On Thu, 27 Mar 2008 22:13:50 +0000, Carl Farrington
<carl@[EMAIL PROTECTED]
> wrote:
>Carl Farrington wrote:
>> Carl Farrington wrote:
>>> (on Phoenix, with both the Trex 450 3D and a Raptor 50 3D..)
>>> This is bugging the hell out of me. I was practicing funnels yesterday
>>> and doing OKish.. (OK, I was well chuffed..) I sort of started doing
>>> them by accident whilst practicing sharp (heli on side) turns.
>>>
>>> Anyway, what's happening now is that I fly the heli sideways, like a
>>> fast sideways drift, and then all of a sudden the heli flicks itself
>>> around so that it's facing the way it's heading. So for example I have
>>> the heli moving sideways to the left, at fairly high speed, then it
>>> just goes "flick" and all of a sudden it's flying forwards but in the
>>> same direction.
>>>
>>> Is this normal? Has the tail authority been overcome or something.
>>> Can't think why it wasn't a problem yesterday when I seemed to be
>>> doing really well at the funnels. Now I have this problem and I can't
>>> seem to do a funnel without the tail going all wrong.
>>>
>>> Any ideas?
>>
>> I meant 90 degrees.
>
>Somebody on Helifreak has complained about "tail blow-out" whilst doing
>hurricanes, whatever they are. Suggestion is to increase "tail power".
>
>I suppose "tail blow-out" kind of sounds like my problem doesn't it?
TR authority is directly related to head speed - not enough head
speed, not enough TR thrust. The 450 you want to see a head speed
2800+ RPM assuming you're running the blue TR drive gear.
I run my Raptor at 1950 RPM on the mains and don't have any blowout
issues.
I think what you're seeing isn't a gyro problem, it's a loss of tail
rotor effectiveness problem. If you're flying sideways to the left,
you're pumping a lot of relative wind through the TR is the same
direction as its thrust. Eventually, the relative wind is the same
(or greater) velocity as the thrust and voila! No more TR thrust
which will windmill the tail back behind the head. Effectively,
you've entered vortex ring state on the TR.
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