按手册上说，洋红色虚线是 FLS 的虚拟航道，但是在执行 ILS 时也会出现。空客第一次回复是有问题的，第二次回复的解释才说得通：只要是能够用 FLS 执行的进近方式，ND 上就会显示相应的虚拟航道，VD 上也会显示相应的虚拟下滑道。因为 LOC F-G/S 是执行 FLS，设计上只要有 LOC，就会出现虚拟航向道。而当执行 ILS 时，由于也包含了 LOC，也就会出现虚拟航向道，注意此时并没有 F-G/S，所以 VD 上并没有虚拟下滑道。
但实际上这个可以算是个小 BUG，完全可以改成只要不是执行 FLS，就不应该出现虚拟航道，没有什么技术难度。
具体参考 TechRequest 原文：
Q:
As FCOM, FLS beam is only appears in NPA. Actually we see it everyday in ILS approach.
Actual flight:
A:
The FLS beam is displayed only if a FLS approach is inserted in the FMS. If you insert an ILS approach the magenta dashed line displayed on the ND represents the LOC beam of the ILS.
Q_2:
Magenta dashed line represents for LOC beam sounds reasonable. However, it seems no description for it in FCOM, at least not in 31-CDS chapter.
A_2:
To clarify my previous answer. You were right when you said that you saw a FLS beam when flying an ILS approach. What you see is a consequence of the implementation of the FLS in your aircraft.
FLS approaches can be LOC or ILS G/S inoperative approaches and they are flown with LOC AND F-G/S. The consequence is that all LOC of ILS approaches are coded with a LOC beam and are displayed even if you flight a full ILS.
You can notice that on an ILS approach, the G/S beam does not exist on the VD and it is only after deselecting the G/S on the RAD/NAV page that you can see the F-G/S beam.
To summarize, an FLS beam can be also a LOC beam and that is why they are describe only as FLS beam.
