Skydive Mag


Skydiving Coordinate System Part 4

Words by Niklas Daniel

Fig 21b, Terminator lines For "body flight theory" article

Skydiving Coordinate System

Terminators, Real world applications and Conclusion

This is the last of four episodes on bodyflight theory:  

Previous Episodes

1 – The Axis system and Frames of reference

2 – Six directions of movement, Orientation borders and Range of motion

3 – Move combinations, including Multi-axis combinations


A terminator is a special OB that dictates when a heading change occurs through rotation. There are three terminator lines in all, which are colored red in the images below. They pass through the jumper at 45 degree angles relative to the Z-AXIS. In order to identify whether a body-pilot has transitioned through a terminator line, we need to compare the person’s MSP with the appropriate orientation border, and then identify the resultant heading. A terminator transition will result in a 180 degree heading change. The exceptions are wormhole transitions, which by definition fly through a terminator, and have a heading change of 90 degrees.

The first can be seen edge-on (side view of the body) on the lateral (X+Z) plane. Here the belly and head-up orientations can be seen sharing the same heading. The back-fly and the head-down orientations also share a joint heading, but in the opposite direction of the first two.

Fig 20, Side view of a flyer shows the first terminator line in red. The blue cones represent a person's visual perspective. For "body flight theory" article
Fig 20, First terminator line, in red, the blue cones are the flyers' visual perspective — Image by Niklas Daniel

In the images below, the two remaining terminator lines form an “X-shape” with respect to the relative wind, on the flyer’s transverse plane, because he is engaged in horizontal flight. The left and right edge-flying orientations can be seen with opposite headings.

Fig 2a, Terminator lines
Fig 2a, Terminator lines — Image by Brianne Thompson
Fig 21b, Terminator lines For "body flight theory" article
Fig 21b, Terminator lines — Image by Brianne Thompson

A side view of the flyer shows the remaining (two) terminator lines in red (x-shape). These highlight the wormhole transition borders. If the flyer in either of the images were to transition to the belly or back-fly orientations, the resultant heading would be facing us; highlighting a 90degree heading change.

Terminators real world applications

Angle and dynamic flying appear to blur the defined borders between the six flying orientations. When incorporating horizontal movement, we need to take note of a flyers heading. If s/he is following a leader of an angle-jump by using the back-flying surfaces, then the heading remains in front of the flyer, no matter how shallow or steep the angle may be. The jumper is driving forward on his or her back when it is shallow (back-tracking), and continues to drive forward as s/he gets steeper (head-down). Even though the pitch of the flight has altered as much as 90 degrees, the heading remains the same, as do the applied flying surfaces.

However, if the jumper is leading an angle jump using his or her belly-flying surfaces, we need to be aware of the fact that when the flight is shallow (belly-tracking), that the jumper is driving forward in the belly orientation. As the angle of the flight gets steeper, at a critical angle the heading will have altered 180 degrees, because the jumper is now driving backwards while flying in the head-down orientation. This means the jumper is ‘out-facing’ with regards to his or her flight path. The leader never stops resting the front side of his or her body on the relative wind and continues to travel in the same compass direction. The challenging part about the steeper flight mode is that you are blind to the direction you are traveling in, and your heading control is counter-intuitive. Your 12 o’clock has become your 6 o’clock through the application of pitch, all the while maintaining your flight path. This heading change is indicated on the orientation wheel in Fig. 20 by the terminator (red line) that divides the image at a 45degree angle. Note a similar change as a belly-forward to head-down-backwards transition occurs when moving from back-fly-backwards drive to a head-up-forwards.

Fig 22, Belly forward drive For "body flight theory" article
Fig 22, Belly forward drive — Image by Niklas Daniel
Fig 23, Head-down backwards drive for bodyflight theory article
Fig 23, Head-down backwards drive — Image by Niklas Daniel

In the images above, both jumpers have a flight-path towards the left but their individual headings vary by 180 degrees: given enough pitch (and thus crossing a terminator), a belly forward drive (fig 22, left) quickly changes to a head-down backwards drive (fig 23, right).

If a jumper is flying at a steep angle, such as carving in a wind tunnel, the jumper will have to rely not just on his or her vertical flying skills, but the horizontal ones as well. In order to add horizontal translation the belly, back, and even edge-flying surfaces need to be involved.

Heading in relation to the wind-tunnel’s center while carving (dynamic)

Table 8: Heading in relation to the wind-tunnel’s center while carving (dynamic)
Table 8: Heading in relation to the wind-tunnel’s center while carving (dynamic)
Fig 24, Nik & Brianne flying dynamic, using their back flying surfaces in mixed orientations For "body flight theory" article
Nik & Brianne flying dynamic, using their back flying surfaces in mixed orientations — Image by David Cherry

An interesting pattern emerges for steep angle flyers who use either their belly or back flying surfaces. While the front flying surfaces of the body are engaged, the jumper is always out-facing, regardless of orientation. And when a person’s back flying surfaces are engaged, s/he is always in-facing regardless of orientation.


There is much we can learn about the sport of body-flight by implementing a coordinate system. Whether tunnel flying or skydiving, in order to continue testing our abilities and knowledge, we must question what we already know and try to see things in a new light. I hope that others can benefit from this system and perform follow-up experiments, even if just to confirm their current knowledge, or to start new conversations. It is my intent to get people to think about body-flight on a deeper level through thought experiment and practical application. The system presented is capable of modeling and tracking a wide range of flight modes and body configurations, which may help better understand the physics behind the sport and help develop more efficient ways of flying, learning, and teaching. With the introduction of a suitable coordinate system and language, the stage is set to discuss the physics and applications of our awesome sport. As always, the intent is to increase people’s appreciation and joy in skydiving and tunnel flying.

Bodyflight Theory

This Episode 4 completes part 1 of this BodyFlight Theory paper, the Skydiving Coordinate System. Other parts will be subsequently added to cover theory and application for all human flight disciplines, through understanding the principles of human flight.

Skydiving Coordinate System

Links to read online:

Episode 1 – The Axis system and Frames of reference

Episode 2 – Six directions of movement, Orientation borders and Range of motion

Episode 3 Move combinations, including Multi-axis combinations

Episode 4 – Terminators, Real world applications and Conclusion

Download pdf of entire Coordinate System paper (4 Episodes) 

Nik invites comments,in order to advance the theoretical knowledge of body-flight (

Article, Drawings and Images by Niklas Daniel of Axis Flight School unless otherwise stated


Niklas Daniel would like to thank the following individuals for their time and feedback:
 Jochen Althoff, Andy Gerner, Scott Roberts, Tom Stokes, Brianne Thompson, and Tina Voeller.


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