"Centerline display" - rule of the air?
 

Pilot A:
As soon as I get radar vectors for an approach I want to have cleared all flightplan waypoints not on the centerline and FAF should be "to waypoint". Now I get a digital readout on navdisplay how many NM right or left of centerline I am and "to waypoint" helps in optimising descent.

Pilot B:
This is unsafe because assisting pilot can not crosscheck navigation anymore. Do not remove any waypoints from flightplan page!

A or B - or C?

Amswer C is correct!

Raw data nav aids are always available to cross-check navigation.


Regards
Exeng

I agree with exeng, with one proviso. Keeping other waypoints on the FMC can assist with situational awareness. Distance off the centreline is not particularly helpful, except once you've intercepted the localiser, to work out how awful your approach is! :) In other words, what is the point of knowing that you're 10 miles off the centreline, if there's a mountain you can't see between you and the centrefix which you're being vectored around?

Update it. Not sure of your kit, but in ours we brief the Nav Accuracy status before ToD, and if that status changes at any stage, the box tells us, thus no need to check it (though obviously good airmanship dictates blah blah etc) Knowing displacement from extended c/line is useful for predicting turn for intercept. e.g. At 180 knots GS, and a 45 degree intercept, if we haven`t been cleared for the approach with 1 mile to c/l then might be worth giving ATC a nudge, much nicer for pax to int off a 45 degree hdg change, than shoot thru, and atttack from the other side. We are there to give a smooth safe ride after all. But one example.
How long is the other guy pushing buttons for? Surely not long enough to get that far out of the loop.

[This message has been edited by jtr (edited 22 January 2001).]

max lenz, the most important reason in favour of doing it your way, (way ‘A’ – clearing all waypoints before the FAF), is that in the event of a go around, you’ll have LNAV and VNAV available to look after the (perhaps complicated) missed approach.

If you’re under radar vectors, you may not (probably won’t) pass within the necessary distance of these waypoints to have the FMS clear them from your active plan. If you have to go around, you’re stuck with steam-driven lateral and vertical navigation until you clean the flight plan up – a potentially distracting process in a what can be a very busy time of flight.

Engaging L and/or VNAV without first taking the time to clean the flight plan up (or after making a mistake in cleaning it up) could turn the whole shootin’ match into a real dog’s breakfast. If you engage LNAV, the aircraft will want to head straight for the first bypassed waypoint after you went on to radar vectors – probably behind you. Selecting VNAV in such circumstances could give you any number of nasty surprises.

On an approach, crosschecking by the non-flying pilot should be done from raw data sources, not the FMC.