Back course ILS

[eludlow]

I was just wondering, is this ever used on take offs, or is it used any other times??
I am NOT a pilot, just a future pilot (I hope!) so please don't get too technical!
While I'm on the topic of ILS, how near to the runway will the localizer be picked up (ie how far from the runway will the plane allign itself with the runway automatically)
Thanks,
Edward Ludlow

[HPSOV]

Start with the back course, yes it can be used in a departure. Some SID's (Standard Instrument Departure) will require you to track the back course after takeoff before executing a turn.
Apart from that the back course can be used as an approach as well, as far as I know it can only be used in the USA, but I may be wrong.
As for how far out the ILS can be used to line the aicraft up is based on the coverage of the localiser beam. The localiser lines the aircraft up, and the glideslope descends the aircraft. The coverage of the localiser is 25nm (18nm in USA). However in a real world situation you will normally not line up until at 10-15nm depending on the approach.

[411A]

Have intercepted and followed the 25L localizer at more than 50nm at LAX many times without difficulity. Backcourse approaches are used in other countries also. For those that are interested, the ILS system was invented in 1938. Even longer than many on this forum (just slightly).

[Air Conditioned]

The Back course may have been used for departures at some time, but is probably rare. One might confuse your question with the case of using the front course for guidance when departing the reciprocal runway. This was done at the old Hong Kong (Kai Tak) when the 31 ILS was used to depart 13, but it was NOT the back course being used.

Back course approaches were relatively common years ago, when a normal ILS installation gave a "free" approach signal for a procedure on the reciprocal runway. I believe modern ILS installations, in producing much better quality front course signals, may not now provide a useable back course, and the procedure is not much in evidence these days.

ILS may certainly be received well beyond the rated coverage of the aid, but should not be considered suitable for autoflight (which appears to be the subject of your question??)

[Dan Winterland]

The one country where they are common is Canada. The Eastern Seabord airfields tend to use them on their westerlty runways, with the back course being used on the more frequently used westerly runways. This is beacause the higher minima on the BC is suitable for the relavely high cloudbases westerly winds bring. But if you get an easterly, it is very wet and vis is poor with low cloudbases.

[twistedenginestarter]

Remind me everyone. If you do a back course approach (without setting BC on any of your fancy computers) the left/right needles have to be interpreted the opposite way to normal? If the needle goes right you have to fly left to pull it back?

[Code Blue]

Flying in bound on a loc/BC, or outbound on a front course ILS gives reverse sensing needles on old standard ILS dial.

The fancy newer HSI will adjust for that if set for appr and give normal sensing.


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[before landing check list]

You need to get one thing straight here. You are not using the ILS for departure, you are using the localizer. I know, I know I am mixing apples and oranges but it is all fun and games till somebody falls down the airstairs, lol. That is what ATC will tell you. Course I have seen some strange things such as cleared for a combination of aproaches while in Tampico, Mx.
j

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For a plane to fly well, it must be beautiful.

— Marcel Dassault

[This message has been edited by before landing check list (edited 20 December 2000).]