VECTORS Waypoint - Boeing FMC

[777300ER]

Can anyone explain what effect a VECTORS waypoint has on ETA and FUEL predictions? I was always under the impression that it had no effect but recently I was told otherwise.

[None]

It depends on the FMS program. With a Pegasus FMS, I have not seen any problem. With the PIP, it depends how the vector is set up in the database, and if you selected the full approach with a transition. Sometimes you will get a situation where you will not have an arrival ETA and Fuel, but you will have that info on preceding waypoints on the legs page.
Most will do what it takes to regain the destination ETA/Fuel, because if the FMS doesn't have it, the passengers will not have an ETA. You can always reselect the full arrival as you get closer to the destination. At that point the pax have a pretty good idea of the ETA.
I haven't seen a vector fix on a 200k FMS yet, but my exposure to the 200k is minimal.

[777300ER]

Interesting. Thanks for the info. I could swear that on the B744 when I saw a VECTORS waypoint, the ETA and FUEL predictions were still there. In fact it almost appeared that the VECTORS waypoint had no effect whatsoever on the predictions. Unfortunately the FMC manual that I have does not go into enough detail to explain how this works.

[TopBunk]

On our 744's we retain ETA and fuel predictions after a vector.

Subjectively, it seems to calculate the track miles and hence times and fuels by calculating a turn from the 'vector' leg when abeam the point furthest out on the inbound course for the approach to that point itself. It does not draw in that track however.

Seems to get the predictions pretty accurate too - thinking here about the arrival to JNB 03 from the north as an example.

[777300ER]

Thanks for that TopBunk. That is the behavior that I have observed as well. I think the fellow that told me otherwise (and confused me in the first place) was confused or coming off older generation equipment.

[alexban]

Same on our 737's with 7.6 or 10.6 software,like topbunk said.We usually remove the vector,and use hdg select when needed to follow the vector .
Also, the FMC computed ETA has nothing to do with what the pax see on their screens,that time is set at departure by the cc ,on our planes.