MLS must have been incredibly expensive piece of kit – definitely into 6 digits.
Only 52 €:
the signal does not require the level of protection that is demanded by ILS.
…which was one of the reasons for introducing MLS. It also means that ground preparation and installation is much simpler.
The GPS position resolution issue is normally addressed with a FOG inertial add-on. The US smart bomb strap-on guidance package is reportedly under $20k now – peanuts for an airliner which already has slightly better stuff than that for navigation. That also means that if GPS is jammed at some vital time, you can just carry on.
In fact there is an off the shelf box for about €20k which takes in a standard active GPS antenna one end and outputs plain old NMEA at the other end, and contains a 3D FOG. I posted the link to it here before. For GA, one would “velcro” it somewhere and then feed the data to a tablet, and have totally jam-proof navigation.
These products are intended for remotely controlled vehicles so the update rate must be very high.
AFAIK only BA ever installed the receivers for MLS – in much of their long haul fleet and in Concorde.
Achim – you will get diabetes if you eat that sort of junk food all the time 
the update rate is relatively slow (normally about 5Hz)
There’s nothing fundamental about the update rate – there are commercial receivers with significantly faster update rate. So IO guess it’s only a matter of time
as proven with NDB, legacy systems tend to have an awfully long period of legacy.
But unlike the NDB, the ILS is quite expensive to operate (mainly due to your calibration flights 8-))
@Peter, I don’t know what flag levels should help. We were very close to the runway, so signal strength must have been plenty.
Another airport much closer to home where the ARP is miles out is EDDB – it has also been repositioned well to the south of the current landing runway in anticipation of the new terminal opening some time this Millenium!
A lot of GA avionics are a bit shagged especially when it comes to the flags. With an IFR4000 plugged in directly into the coax cabling you can check the flag levels but there is no really consistent way to do this with the antennae in the loop.
This is not true, you can perfectly do this test, it is part of avionics testing in most European countries, and works very well.
ok, I have to ask. Whats a side lobe !!?
All directional antenna’s bundle their power in to a beam, the main lob, this is a wanted situation, side lobs are an unwanted product of directional antenna’s and are lobs displaced left and right or up and down of the main lob. In these side lobs their is also some bundeld power. When your flying on side lobe, you are 100% sure out of the main lob, which is dangerous.
As indicated, it is hard to detect without outer means, that is why Peter suggested to use GPS as an aid to see if you are actually on the main beam.
Wikipedia has a nice illustration:
Today, flying to Guernsey EGJB, I saw what looked like a localiser sidelobe
The magenta line is where the real LOC lies (bearing of 268) and you can see the plane was a good 30 degrees off that.
I got a centred bar on both EHSIs (these using two different KX radios sharing nothing but a common LOC/VOR antenna) and on a KI204 CDI (working from #2 radio). No flag on LOC. GS was flagged, as one would damn well hope…
As you can see I was about 17nm from the ILS system.
