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e-E-Sky Honey Bee- Lama- Belt CP- E-Smart > Forward cyclic gives me forward/right cyclic on my crashed HBK2
 
 
BOB WHO?
Senior Heliman
Location: downey, ca., usa

I crashed my King today (practicing figure 8's Doug) and now I have a problem I can't figure out. I broke skids- bent the spindle- trashed the blades of course- broke some teeth on a servo gear and that was about it. So I fixed or replaced everything I had noticed was bad, then checked the entire head (stock) system manually and all seemed ok. I wanted to re-check everything before I installed blades so I fired it up and got some head speed going and tried all cyclic commands. To my surprise, with forward (only) cyclic the plane of the head tilted as if I gave it forward & right cyclic together. Everything's off by about 45 degrees. Right cyclic (only) delivers as if I gave right & back, etc... I thought I checked everything: servos are working correctly, in throttle hold mode all looked like it was working fine as I checked all commands, the swashplate was quite level as I tested the collective. And this heli was flying really well before the crash, everything was dialed in. I hope it is something simple that have overlooked. Any Ideas? Thanks!

Bob
03-11-2008 06:54 AM
 
 
shizack
Key Veteran
Location: Augusta, GA USA

You say you've checked everything, and I believe you (I WANT TO BELIEVE!!), but it sure sounds like the back right servo (PIT servo) isn't moving when you input cyclic.

The more they overthink the plumbing, the easier it is to stop up the drain.
03-11-2008 07:36 AM
HOMEPAGE  
 
 
BOB WHO?
Senior Heliman
Location: downey, ca., usa

I checked each servo indivdually (disconnected from swash) and they work well. I even gave each servo arm some resistance to check them under stress. They seem fine.
03-11-2008 07:51 AM
 
 
shizack
Key Veteran
Location: Augusta, GA USA

OH!!! Just re-read your post. You haven't installed the blades yet? If this is so, then all is well. Just trust me. I don't have the time or sobriety to do a write-up on "gyroscopic precession". Look it up if you feel like having your brain melted. In a nutshell, actual response happens ~90º out of phase with input.

Imagine a bicycle tire spinning horizontally on its bare axle. If you hit the back of it, it will tilt to one side.

The more they overthink the plumbing, the easier it is to stop up the drain.
03-11-2008 08:06 AM
HOMEPAGE  
 
 
Gregor99
Elite Veteran
Location: Western Wa

No need to spool up, just watch the swash and servos. While giving forward cyclic, both rear servos move the same amount up and front should go down. It sounds like your right rear servo is not operating correctly and may not moving up at the same rate as the left rear.
03-11-2008 08:10 AM
 
 
Gregor99
Elite Veteran
Location: Western Wa

Quote 
You haven't installed the blades yet?
Good call, I missed that as well. You can tell if the servos are moving correctly by watching the swash when applying cyclic input. It you push forward, the swash will tilt forward. Tilt sideways and the swash tilts sideways.

As this input makes it's way up to the rotor, its applied 90 degrees counter clockwise of the swash. I've heard it described as the blades needing the additonal rotation time to "fly up" or "fly down" to the desired position. Looking down from the top of the head, from the back, forward input starts applying negative pitch at the 9 O-clock position and stops applying pitch at 12 o-clock.

Likewise positive pitch starts applying at the 3 O-clock position and ends at the 6O-clock position.
03-11-2008 08:36 AM
 
 
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e-E-Sky Honey Bee- Lama- Belt CP- E-Smart > Forward cyclic gives me forward/right cyclic on my crashed HBK2
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