You need to be locked on to fire any of the missiles, i.e in range light 'on' and 'lock on' light lit.

Set the 'Air' & 'Ground' switch according to the selected missile i.e use 'ground' and the Alarm missile and this will lock onto a ground target. Set to 'Air' and the AIM 9 for an AI target, also bear in mind you need to be in range as well. For something like the AIM it ia about 6 miles, for the Alarm it is a lot further.

Ground targets that initiate a lock on are not all scenery items, they have to be models and so things like AI aircraft on the ground at Bournmouth airport in the UK for instance or the little fuel truck that drives around the airfield are all lock on targets. Ordinary scenery items do not act as lock on targets.

If you set the range to 50 miles and have a fly around you will get a lock on, then fly and keep the square inside the circle and when in range you get a tone and can fire the missile.

Pete