SMOC, parabellum et al (who's al?!!) are all on the right lines. I was one of the engineers responsible for the ILS at Heathrow some years ago and I can tell you that the EGLL ILS was flight checked only within the promulgated range and no more.
It did amuse us when we received complaints from crews about g/s + loc deviations outside the promulgated range...and we carried on drinking our tea...
The point is well made by many posts, it's all very well to say that the ILS receivers in the aircraft
can pick up the signal but it's not
certified to work beyond its promulgated range. By all means use it but don't expect it to give you a faultless signal and make sure you have a back up - as one of the previous posts suggested. Like it or not, as professional aircrew, we have to follow the rules, that's the nature of the job. Boring, maybe, but that's the label on the tin.
I could pontificate about other ILSs in other countries which may be different but I'll stick to what I
know and what I've actually stuck my screwdriver/oscilloscope probe into - ooh er missus!!
Does anyone KNOW whether these 'long range' ILSs are actually promulgated/flight tested to these incredible ranges? Getting the lobes and the integrity of the signal out to such a long range would depend on a whole host of factors - nature of the terrain would be a prime problem for propagation of the signal that far.....
