Mathias Fröhlich wrote

> 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 counterpart 
> in JSBSim to the flightgear community ...

As I said, I think the 'wire surface' will do fine. KISS, at least at first.

 
> ... 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 spanned from the hook in the previous time step 
> and the hook in 
> this time step intersect a wire?
> If yes we can have a probability 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.

The wire slips through the hook, so I think that the action of the wire con
be regarded as a decelerating force acting at the hook attachment point,
along the aircraft centreline. Good enough I think.

> > 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!

Just like real life.
 
> > 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've seen it done in another flightsim. Back to bones?
 
> I think I will put several hundred wires onto KSFO's runway 
> to do the first 
> tests :)

Nothing like making it hard :-)

> > I can provide more details if you are interested.
> Yes, whatever you fell that could be useful.
> References ..

I'm looking in my library for some nice photos. 

Regards

Vivian



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