Electronic Systems and Computer Technology - Decreasing Fuel Consumption and Exhaust Gas Emissions in Transportation - page 98

The FMS has one or more Flight Management Computers (FMC) which work
with [ 16 ]:
• Flight plan information which is set by the crew;
• Airplane system data;
• Performance data including airplane drag and engine characteristics, maximum
and minimum speeds, and maximum and optimum altitudes. The flight crew
may display these parameters on a Control Display Unit (CDU) instead of
referring to a performance manual during flight; and
• Navigation data with the database which includes nearly all information that is
portrayed on conventional navigation charts. It can be depicted on navigation
displays or on the CDU [ 17 ].
FMC receives fuel data from the system indicating fuel quantity and predicts
performance based on the last valid fuel quantity with periodic update inputs for
the estimated fuel weight that is needed to keep the current gross weight data. A
message informs the crew when no update has been performed within the pre-
scribed time or when an unexpected drop in fuel quantity is detected. The content
of an automatic FMC report transmitted at pre-defined points can be a message
from the ground to the FMC. Most of them require a pilot action to be accepted.
However, there may be messages that are automatically loaded into the FMC.
The computer technology serves commands and information required to roll on
ground, and to fly an optimum altitude and direction through climbing, cruising,
and descenting. The most important commands and information are:
• Pitch, roll, and thrust commands;
• N1 rotation limits, N1 rotation targets, and commands to flight speed; and
• Position data with the computed position, which is continually updated by
signals from on-board radio navigation, Inertial Reference System (IRS), and
Global Positioning System (GPS) depending on the airplane equipment [ 18 , 19 ].
The information is passed to the Autopilot Flight Director System which
includes two separate Flight Control Computers (FCC) [ 20 ]. They send control
commands to their respective pitch and roll hydraulic systems. The flight control
operates with two separate hydraulic systems and moves F/D command bars on the
altitude indicator [ 21 ].
The Auto Throttle system (AT) provides automatic thrust control by computing
the required thrust level and moving the thrust levers with servo motors which
equalize thrust through the electronic engine controls while CDUs receive map and
route information [ 22 ].
The pilot selects the desired information for the navigation and supervises the
operating modes of the autopilot on the control display of the Electronic Flight
Instrument System (EFIS) [ 23 ].