B C Command

[yvon]

Hello everybody!

  Could someone kindly explain to me the use of this BC command which i never managed to find in the manual.I have been flying for quite

[commoner]

Hi Yvon... say are already set up for an AP ILS approach to a certain runway and you need for some reason to land at the opposite end which does not have ILS,  then if you click on the BC (Back Course) button  AP will still lock you onto the localiser for your new approach direction without making any changes to your settings.  The Glideslope will however not be operating ...and if you are tracking the localiser manually you will have to  the steer the opposite way to the normal to line up.......in other words it allows you to do an ILS approach to a runway which doesn't have ILS providing the opposite end of the runway does....commoner  8)  

[RollerBall]

Just clarifying what Derek has said. Take Cambridge EGSC as an example. It only has ILS on Rwy 23. However, this does not mean that you can't do an ILS landing on Rwy 05 - you can, using the back-beam from the 23 ILS.

But because it's a back beam, your primary ILS instrument, the localiser, works in an opposite sense. So when you are established on the localiser during your approach you click on BC (back course) which makes the aircraft respond in the opposite sense as well, turning left when it needs to and not right, which would be rather embarrassing  ::)

As Derek says, if you are flying a manual approach you have to compensate manually and also back courses don't have GS (glide slope) data, so you have to monitor this visually.

This does not mean that you can't do ILS BC approaches at night or in IFR conditions (subject to your minimums) because approach ATC assist you from a long way out. They say things like 'Golf Alpha Charlie, your height is X thousand feet (assuming you don't have a mode charlie transponder on board) and you have Y miles to run. Turn left 235 degrees and establish a 3 degree glide slope'

Then later during the descent they say 'Golf Alpha Charlie, you have Z miles to run, heading is good, height should be 3500' as you come down the glide slope that they told you to get on. As PIC you are supposed to know what AS and rate of descent will give you the required 3 degree GS.

Lots and lots of fun....

[Nexus]

BC approaches are umm..very seldomly used in my country. Better shoot for an ILS circle-to-land instead  :D

[yvon]

Thanks a lot for both your explainations and i am in a rush  to try.This is good to know because i usually  had to make compulsory manual landings each time ils was in the opposite QFU
       Yvon

[commoner]

LOL...well put Rollerball...even I understand it now..commoner  ;D

[wji]

"What does 'Localizer Back-Course' mean?
It means confusion.
OK, that's cheap humor- sorry.
How about this: "A Localizer Back Course" is just like a regular Localizer Approach except that Left is Right, and Right is Left. In addition, it may, or may not, have a Glide Slope. If it has a Glide Slope, it is called a 'Localizer Back Course with Glide Slope'." -- Hal Stoen.


Reference cited

hope this helps.
bill
P.S. Today we got "Cleared NDB 'A' Approach" from canned FS9 ATC . . . lots of fun in the mounains and zerozero on the ground (yes, we went missed).