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Tutorial: Pushback Tug Default Position

It has been requested on several occasions that ADEX indicate the position of the pushback tug and T Offsets when working with Gate and Cargo type parking spots.

The good news is ADEX has the ability to show where the pushback tug will sit. All the work on this dates back to Version 0.62 (sept 2007) which were beta versions not available to the public since ADE had yet to be released.

I am going to show the math that FSX uses and then show how Jon coded a parking spot to reflect the math.

The distance formula FSX used is very simple. I will use the 10M gate radius as the smallest value and then show the multiple of 10's value.

The measurement is from the center of the parking spot radius to the back of the Tug because its the back of the tug that normally ends up inside a Terminal building.

10M = 18.5M from center of the parking spot to the back of the Tug
20M = 28.5M
30M = 38.5M
40M = 48.5M
50M = 58.5M

You can see that starting with a 10M parking spot the pushback tug moves back by 1M based on a increase of 1M in parking spot radius.

18M = 26.5M from the center of the parking spot to the back of the Tug

The actual Tug is 9.0M long if you measure the total length (drawbar locking wheel mechnism to the hitch on the very back) so where the drawbar attaches to the front of the tug is center of the tug which is 1/2 the length (4.5M)

If you visually look at any size parking space circle the drawbar fork sits just inside the parking circle by a measurement of .5M.

Actually it is .4M do to the Pushback tug being just shy of 9.0M long. If you zoom out it appears the fork is on the parking spot circle line. Zooming in close reveals the end of the fork is actually .4M inside the parking circle.

This standard holds true for every single parking size do to the 1M increase in Parking size pushes the Tug back by 1M.

So how did Jon code this

Lets use a picture to simplify everything I have posted.

In this picture I have 3 different FSX default parking spots that consist of a 18M, 36M and 50M. Each parking spot has a grab circle for rotation when needed. The grab rotation circle in ADEX uses the above math to show where the pushback tug will sit out in front of the planes nose.

In this picture we show that ADEX uses the very bottom of the grab rotation circle for the back of the tug so if any part of the small circle is outside the side of a terminal the tug will also be outside the wall of the terminal.

Many Library Objects such as Terminals do not display the footprint exactly the way the building is built. In the following picture I used the ADE Guideline to illustrate where the wall of the Terminal is located. As you can see a very small part of the grab rotation circle is outside the terminal wall.

In this picture after saving and compiling we start FSX and go look at the pushback tug position. We can see it is backed up right to the terminal wall.

In this picture if we zoom in it shows us the hitch on the pushback tug is not positioned in the wall. ADEX is very precise in setting the pushback tug if you use the grab rotation handle as the measurement tool.

The Luggage Cart and Conveyor Belt are hard coded and move in proportion to the position of the Pushback Tug. As the parking spot becomes larger in meter size the spacing between the 3 pieces of scenery also increases.

Tip: -------- In the above pictures you see the outline of the plane on the apron. FSX hardcoded this outline in the Gate_Heavy type Parking Spot only. Many Airports use a outline for all the smaller type airplane parking spots. The tip is to code the parking spot as a type Gate_Heavy then manually set the radius for smaller planes such as 18.0 meter. The following picture shows the outline for a B737 in a 18.0 meter parking spot.

T Offsets ----------

Currently the only standard ADEX can use is the default FSX planes nose wheel for setting the T Offsets. Those have been posted in previous post on this forum.

Where a nose wheel ends up in a parking spot for all the 3rd party planes is embedded in the model design and aircraft.cfg. There is no standard amoung all the 3rd party plane developers on where the nose wheel stops when the plane is positioned properly in the parking spot.

Two exact airplanes made by two different modelers can cause the nose wheel to stop in different locations. Setting T Offsets is still trial and error.