Mathias Fröhlich wrote a long time ago:

> Sent: 08 July 2004 10:38
> To: FlightGear developers discussions
> Subject: Re: [Flightgear-devel] status of aircraft carrier
> 
> On Mittwoch, 7. Juli 2004 21:32, Vivian Meazza wrote:
> > It would be a shame if we can't model individual wires, then we could
> > experience hook-skip whereby the hook can miss all the wires. A chum of
> > mine went around 14 times trying to catch a wire in a Gannet aboard HMS
> > Hermes. But I think the 'wire-surface' would do quite well.
> Hmm, let me explain a bit.
> I for myself will be happy to model the relality in detail.
> That wire-surface has grown from an experience I have made during the past
> half year when I wanted to push changes into JSBSim. For example, I often
> proposed a mechanical system which much better models gears. This is not
> hard
> to do from my point of view. But Jon always told me that this stuff is
> tooo
> complicated and it is better to keep things as simple as possible.
> So that 'wire surface' has really grown from a extrapolation of my
> couterpart
> in JSBSim to the flightgear community ...
> 
> ... I am happy with individual wires. It is a bit harder since we do only
> have
> the position of the hook at discrete times. But I have also thought about
> that:
> Does the surface spaned from the hook in the prevous timestep and the hook
> in
> this timestep intersect a wire?
> If yes we can have a propability where we catch. And if so apply two
> forces
> from the ends of the wire.
> 
> So the API between the FDM and Flightgear will look something like a
> function
> taking a geometry of a rectangle and returning a bool which tells if a
> wire
> is caught and where the two points are where the wire leaves the deck. And
> as
> usual, how these two points move.
> 
> > It's very difficult to manoeuvre an aircraft onto a cat. You should
> > consider modelling the self-aligning rollers and chocks which bodily
> shift
> > the aircraft into the correct  position. This need be no more than a
> area
> > on the deck on which, if the main wheels are resting on it, a press of a
> > key will automatically correctly position the aircraft.
> So with a little jump to the right :)
> 
> Sounds sensible!
> 
> > A key press should signify when the pilot is ready for launch, then the
> cat
> > should fire after a random interval after.
> >
> > The Jet Blast Deflectors (JBDs) could also be modelled.
> Hehe :)
> 
> And a cat officer showing you where to taxi :)
> And all these guys with yellow and green and whatever jackets :)
> 
> One by one. But yes ...
> 
> I think I will put several hundred wires onto KSFO's runway to do the
> first
> tests :)
> 
> > I can provide more details if you are interested.
> Yes, whatever you fell that could be useful.
> References ...
> 
> Thanks in advance!

In the next couple of days or so I will have completed a model of a Seafire
IIIc. It has a functioning hook, so I was set to wondering if there was any
progress on the arrester wire project???

In the course of the work on Submodels, I realized that it should be
possible to re-use some of that code to provide the location of the hook on
a near frame-by-frame basis in geodetic terms. Intersection with a 'wire
surface' should be possible to calculate. But then we need to apply a
suitable force to the fdm. I wonder if a mega-brake would do the trick??? At
least as a first try.

A couple of pictures are at:

http://myweb.tiscali.co.uk/vmeazza/FlightGear/seafire-001.jpg

http://myweb.tiscali.co.uk/vmeazza/FlightGear/seafire-002.jpg



Regards,

Vivian 




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