FMS Flashcards
Main functions of the FMS
Manage automatic navigation
Optimise fuel efficiency and performance
Generate information for the f/d displays
Different modes and functions of FMC
Dual - independent calculations, outputs compared a synchronised on both pilots displays
Independent
Single - failure mode, 1 FMC feeds both displays
FMC takes inputs from
Engine and fuel data Navigation and performance databases ADC Nav aids IRS Airspeed, temp, alt Air/ground sensing - notifies when airborne Clocktime Flap position Fuel quantity sensors
Nav database
Contains nav info, normally seen on aprch plates
2 sets, updated every 28days
Pilot can Input temporary waypoints - erased when we land
Performance database
Contains info that’s normally found in the perf manual
Used to calc optimum pitch, speed and thrust control
Can’t be modified by the pilot - engineers can refine the performance factors
What would you find on the IDENT page
A/c type
Engine rating
Database update dates and serial numbers
Operation program
What would you find on the POS INIT page
Last position
Ref airport and gate
What would you find on the ROUTE page
Co route Origin Destination R/y FL no
What’s on the PERF page
Gross weight ZFW Cost index Reserves Cruising alt
What’s on the T/O page
V speeds Flap setting OAT N1 TOW
What’s on the PROG page
XTRK error VTRK error H/wind SAT Fuel quantity
How is FMC position found out
Tunes to the closest nav aids that give a line of position crossing angle between 30 and 50 degrees
Combines radio position with IRS position to obtain FMC
Continually updates
Order of priority for selection of nav aids to find FMC pos
1st - 2 or more DME stations 2nd - DME/VOR 3rd - VOR 4th - LOC and co located DME 5th - LOC
FMC calc fuel data by
Totaliser system
- measures the mass of fuel in each tank and adds up all the values to find the mass
Calculated system
- measures the amount of fuel being consumed and takes it away fro the starting fuel
Both should be =
Typical data provided by the FMS
Lateral and vertical guidance Present position Time projections Fuel projections Altitude projections
