Permafrost,
Work is the curse of the Pruning classes, and your question to me disappeared onto Page 2 whilst I was off on a foray into
Muttland.
The Boeing reference that I was alluding to earlier was to do with manually entering FMC predicted landing Fuel into the Perf Init page (which does cause an INSUFFICIENT FUEL message), and not to do with wind entry procedures. It's an untidy procedure, but it does cause the entire fuel calculation to re-initialise which is a good thing.
There's lots of good practical methods of wind entry. I find it best to enter the mean wind pre-flight to give fairly good initial Arrival Time and Fuel. For short sectors, say 2 hours or less, this is probably quite OK.
Where a significant wind gradient exists, the "I am always right" guy who told you to enter the initial cruise wind was right also, but only if you enter a series of winds at different levels to ascertain the most favourable initial level. A single cruise wind in this case is of no significant value.
On longer flights (e.g. more than 2 hours), a series of winds at a sensible selection above and below the Optimum Level will again allow the FMC to sensibly predict the point of Step Climb. Again, a single level wind entry will be of no use here, it will simply be extrapolated up and down, with Step Climb scheduled at close to the Still Air Optimum Level, which is OK UNLESS there's a significant wind gradient. After entering winds above and below the present Cruise Level, I've seen the Step Climb prediction change by 600 miles, that's significant!
This is the sort of thing that can consume a great deal of time between Instructor and Trainee if he/she is to get the best from the aircraft. We operate very short (20 minute) sectors and very long (14 hours) sectors on the B777. My recommendation to trainees is -
(1) Short sectors : Step Climb is not a real consideration, mean cruise wind will suffice nicely, but do put in the descent winds so that VNAV can better optimise the descent profile.
(2) Long Sectors : Pre-flight available time usually prohibits entry of a full set of winds, so enter the mean cruise wind component to obtain reasonable Destination ETA (for you and the passengers) and Fuel (for you).
(i) Examine the wind gradient for the first few hundred miles. If there's a significant change with altitude (more than about 3 knots per 1000 feet), enter the winds from the lowest to the highest feasible cruise level. (after the initial few hundred miles, leave the mean wind for the moment). Climbing into a Jetstream can have a profound effect, Ive seen Recommended level drop from 340 to 260 after doing this on a Melbourne-Singapore flight.
(ii) On cruise, first enter the sector winds for the initial cruise level all of the way to destination.
(iii) After that, enter a good selection of winds for all of the expected levels. Now the FMC can ACCURATELY predict valid Step Climb points. If you don't have the higher level winds until later in the flight, copy the highest available winds to the higher level, remember that the wind information available down-track will propogate backwards giving you some weird FMC recommendations.
(iv) Finally, put in the descent winds so that VNAV can better optimise the descent profile.
It's time consuming, but pays dividends on long distance flights. I've seen 30 minute and several Tonnes of fuel difference at Destination after refining the winds on long flights. On short flights, it hardly makes a difference.
Regards,
Old Smokey