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Parking positions - Stop at front wheel of aircraft

Z

Ziegenhorn

Messages
79
It appears that AFCAD parking positions use the aircraft centre point. How can I make different size aircraft types stop at the same position of the front wheel with AFCAD? (or have the the same start position of different sized aircraft when starting up at an airport from the menu)?

Burkhard
 
Hi, Burkhard

Ziegenhorn said:
How can I make different size aircraft types stop at the same position of the front wheel with AFCAD?
Burkhard
Click to expand...

Since you mention AFCAD, I guess you refer to FS9. However, for FSX, the SDK says:

There are two ways to specify the position of the parking spot. The first is to use a lat/lon pair that will give the exact coordinate. The second is to use a biasX/biasZ pair that specifies the displacement of the parking space from the airport reference point.
Click to expand...

Code: 
<TaxiwayParking
      index="0"      
      biasX="96.336998" 
      biasZ="-620.479980"
      heading="178.700000"   
      radius="31.000000"   
      type="GATE_SMALL"  
      name="GATE"  
      number="1"
      airlineCodes="UAL, AA, BA"
      pushBack="BOTH"/>

Regards,

José
 
José said:
There are two ways to specify the position of the parking spot. The first is to use a lat/lon pair that will give the exact coordinate. The second is to use a biasX/biasZ pair that specifies the displacement of the parking space from the airport reference point.
Click to expand...
I don't think that using biasX/biasZ will help, since biasX/biasZ is converted to lat/lon by bglcomp. Incidentally, FS9 also supports biasX/biasZ.
 
In FSX there are teeOffsets that can perform this function. In Fs9 I do not think those attributes existed.
 
It appears that AFCAD parking positions use the aircraft centre point. How can I make different size aircraft types stop at the same position of the front wheel with AFCAD? (or have the the same start position of different sized aircraft when starting up at an airport from the menu)?
Click to expand...

Like Scruffyduck said, in FSX we are now using a teeoff Meter dimension to simulate where the front wheel is positioned on the ramp. However, where the plane stops is a function of one half wingspan, center postion, and the parking spot radius.

In FS9 we simulate where the front wheel stops by using a standard that was developed by PAI. This parking standard works with adjusting the model.mdl value to match the size parking spot. All of this is once again dependent on where the AI Plane designer set the center point of the plane.

Go to the PAI AFCAD site and download the Recommened Radius.htm parking standard document. This document will tell you what to set the model.mdl radius to (same radius for same type size plane) and what size to set the parking spot radius.

Once this is done as per the standard then all aircraft of type and size will park more precisely.

Work is being done on a standard for FSX using the half wingspan rather then the model.mdl radius. Once the FSX standard parking document is finished then a standard teeoff distance will be established for many different type AI Planes.

Model.mdl radius is still equally important in FSX for Pushback distance, hold short nodes entering and leaving the runway and the spacing between AI Planes such as inline on a taxiway so the nose of one AI Plane is not in the restroom (toilet) of another AI Plane.
 
Last edited:
A key, perhaps the key issue is that aircraft modelers do not have a standard, or common way of building their aircraft so that a common reference point is used.

When one AI B747 is lined up in a parking spot, a different B747 by a different modeler will usually line-up with the nose wheel in a different location.
 
Ziegenhorn said:
What about in FS9?
Click to expand...

I think Jim answered that

In FS9 we simulate where the front wheel stops by using a standard that was developed by PAI. This parking standard works with adjusting the model.mdl value to match the size parking spot. All of this is once again dependent on where the AI Plane designer set the center point of the plane.

Go to the PAI AFCAD site and download the Recommened Radius.htm parking standard document. This document will tell you what to set the model.mdl radius to (same radius for same type size plane) and what size to set the parking spot radius.

Once this is done as per the standard then all aircraft of type and size will park more precisely.
 
Hallo Jim,

in one of your postings above you wrote:
All of this is once again dependent on where the AI Plane designer set the center point of the plane.
Click to expand...

Where is this center point defined?
I looked through several "aircraft.cfg-files", all I could find is the "reference_datum" under [weight and balance] and as I understand that datum, it defines only three planes, not a point.

And further: is this point during the design process defined in GMax?
If yes, Where?

your advice (as always) is highly appreciated by

Helli
 
reference_datum_position is a point.

If the position is 0, 0, 0, that is zero in 'x' plus zero in 'y' plus zero in 'z' and that is a single point.
 
Helli said:
Where is this center point defined?
Click to expand...

I am no aircraft designer, but I do believe the center point is defined in the model (mdl file) itself.

That's why aircraft designers need a standard of sorts. If it could be set in the aircraft.cfg then that would be gravy for us.[/QUOTE]
 
Hello Graham
Hello Rhett

@Graham: the 3 values, which you show for the reference datum are - as far as I understand it - 3 horizontal "planes" (1/4 Chord, centerline, waterline). I do not see them intersecting each other (or do they?).
So where is the point?

@Rhett: that is exactly my question: where in a GMax-model is the "central point" defined - I am aware, that the various designers define their own point.
But for an existing aircraft I would like to be in the position to see, where the designer placed it.

So the question is still open.

But many thanks for your replies.

Helli
 
I don't have it on this computer - but didn't/ doesn't ACM - Aircraft Container Manager display the reference point?

Unfortunately it's apparently no longer available or supported.

And it doesn't properly display new models with XML based animations.

I have a computer at home with the full paid version and will let you know.
 
I know a lot of people wonder why there seems to be no consistency with the use of these three reference points between different vendors. Some of the differences result from from ignorance as to how these three ref points are related, but probably most of it is the result of different ways that 3-views report the datum to the modeler.

In many cases, the manufacturer uses the notional arrangement whereby the reference_datum_position is the "furthest point forward on the aircraft" (i.e., tip of the nose or prop spinner), and the CoG is then shown from that point, as shown as the "gold point" in the picture below.

In other cases, the manufacturer (or 3 view author) has specified the 1/4th chord point as the x-dimension based on it's distance from the furthest point forward on the fuselage (again, the tip of the nose or prop spinner). This is illustrated as the "blue point" in the picture below.

In some cases though, neither the 3-view author or the manufacturer has provided complete dimensional data, so "best guesses" must be made, such as in the picture below! ;)

In every case however, the only way for the SIM to know where these points are located is to make reference to a common, established point in the .mdl file itself, which is of course the "zero point: 0,0,0" Hence, all measurements begin there.

Also, in every case, the FDE author and/or modeler must establish the reference_datum_position according to the SDK's definition: 1/4 chord, centerline, waterline!

Many modelers and/or FDE authors wimp out and simply make the "Origin" and "reference_datum_position" identical. This will work in the case of small a/c because there likely isn't much - if any - distance offset to begin with.

Obviously, in the case of those flying cigar tubes, the difference is much greater, so it is critical to establish early in FDE development those points accurately.

fsreferencepoints1fu.jpg
 
Helli said:
@Graham: the 3 values, which you show for the reference datum are - as far as I understand it - 3 horizontal "planes" (1/4 Chord, centerline, waterline). I do not see them intersecting each other (or do they?).
So where is the point?
Click to expand...

That is an incorrect understanding. The three values represent a single point in space, as measured from the model's visual origin coordinate system: 0,0,0...
 
Sorry, Bill, that I took so long to tell you my appreciation of your help and explanation.
Working on an urgently requested translation for several days my mind was taken away from aircraft design.

But now thanks to you and to the other thread participants I have ample info to carry on.

best greetings

Helli
 
Hello Bill

some second thoughts:

the figure, which you postet above showing the reference-point situation suggests, that it came from a manual, handbook or such.

Where did you get it from (or is it your own making?)

Since aircraft design is so complicated, any further reading material on the subject would be highly welcome.

Many thanks

Helli
 
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