lyk2fly

My Feedback: (3)

Hi all, I just recently purchased a used Hawk IV on ebay. I'm used to a Lite Machines so to me this thing was huge. I wasn't too sure about flying it but apparently 1 1/2 years with my LMH has done me some good. The Hawk flew great......I can't believe the lift off speed!!!! It is obviously a great heli!!! The LMH is fixed pitch so it doesn't hop off the pad like the Hawk. I do however have one problem that I hope someone can help me with. Every so often during the flight.....usually when lowering throttle and collective......the blades go wildly out of track. The heli shakes violently. You can hear the noise....sounds like a flag flapping in the breeze. When you raise the throttle and collective the episode usually stops and all is well again. What do you think???? Where should I start to look????? Any help will be appreciated.
Thanks,
Mark
P.S. I have balanced the blades per owners' manual instructions.

wisdom-seeker

The next place I would look is at the blade grips. Check to see how tight they grip the blades. It must not be too tight or too loose. Also check to see if you may have a problem with the dampers. Perhaps they need lubrication. If one is sticky, it might explain what you are seeing. If it's not one of those two things, then I would go over the entire head from the swash on up, looking for loose or sticky parts.

An additional thought is that you could have a thrust bearing installed backwards as well.

lyk2fly

My Feedback: (3)

Thanks wisdom-seeker, I tightened the feathering spindle nuts.....it seemed that the blade grips had a good amount of "slop". It seemed to correct the problem until another problem occurred. The collective suddenly lowered without any input from me......the heli hit hard but wasn't harmed. I'm now trying to find out what happened to cause this.....servo or glitch???? Anyway....about the feathering spindle nuts.....how tight should they be? The manual doesn't make reference to how snug they should be.
Thanks
Mark

fiat

Mark, Alan here, first you made a good choice in heli's. As you know I bought a hawk sport and I have 8 gallons thru it so far I LOVE IT. I now have carbon blades on it and I am looping and doing some little inverted flight as well. As far as your question about the feathering shaft nuts, They get tightend down snug I made mine as tight as I could concidering the size of the feathering shaft and nuts.. I have NEVER had any wild blade problems like you described. Make sure that both blades are very free to move in the pitch control and if you think you have a glitch problem try another crystal I had 2 bad ones. P.S. nice not to have to play with the engine before each flight huh ?? Alan

lyk2fly

My Feedback: (3)

Thanks Alan for the info.....I think that the nuts were loose.....they certainly were not "snug". I think that I corrected the "glitch" as well. I hovered one tank.....and will hover a 2nd tank before flyin' high and far. I think the problem with the collective dropping was my mis-use of the Futaba transmitter. I was using the idle-up feature to keep the engine at idle not realizing that the switch done some collective changes as well......too much radio for my simple mind!! Anyway I have "inhibited" that particular function until I need it. It is good to hear from you.....loops and inverted flying......too cool!!!! Once I get used to this machine I will probably try it......I have done some on the sim. And yes.....the Hawk seems to be an excellent machine.
Mark

AutoMike

You might have the throttle curve to low at low pitch as well. I've had things like that happen to helis in the past and the rotor speed was usually the problem if everything else is in balance. Mike

lyk2fly

My Feedback: (3)

Thanks to all......I have a lot to learn about this collective pitch but the heli flew great this evening......lots of fff. I still feel like I am having a slight glitch in the collective but the wind was blowing also.....it may just be my imagination.....also I am not using the best of servos on the collective.....I plan on upgrading before I fly too much more. I will be back with more questions.....believe me!!!!
Mark