This is a fairly hair-raising incident: http://avherald.com/h?article=45f1317a
I've never come across mirror glideslopes - does every ILS installation have these?
False glidescopes may exist in multiples of the glide path angle, the first being approximately 6ยบ degrees above horizontal.
That's why you should always capture the glide scope from below, and check the altitude when over the FAF...
As to why this incident happened... Guess they where relying too much on the systems. The video below springs in mind...
I don't think it is possible to radiate a glideslope without the in-between opposite ones.
On those, the GS bar and autopilot VNAV will work backwards !
You don't actually have to intercept the GS from underneath but interception of the lowest one from underneath is the best way to avoid getting one of the false ones above it.
However how are continuous descents done ? Can you always intercept from underneath ?
Localizers have side beams as well. Condor Crash
At least it means that you are higher than expected.
At least it means that you are higher than expected.
Yeah, but it means that you are not stabilized in the approach, coming in too high, too fast with a high RoD... Air India Express Flight 812 is a sad example of a sleepy captain pushing on ("runway fixation") while it was apparent that they where on a false glide scope...
Yeah, but it means that you are not stabilized in the approach, coming in too high, too fast with a high RoD
Sound like one of my normal landings !
There are no false glideslopes on a LPV.
There are no false glideslopes on a LPV.
+1
There are no false glideslopes on a LPV.
Yeah, but we have exactly
+1
LPV approaches in the UK 
Isn't "+1" something from twitter?
One can get dodgy LOC radiation too. I recall my autopilot intercepting a false LOC a few times. The HSI deflection was off-scale though. Or maybe just exactly full scale. Now I delay pressing APR until only a few miles off the real one.
Also, to see the real one, I set up the GPS in the OBS mode, showing a magenta-line bearing where the LOC can be expected. Unfortunately I don't think there is any way to do this with the GS.
How do jet continuous descents deal with this? It would be very tricky to always intercept the GS from underneath. A while ago I tried to find out on some ATC forum and the few replies I got that made sense suggested that they intercept the GS from both below and above. And I can confirm that works even with my KFC225; there is no reason why it should not unless the software is brain-dead. There may be some GA autopilots which can do only an "underneath" GS intercept but as I say that is brain-dead.
