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HomeAircraftHelicopterCentury Radikal G20-30 N640 Hawk Predator › When the madien goes bad.............
05-11-2011 11:31 AM  7 years agoPost 1
Frank Bostwick

rrElite Veteran

Cincinnati Ohio

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Ive built and crashed many many Century 50s. I consider myself at the very least competent. I rarely have more than tracking and Norm mode tail adjustments to make on a maiden. I used to fly woodies on the first few flights, just in case but have not done so in a year or so.

After last nights maiden, I guess Ill go back to woodies

Think is, Im not sure what the problem was........
I only had about 1/2 tank burned and could tell I had some issue with tail control. It was kicking, nose left in a hover. I landed, adjusted gain and took off, with the same result. Not wanting to push it, I brought it back and hit T hold (from 5'.
Never had this happen but as soon as I hit T.hold, the tail gave out and it started spinning nose left.........the result was an off kilter auto, boom strike and new set of blades needed. But why?

Ive come up with 2 possibilities. I noticed I needed a lot more RPMs to engage the clutch (after a pretty good crash in which clutch saw some wear) So I thought perhaps the clutch was sprung sticking in the ON position. Hit T.H., Motor to idle clutch on, Head speed drops quick, resulting in loss of tail authority....
Checked it just now, clutch bell spins freely so its not the cause

Next up, the one way........Seems to be working correctly. Gear on the crown gear is tight, Ill inspect tail internals later but doubt the problem is there......New (4-5 flight old) BLS251, miniG with many flights on it.

Your guesses, please

RIP ROMAN

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05-11-2011 02:29 PM  7 years agoPost 2
al_voisine

rrNovice

Grand Falls, New Brunswick, Canada

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I don't have the expertise of the others, but something to think about:
With the TH on and thus no torque forcing the nose to turn left, the gyro and tail servo should have re-centered. The fact that it turned left says that the tail pitch did not change back to neutral.

My understanding is that without torque from the motor, the heli should not rotate unless the tail blade pitch is somehow forcing it around.

Experts will chime in and correct me if I'm wrong.

Al

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05-12-2011 08:37 PM  7 years agoPost 3
Frank Bostwick

rrElite Veteran

Cincinnati Ohio

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Its a new Tail servo and newer gyro.....
Only other thing I can think of is the fact I added the 2 bearing mod to the counter gear.....
No other help guys? What I gotta pull teeth now?
I still can believe I took out a new set of rotortechs a boom, boom supports and a TT!
They didnt even get a full tank on em

RIP ROMAN

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05-13-2011 12:23 AM  7 years agoPost 4
rotormonkey

rrKey Veteran

Ottawa, ON - Canada

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Al: Your logic is solid with one small exception. Torque causes the heli to nose left, so the tail is pushing the nose RIGHT to compensate when hovering. If the slider never moved when he hit TH then it would have spun to the right when the torque was removed - not left.

That said, with just about any failure the gyro should have moved the tail servo to compensate unless there's a problem with the gyro or tail servo. Just because your stuff is new doesn't mean it works. Check for bad connections, frayed wires, or just odd behavior with the tail servo. That's where my money's going just because I can't think of anything else really.

Could be a stripped TT gear or something too...

If it can't hover, it ain't worth flying.

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05-13-2011 12:28 AM  7 years agoPost 5
Heli_n_Back

rrNovice

melbourne,victoria - australia

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A possible thought, were you adjusting the rudder digital trim on the radio.
Some sets like the Dx7 can have different trims for flight modes and TH.

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05-13-2011 01:02 AM  7 years agoPost 6
CX1

rrKey Veteran

Canada

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Its a new Tail servo and newer gyro.....
Only other thing I can think of is the fact I added the 2 bearing mod to the counter gear.....
the intermediate gear either holds or slips and has nothing to do with tail rotor.

was the tail rotor spinning before it hit ?

either a radio setting or something in tail drive ( grub screw)

.
I'll guess on a grub screw

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05-13-2011 02:08 PM  7 years agoPost 7
Frank Bostwick

rrElite Veteran

Cincinnati Ohio

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T rotor was spinning prior to ground contact. I have not had time to dig into this one as I have 2 others (t600s) that I am trying to get on the flight line.
Was not adjusting trim (I never adjust trim on the tail servo)
Radio set up is years old, w/o changes (excepting t/r gain). Not impossible the programming got messed up but unlikely

I am going to inspect all of it this weekend and see whats to see.

If the counter gear and or one way was slipping in flight, Id see a tail twitch (what I had), If it was locked up, that would cause a rapid HS loss at T hold. Hey Im guessing at this point.
Never seen a problem like this one.....

RIP ROMAN

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05-13-2011 11:47 PM  7 years agoPost 8
al_voisine

rrNovice

Grand Falls, New Brunswick, Canada

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Rotormonkey - Thanks for catching my mistake. You're absolutely correct.

Next time - pay attention to what I mean, not what I say! ....LOL

Good catch!

Al

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05-14-2011 02:18 AM  7 years agoPost 9
CX1

rrKey Veteran

Canada

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anythings possible
when I had a owb intermediate gear slip, the engine would rev up making me auto but I had rudder

any pics of the carnage ??

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05-20-2011 12:58 PM  7 years agoPost 10
jschenck

rrProfessor

La Vista, NE.

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I'd bet the gyro gain was at 0 for throttle hold flight mode. I've done that.

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