Fluttering blades!!?? HELP PLEASE

[Andy Man]

Have a Raptor V1.. and it has recently developed a problem...and hoping some
one here could help.

On fast decents and coming down to a quick stable hover, the blades seem to
start fluttering for a second or two, causing the heli to shake
quite violently. Throwing a tight loop, or roll can also sometimes cause
this problem.

The only way I can describe it, is that the blades look like a humming
birds wings for that second or two.

The blades are tracked, all the links are OK, the flybar is straight, and
everything on the head seems tight and as it should be.

I've come to the conclusion that the damper rubbers may have worn, but
before I go and order some, and take the head apart, can anyone
confirm my conclusions, or can anyone suggest any other cause for this.

The blades I'm using are BBT.


Andy Man.

[RJ]

Hi there.
Seems like you have encountered the problems approx. 50% of the people
flying Raptor V1 have.... Blade flutter around zero pitch.
There is a way of fixing this, by reversing the blade-holders and flybar
setup. Go here: http://www.raptortechnique.com/ for details and additional
tips for your Raptor.

Good luck!
:)RJ
"Andy Man" <andy@acwman.freeserve.co.uk> wrote in message
news:bc0u32$rjh$1@news6.svr.pol.co.uk...
> Have a Raptor V1.. and it has recently developed a problem...and hoping
some
> one here could help.
>
> On fast decents and coming down to a quick stable hover, the blades seem
to
> start fluttering for a second or two, causing the heli to shake
> quite violently. Throwing a tight loop, or roll can also sometimes cause
> this problem.
>
> The only way I can describe it, is that the blades look like a humming
> birds wings for that second or two.
>
> The blades are tracked, all the links are OK, the flybar is straight, and
> everything on the head seems tight and as it should be.
>
> I've come to the conclusion that the damper rubbers may have worn, but
> before I go and order some, and take the head apart, can anyone
> confirm my conclusions, or can anyone suggest any other cause for this.
>
> The blades I'm using are BBT.
>
>
> Andy Man.
>
>

[Andy Man]

Cheers RJ

Now I do recall this problem with the V1, and having looked back in my past
heli magazine, has the solution to the problem...Just as you
have described on raptortechnique.

Never had the problem before, but will try and just stiffen up the head to
see if the problem dissapears, and if not will go
the whole way and change all the bits round on the head!

Cheers for that

Andy Man

"RJ" <rujoh2@tiscali.no> wrote in message
news:hl_Ea.14652$Jp3.463199@news010.worldonline.dk ...
> Hi there.
> Seems like you have encountered the problems approx. 50% of the people
> flying Raptor V1 have.... Blade flutter around zero pitch.
> There is a way of fixing this, by reversing the blade-holders and flybar
> setup. Go here: http://www.raptortechnique.com/ for details and additional
> tips for your Raptor.
>
> Good luck!
> :)RJ
> "Andy Man" <andy@acwman.freeserve.co.uk> wrote in message
> news:bc0u32$rjh$1@news6.svr.pol.co.uk...
> > Have a Raptor V1.. and it has recently developed a problem...and hoping
> some
> > one here could help.
> >
> > On fast decents and coming down to a quick stable hover, the blades seem
> to
> > start fluttering for a second or two, causing the heli to shake
> > quite violently. Throwing a tight loop, or roll can also sometimes cause
> > this problem.
> >
> > The only way I can describe it, is that the blades look like a humming
> > birds wings for that second or two.
> >
> > The blades are tracked, all the links are OK, the flybar is straight,
and
> > everything on the head seems tight and as it should be.
> >
> > I've come to the conclusion that the damper rubbers may have worn, but
> > before I go and order some, and take the head apart, can anyone
> > confirm my conclusions, or can anyone suggest any other cause for this.
> >
> > The blades I'm using are BBT.
> >
> >
> > Andy Man.
> >
> >
>
>

[Paul Goelz]

On Mon, 9 Jun 2003 13:40:55 +0200, "RJ" <rujoh2@tiscali.no> wrote:

>Hi there.
>Seems like you have encountered the problems approx. 50% of the people
>flying Raptor V1 have.... Blade flutter around zero pitch.
>There is a way of fixing this, by reversing the blade-holders and flybar
>setup. Go here: http://www.raptortechnique.com/ for details and additional
>tips for your Raptor.

I had it bad with the second or third set of TT woodies I used. It
would woof at anything over about 1700 RPM..... violntly and
unpredictably. Cured it totally completely and utterly by changing to
Hobby Taiwan woodies after a crash. The Hobby Taiwan blades are
cheaper, better balanced and they fly great considering they are cheap
woodies.

A very knowledgeable flying buddy maintains that blade flutter is
primarily a blade chordwise CG issue and I tend to agree with him.
You can stiffen things and do all sorts of other changes but if the
blades are unstable all you can do by changing the head setup is cover
it up. If however the blades are stable, there is no need.

He also thinks there might be an issue with the blade covering
material lifting in flight, changing the airfoil and center of lift
enough to possibly cause instability.

Remember, I changed virtually nothing other than the blades themselves
and the flutter went away never to return..... it's been almost two
years now since my last woof. I am still flying the same (original)
thrust bearings, swashbar, linkages and ball links. Changed a couple
feathering spindles.....

Paul

Paul Goelz
Rochester Hills, MI
paul at pgoelz dot com
http://pgoelz.com

[Peter Seddon]

This sounds like VRS (Vortex ring state) that occurs when the heli descends
with very low forward speed in its own rotor downwash. To overcome it push
the stick forward to give some forward speed. For full size there are three
conditions for VRS to occur:
1. Powered flight (as opposed to autorotation)
2. An upward flow of air from below that opposes the induced flow
3. Low airspeed
I can only talk fullsize. What it does is to create very high rates of sink
and loss of control with some vibrations. To recover push the stick forward
to exit the dirty descending air.

Regards Peter


"Andy Man" <andy@acwman.freeserve.co.uk> wrote in message
news:bc0u32$rjh$1@news6.svr.pol.co.uk...
> Have a Raptor V1.. and it has recently developed a problem...and hoping
some
> one here could help.
>
> On fast decents and coming down to a quick stable hover, the blades seem
to
> start fluttering for a second or two, causing the heli to shake
> quite violently. Throwing a tight loop, or roll can also sometimes cause
> this problem.
>
> The only way I can describe it, is that the blades look like a humming
> birds wings for that second or two.
>
> The blades are tracked, all the links are OK, the flybar is straight, and
> everything on the head seems tight and as it should be.
>
> I've come to the conclusion that the damper rubbers may have worn, but
> before I go and order some, and take the head apart, can anyone
> confirm my conclusions, or can anyone suggest any other cause for this.
>
> The blades I'm using are BBT.
>
>
> Andy Man.
>
>