Re: [Jsbsim-devel] Fwd: Helicopter

[Sean M. <se...@se...>]

Hi Simon

Are you adding code to FGPropeller to implement some of the functionality that is currently in FGRotor but not in FGPropeller currently?

Are there some aspects of FGRotor’s functionality that you’re ignoring because you don’t think they’re useful for your needs?

What things did you notice in FGPropeller that FGRotor can’t currently do? Could potentially be useful to add them to FGRotor for users of FGRotor.

What’s quite useful is Thomas references the equations etc. that his code is based on, e.g.

// Flapping angles relative to control axes /SH79/ eqn(32)
void FGRotor::calc_flapping_angles(double theta_0, const FGColumnVector3 &pqr_fus_w)

    <dt>/SH79/</dt><dd>Shaugnessy, J. D., Deaux, Thomas N., and Yenni, Kenneth R.,
              "Development and Validation of a Piloted Simulation of a
              Helicopter and External Sling Load",  NASA TP-1285, 1979.</dd>

https://ntrs.nasa.gov/citations/19790005912

I’m currently using FGotor for the helicopter models I’m working on so I’d be interested to know what you see as the pros and cons of using FGRotor versus FGPropeller.

Cheers

From: Simon Julie Morley via Jsbsim-devel <jsb...@li...>
Sent: Monday, October 26, 2020 10:09 PM
To: Development issues <Jsb...@li...>
Cc: Simon Julie Morley <sim...@go...>
Subject: [Jsbsim-devel] Fwd: Helicopter


  yeh I have, and there's nothing in it I can't do with a propeller, and actually there are things in the propeller code that the rotor can't do.... so using rotor is a net less...

Simon

---------- Forwarded message ---------
From: Sean McLeod <se...@se...<mailto:se...@se...>>
Date: Mon, 26 Oct 2020 at 20:00
Subject: RE: [Jsbsim-devel] Helicopter
To: Simon Julie Morley <sim...@go...<mailto:sim...@go...>>

Hi Simon

Have you looked at the FGRotor code to see what helicopter specific stuff it models that isn’t modeled by FGPropeller?

Cheers

From: Simon Julie Morley <sim...@go...<mailto:sim...@go...>>
Sent: Monday, October 26, 2020 5:19 PM
To: Sean McLeod <se...@se...<mailto:se...@se...>>
Subject: Re: [Jsbsim-devel] Helicopter

Hi Sean,

I'm not sure about using prop resulting in a lesser quality or that rotor offering greater functionality...

I remain open minded to the possibilities

Simon.

On Mon, 26 Oct 2020, 13:08 Sean McLeod, <se...@se...<mailto:se...@se...>> wrote:
Hi Simon

I’m sure you can model a helicopter using FGPropeller etc. as a basis, but I would imagine it would be a 1st order approximation since there are a number of dynamics that FGPropeller doesn’t model compared to FGRotor, so FGRotor would more easily allow for a higher fidelity model.

Cheers

From: Simon Julie Morley via Jsbsim-devel <jsb...@li...<mailto:jsb...@li...>>
Sent: Sunday, October 25, 2020 11:59 PM
To: Development issues <jsb...@li...<mailto:jsb...@li...>>
Cc: Simon Julie Morley <sim...@go...<mailto:sim...@go...>>
Subject: Re: [Jsbsim-devel] Helicopter

Hi Sean,

To be honest I wanted to try and see if I could make a helicopter using the prop code, because I couldn't see why not.

On Sun, 25 Oct 2020 at 21:12, Sean McLeod <se...@se...<mailto:se...@se...>> wrote:
Hi Simon

I’m just getting started again in terms of looking at JSBSim based helicopter models.

Thomas Kreitler improved the FGRotor model between 2010 – 2012.

https://github.com/JSBSim-Team/jsbsim/blob/4840a621dafe1ce64970990ddaec3e86a1c7e082/src/models/propulsion/FGRotor.cpp

He also added a fairly detailed helicopter model for the AH1S:

https://github.com/JSBSim-Team/jsbsim/tree/4840a621dafe1ce64970990ddaec3e86a1c7e082/aircraft/ah1s

In general there are very few JSBSim based helicopter models around when I last looked.

Cheers

From: Bill Galbraith <bil...@gm...<mailto:bil...@gm...>>
Sent: Sunday, October 25, 2020 8:08 PM
To: 'Development issues' <jsb...@li...<mailto:jsb...@li...>>
Subject: Re: [Jsbsim-devel] Helicopter

Simon,

I had devoted some brain cells towards that idea a while ago, but never implemented it.

Imagine a point mass, with a point vertical force located above it. At 50% collective, vertical force equals weight. Cyclic tilts that vertical force fore/aft, left/right. Displacing the cyclic yields a slight loss (sine of angle) loss of lift, requiring slightly more collective.

The painful part comes when you try to fly it with a joystick. When you release the joystick, the cyclic returns back to neutral, the aircraft will slow to a hover. You basically need a joystick that has a trim lever, or allows you to reestablish the trim point.

Enough to get your brain cells excited?

Bill

From: Simon Julie Morley via Jsbsim-devel [mailto:jsb...@li...]
Sent: Sunday, October 25, 2020 1:41 PM
To: Development issues <Jsb...@li...<mailto:Jsb...@li...>>
Cc: Simon Julie Morley <sim...@go...<mailto:sim...@go...>>
Subject: [Jsbsim-devel] Helicopter

Anyone here ever done one ?

Want to talk about it, share knowledge ?

Simon



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