Dzaken2800

Everything was fine with my Falcon 3D until yesterday. I took my Falcon 3D out for flight and once I took off, the tail started to tilt slightly down to the right and it stayed that way the whole flight. I tried to tighten all of the screws on the tail boom so it would stay put and wouldn't tilt, but that didn't help at all. I took my Falcon 3D out for another flight today and now the same thing happened, but the tail started to wag side to side when it happened.
I'm not sure whats wrong and how to fix it since I haven't crashed my Falcon 3D once and everything seemed to be running fine before.
Has anyone ever experienced this problem?
Does anyone know what might be causing this problem and how to fix it?
I would really appreciate any help or suggestions.
Thanks in Advance.

juneebear

Dzaken2800,

You might want to check your tail gears beacause sometimes the gear sitting on the shaft breaks apart. If everything looks fine there you might need to adjust your gain manually on your gyro that's if your are still using the stock Tx. And after that a slight adjustment on your Tx trim for rudder might be needed. I hope this helps.

juneebear

Dzaken2800

Thanks,
I checked the gears and everything seems to be fine, but I'm still not sure what I need to do to stop the tail from tilting.

Michael211

My Feedback: (1)

Mine did the same thing. If you take a look at the top of the front of the tailboom you'll notice a clamp with 2 screws on either side and a slightly larger screw directly on top of where the boom should be under this clamp. The screw directly on top of the clamp goes down and into the boom itself, to prevent it from turning clockwise as the shaft is turned.

However, the boom is of very soft aluminum and it's managed to turn anyway and has ripped open the hole this top screw goes thru. You can remove these 5 screws and take that clamp off and you'll see that the hole in the tube has ripped as the boom turned.

My solution is to put a drop of thick CA (superglue basically) onto the center of that clamp and then put it back onto the boom (with the boom straight!) and screw it back down... this effectively glues the clamp to the boom so that the boom cannot turn anymore. If you ever have to replace the tailboom you will probably have to replace that clamp as well, but that clamp is available thru Hobby-Lobby and it's only a buck or so.

Regards and good luck!

- Michael

Dzaken2800

Thanks for your help,
It's just that I don't have any thick CA, I only have thin CA. Will it be fine If I just use the thin CA?

Michael211

My Feedback: (1)

Best to get some thick CA. Thin tends to run everywhere and could get into some place you don't want it to!

A dab of epoxy would probably work also, like the 5 minute stuff. Just use something to glue the tail boom to that black clamp so the boom won't turn anymore is all you need.

Good luck.

- Michael

Dzaken2800

Ok Thanks.

Dzaken2800

Well, I did what you told me to and the tail boom stayed straight, but now there is a different problem.
I took my Falcon 3D out for a flight today and it started spinning extremely fast counter clockwise. It wouldn't stop so I tried setting the rudder trim all the way to the right and rudder stick all the way to the right, but that didn't help at all.
Then I tried to switch the rudder reverse switch, but that didn't even do anything. So then I unscrewed the tail rotor blades and I flipped them over, but that also didn't do anything.
Does anyone know What could be the problem?
How do I fix it?

Michael211

My Feedback: (1)

Hmmm.... I read the replies to your post on this in the other Falcon 3D topic (none seemed likely to help though).

Your description and the fact that it's flown before (with the gyro functioning correctly and all) and it hasn't been crashed leads me to believe that your tail drive gear that runs against the main gear may be slipping, causing the tail rotors to not spin up fast enough to develop holding power against the engine torque. Your tail may be spinning but if it's slipping or jumping teeth on the gears it won't develop any power when the gyro changes the tail blade's pitch to counteract motor torque.

Put everything back to the way it was 1st off (tailblade direction, gyro direction, rudder trims etc.). Check that the tail gear isn't slipping by holding the rotor head with 1 hand and trying to gently turn the tail rotor with the other. Turning the tail rotor in 1 direction it should turn easily without trying to turn the rotor head (which you're holding still with the other hand); the auto rotation bearing allows this. However turning the tail rotor in the other direction should cause the rotor head to try to turn (as the auto rotation bearing locks up). Apply force gently and see if anything slips. Then get back with us on here. [8D]

- Michael

Dzaken2800

I checked, the gears aren't slipping and they are running fine. I saw that the tail rotor pitch was facing the other way and it was blowing wind to the left instead of the right. So that is probably what's causing it to turn counter clockwise, but I still don't know how to fix it after all of the things I tried to do. Do you have any Idea what might be the problem?

Gary Morris

Here's the solution in a nutshell: Plug your rudder servo directly into channel 4 on your receiver. Once you do this be sure that the servo arm is at 90 degrees to the body of the servo. Center your rudder trim and once you do this reconnect your servo to the gyro and the gyro back to channel 4. Loosen the tail servo and looking to be sure the servo arm is at 90 degrees to the servo body, slide the whole servo either backwards or forwards until the tail blades have zero pitch. You can eyeball them to be sure they look flat, that would be zero pitch. Check that you have no binding with full rudder either left or right. Don't worry if you can go far one way, that's normal for a heading hold gyro. Now take off and do a test hover. Watching the tail if it drifts slightly one way or the other, slide the servo backwards or forwards in very very small amounts until the tail holds with no trim settings or stick input. This may take a few test hovers but it's important you do it in order to get no drift of the tail in flight. One last thing, the gyro is temperature sensitive so if your in your nice cool home and go outside where it's either very hot or cold give the gyro a chance to adjust to the temperature difference. If you follow these instructions to the letter you'll have a perfectly working setup. The main points are: No binding with full rudder stick inputs either left or right. Tail blades have zero pitch with servo in neutral position and servo arm at 90 degrees to the servo body. Have enough head speed so that your tail functions properly. Note: If your head speed is low your tail won't hold correctly so better to have higher head speed than lower.
Hope this helps you and anyone else who's having trouble with there Falcon tail holding. Also, if your tail keeps twisting put a little wrap of scotch tape on the boom at the boom clamp above the motor. This will give it a better hold and keep the boom from slipping in flight.

Good Luck!!


Gary Morris

Dzaken2800

Thanks a lot Gary.
Your information was very helpful and I'm sure it will also help others that might have this problem.
Thanks again

Michael211

My Feedback: (1)

Did Gary's suggestion fix your problem then?

- Michael

Dzaken2800

Hi Gary,
I thought everything would go well after I did the adjustments, but it didn't turn out well today when I took my Falcon out for a test flight for the first time after the adjustments (I only had a chance to take my Falcon 3D out for a test flight today).
So anyways, I did the adjustments just like you told me to, I moved the servo to the right position so the blades would be leveled and I tightened the screws. Then when I took my Falcon out for a test flight, it started spinning like crazy, counter clockwise just like before. So I checked my Falcon 3D and it seemed like everything changed back to the way it was before I made the adjustments. The blades also changed back and were completely off level.
After that, I adjusted it again and again and again, test flight after test flight, 6 more times, and still, the same thing happened. Everything changed to the same way it was before the adjustments.
I have no Idea what's wrong now and how to fix it, so I would be happy if you could help me out.
Thanks.

tippy

Are you sure about that???

I believe that with your t/r stick and trim at center, you SHOULD have some amount of YAW NOSE RIGHT pitch.

At hover ... there is a torque difference between the main rotor and the fuse that causes the fuse to YAW nose left. To counteract this force, you have to have some YAW nose right offset (deflection) at the t/r blades.

Most helis have this offset built into the t/r system. This means that when the slider is at the center of it's travel range ... the blades will have some YAW nose right pitch induced.

So when you set everything to neutral (t/r stick, t/r trim, 90° at the servo arm, slider centered) ... there SHOULD be something other than 0° at the t/r blades. Since this offset pitch is nominally what you need to counteract the YAW induced by torque ... you will not have to compensate (much) at the stick or trim while hovering. That's assuming that the heli is assembled and setup correctly.

If you are setting your t/r system up so that you have 0° t/r pitch at center stick and trim then your heli will spin like a top.

tippy

First, if you followed the instructions to have your t/r blade pitch at 0° when your t/r stick and trim are centered ... you may have been lead astray.

At hover, there is a YAW nose left force induced by the torque difference between the main rotor and the fuselage. This causes the fuselage to YAW opposite to the main rotor rotation ... YAW nose left ( ... "it started spinning like crazy, counter clockwise" ... ).

So ... at hover, with t/r stick and trim at center, you SHOULD have some YAW nose RIGHT pitch induced at the t/r blades.

Most heli's have this "hover pitch" built into their t/r system as an offset. This means when the t/r slider is centered in it's travel range, the t/r blade pitch should NOT be 0° pitch ... instead the blades should be at their offset pitch (YAW nose right). This YAW nose right pitch counters the YAW nose left force induced by torque.
In a perfect world, with everything centered (t/r stick, t/r trim, 90° at the servo/linkage, slider centered) ... you should need very little trim (or even stick movement for that matter) to maintain a steady YAW at hover. That's assumming everything is assembled and setup up correctly.

Getting the relationship between servo arm position and t/r slider position correct is what is called "mechanically trimming" the heli.
Small "tweeks" are done by just lengthening or shortening the servo-to-bell crank linkage (if you have normal ball connections on your linkage). If this is way off ... a re-adjustment of the t/r servo mount (assuming boom mounted) may be called for.

The final result should be, while evertything is centered, the t/r slider bell crank arms should be 90° to the t/r shaft and boom. When the bell crank is squared, the slider should be near it's center of travel. The slider being centered, should produce a pitch offset at the t/r blades (which compensates for torques force that cause the heli to YAW).

All these "mechanical" adjustments should be done while the gyro is in RATE mode. If you don't have the ability to switch to RATE mode ... then plug the t/r servo directly to the receiver while adjusting and then switch back to the gyro afterwards.

Dzaken2800

When I made the adjustments before, I did realize that the blades should be at their offset pitch since the first 3 times that I adjusted the blade pitch to 0°, the heli kept on spinning.
so I adjusted the blade pitch again so that the blades would be at their offset pitch, but when I took my heli out for a test flight, everything changed back to the way it was before I made the adjustments and it caused the heli to yaw nose left just like before.
I made all of these adjustments while the Gyro was in heading hold mode, so maybe that's what caused everything to go back to the way it was before I made the adjustments, which kept on causing the heli to yaw nose left.
Though I'm still not sure if that's what caused the problem. Is it?
Anyways, I'll try making these adjustments while the rudder servo is plugged directly to the receiver.

tippy

Still don't know what gyro you have.

Typically, if to perform the mechanical adjustmenst, the TX and heli needs to be powered ON (w/the motor disconnected) and the gyro needs to be set to RATE (normal) mode via the TX or at the gyro (however that is down on your gyro). If it's not, then you'll need to plug the servo directly to the receiver during adjustments.

Since I'm not familar with the Falcon, you'll have to see this for your self. Besides moving the servo mount back and forth to adjust mehcanical trim ... see if you can make adjustments at one end or the other of the tail rotor linkage. If the linkage ends are ball links you may be able to disconnect the link from the ball and rotate the clevice if threaded. This is how you normally make length adjustmeents to the linkage. Normally, once the servo mount is set ... you want to leave it alone.


If you keep adjusting things and they seem to change ... I'd look at how secure the t/r servo mount is to the tail boom. If this mount is allowed to move fore/aft ... your mechanical settings will go out the window.

Even after setting up everything ... only a test flight will tell the results. If it still wants to go nose left ... make adjustments to the linkage length (if possible). Tiny little adjustments can cause lots of control change.

Also ... if there is a directional switch (normal / reverse) on the gyro ... make sure it is set correctly. If it is wrong ... it will also cause the heli to spin out of control.

Michael211

My Feedback: (1)

Guys this is overkill with all the adjustments! Even if the t/r is a little out of adjustment there's no way it should spin uncontrollably at lift off because of that.

To summarize this issue:

1). Tailboom was turning in it's clamp several degrees clockwise... the screw that holds it
in place had ripped the hole in the soft aluminum tail tube, but heli flew fairly normally
otherwise.
2). Dzaken removes said screw and the clamp it goes thru, then added some glue
between the tail tube clamp and the tail tube and re-installed the clamp and screw
so that the tube will no longer turn in it's mount.
3). Heli now spins uncontrollably when spooled up.


So, what is most likely wrong here? Heli has not been crashed and was holding heading prior to this small modification to secure the tail tube. Rudder servo was not moved during this procedure, correct Dzaken?

- Michael

tigermeet

I had the same problem with my Falcon after replacing the main gear.. It flew good for the first couple of flights and then started the spinning in circles. Turned out the smaller gear that drives the tail shaft was installed on the wrong side of the main gear. This lets the main gear sit too low and it causes the tail shaft gear to slip when you spool up'. Don't know if this is your problem, but worth looking at.

Dzaken2800

This is exactly what happened from the beginning. I secured the tail boom with some glue between it and the clamp, I screwed the clamp back in, then I took my heli out for a test flight and I hovered for a few seconds, everything went fine. Then I landed after those 2 seconds of hovering and I wanted to take off one more time to make sure everything was fine, but when I spooled up the rotors, the heli started spinning out of control.
I didn't even touch the Rudder servo during the procedure, so I have no Idea why it's spinning out of control like that.

Dzaken2800

Well, I made the adjustments today with the rudder servo plugged directly to the receiver and now I want to do the test flight, but there is a different problem[]. I plugged the rudder servo to the Gyro, but now I can't get the Gyro plugged back in to channel 4. I tried plugging it in as hard as I could on each side of the plug. I even tried plugging it in carefully with small pliers.
I've been sitting for a whole hour trying to plug it in, but nothing works.
What should I do now?

tippy

0° pitch at center stick and trim is more than " ... a little out of adjustment ... ". Even in HH, the gyro can't give enough defelection to correct for the "mis-alignment".

One or two turns of the ball linkage ... yeah ... a functioning gyro in HH will probably compensate ... but a degree or two of pitch mis-alignment will cause a significant amount of YAW in which lots of trim and stick will be needed to compensate.

If the gears are slipping ... you will not have the RPM/authority you need at the tail ... which will also allow the YAW.

And if the gyro is in the wrong normal/reversed mode, it will continually YAW.

BTW ... Dzaken2800 ... what gyro do you have??

Does the gyro plug / RX socket have some sort of polarity tab/shape??? Make sure you are plugging it in correctly.

Dzaken2800

I have an Art-Tech Heading Hold Gyro.
I tried plugging it in both ways, but I couldn't get it in no matter how hard I tried.
I have no Idea what to do now[]

PappyFarland

I had a similar problem that turned out to be a servo biting the dust. The servo would hlod for a little while then itwould seem to "Let go" after a while it would not hold at all. I was able to trim it out tho. so I dont know if you have this problem or not.