Intercepting from Above

[keithl]

For years I have taught that the ILS G/S should be approached from below, to avoid the (first) false lobe. Now this (http://www.caa.co.uk/docs/33/srg_gad_gasil4of2003.pdf) (page 16) indicates that some A/Ds have some procedure annotation indicating that it may be intercepted from above.

I know about CDAs and am not interested in them (helo ops). I really want to read the words so I can see exactly what is intended. I have asked on Tech Log, and I have contacted the publication's editor, but no-one can provide examples.

Can anyone here point me in the right direction? (That being an air trafficker's job, after all!) Otherwise this would appear to be an unsupported assertion.

[brimstone]

Hi keith - I've been following your thread on Tech Log with interest.

I am of the opinion that the author of the article in GASIL 4/2003 may be guilty of loose wording and is in fact referring to airports where CDAs are standard procedure. ie the London airports and where the ideal profile is to intercept the glide-path at the appropriate height for the distance without recourse to level flight.

I think the phrase "specifically published" probably refers to the UK AIP entries for these airports where detailed procedures regarding the requirement to attempt to achieve CDAs at all times are laid out.

As far as I am aware at other UK airports CDAs are considered to be a "best practice" to be aspired to when possible, but normal practice would be to intercept the glide-path from below.

[Jerricho]

For Heathrow, CDA's are considered not only best practice, but are monitored and evaluated as well, being one of our Key Performance Indicators (KPI's) between the hours of 2300 and 0600 local (or 0700 for Easterly operations). If for any reason during a night shift, when the noise thing is the most "sensitive" to the locals, a CDA is not complied with, the details (operator, time etc) are recorded and past on to the powers that be, who I believe contact the operator if it resulted from the operation of the aircraft.

[keithl]

Thanks, Brimstone, I am inclined to agree that it is a case of loose wording. I am taking it up "through channels", but before I make official waves, I need to see if anyone out there can find an example of what he appears to mean.

Jerricho, I'm still trying to see the connection betwen your reply and my question! Could you elaborate, please?
But as you're at Heathrow, perhaps you are familiar with the words the GASIL Ed. is talking about, in which case I'd be very grateful for Chapter and Verse.

[Jerricho]

Sorry Keith, my reply was more towards Brim's comment about CDA's being best practice to be aspired to whenever possible.

Of course, saftey is always a factor. And we do try to issue descent instructions to prevent you guys being above the glide path. But there are one or two operators that during our "CDA critical" night movements point the nose at the ground and level for ages and ages.

Gotta be honest...........that GASIL stuff is white man speaking with forked tongue.

[PPRuNe Radar]

The Tech Log thread is here

Tech Log Thread (http://www.pprune.org/forums/showthread.php?s=&threadid=112585)

Maybe better to keep all the discussion in one place ???

[Jerricho]

Just like NATS stuff, eh Radar Boss ;)