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Tandem Rotor Helis Vertol Chinook > Problems with my Chinook's first flight attempt...
 
 
errece
Senior Heliman
Location: Estevan, SK - Canada

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I took my Chinook for it's first flight but had some problems and couldn't lift it up. It's a nitro Chinook, with OS 50 Hyper and 6 volt battery regulated to 5.3volts, It has 6 S9252 servos

First when I turned it on, after the receiver connects with the radio all the servos started making small movements and I don't have a clue what could be the cause of that. I don't know if it's a gain problem but if I leave it without any movements input for some seconds it remains calm and then starts shaking all the servos again (Throttle not included in the movements, just both cyclics) and the movements are less than 1/2 mm but you can hear and see them moving a little bit. Even with the small movements the servos responded perfect to the input from the transmitter. I have a Futaba 12FGH with 2.4Ghz FASST and the receiver is a R6014FS, both brand new. I've been flying my Raptor and T-Rex500 with the same radio and 7 channel FASST receivers with no problems.

So since the movements were so little I decided to give it a try and started the engine.

When the rotors were picking up some speed the helicopter tried to lift up but the rear rotor first and I had to bring it down again. I tried again to take it into a hover but the rear rotor is lifting first and makes it impossible to leave the ground, the front rotor almost hits the ground. My question is if I have to make the rear rotor pitch lower than the front rotor since the manual does not mention anything about it but I think would be the only way to take off.

If anybody is running the same radio setup I would really appreciate if you can give me you end points values and/or the Mixer's values just to try if this would fix the problem.

Thank you...
06-14-2009 07:19 AM
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michael f
Heliman
Location: Adelaide - South Australia

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Errece, it's good to hear that another one has taken to the air (well almost), I don't have the same radio as you but I do run 2.4Ghz. You will probably find that a little gitter is normal, so I wouldn’t worry unduly about that. As far as the rear lifting off first that is quite normal, you have to hold rear elevator to get the front off the ground and both blades tracking horizontally, once they are in line it should lift off in that plane.
I would say that if you have the mixer values set as per instructions you should be well on the way to lift-off and your first flight.

Michael
06-14-2009 08:21 AM
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Helitronix
Senior Heliman
Location: Marlborough, MA - USA

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It's a good idea to get the collective pitch as balanced as possible between the front and rear so that you get a take off attitude that is what you want. This does not mean that the pitch is equal between both rotor heads. They could easy be different by a few degrees.

You certainly could hold in some elevator to counteract the movement. But, until you fly it, you don't know how much stick is required to alter the DCP enough to hold it steady. The approach of tuning the pitch on one of the heads so that it lifts off with little or no correction from you is a very reasonable thing to do. Once you have it working that way, you can always alter the pitch settings to make it take off differently.

Getting it right is a balancing act. When you adjust the pitch of the heads, you might induce a yaw due to the pitch differential. Which means you might need to trim that out, too. It can be a cyclical process for a while as you attempt to balance it all out.

Joel-
06-15-2009 04:12 PM
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michael f
Heliman
Location: Adelaide - South Australia

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Because of the weight distribution between the front and rear wheels it will always tip forward without any input with elevator to counteract this. I believe that if your C of G is in the correct position and you have equal pitch on front and rear blades and you lift the front with back elevator it will rise into a hover with front and rear rotor heads level.
When you set up your C of G, make sure that both rotor heads are at the same height.
The way to do this is to remove the body and blades, turn the model upside down, support the model at the C of G point and adjust weights so that both rotor heads leave the floor at the same time.

Michael
06-16-2009 12:51 AM
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doorman
Elite Veteran
Location: E.Berne, NY

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Front And Rear Pitch...

I agree with Joel on there being a slight diffenence between the fore and aft pitch....

There is a "fine" balance needed and starting at the "same" is absolutly correct, and then adjust from there slowly.... I do run a bit more in my front head then the rear.... and again, it is not a BIG difference, maybe one turn per link at the blade holder to help raise the front a little first....
But I also still have to put a little rear cyclic in at take off to go into the hover.... and then as stated, once the heads are level it should just about stay there....

Good Luck, Stan

Team Hirobo/MRC --- RCLIGHTS.NET ----- If there is a cure for this, please don't tell me about
06-16-2009 01:11 AM
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errece
Senior Heliman
Location: Estevan, SK - Canada

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Thank you very much for the tips... now I know that it's actually supposed to do that. I'll try next week to fly it and will keep you posted...

What about the servo movements?? is it a glitch or is it normal because of the mixer? maybe a gain adjustment?

Thanks
06-16-2009 05:28 AM
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autorotater
Heliman
Location: California

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There is something you need to check before your next flight. When I first got my chinook I tried to lift off and had some really strange repsonses. I checked the multi axis gyro settings by holding the helicopter with the engine off but the servos on. I would tilt the heli forward and see if the servos were reacting in the correct direction and found the manuals settings for the elev were backwards. I have heard of others having this same problem so definitely check this before flying.

As for the servos twitching I haven't seen this happen before so I would double check all your settings and make sure everything is where it needs to be.

Dan
06-17-2009 12:38 AM
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Tandem Rotor Helis Vertol Chinook > Problems with my Chinook's first flight attempt...
 
 
doorman
Elite Veteran
Location: E.Berne, NY

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Jitters.....

I am going to have to wait until I get home to see if mine is doing any jittering... but I do not recall seeing anything... but will look... I am wondering if you are getting a bit more then the 5.3 listed... have you checked that at the servo output on the rx.. especailly with a hot charge????
With all Futaba equipment, the default settings SHOULD be OK, but definetly a GOOD IDEA to check them.....
And you may want to reduce the elevator gyro gain by about 20 points to help you get started.... but try to get it into a hover first and see if it "bobs"!!! Then reduce if needed... mine would set pretty good, but once in forward it would pop the nose up pretty good... so I run about 20 points down from default on it....
Let us know how it goes.....

Good Luck, Stan

Team Hirobo/MRC --- RCLIGHTS.NET ----- If there is a cure for this, please don't tell me about
06-17-2009 04:01 AM
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Experience RC . Heli-Max . Hobby Hut

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Tandem Rotor Helis Vertol Chinook > Problems with my Chinook's first flight attempt...
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