Problem Capturing Localizer

[Airbus 14]

I was cleared for the "armed" approach to KBOS runway 22L (I-LQN)and the FMC correctly displayed the frequency (110.3)and course. As I started to intercept the localizer on a heading of 310 with the expectation that the aircraft would turn to a heading of 220, the A320 turned AWAY from the airport. I had to disengage the AP and manually fly the approach. What did I do wrong?Thanks!Airbus

[guy 24]

The Pss airbus behaves the way you described on ILS if the FS NAV/GPS switch is set to GPS. So this could be a possible explanation. Guy

[Airbus 14]

I don't think the PSS Airbus panel has a NAV/GPS switch. However it has an FMC managed mode which I was not using. I had the AP engaged in heading hold mode at 310 degrees with the ILS 22L approach armed. The bus should have captured the localizer and turned toward the runway, but it turned in the opposite direction.Thanks for your help!Airbus

[guy 24]

The PSS Airbus panel has evidently no physical NAV/GPS switch itself as it has the MCDU, but this switch could nevertheless be positioned to on ! If you had set the Nav/Gps switch to ON in another aircraft before you load the PSS bus, it will remain ON for the PSS bus and the ILS intercept will NOT work, independently of the way of lateral navigation you use (Managed/Selected(Hdg)) ! The position of this switch should normally not interfere with the PSS programming, but it does ! I suppose it's a bug. I have myself had this problem often. It is exactly for that reason that I equipped my PSS airbus panels finally with an Nav/Gps switch, so that I am absolutly sure that it is turned OFF. You can also define a key for the Nav/gps switch, but this way you never know directly if it is on or off. I am almost sure that this is the cause of your problem. :( Guy