Jenbel

My understanding was that all electronic devices had to be off for both take-off and landing.

However, on approach to an airport, an aircraft will be (usually) landing using the ILS - Instrument Landing System. It's effectively following a (radar?) beam from the airport, which tells the aircraft where it is in relation to the airport - how far out, what heading, what altitude. This is used to guide the aircraft into the airport and ensure it is lined up correctly on the runway. ILS are quite sensitive things - they are safeguarded fiercly, and even within the airport, there is a clear area maintained around the ILS to ensure that nothing interferes with the beam - having been working on an airport where we accidentally set fire to the grass within the ILS zone, and had permission refused from ATC to enter it to put it out as they had aircraft on approach and so couldn't risk either turning the ILS off or scatter to the beam, then I'm aware of how fiercely these are guarded! (the fire went out by itself, much to our relief, that we didn't need to alert the fire service to what we had been up to as we'd never have been able to live it down ). So anything which could interfere with reception of the ILS on board would also be a huge no-no!

Hopefully the pilots will be along to correct anything wrong I've said - while I had to consider the effects ILS had on the airfield, I only had the whole system explained to me one drunken evening in a bar somewhere. And although Ive watched RAF Precision Approach with awe (and jealousy, it is exactly like a game!), I've never seen civilian ATC in action...