Originally Posted by
Gonzo
MLS is not supplanting ILS, in fact MLS will be dead and buried within a few years. It's not that funding is going to run out, it's that nobody manufactures the system any more, and the current one is about to reach it's end of life. The main benefits of MLS (smaller sensitive area in CAT II/III ops) have largely been replicated by the new 32-element array ILS localiser antenna on the market now anyway.
On my NATS Staff Course in 1986, we were told no new ILS' were to be commisoned after about 1992 and old ones would be phased out in favour of MLS'.
Based on this, we decided not to go for ILS at Farnborough but go straight for MLS. In the interim, until a 'rich' civil operator took over the airfield, we toyed with another much cheaper system called 'TLS', a transponder based precision guidance system which, as it had been approved by the FAA, the CAA said they would 'rubber stamp'.
As soon as it was installed, the CAA decided it would need 5 years of evaluation before they could approve it for IFR use!!
So Farnborough ended up with ILS after all, with some operators cleared to operate to less than Cat 1 minima ie RVR 300m.