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Century Hawk - Falcon - Raven - Predator > ***SOS*** Interference.... or maybe not...

LongbowAV8R
Senior Heliman
Location: Aberdeen, MD

Ok all... here is a general question for you all...

I have a Raven, os50, airtronics 6000super/ 94322 servos, and the standard 401 combo... channel 57....6000(standard) ch. 35....

I have had a signal problem that started the first flight after this aircraft was built and I can not chase it out... it is very frustrating as the radio equipment is all fully operational, no problems in any other aircraft that it is installed in. It isn't a location problem as the Raven is the only aircraft that has issues. It isn't only a problem with the super set, but has the same glitch with every radio system low or high band and with both the 401 and a 601 gyro system. There are no loose screws and any questionable screws (such as the small phillips self-taps used to tack the cooling fan shroud to the lower frame) have been moved to secure plastic locations. (only has issues while engine is running.)

I need to know what other Raven/Falcon pilots have been experiencing this problem and what you are doing to fix it.

The aircraft experiences the same glitches with four receivers, 3 different transmitters, 2 gyro systems, and both an os46 and os50 engines.

Any help would be much appreciated... pretty soon the Longbow's out here are going to start accumulating more flight time than my Raven.

Thanks for the advice.

Never Leave Your Wingman!!!
The models will (and normally do) follow me everywhere....

09-26-2002 Over year old.

Ray Fernandez
Elite Veteran
Location: Guam (U.S.A.)

Cory,

One of my club member (Jimmyhua) had a similar problem. After tweeking the engine, it was apparent that was not the problem. He later attributed the interference to a faulty switch (or placement of where the switch should be on his Falcon v2. Lately, some of our other club members have been experiencing the same problem and we are finding more switches and "Y" connections that were faulty.

You might want to check it out.

Ray Fernandez - GUAM

09-26-2002 Over year old.

LongbowAV8R
Senior Heliman
Location: Aberdeen, MD

Switches...

Ray,

I am on the same sheet of music with you.... that is one of the first things that I isolated by removing it completely out of the system. I can reproduce the glitching by starting the aircraft and then taking the mechanics and moving it around by hand (going through the basic maneuvers and transitions)... you can watch all the channels just go nuts in different attitudes.

I was working with one of the civilian contractors out here and we took the entire aircraft into three section: the tail, the rotorhead, and the main mechanics. We plugged one servo in at a time and would move the mechanics around as if it were flying and we couldn't find a particular trigger to start or stop the servos from jumping. Then we would add another subassembly until we were completely together and we still couldn't isolate anything.

I just refuse to believe that I am the only owner of a Century helicopter experiencing this.

I like the way Century aircraft are designed, and I know that they do fly very nice... so I know that this is somehow due to a malfunction somewhere... I just can not find the problem. I have checked the bearings and I personally can't find any problems with them... but then again I may not be looking/feeling for the right things either....

I am just really getting frustrated.... this has been going on for about a year now.

Thanks for the help.

Never Leave Your Wingman!!!
The models will (and normally do) follow me everywhere....

09-26-2002 Over year old.

Pete
Senior Heliman
Location: Mcdonough, Georgia

glitches

My heli has been killin me too I am down for a long while due to a pcm lockout/crash that creamed 200+ worth of stuff. One guy at century said he found the little set screws that secure the landing gear skids to the plastic struts were a little loose and that tiny bit of rubbing was what was glitching him. I looked a t mine and there are alot of rub marks ! I cant check if that is the source of my stinkin problem cause of the lack of funds to keep on changing parts looking for a glitch that augers the heli in 5 times !! I too have changed engines all radio gear, and a lot of parts. Seems to me even if you tighten up the skid screws, a couple of not perfect landings and you could work the skids loose again.

09-26-2002 Over year old.

LongbowAV8R
Senior Heliman
Location: Aberdeen, MD

a fix for skid issues...

Use self tapping screws to mount skids.... I don't believe my issues are generating at the skid set screws though.

Fly safe,

Never Leave Your Wingman!!!
The models will (and normally do) follow me everywhere....

09-26-2002 Over year old.

rcpylon
Senior Heliman
Location: Saltillo, MS

is the glitching only showing up in the tail servo or is it in other servos?

are you runnig a GEM 2000?

you said you checked everything in sections and only when the engine was running, did you have problems, correct?

If this is the case, did you try and spin up the mechanics without the engine to see if the glitch was caused by the moving mechs. you may also try and apply something to the mechs to make them 'vibrate'. the radio companies use an engraver or a vibrating plate to check things out. if all this checks out okay, i'd suspect something with your engine. maybe a loose screw, bad bearings (yes, even if new), loose muffler, etc.

on that note, is there plenty of clearance between your muffler and the lower frame. I am using the centruy os 50 pipe (CN3033B) and I had to shave a good bit off the frame to clear the muffler.

I can say that I've now built 2 of these birds now (raven 30 & 50) and the only glitching problem I've had was on my 50. I had run my GEM along some of my servo wires and it was driving the tail crazy. all I had to do was relocate the GEM away from the wires and all was well.

Good Luck,

-------------------------
Alan Warfield
-------------------------

09-26-2002 Over year old.

jimmyhua
Veteran
Location: Guam

(only has issues while engine is running.)

I think this is your big clue right here. For sure, your problem is probably not bad electronics. Most likely, you've got metal-on-metal rubbing somewhere or a bad bearing somewhere, and the engine running is enough to get it going.

You can stop trying to swap out electronic components and concentrate on mechanical components.

Is the engine idling away enough that you see the servo's jiggle around? If so, you've got it made.

First re-orient antenna such that interference goes away (easiest is to have antenna stick straight forward away from heli. Then re-orient antenna, where the interference is the worst.

If you're lucky the metal-on-metal rubbing is 2 small pieces of metal, and the antennae is close by picking it up. So it will be easy to find. If you're unlucky, you will find the interference is equally bad however you route the antenna, and in this case, for the Falcon, there's only one place to look (maybe a loose muffler?).

All you usually need is about 7cm gap from metal-on-metal interference source from antennae/receiver, and it's usually too weak to cause a nuisance (well, unless you have a LONG piece of metal that's rubbing, then it'll look like it's coming from everywhere).

Finally, I don't think a sheet metal screw to afix the landing gear fixes the problem. If the screw gets loose, you will still get interference. My solution was just to CA the landing gear onto the plastic struts.

To set the record straight. My switch wasn't causing interference. The 4-40 bolts that attached the switch to the heli was rubbing against the metal sideframes. It felt tight to me, I had rubber grommets to hold them still (it worked great for the first 10 flights or so, but then I think the grommets then softened out). But it wasn't enough! I ended up completely insulating the bolts from the rest of the heli.

Jimmy

09-26-2002 Over year old.

LongbowAV8R
Senior Heliman
Location: Aberdeen, MD

Alan (GEM2000)

Yes Alan, I do have a GEM onboard. The issues I am running into are not the GEM's warnings being misdiagnosed (this is what I originally thought.)

I have checked both my engines (as one of the Century reps in Northern Alabama let me know that there can be issues with the 46/50 class engines and the rear bearings.) I can't see any mechanical problems with the engines or aircraft, but I feel as I may be missing something...

I think that I have rebuilt this thing so many times that I just ran out of ideas to troubleshoot.

Is there issues with the GEM that I am not aware of?

Thank you all for your input... it's giving me a fresh look.

Never Leave Your Wingman!!!
The models will (and normally do) follow me everywhere....

09-26-2002 Over year old.

jimmyhua
Veteran
Location: Guam

I am just really getting frustrated.... this has been going on for about a year now.

Wow a whole year! I would have just flown the thing until it crashed, glitching and all. Wait a minute, I did that, and then found the source my glitching after I crashed it.

Anyways, based on past posts. Here's the short list of common sources of glitching on Falcon/Hawks. Although, I believe these really aren't that specific to this heli.
a) dual tail boom supports. The bolts on the mainframes that holds on this has to be on abnormally tight. Really tight. The self-tapping screws on the otherside have to be tight too. They have a tendency to vibrate in the air. I hear the plastic support of the support helps. But I just crank down hard, on mine and that works good too.
b) metal sideframes. On one side you have 2 servos with brass eyelets. If these get loose you will have it. If you don't have the brass eyelets, and the screws touch the metal frames, you will have it! On the other side you have a switch mount screwed on with 4 self tapping screws. If these loosen you will have problems too.
c) loose landing gear bolts.
d) loose muffler
e) set screw into landing gear tubes.
f) sheet metal screw into fan shroud
g) loose bolt going into header tank mount
h) tuned pipe rubbing against header
i) tuned pipe rubbing against tuned pipe support
j) self tapping screws not tight enough holding metal sideframes for servo tray.
k) screw that holds the lower sideframes with the servo sideframes together has to be on real tight.

That's about it that will cause you grief. Most bearings, if they go, will die w/out causing interference. The only bearings that will cause interference problems are in the engine itself and clutch bell.

Wait a minute. You said Raven not Falcon. Are your servos mounted on a metal tray? Well, b) j) and k) prolly don't apply then (I think). However, do make sure that you got the brass eyelets on, and you crank the screw down so that the brass makes positive contact with the metal servo mounts.

Well, I hope you find it. Let us know, what it is when you do.

Jimmy

09-26-2002 Over year old.

LongbowAV8R
Senior Heliman
Location: Aberdeen, MD

I'll definitely let you all know....

I was initially under the impression that brass couldn't cause radio problems... hmmmm...

Well, all... I am going to start back at the engine once again (after checking the radio and servos in the Nexus one more time)

I have a feeling that the solution to this is going to hit me like a ton of bricks (eventually...I hope)

I'll keep you all posted... please keep the ideas coming, we have to find this problem somehow.

Yes, Jimmie.... I bought the Raven last October... and I haven't really had the chance to actually take it out and feel confident yet. Back home I had my Jetranger and Nexus to fly, so it wasn't a really big deal, but the only ship that I brought to Korea with me was the Raven. I have since bought another Nexus to finish up my scale OH-58, so at least I have something to fly, but the Raven is still my aerobatic ship and FAI trainer... just not training me too well right now... lol

Oh well,

I thank you again for all the assistance... all of you.

Never Leave Your Wingman!!!
The models will (and normally do) follow me everywhere....

09-26-2002 Over year old.

rcpylon
Senior Heliman
Location: Saltillo, MS

GEM trouble

my trouble with the GEM was only how I had it run. It was running along my servo wires going to my CCPM servos as well as the tail servo. you may try and unplug it and see if it goes away. if that's the case try it in a different location. This was the first 'trouble' I'd had with a GEM. I've also found out that these tail serovs are REALLY FAST. they will show a glitch of just about any magnitude, which is a good/bad thing

As for the rep, that would be Bruce, TAILBLADE1, one of my flying buddies. he had a 'noise' coming from his heli and he ended up changin out a bunch of stuff to no avail. he finally pulled the engine and it was the rear bearing. I can personally attest it sure didn't sound like an engine bearing but now we know

The only thing we can come up with is that the mechs were resonating the bad bearings problem. It was truly a wierd one.

-------------------------
Alan Warfield
-------------------------

09-26-2002 Over year old.

jimmyhua
Veteran
Location: Guam

brass is good but.

When brass is combined with aluminum, they stick better to each other, than say aluminum against aluminum.

But, if they rub, they will cause just as much interference as alumimum rubbing against aluminum (actually, much more interference).

At least, this is my understanding of it.

So with equal amounts of torque, brass is less likely to rub. You need significantly less torque to afix brass onto aluminum. This is why we like brass, I think. Brass sticks even better onto steel.

Jimmy

09-26-2002 Over year old.

oldfart
Elite Veteran
Location: Vancouver, Canada

glitching

Jimmy gave a pretty complete list of glitch causing items in any heli, not just the Falcon/Raven.
1 - Recently I experienced glitching and found it to be caused by a disintegrating bearing on a NEW OS-50!!!!, (OS replaced the engine at no charge but I haven't reinstalled it yet as it is flying great on the old 46. So I wll wait for my next "forced" maintainance to do so). Changed the engine and it went away. It was the last item I suspected because it was a new engine.
2 - A fellow clubmate had the same problem with an OS-46 he had that had been in storage for about nine months. When he put it away he had not scavenged the crankcase properly and the rear bearing had rusted. Replaced the rear bearing and solved his glitch problem. Again, he did not suspect the engine because "it was not causing any glitching when he used it last".
3 - I understand there was a recall on some 401 gyros that would cause RF interference (a problem with their internal shielding not grounding).
4 - Another local also had a glitch issue on a 60 that we chased forever. It turned out to be simply that he had not used the proper double sided tape to support his 401. (note also that loose wiring etc. should not be allowed to touch the case of a gyro as the vibration of these when the engine is running can solicit abnormal responses from the gyro that can be preceived as glitches.
5 - I also had a lockout issue a few years ago on one of my 60's. Turned out to be a problem with the NEW battery pack. One of the tabs that join the cells was intermitant. (again the last item I suspected because it was new!!)
6 - Yes, there has been some issues with the GEM's.

From your desriptions and the history of your trouble shooting, I would first suspect bearing R/F. This generally has to be from bearings that are turning at high RPM's. So again, I would suspect the engine (try another, different from the two you tried) or possibly the bearings supporting the primary gear.

If you set your throttle / pitch curve for a much lower rotor speed and the glitching seems to be less this will support this bearing theory.

09-26-2002 Over year old.

jimmyhua
Veteran
Location: Guam

Now if it was not the engine, the boom could be shoved up the helis ass so tight that the tail pinion bearings are loaded incorrectly.

Heheheh! I've done this before, but it didn't result in glitching. Gyro didn't like it one bit though. Of course, being the dummy that I was/am. I just turned the gyro off, and continued flying until the heli started piroetting out of control. Them bearings heated up so much, they melted the torque tube couplers! Yikes! Lost all tail control and had to do a piroetting auto

. It looked cool, but broke my vertical fin doing it.

If all this didn't work, I'd find the biggest sluge hammer I could find and reduce the heli to its basic materials for recycling.

Nah! Just fly it until you crash it (out in an open space w/ no one around). You'll eventually find the glitching.

.

Jimmy

09-27-2002 Over year old.

MisterOught
Senior Heliman
Location: E'prise Al

Quote
The aircraft experiences the same glitches with four receivers, 3 different transmitters, 2 gyro systems, and both an os46 and os50 engines.

do you change cyrstals use the same ones everytime .??

"a little search goes along way" and "copy and paste" works just as well.

09-27-2002 Over year old.

Ray Fernandez
Elite Veteran
Location: Guam (U.S.A.)

Jimmy,

You crack me up

Ray Fernandez - GUAM

09-27-2002 Over year old.

gforce
Veteran
Location: Jacksonville FL

Antenna location????????? Are you always using the same antenna location?

Try using a whip antenna

09-27-2002 Over year old.

LongbowAV8R
Senior Heliman
Location: Aberdeen, MD

Updates....

For antenna location, I am running the antenna through the stock antenna mount on the skid crosstubes (right side away from exhaust). Regarding whips... I used to be all for them, I previously had a Revolution installed on this ship, but the coil failed or something happened and the antenna (though visibly undamaged) just stopped being effective. Almost lost the machine in the drink... I replaced the antenna with the stock one and haven't had range problems since (at least not with the engine off.)

Xtals... no, not same xtals every time. I have a receiver that is on ch 35 and the other 2 are on ch. 57. The two on 57 are the airtronics 92777 that came with my super radio set and a hitec rcd3800... the one on ch. 35 is a different airtronics 92777 (the aircraft had the same issues with the Futaba receiver that I recently gave to one of the guys that I fly with). I don't believe my issues are radio related, but I should find out today... I relocated all radio components into my Nexus for testing. If I have no issues I'll know it is the Raven and something mechanical on it.

Keep the info coming.... eventually someone is going to hit the hammer on the nail and my problems are going to be fixed.

Thanks for all the support.... you all are very right about glitching being a pain in the a** to fix.

Fly safe,

Never Leave Your Wingman!!!
The models will (and normally do) follow me everywhere....

09-28-2002 Over year old.

LongbowAV8R
Senior Heliman
Location: Aberdeen, MD

any of you that are radio smart please explain....

I have had a burning question in regards to FM band and Xtals.

I understand that channels 1 to 35 are considered "low band" and 36 to 60 are considered "high band" but exactly what does this mean... and how does it affect the swapping of Xtals.

I have been told that you can't use a low band Xtal in a transmitter or receiver that was manufactured with a high band Xtal... what effects are a cross-band Xtal going to display.

I only ask because I have an RD6000 (standard) on ch 35 and an RD6000 Super on ch 57... I have been trying to troubleshoot my glitching (as you all know) and I have been isolating radio components. I transfered all radio gear from the Raven into the Nexus and tried an on ground range check (as I am still waiting for a throttle arm) and I couldn't get more than 30 feet or so with the GEM plugged in... about 35 with the GEM unplugged, but still a very dirty signal (as displayed by the 401's indicator light.) It would be worse when I moved the rudder channel left while in HH. The light normally will go solid once input is released, but all it would do is flicker and you could watch the tail control rod jittering (rudder is the only channel that would act this way.)

The range check affected all channels.

I want to know if there is any adverse things that will turn up if I start to use my ch 35 Xtals in the transmitter nad receiver that were manufactured with ch 57. That's the just of it.

Thanks,

Never Leave Your Wingman!!!
The models will (and normally do) follow me everywhere....

09-28-2002 Over year old.

jimmyhua
Veteran
Location: Guam

yeah, I'd have to agree with alexander. 35 feet is way too short.

A proper range check consists of two guys. One guy holding the transmitter shouting out the command inputs he is giving. The other guy is holding the heli (with engine off, this part is important), 3-4 feet in the air.

The guy holding the x-mitter starts walking away. Usually he gets so far away, that the guy holding the heli can no longer hear him, and then only rudder input is given, and hand signals to communicate which rudder input he gave.

With Tx antennae collapsed, on a PPM setup, it's usually about 250+ feet before glitching starts. On a PCM setup, it sucks, we've measured the length of our field, and still no signs of lockup (close to 1000ft).

If the heli is on the ground the range check isn't as accurate, as the antennae is on the ground too. However, people do it this way all the time (one man range check). Usually we lose sight of the control surfaces before glitching starts (around 75 feet).

Jimmy

09-28-2002 Over year old.

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