experienced false glideslopes
I inadvertently set up a situation in a 737 simulator some years ago (which the crew, unfortunately, managed to blunder/stumble into) where the autopilot merrily and quite cheerfully intercepted a false localiser signal. Interestingly, the crew realised that something was not quite right .. but it still took them a frightening period of time before the penny dropped.
Until the jungle drums got the message to all and sundry, I was able to reconstruct the situation for the training benefit of a reasonable number of crews ..
Message is to use the ILS entry keyhole positively and every time. Shortcuts might well prove to be direct to the smoking hole in the ground.
It's well worth a read of the Air New Zealand B767 fright at Apia ..