Thanks Matt,

it sounds a bit strange to me that - on an armed precision approach - the airplane is being so easily to confuse by a pilot error (don't get me wrong) instead of following the hard facts of a dialed-in frequency and armed approach mode. I would have expected it to primarily follow the ILS instead of being dependent on something that can more or less easily be messed. So simple transposed digits could spool up an ILS approach although frequency and mode are correct.. Thanks for the explanation, I will definitely try this out!

Hi Marc,

I can't speak to the specifics of the 737 but most modern aircraft use some inertial inputs (for which it is necessary to set the correct inbound course) alongside the raw localiser signal - the A320 for instance will do very odd things like S-turn down the approach if the course is not properly set.

The difference of course is that in most other aircraft apart from the 737 and 767 the ILS course is set automatically from the navigation database and so the likelihood of an error is much smaller!

The Jurassic 737 was renowned for turning the wrong way on ILS LOC capture, so I was told by an old Skygod one day. The FlyJSim 737-200ADV simulates this really well when I try it in X-Plane. It's fun flying the relic sometimes. You can stick to Boeing SOP as per the NG and it works just fine too.