Hi,

 

I tested INTC CRS FROM function yestarday... and observed strange behaviour of aircraft (200LR).

Aircraft, fly over fix from which I set outbound course and then turns to intercept this course but turn was fairly steep – thus it crossed outbound course. After few seconds, it tried back to course, so started turn in opposite direction to catch course, but crossed the course again. Generally speaking – it looked like „zigzag pattern” flight.

After a few „crosses” it finally stabilized on outbound course.

I think it should starts turn to intercept course from fix around 2 nm before that fix – right?

 

 

Is it a bug or there is something I’m doing wrong?

 

 

Lucas

How did you program the course from a fix? Also, is there a possibility that the fix had a FLY OVER condition on it, perhaps as part of SID/STAR coding. 

No, fix wasn't part of the STAR. I programmed it by entering fix name and outbound course. For example:

- fix ABCDE (and ABCDE was the last fix of route; STAR procedure was not enter; current heading: 160)

- so I typed "ABCDE180" on scratchpad, then pressed 1LSK LEFT on LEGS page

- "(180)" appeared in first line

...hmm, so, can you advice me where is the reason of this issue?

I've noticed since first tests that the B777 AFDS does overshoot/undershoot turns and ends up correcting in zigs and zags. Not just INTC CRS FROM but even in situations like terminal procedures where a change in heading is significant. Of course I mentioned it but it appears that this behavior is realistic. I guess, and that's all I've got, that it might have something to do with being a 1995 system.

 

I have gotten used to it and override the active leg tracking using the MCP or reloading the next waypoint on top of itself to reset the leg, which stops the zig zags.  Good topic, always wondered about this behavior.

Thanks for reply, Dan.