causing the Receiver to Reboot. I do not know if Futaba Receivers can suffer from Brownouts, which for JR/Spektrum, is a sudden drop in Voltage to the Receiver. If you had a faulty wire to any Servo, or in the Switch Harness/Battery, it could cause strange Glitches.
Old 06-24-2011, 04:42 AM
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DougV
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Default RE: 2.4 glitching?

Also, check the module and the pins on the radio/module base, I've seen a few issues (with the 9C's) that was tracked down to the module/radio pins, specially if you swap modules all the time.

Futaba receivers.... the servos will stop working and the receiver will still be connected, they can go down to 2.6v.

Doug.
Old 06-24-2011, 04:58 AM
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DougV
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Default RE: 2.4 glitching?

Another thing that comes to mind… What model 6 channel receiver? Single antenna (no diversity) on a parkflyer or mid range receiver on that big airplane can bring RF signal issues.

Doug.
Old 06-24-2011, 04:59 AM
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landeck
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Default RE: 2.4 glitching?

The 6 channel Fasst receivers are all park flyer or medium range receivers. With your size plane you could have easily flown out of range and the system went into fail safe mode.

Bruce
Old 06-24-2011, 05:54 AM
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Default RE: 2.4 glitching?

Sorry to hear of your loss as losing most any model hurts. I had a very similar glitch experience to you on take off last year, caused by a faulty Rx switch. Luckily I was able to save the model as I regained control at almost zero altitude. It was a real scary moment as I had given up all hope of saving the model. Hopefully you will find the cause of your problem as there is nothing worst than not knowing for sure.

Karol
Old 06-24-2011, 07:42 AM
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vertical grimmace
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Default RE: 2.4 glitching?

Yah, a little more info. The RX is actually one of the 7 channels sorry. It is full range. This airplane has flown with essentially the same set up for 4 years. It has been very reliable. I run 2 switches and 2 RX batteries. I have experienced brown outs and that was not what happened.
I am thinking more along the lines of a faulty wire possibly. I had just replaced 4 servos, the 2 ailerons and the 2 elevators. I doubt they were the cause. The fact that it flicked over so quickly, it had to have hit full aileron rate momentarily, unless it was torque that flipped it over. This aircraft was really overpowered with the 50 cc, and it only weighing 15 lbs.
I use the same transmitter for most of my planes and this is the first time I have experienced this. I am also leaning towards the opto kill, or some issue with ignition noise. I have been hearing good things about the brand that I am using, so I will probably pull this product out of all of my planes.
Since I was able to get it shut down, and I was not to high, damage was mitigated. After pondering the incident for the past week, and taking a closer look at the damage, I plan on repairing this aircraft. I wanted to change some things anyway. It just sucks that I lost a warbird for the season.
Old 06-24-2011, 08:17 AM
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JIMF14D
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Default RE: 2.4 glitching?

The last thing you did was change 4 servos.....hummmm
Old 06-24-2011, 11:36 AM
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SharpProp
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Default RE: 2.4 glitching?

sure you didn't have your ailerons reversed?
Old 06-24-2011, 01:09 PM
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Default RE: 2.4 glitching?

I did not want to say it...!
Old 06-24-2011, 01:55 PM
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Default RE: 2.4 glitching?

Me either.
Old 06-24-2011, 02:51 PM
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rmh
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Default RE: 2.4 glitching?

A test I have run using 2.4 shows a characteristic of these systems which is kinda nasty
The cause is loose power connections and or failing power under a load..
If the power shuts off then on (or does this in a rapid fashion ) the servos may go nuts.
Ditto if power fades to below minimum voltage threshhold- causing the system to shut down power -which then allows voltage to slightly rise as load is removed - then fall again as the servos -trying to reassume position causes a power drain.
I had this happen on the bench -using a almost depeleted battery.
Once I saw what was happening -it was easy to repeat the problem
IF it had happened in the air - it would have looked like a huge glitch- servos moving wildly
It goes back to th original weak link in 2.4- You must have a solid power supply- or a disaster can occur

The old 72 systems were more tolerant of low power -because a "reset" was not part of the results.
Old 06-24-2011, 05:23 PM
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aussiesteve
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Default RE: 2.4 glitching?

It had an Optokill, The engine kept running and the OP is not sure whether or not he had control due ot the "oh *****" nature of these events catching the pilot out. (we have pretty well all been there and those that haven't will be there one day - I feel for you mate, it is a bad feeling).

Failsafe would have killed the engine wouldn't it? No matter if it was caused by low voltage a glitch or any other cause if it went into failsafe, the optokill should have used its designed in failsafe and killed the engine. I would be looking at the connecters from the servo changeout or perhaps something a silly as a spark plug cap not being on the engine properly.
2.4 can suffer glitches, it is just a heck of a lot more rare than other systems.

Which switches were you using for your manual switches? I have seen (even some very good brands) of those have a connection issue inside the switch when vibrated (try it some time - hook up a meter or a scope to a switch ad see what happens when you wiggle the swtich actuator).

Which Servos and which battery packs were you using? IT is possible that you were above the voltage threshold for the receiver but below it for the servos.

One last question - did you have your cell phone with you at the time? (maybe you took it out your pocket at the crash site to take photos) - or did anyone else on the flight line have theirs with them? This is a contentious issue but there is a possibility of a problem from those.
Old 06-24-2011, 06:03 PM
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Default RE: 2.4 glitching?


ORIGINAL: aussiesteve

It had an Optokill, The engine kept running and the OP is not sure whether or not he had control due ot the ''oh *****'' nature of these events catching the pilot out. (we have pretty well all been there and those that haven't will be there one day - I feel for you mate, it is a bad feeling).

Failsafe would have killed the engine wouldn't it? No matter if it was caused by low voltage a glitch or any other cause if it went into failsafe, the optokill should have used its designed in failsafe and killed the engine. I would be looking at the connecters from the servo changeout or perhaps something a silly as a spark plug cap not being on the engine properly.
2.4 can suffer glitches, it is just a heck of a lot more rare than other systems.

Which switches were you using for your manual switches? I have seen (even some very good brands) of those have a connection issue inside the switch when vibrated (try it some time - hook up a meter or a scope to a switch ad see what happens when you wiggle the swtich actuator).

Which Servos and which battery packs were you using? IT is possible that you were above the voltage threshold for the receiver but below it for the servos.

One last question - did you have your cell phone with you at the time? (maybe you took it out your pocket at the crash site to take photos) - or did anyone else on the flight line have theirs with them? This is a contentious issue but there is a possibility of a problem from those.
The Receiver will not go into Failsafe if the Voltage drops and a Brownout occurs. The Receiver needs Power in order to move the servos to the Failsafe positions.
Failsafe will occur when the Signal from the Tx is Interrupted or Lost.
Old 06-24-2011, 06:09 PM
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vertical grimmace
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Default RE: 2.4 glitching?

Well, the ailerons were not reversed. I had flown her before with no changes. This was not the first flight after the new servos. More like the 10th or 11th.

I was using 5 cell DaiPhan packs, 2500 mah. Both were fully charged, checked just before the flight. The switches were the dual toggle variety that Valley view sells. I had a typical RX on off for the ignition. I know the batteries were not an issue. They were reading full after the crash and the radio worked as well.

I am not sure I will ever know, but I will send the RX to Futaba to have it looked at. That is just part of the deal. Maybe my wiring needed to be better organized inside the plane. I could have had the opto kill too close to other radio gear instead of being isolated.

I am sure it was something I did wrong. If my flying was a little more polished, I probably would have flown out of it. With the weather though, it has been a long off season. I will be repairing this plane, and it will be better than before. Kind of needed improvements anyway. But dang, this thing flew really good.

http://www.youtube.com/watch?v=I8fmJWvp3E8

I did change the colors last year. Bad move I guess as I have had several issues ever since. Mainly with the landing gear.
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Old 06-24-2011, 06:29 PM
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Default RE: 2.4 glitching?

What does your R/C installation look like? More information is required. Just because it worked before does not mean it's correct. I know you're a regular contributor to RCU, so you have a lot of experience. Did you follow Futaba's advice at this website? Dan.
http://www.futaba-rc.com/faq/faq-gas.html
Old 06-24-2011, 07:29 PM
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vertical grimmace
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Default RE: 2.4 glitching?

Well, that is where it is most likely. The opto was kinda floating around in there. I know, should know better. Maybe I got lazy thinking 2.4 would not care. Well, that may be the upside of this thread. The interior of our planes need good house keeping. Even with 2.4.
Old 06-26-2011, 02:58 AM
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Default RE: 2.4 glitching?


ORIGINAL: BuschBarber
The Receiver will not go into Failsafe if the Voltage drops and a Brownout occurs. The Receiver needs Power in order to move the servos to the Failsafe positions.
Failsafe will occur when the Signal from the Tx is Interrupted or Lost.
Even though the Receiver won't hit failsafe, won't the optokill kill the engine under brownout conditions?
I know the Smartfly ones I use did when I was using "the other common brand" 2.4, I am not sure about the other brands of optokills.

Either way, it is almost entirely certain that it was an installation issue. 2.4 is not totally forginving and installs should have the same car taken as for any other system. We tend to get a bitl lax with it because it tends to be a little more forgiving (I am guilty of that too).
Old 06-26-2011, 03:38 AM
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Default RE: 2.4 glitching?

I cannot speak for the Optikill Switch. I have only owned the Smartfly and the EDR Optical Kill Switches, but I would not want the Switch to cut power to the engine in the event of a Brownout or a Failsafe Event. With JR/Spektrum, for example, if you have the most recent Firmware for the Rx, a Brownout only lasts .5 sec.

I have never had a Brownout, but it could be easily replicated by just turning the Rx power Off and On. You can leave the Tx On and you will see that the Rx will not go into Failsafe. The newer Rx Firmware will display Blinking Lights, on the Rx, indicating a Power Loss has occurred.
Old 06-26-2011, 06:16 AM
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Default RE: 2.4 glitching?

I can say with 99.9% accuracy that it wouldn't have been your optokil i would think more like maybe your sparkplug lead was vibrating and rubbing on the fuselage or on the motor this has caused alot of problems before with glitches on 2.4 and on fm /pcm Even the sparkplug lead rubbing on a fiberglass cowl can sometimes cause a glitch, I have run many different types of optokil switches with DSM and FASST with no issues and most of them were just sitting in the fuselage not tied down and left to float around.As for modile phones and cell phones etc interfering with 2.4ghz that is a myth.
regards Bill  
Old 06-26-2011, 06:18 PM
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vertical grimmace
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Default RE: 2.4 glitching?

My spark plug wire was touching the fuselage where it exited on the bottom. I did not know that could be an issue. That is why we start these threads I guess! What is the best way to insulate them when contact is being made? Or do you just have to position them so they do not touch?
Old 06-27-2011, 09:41 AM
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Default RE: 2.4 glitching?


ORIGINAL: rmh

A test I have run using 2.4 shows a characteristic of these systems which is kinda nasty
The cause is loose power connections and or failing power under a load..
If the power shuts off then on (or does this in a rapid fashion ) the servos may go nuts.
Ditto if power fades to below minimum voltage threshhold- causing the system to shut down power -which then allows voltage to slightly rise as load is removed - then fall again as the servos -trying to reassume position causes a power drain.
I had this happen on the bench -using a almost depeleted battery.
Once I saw what was happening -it was easy to repeat the problem
IF it had happened in the air - it would have looked like a huge glitch- servos moving wildly
It goes back to th original weak link in 2.4- You must have a solid power supply- or a disaster can occur

The old 72 systems were more tolerant of low power -because a ''reset'' was not part of the results.
2.4 is a frequency.....What brand of equipment were you testing? The equipment to proccess the 2.4 signal is what you had a problem with not the frequency of 2.4. It does no good to post that 2.4 has problems unless you include the manufacturer as it may be a problem with thier design.
Old 06-27-2011, 10:44 AM
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rmh
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Default RE: 2.4 glitching?

ORIGINAL: pkoury


ORIGINAL: rmh

A test I have run using 2.4 shows a characteristic of these systems which is kinda nasty
The cause is loose power connections and or failing power under a load..
If the power shuts off then on (or does this in a rapid fashion ) the servos may go nuts.
Ditto if power fades to below minimum voltage threshhold- causing the system to shut down power -which then allows voltage to slightly rise as load is removed - then fall again as the servos -trying to reassume position causes a power drain.
I had this happen on the bench -using a almost depeleted battery.
Once I saw what was happening -it was easy to repeat the problem
IF it had happened in the air - it would have looked like a huge glitch- servos moving wildly
It goes back to th original weak link in 2.4- You must have a solid power supply- or a disaster can occur

The old 72 systems were more tolerant of low power -because a ''reset'' was not part of the results.
2.4 is a frequency.....What brand of equipment were you testing? The equipment to proccess the 2.4 signal is what you had a problem with not the frequency of 2.4. It does no good to post that 2.4 has problems unless you include the manufacturer as it may be a problem with thier design.
ANY 2.4 Spread Spectrum is subject in this case.
The reason being is that these basically are "computer setups" which have to boot up and- aquire signal.
this process (the boot n reboot ) takes place any time power is removed or falls below minimums.
That is the weak link in Spread Spectrum.
This sequence is almost always accompanied by a servo reset-so servo positions can and will change with each attempt at boot.
Having said that - the problem is easy to detect and prevent -if one pays attention to system requirements .
Please let me know if you have found any 2.4 system used in models which does not operate in this fashion.
Frankly having used 2.4 since it was released for our use in flying models - I would never consider going back to the old discrete systems.
I have no problems with my systems but I did a fair bit of investigating to see what problems I might encounter.
These were for the most part , the power to the system-
Easy to detect - and prevent.
Old 06-27-2011, 01:04 PM
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Jezmo
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Default RE: 2.4 glitching?

I do have the Smart-Fly Optical kill switch in all of my big stuff and if I have a "brownout" then yes I want the engine dead so as not to hit anything or anyone, God forbid, with the engine still running. If my receiver stops putting out a signal for any reason then the Smart-Fly kills the engine as it is designed to do. With the redundancy and voltage/amperage level I am using (A123/2300) there will be NO brownout unless something is seriously wrong. At that stage of the game the chances of me regaining control are pretty slim and if I do it's no problem to land dead stick. Heck, I use the Opto-Kill to kill it in the air all the time and land dead stick so I can check the plug/plugs for mixture signs. Just my two cents.

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