kamakasi

My Feedback: (3)

While flying yesterday. My servos started doing weird things. After 3 flights I was ready to launch again. As a matter of form I always check servo movement before each flight. This time the servos were moving in a most peculiar way. This description applies to all servos. If I gave the servo full or even partial stick the servo would move to it's new position in 3 or 4 jerky steps. It would then hang there for several second before jerking it's way back to neutral. With no stick input the servos did not jitter or buzz.
I gave up flying and went home to try to sort out this behavior. When I got home everything worked fine. I tested the rx and tx batteries and they both had plenty of charge and voltage.
A couple of hours later I'm back at the field and flying just fine, until my 3rd. flight. I was trimming out a home designed sailplane and decided to try a mild zoom off the launch. Well thats when what ever this phenomena is hit again. I have the pieces of the plane to prove it. Straight in from 500'.
When I got home the radio worked fine.
I've been flying at this field for 3 years and others have been here going on 20 years and no one has has a glitch ( outside of human error). Does this sound like interference? Does the FCC have a listing of active frequencies for an area? This has got me bugged.

aeajr

My Feedback: (2)

Let's do some fishing:

Was it very humid, or was there fog. Was the ground very wet?

Check your wires. It is possible you have wire or solder joint that is loose. You might have to go under the shrink wrap to find it. I had this happen recently. A solder joint let go and all that was holding it together was the shrink wrap. Worked fine on the ground but with the movement of flight, response was very eraddic.

You could have a wire that is getting a lot of stress or vibration resulting in some of the fibers breaking. Depending on the position of he wire you might be getting intermittent moments of low amperage.

Assuming nothing is wet, since it works fine on the ground, went wild on the zoom and gets twitchy as you prepare to launch, I would suspect a bad battery wire or plug to the reciever. Could be at or inside the battery pack itself. Since ALL the servos are impacted and the all get weird at once, I would look to the receiver or the battery connection. Doesn't sound like interference.

kamakasi

My Feedback: (3)

aeajr.

No it was not humid no fog and the ground was damp but not wet.
when it got twitchy the first time it was on the ground and not moving.
no hard landings with this plane or the battery pack.
I checked all the wires and connections after the first try and everything was fine.
I even had the battery out and while hooked up to the meter I was physically handling it the see if there was a loose wire or a bad tab but the meter never flinched.
the first time it happened I was at the field for several hours after and even after that time the thing still acted weird. I might be getting thrown for a loop because it worked fine at home. And then again fine ( at first at the field) until the oopsie. Now that the thing is in more than the designed numbers of components I am going to take the wrap off the battery and take a good hard look.
The zoom was very mild the hi-start had almost run out off steam so I don't think that I put any undue stress on the plane.
Of course any thing I find out now will be subject to interpretation as to the cause of any damage
being from before the crash or caused by the crash.
As of now the dam thing still works right in the house. I'll let you know if I find anything suspicious.

aeajr

My Feedback: (2)

Hunting down interference - The hunt for the off field flyer

If you have eliminated all possible electrical and predictable interference sources from your area and you still seem to get intermittent interference with your plane, you may have an off field flier that is close enough to impact your plane when he has his radio on. This can be a bear to deal with.

What you need is a scanner/direction finder that can home in on a 72 MHz signal on your channel. If you don't have something like that, here is the only thing I can suggest and this is pretty tricky to do.

Before you turn on your radio, turn on your plane. Are your servos normally quiet if the radio is off or do they chatter. Some receivers hold 'em still and some don't. For example the Hitec micro 555, a fine receiver, does not always hold them quiet. The Hitec Electron 6 does.

If yours holds 'em quiet, then you have an indicator. I suggest you need two friends to help you with this wild signal chase. Good luck if you try this.

Turn the plane on and observe. If you are getting unexpected activity, you have a signal coming in. Get two friends and the plane and get in the car. You can do this with just a receiver, battery, and a couple of servos. You don't actually need a plane.

You will have 5 to 15 minutes to do your hunt at each stage. As long as the servos twitch, the interference is there. If it stops, you may have gone out of range or he may have turned off. Try back tracking and see if it comes back. Try to keep the antenna outside the car as the car will shield the signal. you can mount it on a pole or something so that it sits above the car.

The third friend has binoculars to scan the skies for a plane that is off your field. If it is a sailplane pilot, or someone flying a large plane, you may see the plane. If it is a small plane, or if he flies low, you may not.

If back tracking doesn't help, pull over somewhere where you had the problem and wait to see if it starts again. If 30 minutes go by, he probably went home. If he is going to fly again, you should see some activity again within 30 minutes.

Servos chatter, start driving! Scan the skies.

Drive to places you would expect to see a plane for a non-club flier. School yard, park, etc.

This is a terrible approach but I can offer not better recommendations if you don't have some kind of scanner/direction finder.

The guy could be in his yard or basement doing adjustments, but he is close enough to interfere with you. You are also close enough to likely be interfering with him.

Last thought. Post a notice at the local hobby shops, the supermarkets, malls and on the forums.

LOOKING FOR RC AIRPLANE PILOT ON CHANNEL ## TO HELP RESOLVE CHANNEL CONFLICT.

Identify your field and ask if anyone is flying on your channel within 3 miles of the field location. Post a copy of a map with a 3 mile circle drawn on it. If there is another flier, he is probably going nuts trying to figure out what is wrong with HIS plane every time you turn on your radio. Make the notice friendly. Seeking to work toghether for mutual benefit.

If you find him, try to work out some method of frequency control, or convince him to join your club. He likely doesn't even know your field is there and might be very pleased to become a member rather than have his plane crashed all the time.

kamakasi

My Feedback: (3)

aeajr,
I highly doubt it is another flyer or someone tweaking stuff in there shop. Were I fly is out in a remote area. Any other flying sight is miles away. No houses within say 3/4 mile. We ( the local flyer's) all know each other and know where we live. While not a !QUOT!club!QUOT! in the formal sense we are aware of each other and the problems we can cause through inadvertent operation of our radios.
Until I can mooch my sisters scanner I am going to chalk it up to a funky battery pack.
I was out at the field today, same frequency and had no problems. (read different plane and battery). So for now (until I can get the scanner) I have no more gripes.
As a post note the local guru hobby shop owner stated that ch. 21 was a problem at the field, but I was on 59. 1.015 harmonic interference I think not. close but with the distances involved not good enough. The FMA rx should have rejected it.
Good thing I was already building the real fuse (the one that was lost was only a prototype). The wings survived, the tail feathers did not. No great loss as the back end was in need of a weight reduction anyway.
This just settled the issue of going with a spectra mod and a tracker rx. Coupled with a scanner if I don't like what I see I can go to any legal channel.
As I fly in the northwoods I can find no reason to blame interference. There is really nothing going on up here. They even shut down the ELF array. And as far as I know the full scale guys are way out of our frequency band.

aeajr

My Feedback: (2)

Makes sense to me. As I said, I would look at the battery and the receiver.

GoNavy

My Feedback: (15)

I fly in northern Wisconsin, near Stetsonville, 80 miles or so South of Butternut.
About every other season, I lose total signal to a plane, and "fall down go boom".
I always do a thorough post mortem, and send the electronics back to the manufacturer...and we never find anything.
We have had the AMA scanner for the better part of a season a few years back, with nothing noted, but I find it hard to believe I would suffer total signal loss without finding an electric problem, unless there was interference. This occured with three different radios and receivers on two different channels. I fly only glow.
I am going to invest in a scanner. I am tired of moving all the sticks while watching my plane fall out of the sky.
We fly in the country, but from what I read in forums here, pagers signals may be transmitted with 1000 watts, and on and on.
The air force has some sort of radio tower three miles away. There is a relay tower nearby. Maybe farmer Brown has radios.
By the way, ELF transmitted on 50 cycles per second, if memory serves.

CP140

Let me share something that happened to us a couple weeks ago. There were two of us(One on 57 and one on 58) who were getting glitches like crazy while sitting on the ground. Both aircraft had checked out fine the previous week with no problems and neither of us had changed anything nor had we "landed heavily".

One of the other club members pulled out his scanner and confirmed that there was intermittant interference on both of those channels. While we stood there wondering what was going on, another club member walked over and told us there was someone in the parking lot a couple hundred feet away running a grinder off an inverter. We found out later that he was a rockhound who had collected a few specimens from the local river and was grinding the rocks to get a fresh face on them and that he lived in an apartment. Apparently his neighbours didn't like the sound of rocks being ground.

We went over and (nicely) asked if he could shut everthing down for a minute or two as we were picking up some radio interference and were trying to isolate the cause...you guessed it, he shut everthing down... the interference went away. He turned it all back on and our servos started dancing again. From what we could figure out, he had a bad ground or something on the grinder because the inverter alone didn't cause a problem. He apologized for causing any trouble, we thanked him for being understanding and off he went.

Almost anything that runs off electricity can cause interference. We were lucky... neither of us were flying at the time... but both of us had been not half an hour earlier.

BillS

An inexpensive and easy to use glitch counter would be nice to have for testing and verification purposes. We probably get hundreds more glitches than we realize. As you stated unfortunately the crash modifies or destroys the evidence.

PCM receivers could probably easily have the ability to count glitches but unfortunately none that I know of do.

Often I would like continuous in air receiver battery monitoring. Voltwatch is a good first step but short of the mark.

Bill

rc4flying

My Feedback: (21)

kamakasi,

Was the plane sitting in the hot sun for a long time? My friends over the last few weekends experience what sounds like the same thing I was asked to trouble shoot, after having seen the problem and seeing the plane sitting in the sun for most of the day, I quickly swapped out their hot receiver for a cold one from one of my spares. Solved their problem. May be something to look at. That is why you say it worked at home. Theirs did too. Just my opinion.

rc4flying

dirtybird

My Feedback: (5)

Check the Eagletree Data recorder. It provides inflight battery monitoring and glitch counting. For PCM it will record when failsafe occurs. The best money I ever spent!
PS you also get RPM, head temp. air speed and altitude. All recorded so you can play it back.

former spad

Welcome to radio control. I have had too many problems like this. I sometimes take two planes on the same channel and switch from one to the other to see if the problem is in the electronics of one plane and not the other, and assuming that outside interference would affect both planes. I have also switched components from one to the other to see if the problem also moves. I suppose an intermitent short in any wire or circuit could could cause this.

former spad

Welcome to radio control. I have had too many problems like this. I sometimes take two planes on the same channel and switch from one to the other to see if the problem is in the electronics of one plane and not the other, and assuming that outside interference would affect both planes. I have also switched components from one to the other to see if the problem also moves. I suppose an intermitent short in any wire or circuit could could cause this.

BillS

dirtybird,

The Data Recorder is interesting. Thanks.

Are you using the Data Recorder for trouble shooting a problem? How would the Data recorder be used to trouble shoot a Futaba or JR system. How many glitches do you normally see in a ten-minute flight? When you get home at the end of a flying session can today’s flights be evaluated?

Thanks again.

Bill

Stripes

My Feedback: (19)

Last Tuesday I launched a Tufflight Panther and immediately had very little control. The plane danced all around the sky finally crashing in a nearby field. Upon recovery I found the servos quiet but if I moved the sticks they went nuts. Just touching the throttle caused the throttle servo to go to maximum throw and the right aileron to also move. Moving the ailerons caused them both to go to maximum throw. Bad receiver I thought, maybe the crystal. I showed it to several others and got just about as many opinions on what it was. An hour later I again went to show it off and all was normal. Do receivers fix themselves? No real suspicion of anybody else on the frequency and if they were wouldn't the radio pick them up and move the servos in accord with their radio?
Electron 6 receiver almost new
Hydramax Nimh 650 pack also relatively new
Hitec 225MG servos
No switch just a plug-in for the battery

aeajr

My Feedback: (2)

I was landing a plane once when it decided to go into a roll and crashed inverted. Had no idea what happened. Chalked it up to dumb thumb, but could not figure what I had done.

The following week I was range checking my glider when I noticed the rudder take a hard right all on its own. I move the sticks but all seemed fine, then it did it again.

Turned out to be a short in the trim for channel 1 on my radio. That held my rudder on the glider, but the ailerons on my other plane. Whenever I touched it, it would cause channel one to go hard right.

I don't know if this relates to your problem, but it is another one of "those things" that can happen. Worth checking.

GoNavy

My Feedback: (15)

What are "glitches" which can be counted? Is this information that is displayed, visually, by the device after the electronics have been on, and while you are still at the field?
If our goal is to avoid the interference induced crash, do you leave your transmitter and receiver on for awhile before flying and count the glitches? Do these simply tell us if there was interference, a glitch, or can ithey indicate that the glitching was sufficient to cause the crash?

apteryx

I just posted a few notes on making a cheap scanner on RCU ....you might try that.

BillS

GoNavy,

I don’t know what the rules are about glitch counting. A glitch is usually considered a twitch of the airplane but I don’t fly well enough to know when the damn thing has twitched.

A glitch should be a bad frame that is being passed to the servo or in the case of PCM a frame that is being discarded. Some rough examples come to mind. If the receiver receives instructions to go to a location that it cannot go to then the frame is bad. If out of 100 frames received a single frame is grossly different from the others a bad frame has probably been received. In the computer world data validity is often checked against the rate of change. It the mechanical device on the sending end and the human cannot possibly move the elevator stick from full up to full down in one frame then the frame is bad. The Eisenhower cannot possibly be headed due north at 12:00 and due East at 12:05.

If during a 10-minute flight you normally receive 200 glitches and today you are receiving 1000 glitches per flight investigation could begin. Maybe you changed an engine last week. Maybe the construction workers are working this Saturday. Maybe the new flyer is at the field. Maybe the field is crowded. Tools are needed to inform us that danger is lurking before the fatal crash destroys the evidence. Seems that a simple inexpensive measuring tool is needed to determining the current circumstances against the normal.

What we might hope for is a device that would count the bad frames received. The original poster simply needs a method to determine if unusual interference exists.

Someone else will likely have better answers.

Bill

PS:
I think we know that PCM receivers can and do receive bad frames that are not passed to the servos. They also do not immediately go to fail-safe. Does anyone know how many bad frames are required before PCM goes to fail-safe? I also think that PCM will reject frames that are out of range of servo travel but don’t know how to prove it.

BillS

Stripes,

No the problem will come back to visit again.

In the past I have put a rubber pencil eraser on the end of an engraver and shook the beejesus out of the receiver while operating the transmitter. Sometimes a cold solder joint will be found.

We need better troubleshooting tools rather than a bunch of opinions. This feels like trouble shooting an electrical problem without a voltmeter.

Bill