Backcourse ILS Approaches in the UK

[Simtech]

Do any airports in the UK have a published ILS backcourse procedure? I was under the impression (rightly or wrongly) that the CAA regarded such procedures as a no-no and that all UK localisers have their back beams suppressed. Any references to documentation that gives a definitive answer would be appreciated.

Thanks in advance,

Simtech

[JetSetJ]

Hello there,

I've been studying Radio Navigation as part of my ATPL syllabus and we have been given the impression that back course approaches are a no go area here in the UK. I therefore presume that the powers that be at the CAA have said no. I was under the impression that the back course indications provided for both the localiser and glideslope are not accurate enough to be utilised to carry out an approach.

I also would be very interested to hear anyone elses opinion on this particular topic

Hope this helps

JetSetJ:ok:

[Spitoon]

Official answer - in the UK there are no back-course approaches published and yes some locs are fixed to reduce the signal strength behind the antenna (I think improved antenna designs now makes this less common). It's hard to know whether the back-course signal is accurate 'enough', it simply isn't flight-checked because it is not used for any procedures.

It's interesting that you ask though - a while back I (a simple controller) mentioned that I thought some crews set up the ILS/loc on departure to use the back beam to assist in staying on the centreline if required (not wishing to open another debate but this would be if the clearance was to climb straight ahead). This comment was based on discussions with locally based crews and, in the old days, a fair few trips on the flight deck. It also helps if there is a need to return quickly. It all seemed perfectly sensible to me. The response from some pilots was along the lines of "get real". I'd be interested in any pilot comments.


P.S. JSJ, the idea of following a glidepath back-course is slightly worrying. :)

[Jerricho]

that the back course indications provided for both the localiser and glideslope are not accurate enough to be utilised to carry out an approach.

Localiser indications are certainly accurate enough (for a non directional localiser). Glide slope..............no way! That's why you'll find places around the world have "IGNORE/DISREGARD GLIDE SLOPE INDICATIONS" in big black bold lettering on the approach plates.

[ecj]

The FMS will be set up for the SID, and once engaged with the automatics shortly after take off, it is programmed to fly a far more accurate track than by hand.

[Simtech]

Thanks for the replies gentlemen - very helpful :ok:

Regards,

Simtech

[HEATHROW DIRECTOR]

Jerricho's posting about warnings interests me. I'm astounded that anyone would even consider the possibility of a "back-beam" glidepath! And what on earth is a "non-directional localiser".

I recall that back-beam approaches were published in the UK many, many years ago but not in recent times.

[30W]

The FMS will be set up for the SID, and once engaged with the automatics shortly after take off, it is programmed to fly a far more accurate track than by hand.

That assumes the MAP is exactly accurate prior to commencement of the take-off run. Remember not all FMSs are either GPS fed, or have a R/W Update feature.......

Many years ago now I used to operate into Norwich on the overnight mail from LPL/EMA. Several times I had NDB approaches to R/W09 in very marginal weather (does 09 still have no ILS????). I always flew the backcourse LOC for 27, supported and monitored by the NDB needles. Although flying the NDB approach, it seemed silly to ignore more accurate data that was available, as long as that data was fully supported by the NDB indications.

It's interesting that you ask though - a while back I (a simple controller) mentioned that I thought some crews set up the ILS/loc on departure to use the back beam to assist in staying on the centreline if required (not wishing to open another debate but this would be if the clearance was to climb straight ahead).

R/W33 BHX is straight ahead 2miles, I always if handflying backtrack the 33 LOC. Produces perfect results and is I.M.A.O the best way to achieve accurate 'stright ahead'!

30W

[Jerricho]

JAnd what on earth is a "non-directional localiser"

What do you mean "what on earth"? Newer modern locs are highly directional, transmitting in one direction. The localiser we have here on Runway 36 at Winnipeg does not allow for a back-course approach for runway 18 (as 18 doesn't have a localiser). Now I'm no techie, but the way I understand it they reduce carrier power needs and channel frequency protection requirements.

[RAC/OPS]

It says you can't have it here (http://www.caa.co.uk/application.aspx?categoryid=33&pagetype=65&applicationid=11&mode=detail&id=200)



ILS 10 Genereal Requirements for ILS\Localiser Backbeam

[Spitoon]

Now I'm no techie ..................Uh-huh :)

[HEATHROW DIRECTOR]

Precisely! A localiser is just about the most directional radio aid you can have. I'm not aware that there is such a thing as a "non-directional" localiser, although I think I know what J is getting at.

[Jerricho]

How about "A localiser that transmits in one direction" :\

[Spitoon]

Sorry J, I still don't understand. An ILS localiser is designed to send out a narrow beam in one direction. The reason that the antenna array is so wide is to focus the signal in the desired direction - because of the way that antennas work there is a 'mirror' signal in the opposite direction, the back-beam. In the UK the back-beam is supressed to minimise the signal strength.

Have you got an example of something different to show what you mean?

[Jerricho]

Ah, that supression thing. That's the word I was thinking of.

Geezus I suck at engineering stuff.

[OwnNav]

I find backcourse good for rwy hdg info, used it the other day out of Dundee when instructed to maintain in a stonking xwind, it was vmc though

[ComJam]

I love the idea of a "non-directional localiser", how on earth would we flight-check that?! :}

How about an omni-directional glipeslope? Or am i just being silly now....

[Jerricho]

Not as silly as me ;)