SimSoft Working Group

Rev:03ARINC 610 Analogy Article11. Heading ChangeHeading Change flags that the heading of the aircraft has been changed artificially, so notdue to normal flight; it signifies a step-change in heading.So, consider Analogy Vehicle: Let’s assume it is being driven normally along a highway, isjust crossing an intersection, and that Heading Change is asserted.• The vehicle direction [heading] is suddenly different and the driver finds himselfdriving along the other road at the intersection;• The driver sees no changes on his instruments other than a jump in the Sat-Nav[EHSI] image that is set to “Direction Of Travel Up”;• The Sat-Nav [FMS] starts to recompute the route taking into account the change ofroad;• The driver feels no jolt as the direction changes [motion cues].Contrary to the effect of an altitude change, a heading change will generally not cause anautopilot disconnect; the autopilot will re-acquire the set heading. (Often an instructor willactivate a heading change function to bring the aircraft heading closer to the heading thathas been set and so the effect is to shorten the turn both in time and space.)10 July 08 Page 15 of 28