How does the FMS get the winds?; is it "actuals on climb up"/"forecast BOM product"/"capture when last here" Is any data shared (uploaded) across company fleets/types/frames etc.
Blockla, thank you for the question!!!
All things being equal, a 717 pilot in our operation will enter forecast winds and temps for the climb, for each enroute waypoint, and for the descent prior to engine start at the departure point. The ATIS is used for the surface wind and temp at the departure point, and the SPFIB winds derived from BoM GRIB data are used for climb, enroute and descent.
You might tell it something like this...
Climb Forecast page
F340/270/80
F265/300/45
F185/310/30
YBXX/095/10 +22C
ITSMA
F385/290/115 F340/-42
F340/280/95
F300/260/82
F265/200/42
PARTI
F385/280/120 F340/-43
F340/275/102
F300/255/92
F265/210/50
Descent Forecast
F300/260/85
F265/195/44
F100/080/30
YBYY/060/22 +15C
Once the engines are started, the Honeywell FMS interpolates the winds for all levels, and calculates a vertical profile from takeoff to touchdown, based on these winds, weight, cost index, and flight planned cruise level.
Once airborne, the aircraft 'knows' the actual wind and temperature affecting it where it is, right now, from it Air Data and Inertial/GPS solutions.
It then "blends" the actual wind with the forecast winds. Eg in the climb winds above, climbing through 8,500 feet, it gives 100 percent weight to the FL185 forecast.. It uses the actual wind for where it is right now. It blends the actual and forecast winds for intermediate levels, that is, 2,500 above, the blend is 75/25 actual/forecast. 5k above, 50/50. 7,500' above, 25/75 actual/forecast. This happens automatically, and is updating several times a second.
After the calculated TOPC, or in the cruise, it blends vertically, and ahead.
Approaching TOPD, it looks down 10,000', and blends the actual/forecast winds in the same ratios as the climb.
The only 'wind' that we enter after departure, is the surface wind and temperature at the destination, when we are within range of the ATIS. Then it is usuall the OAT at YBYY that will make a change in the TOPD, sometimes eight miles for a 10C variation from ISA.
This means....