Localiser intercept outside 25nm into BFS
 

I operate regularly GLA-BFS on a 'bus and we usually are given a heading to intercept the 25 localiser when still 40-45 miles to run, which in practice means that if we arm the LOC we will get capture still well outside the range promulgated in the AIP (dangers of false LOC capture etc, etc). The 'bus has the software to allow us to intercept and track the extended centreline from the allocated heading , which more or less corresponds to the LOC signal, and then once within the 25nm we can arm the LOC mode and call 'established'.

It seems to be to be a bit of a grey area as for a period of about 15 miles we are essentially BRNAVing to the LOC.

Anyone in ATC any thoughts on the implications of the initial clearance?

I have offered similar (though not into BFS :)) but always on the understanding that I need to be aware of the 25mile limitations and provide separation accordingly.

I tend to do it when there's no other traffic to effect...;)

Done it elsewhere many times - no problems. But I'd always watch on radar and actively assign levels until the aircraft approached the glide (when it was well inside the protected range).

FD

Stop trying to make life harder for yourself! The controller is trying to make your life as simple as possible!

It might be "making it easier" but anything outside 25nm is outside the area Flight Checked for the Localiser. It's not uncommon for LOC's to be fairly poor outside 25nm depending on terrain etc etc

Up until last year a major UK Airport was regularly establishing a/c on the Glideslope outside the Flight Checked range....once it was noticed by the appropriate people it was stopped until the GS could be checked at the extended range. I would suggest this should be the same for a LOC, don't use it outwith the promulgated range.

I remember a C130 getting the Loc for EGYP at 180nm once :rolleyes: Being a bit outside protected range, I guess they put the kettle on and had another brew before commencing the approach.

As far as real world is concerned, it sounds a little dodgy and worthy of a quiet telephone conversation with ATC.

This has absolutely nothing to do with other traffic or separation.

Whilst most modern aircraft can indeed utilise B-RNAV systems to maintain the localiser course until within the protected range, the use of the localiser (and glide-path) outside the prescribed DOCs is incorrect and potentially unsafe and should certainly not be something that ATC routinely provides, offers or encourages.

If the PIC requests it, then ATC should issue an appropriate warning and leave it up to the flight deck to self-position, all responsibility then transfers to the aircraft's Commander.

Radar monitoring may well be a pragmatic and sensible course of action in such circumstances but ATC should never actively participate in the use of any ILS signal outside its DOC.

From the relevant UK AIC:-

2.1 ILS facilities in the United Kingdom conform to ICAO Annex 10 Volume 1, Radio Navigation Aids Standards and Recommended Practices (SARPs) appropriate to the promulgated Facility Performance Category. Where the UK has differences filed to the SARPs, these will be published in Supplements to the ICAO Annex and notified in the UK AIP General section GEN 1.7 - Differences From ICAO Standards, Recommended Practices and Procedures.

2.2 An ILS can therefore be relied upon to provide navigational information to the required accuracy providing:

(a) It is only used inside the specified coverage areas;
(b) the signal-in-space is being adequately protected by Air Traffic Control;
(c) due account is taken of any warnings or differences notified in the UK AIP or by NOTAM

2.3 An aerodrome's ILS facilities should only be used when an Air Traffic Control Service is available for the airport. No attempt should be made to use the ILS outside the aerodrome's promulgated hours of operation, unless specific arrangements have been made with the aerodrome operating authority for this purpose which include the provision of an Air Traffic Control Service.

3 Localiser
3.1 The standard ILS Localiser Designated Operational Coverage (DOC) provides coverage in the following overlapping areas.

From the centre of the Localiser antenna to distances of:

(a) 25 nm within plus and minus 10° of the front course line;
(b) 17 nm within plus and minus 35° from the front course line.

3.2 Where topographical features dictate or operational requirements permit the DOC may be reduced to the following coverage areas. From the centre of the Localiser antenna to distances of:

(a) 18 nm within plus or minus 10° of the front course line;
(b) 10 nm within plus and minus 35° from the front course line.

In these circumstances the coverage will be notified in the UK AIP Part 3 Aerodromes, AD 2.19 - Radio Navigation and Landing Aids, specific to that facility.

3.3 Flight crews are warned that use of the Localiser outside these coverage areas can lead to false course and reverse sense indications being received. Such use should not be attempted.

You have been warned... := :8

Do aircrew find it preferable being routed direct to an 8 mile final?
This option has to be tied up between an en - route or TMA sector with the relevant approach unit before being issued, as APC need to know where the a/c is going to fit into the sequence. It carries no ambiguity about using the LOC or G/P outside the protected range, as the approach unit will be working the a/c when it approaches the 8 mile final, from which point they can issue descent clearance within the RMA or in accordance with unit vectoring instuctions. It can also be utilised within a 270 degree arc from the 8 mile final (or centre - fix ) of the R/W in use.

Many thanks for all your responses.

We have the ability on the 'bus to route direct to a 'centre fix' (which is what airbus call a 'pseudo waypoint') for any ILS approach, which is usually 4-5 miles from the FAF. This might be prove to be the best option.

If yer coming down from Blaca, what's the problem, just fly yerself towards the LOC and report established once yer inside 25D.
We may (or may not) do something similar at my unit and no pilots complain (not even the orange mob).

Why not just ask 'can we fly direct the c/fix?'

Quote:

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3.3

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Quite right - flight crews should never attempt such a thing.

However, ATC may exceed navaid limitations under several conditions, among them if radar monitoring is provided:

a. Routing is initiated by ATC or requested by the pilot and the following is provided:
1. Radar monitoring.
2. As necessary, course guidance unless the aircraft is /E, /F, /G, or /R equipped.

What is the service volume of the LOC in question?

Standard service volume in the states is 18nm but if an extended service volume flight check is flown it can be extended well beyond. Perhaps this LOC has had a similar check.

Thanks Hold West ~ naturally, I wouldn't presume to question what your FAA Controllers' Handbook and the FAA AIP might permit on your side of the Pond.

However, the UK position is based on ICAO SARPS, specifically Annex 10 and as the UK hasn't filed a Difference (which presumably, the USA has...??) the aforementioned operating restriction still applies over here.

It's entirely possible that under SESAR II, all participating European states including the UK may move towards a common position similar to the US, and which will be promulgated via JAROPS (now EUOPS) but until that happens, rightly or wrongly, the UK status quo remains as detailed in the UK AIP.

For goodness sake...........

I appreciate the controllers helping me when they ask me to establish at whatever distance.

The ability to do so may be type related but the VAST majority of modern a/c can easily achieve what the controller wants with NO problem!

Extend the centreline from the CentreFix then use LNAV /ManagedNav until within 25nm (UK) then arm approach!

.......OR we can complicate everything to destruction?

If you think it's a grey area just don't accept it the next time it's offered to you....

can you descent on the GS(let's say 15 NM from the threshold) before minimum interception GS altitude?Let's say you've been cleared to certain point and to descent 6000',and also you got the clearance for straight in ILS approach.
Example:GS interception altitude is 3300' at 7 DME.On the approach plate your minimum flight altitude from the feeder route to a point you intercept the LOC is 5100 at 15 DME.Then you have a step down to 3300 until 7 DME.

So the ATC vector you for straight in approach and position you 25nm on the locolizer.then say xxx descent to 6000' by 1019,cleared straight in ils approach.
Can you arm the GS and start descent when you intercept the glide slope earlier or you have to descent to 3300' and then intercept it?

Sorry if this sounds like a non-sense to you you guys.It would have been much easier if I could show you the approach plate([SOFIA ILS rwy 27)but I don't know how to post it online.:(

Cskafan123

The same applies, the G/S is usually only flight-checked to 10nm, there are places where it's also checked at extended range. MAN being one in the UK i can think of. Unless you know it's checked to the longer range you're advised not to use it outside the standard 10.