This is very interesting. Out of yet more interest, does anybody know of situations where under normal operation the FPV would be spitting out nonsense? One of our aircraft gets the lateral trajectory wrong pretty consistently in light to medium crosswinds. After flying a couple of visuals I had a hunch, so the other day I flew a raw data ILS and found that every time I placed the tail of the bird on the blue line (once LOC initially centred), I'd be off the LOC pretty quickly with an undesired trend forming. Flying "close" to the blue line (3-4 degs) resulted in a better profile (Yes, runway track was correct)