Fault Detection Control Logic in an Aircraft Elevator Control
System  This example shows how to design a fault detection,
isolation, and recovery (FDIR) application for a pair of
aircraft elevators with redundant actuators. The fault detection
control logic used in this model is the same that is used in the
Avionics subsystem of the Aerospace Blockset™ example entitled
"NASA HL-20 with FlightGear Interface."  Figure 1: Top level of
aircraft elevator control system model  Description of Elevator
Control System  A typical aircraft has two elevators attached on
the horizontal tails (one on each side of the fuselage). There
are a number of redundant parts in the system to enhance safety
of the aircraft.  Figure 2: Schematic showing how the components
of the elevator system are connected to one another  For
example, as shown in Figure 2, there are:    • Two independent
hydraulic actuators per elevator (four total)    • Three
separate hydraulic circuits to drive the actuators    • Two
primary flight control units (