|Quoting VuelingAirbus (Reply 6):|
Spacing of landing traffic is double or more in actual low visibility operations
...Lawson was referring to the approximate doubling of the normal Cat I spacing between aircraft when they fly Cat III ILS approaches or, as the Europeans describe them, low-visibility procedures (LVPs). The additional spacing is required because aircraft on final during an ILS approach create signal multipath disturbances to the localizer beam, which, depending on the shape and size of the aircraft can last many seconds, and even minutes, before becoming stable again. Call it electronic wake turbulence.
This effect was dramatically demonstrated at London Gatwick Airport some years ago when a Swissair MD
-80 requested a practice ILS autoland on a VFR day while following a Boeing 737 on final. All went well until the MD
-80 was crossing the threshold, just as the 737 exited the runway and presented its vertical fin broadside on to the ILS localizer transmitter at the stop end of the runway. At 50 ft, the MD
-80 went into a steeply banked right turn as its autopilot attempted to follow the localizer, which had been momentarily reflected off the centerline by the 737, and only quick action by the crew avoided a disaster."
|Quoting A350 (Reply 7):|
IS it an urban legend or is it true that the cars and trucks at the motorway at FRA are also disturbing the ILS signal?
.."Frankfurt’s Runway 25R ILS currently has a notam describing random but severe interference that affects its ILS guidance, and advises extreme operator caution. The interference is thought to come from a nearby satellite cable TV
transmitter, but the airport authority is reportedly finding it difficult to prove that this is the source of the problem.
Several years ago, it was forecast that many ILS installations in Europe could be down-categorized due to expected interference from commercial FM
broadcast stations operating just outside the ILS frequency band, and which were about to be allowed to increase their transmitter power. As a result, the Europeans mandated the carriage of interference-rejecting ILS receivers in aircraft operating in their airspace. Before the mandate went into effect, pilots frequently reported hearing rock music and radio commercials while listening for the ILS idents at certain European airports."
I'd rather be on the ground wishing I was in the air, than in the air wishing I was on the ground!