fly-dad

Quick question for those that frequent the NAT OTS:

The FMS auto sequences between waypoints. When it does this, the time displayed by the waypoint in the FMS is the time it made the turn, not the time actually over the waypoint.

What time do you report to Gander/Shanwick, the FMS time when it made the turn to the next waypoint or the time actually over the waypoint?

Thanks

Rainboe

There is only a relatively few seconds in it. Everybody I knew just reported the time displayed on Progress page giving time at waypoint, ETA next waypoint and waypoint after that. Everybody reads it off the box, and I think hardly anybody is actually aware of the difference you advise, if indeed that is the case! Course changes are not drastic on the NAT tracks, so turning time is pretty short as the FMS does control the autopilot into quite strong banks.

411A

L1011 Hamilton Sundstrand FMS units displayed the time over the specified waypoint.
Honeywell HT9100 GPS units, likewise.
Little difference otherwise, as Rainboe clearly pointed out.

fly-dad

I always use the FMS time as well. On my last flight, however, I noticed it was a good 30 seconds when turning from 5540N to 5230N. I'm in a G-IV with a Honeywell SPZ-8000. Not much I know, but if the ETA is already two minutes off from the last position report, the early turn occasionally makes it three minutes off the estimate.

Thanks for the input.

411A

Ohhh, nice bit of kit!
If the ETA drifts off by more than three minutes, a simple call on HF fixes things jolly quick.

EMIT

Perhaps the difference between your clock and your reported time is just due to rounding or truncating. The clock usually shows minutes, not seconds.
10:52:59 will show as 10:52 on your clock, but may cause a reported waypoint time of 10:53.

I am not familiar with your FMC, but if you are really nitpicky, you may observe that waypoints are normally not "overflown", but passed by. The aircraft starts the turn slightly before reaching the waypoint so that it can transition from one leg to the other in one movement. If it waited with turning untill reaching the waypoint, it would have to re-intercept the next leg. The passage time is calculated by the FMC as the moment that the a/c is abeam the waypoint, and slight delays in drawing the new picture, with updated times and colours, may make it look like slightly different from abeam.

In short, use FMC report time for your position report (make sure your clock runs on time).