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Miniature Aircraft Nitro/Gas Helicopters > Strange reaction from a CT
 
 
Jeff H
Key Veteran
Location: Cincinnati, OH

I was out flying my 91 CT yesterday. I came out of a dive with full pitch (11.5) man this thing was going super fast, and all of the sudden it did a violent pitch up to the canopy. What could cause this.


Specs are:
OS91 geared @8.18 w/ KSJ muffler
X-cell CT
mostly 9202 servos except rudder
Sab 680s
black MA 3D paddles
head speed better than 1800

My first thought was that the high speed (maybe 80-90mph) was to much for the 9202 servos and the elev servo couldn't hold the swash level but I'm not sure. Would stalling the retreating blade cause this? or maybe the dampening being too soft?

Never had this problem with the 61 in it, but it was alot slower.
03-25-2002 Over year old.
 
 
Doug
Elite Veteran
Location: Naples Florida....

As a Wag I would think the retreating paddle stalled.
03-25-2002 Over year old.
 
 
Phil Cole
Veteran
Location: Redwood City CA

It could be blades with the chord-wise CG too far to the rear, or the paddles. My X-Cell does similar things, using either the black or white 3D paddles. I can sometimes prevent it by being careful with the fore-aft cyclic pulling out of a dive, but not always.

Currently, I have the white 3D paddles with some weights about a third of the way out. Blades are 680 mm V-Blades.

Prior to that, I was using the Pro-II plastic paddles and I don't remember it being as bad. I may go back to them to see what happens.

I have heard that the V-Blade paddles are really good at not pitching up, but I have not tried them. I was going to try a set next time I felt like spending money on such things.
03-25-2002 Over year old.
 
 
Doug
Elite Veteran
Location: Naples Florida....

I think paddles with small leading edges might be more prone to stall. That may be why the "V" paddles are less prone.
03-25-2002 Over year old.
 
 
col
Veteran
Location: U.K. Ipswich.

hi, with retreating blade stall you should expect roll not pitch. more likely the servos letting go
cheers
col
03-25-2002 Over year old.
 
 
Doug
Elite Veteran
Location: Naples Florida....

I disagree retreating blade stall would cause loss of lift on the retreating blade which would presses 90 deg and cause a pitch up. In reality this starts at the root and slowly progresses outboard and causes heavy one per rev. vibration and a gradual pitch up that's why I wag'd that it was the paddles.
03-26-2002 Over year old.
 
 
FlyinBrian
Veteran
Location: USA

Hi,

Which fore/aft bellcrank do you have on it, new style plastic or metal?

The newstyle plastic one is not quite rite, full throw of the swashplate means you end up with near 50% atv's in the radio. Cut your atv's in half and you have just cut your servo's tourqe in half as well...

03-26-2002 Over year old.
 
 
Jeff H
Key Veteran
Location: Cincinnati, OH

Hi Auger,
I've got the pro bell mixers set at 1.6:1
03-26-2002 Over year old.
 
 
FlyinBrian
Veteran
Location: USA

Hi,

Thats a strange thing to be using in place of the fore/aft bellcrank
03-26-2002 Over year old.
 
 
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Miniature Aircraft Nitro/Gas Helicopters > Strange reaction from a CT
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