Increase bandwidth for ILS systems?
 

In a discussion on another forum about the proposed switch off of the FM service in the UK (a dumb idea but that's another matter), the question was raised as to what commercial use could be made of the freed up spectrum. One suggestion was greater bandwidth for airfield ILS systems.

Is that a problem and, if so, could the FM spectrum be used to provide a solution?

TIA

Technically anything is possible, but the cost of ground based approaches verses using modern satellite based approaches will probably mean less and less ground based equipment in time.

But is there actually a problem or someone trying to find a solution to a non-existent problem!

Good point re satellite tech.

so the ILS would have another transmitter installed?

There are currently only 40 ILS frequencies. The directional nature of the beams and relatively low power mean there is not much interference. However that's not to say it doesn't happen. A few more would always help.

Contrary to certain opinion GPS alone does not meet the accuracy requirements for low vis approach (I think we're currently at RNP 0.1 which is about 15 meters. ILS accuracy is the order of one to two meters at touchdown). In order to do so, at least one (thought to be 2 or more) ground based devices need to be located at extremely accurately defined positions, to transmit to the aircraft the local error in the GPS signal, so the aircraft can accurately fly the vertical/horizontal profile (called differential GPS)

ILS is old, established and certified. DGPS is not.

That band could be useful for VOR as well.

The question isn't just whether you need the extra bandwidth. Reserving some of it (at the upper end of the old FM band) could keep some incompatible service from grabbing it and bleeding into the existing channels.

:8

The strength of signal is allready a problem in congested environments (multiple airports in close proximity)

@mono, DGPS is now commonly used as GLS. Standard Equipment on Boeings for the last eight years or so. But not certified for low vis yet, just normal CAT I (and LTS CAT I). Certification for low vis is in progress though. I flew a few test runs for that in germany and GLS is both more stable, "smoother" and quite a bit more precise than ILS. Autolands work like a charm, same as rollout guidance of course (B737).

The problem with allocating a new frequency band for an industry, that is based worldwide and not only within the UK, is that the use of that frequency band can not be guaranteed outside the UK. So there is simply no business case to exchange current NAV radios for new ones that could use that band if the use is only possible within one country in the world. In central europe for example that FM radio band will be in use for the next 30 to 50 years, although some of it will be used by digital radio services.