Originally Posted by
Gilles Hudicourt
I noted that several people asked why this runway does not have an ILS.
There are terrain features that prohibit the installations of an ILS, and one of those is if the terrain on the runway axis a certain distance before the threshold is nor fairly flat for a certain distance, in order for the Radio altimeter, which does not measure the height of the aircraft above the runway, but the height of the aircraft above the terrain directly below it, to be able to activate certain features such as flare mode, or changes flight laws, elevator trim, auto thrust etc. Even a dinosaur like the 737NG has such RA dependent features.
Such features would not work correctly if the terrain half a mile before the threshold was significantly higher or lower than the runway threshold.
I remember in a distant past flying ILS approaches in aircraft that did not even have a RA, but the aircraft I now fly prohibits ILS approaches if both RA are U/S.
Only problem would be with Cat II/III because they have a decision altitude based on the radar altimeter. Cat I ILS uses the barometric altimeter for minimums. Thus you can have dropping terrain approaching the runway.
And with Cat I there is of course no autoland. You say several features would not work, so how do they work on a visual approach to the same runway?
While i'm not saying an ILS could definitely installed at the location i would not be surprised if the non-existent ILS was just due to cost.
Edit: google says it is due to cost.
"The Halifax airport, and every other airport in the country, has financial constraints," Williams said. "They don't have an unlimited supply of money. And let me tell you, passengers would be the first to complain about increased costs if the airlines were required to pay for it."
http://www.cbc.ca/news/canada/nova-s...nway-1.3015771