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Old Aug 24, 2012, 05:10 PM
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Help!
DH 9116 Help

This is my first post so i hope i dont mess it up. I got my DH 9116 about 2 weeks ago and as my first heli (other than the $19.95 Wal-Mart specials you fly in the house) it probably wasnt the best choice. Not going to lie it went through a few crashes before i got the hang of flying it but now i'm able to take off and fly around the house to a fixed point landing with little trouble. The problem is when i fly forward sometimes it moves so slow you could walk faster than the heli is flying and other times it lunges forward so fast it does a front flip in mid air. It does this on both the Q and S settings, I'm sure its not due to wind because it does the same thing while flying in the house. Any help would be greatly appreciated.
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Old Aug 24, 2012, 07:47 PM
Crash and learn
United States, PA
Joined Dec 2011
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Quote:
Originally Posted by Akira38 View Post
The problem is when i fly forward sometimes it moves so slow you could walk faster than the heli is flying and other times it lunges forward so fast it does a front flip in mid air. It does this on both the Q and S settings, I'm sure its not due to wind because it does the same thing while flying in the house. Any help would be greatly appreciated.
What does it do when you hover?

Suggest you remove the blades, blade grips, and put them back on. Look for cracks and see how easy the blades pivot (no binding) when you put them back on.

A sudden lunge forward while moving forward is unusual. I don't think a servo problem would cause that.

DH9116 thread has people who know - post there after trying a long hover
http://www.rcgroups.com/forums/showt...ather&page=225
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Last edited by Ribble; Aug 24, 2012 at 07:56 PM.
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Old Aug 24, 2012, 08:32 PM
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Just got back in from flying and it hovers well, requires little to no assistance from the transmitter. I did as you suggested Ribble and the blades pivot very easily, doesn't seem to be any friction at all (not sure if thats a good or a bad thing). i didn't mention this before and i can't believe that i didnt, a few days ago i adjusted some of the settings on the transmitter before taking it out to fly and it didn't seem to be acting right and it crashed. I ended up having to replace the Inner Shaft so i bought a kit that contained everything from the swashplate up. I figured since it had been through a few crashes that when i got the new parts to just replace everything. I did and when i finished putting it all back together the blades and fly bad were extremely tight so i decided to put the old parts back on with just the new Inner Shaft. I'm not sure if it could be the transmitter or another broken part. The heli is far from unflyable its just very unpredictible while moving forward. Thank you for taking the time to help.
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Old Aug 24, 2012, 10:26 PM
Crash and learn
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Joined Dec 2011
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I do not have a DH9116. Just the bigger version 3 channel DH9104. Will look at some DH9116 photos.

Look for a link off a ball (pushed in toward main shaft).

The flybar has to be loose enough to bounce when tapped.

The blades should just barely hold straight when the helicopter is tilted. Blades should fall to the side with a small jolt.

Check that the swashplate upper and lower plates are not separated (no major gap).

Does not sound like a transmitter problem because you should be able to see a sudden move in the servos when moving sticks slowly.

Flybar strikes on the canopy or tail boom. My DH9104 has multiple tail boom dents in the same place from the flybar, but I have never heard an actual strike. A flybar strike would be enough to crash the DH9116.

A bent or broken feathering shaft is common on the DH9116 but usually only causes a circular orbit when hovering.

Look again for a broken main blade by flexing the blades and looking closely near the blade grips.
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Old Aug 25, 2012, 11:22 AM
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Unexpected and unpredictable movement (or lack of) in any direction would be a sign of a bad PCB, bad transmitter or separated swashplate. The 9116 has a 120į swashplate which requires both servos to move to provide movement in any direction, which means it has to be mixed by the PCB. A bad PCB or transmitter is quite common to this heli.
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Old Aug 25, 2012, 08:49 PM
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I wasn't able to fly today due to rain, tomorrow ill be able to take it out and see what i can find out. i did check the blades again and didnt find anything but i went ahead and put new ones on so that should help. Sorry i don't know what they are called but they are the little ball joints on the blade grips that hold the connectors that attach to the connect the blade grips to the swashplate, are they supposed to be loose or tight? i noticed that they were extremely loose and if i tightened the screw a little tighter it made a dramatic difference in how they move.

Thank you Balr, sadly i'm not sure what the PCB is but ill look it up. I'm still new to RC helis and im not quite sure if my swashplate is correct or not. By looking at pictures of other 9116's from what i can tell mine is still in good condition.

Thank you both for the help i really appreciate it. I'm going to put your suggestions to work and fly tomorrow. I'll be sure to get back with you when im done. Thanks again.
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Old Aug 26, 2012, 01:59 AM
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The PCB is the board. I'd have to see a picture of what you tightened to see if that would have any impact. But do remember, in order to move forward (or not move forward) it has to be something that is effected by the movement of both servos. It's unlikely to be something that rotates as rotation is non-directional.
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Old Aug 26, 2012, 03:34 PM
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I'll see if i can take a detailed video of it with the canopy off and show you the moving parts then another of it in flight if i can. I have never posted a video on youtube but im going to try then I'll post a link here. I noticed as well today that it is indeed constantly turning to the left and no matter how much i adjusted the trim it had no effect.
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Old Aug 26, 2012, 04:11 PM
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If you mean rotating left, that would indicate the tail motor isn't functioning correctly. It's either worn out ( they don't last long) or the PCB is indeed bad.
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Old Aug 26, 2012, 09:32 PM
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I wasn't able to get a video up my phone wont let me send videos to my email but i did manage to send some pics. If either of you would like i could email you some of the pics i took and if not thats perfectly fine.
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Old Aug 26, 2012, 10:58 PM
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Just post them here. Scroll the reply box down to manage attachments. But, evidence is mounting that your problems are PCB related.
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Old Aug 27, 2012, 01:35 AM
Crash and learn
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With throttle off, move the elevator stick up and down slowly. Watch and listen to the servos. Look for binding (servo stops moving) and sudden jerky movements. Servo hangups are common on the DH9116 (and other helicopters). If there is a stripped gear in the servo, you should be able to hear it.

The other issue could be a loss of signal. The DH9116 losing radio signal will cause it to freeze the controls for a second, then continue what it was doing before when it regains the radio signal. You can test this with the DH9116 on the ground with the blades spinning and power off the transmitter. Note that nothing happens (no changes) for a second. Could be that you are flying forward, and instead of "lunging" it actually freezes for a second then falls out of the sky.

A common DH9116 problem is the radio noise (hash) suppression on the motors fails when the wires from the motor terminal end-cap are not soldered well to the metal motor case.

Note in the photos the wire soldered to the motor metal housing. Re-solder if you can, or see if you can easily break the wire off the case. It is very hard to solder to the motor metal case, made harder when they stopped using lead solder.
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Old Aug 27, 2012, 02:25 AM
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Old Aug 27, 2012, 02:29 AM
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Not sure exactly what you need to see if you need me to take a picture of a different area just let me know. I'll check that out when tomorrow when i take it out to fly Ribble thank you and i will check the motor as well.
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Old Aug 27, 2012, 01:13 PM
Crash and learn
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Originally Posted by Akira38 View Post
Not sure exactly what you need to see if you need me to take a picture of a different area just let me know. I'll check that out when tomorrow when i take it out to fly Ribble thank you and i will check the motor as well.
I don't see anything obvious.

Looks like you main motor does not have any wire soldered to the motor case.

Look under the daughter printed circuit board (PCB) at the nose. There should be a cylinder shaped 16MHz metal can crystal. Make sure the metal is not touching other components above or below.
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