Bell UH-1

[IAHM-COL]

and I ve come to the conclusion that many of this community dont' treat the forum as a means to exchange expertise and guidance, more like a stomping sand box where to jerk egos and validate envy. So their posts are not informative but more like riddles from the sphinx

[bomber]

I don't understand the people that criticise my methods, saying your flight model doesn't do this that or the other.... They never say, unlike this flight model which does. I asked do other flight models do that..... and it goes deathly quiet.

I remember Alan telling everyone how I couldn't model bi-plane wings, I sent him my spreadsheets with calcs, references to the books I got them from and how I implemented the results of the equations in my flight models and he never replied, it went deathly quiet on the forum from him... but he never retracted what he said, he just left it there.

And those people that post up page images from a book, saying you should consider this... I engage them and ask them questions and I get no response, they don't have a clue. They just see something in a book and think that'll make me look good, ask them if they understand it and deathly silence ensues.

I have never insulted any flight modeler, I've tried to steer them into thinking a problem through, but that's as far as I've ever gone to saying 'that's wrong'... and there are a hell of a lot of wrong jsbsim flight models out there.

Thorsten is an absolute disgrace to the community and the moderators for allowing his posts are complicit.

[bomber]

Wrestling with the turbine rpm's at the moment...

Question.... the rotor clutch, does it disengage at over speed ?

[bomber]

ok I see the problem.

The turbine has low inertia, you start it and run it up. At a certain rpm the clutch slowly engages spinning the rotors. The rotors have high inertia and acts as a 'flywheel' on the turbine. This steadies the rpm fluctuation on the turbine with sudden increased load.

[bell_pilot]

Question.... the rotor clutch, does it disengage at over speed ?

No it does not. It disengages the rotor only at autorotation condition.

[bomber]

I have another question....

It's to do with turbine power output and the rotor blade pitch and how the 'collective' works.

A) In my mind I have raising the collective adjusts the rotor blade pitch directly.. doing so the power needed to maintain rotor (and by direct connection) the turbine running at the correct rpm's increases. But there's lag, power demand on the turbine increases, rpm's fall, governor opens throttle resulting in rpm's increasing and power increasing... best described turbines power follows rotor load

But if could just as easily be done a different way..

B) The alternative is that the collective adjusts the turbine throttle directly.. doing so the power output of the engine increases and the rpm's of the turbine and rotor (by direct connection) increases. The rotor governor adjusts the rotor pitch to reduce the rpm's to the desired value.. But there's a lag, rpm's on the rotor increases, governor adjusts rotor pitch to reduce rpm's... best described rotor rpm follows turbine power. (this is similar to constant speed prop)

Is B) ever used to your knowledge ?

[bomber]

And whilst I'm on....

The rpm gauge, rotor and engine rpm...

My thoughts on this are that the engine cranks up, the engine needle moves slowly to 60% at which point the engine starts. Rpm's above 60% start to engage the rotor clutch and as such the rotor rpm's start to increase. The turbine now has an ever increasing load on it as the clutch engages more and more with increased turbine rpm's. This has a slowly down effect on the rpm increase, but still it's increases... At about 85% the two needles become one as the clutch fully engages and remain as one through out normal operation.

Have I got this correct ?

[bell_pilot]

No.
Clutch is always fully engaged when engine powered on. We check if the blades start to turn or not at Ng %10. Start switch is also released at Ng %40, which is the point of engine start. Your thoughts about %60 and the others are unfortunatelly wrong.

This video is a good tutorial for huey engine start.
https://youtu.be/GxG5faTS_c4

[bomber]

not a problem

So are the two needles on the RPM gauge always together after 10% N1 ?

I'm assuming the RPM engine is N1 and not N2

And is the rotor rpm's the actual rotor rpm's or N2 ?

[bell_pilot]

1- Yes

2-) N1, N2 and Nr are all different gauges.
N1, as Ng (gas turbine) in huey is placed in a single gauge.
N2 (power turbine) is placed in double tachometer which you mentioned above.
Nr is rotor rpm.
So, you see N2 and Nr on the big double gauge.