ADVANCED FLIGHT CONTROL SYSTEM
The advanced flight control system (AFCS)
is an electronic system that independently
changes the position of the flight controls as
needed to keep the helicopter steady in flight.
The system stabilizes the helicopter in the pitch,
roll, and yaw axes. It also maintains a pilot-selected
airspeed, altitude, bank angle, and heading. An
automatic turn (heading select) feature is also
included. With this feature, the pilot selects a
heading and the AFCS automatically puts the
helicopter into a coordinated turn to that heading.
During flight, sensors in each flight axis sense changes
in helicopter attitude caused by outside forces such
as wind gusts. The system automatically reacts to
change the position of the flight controls to hold attitude
steady. During a maneuver, transducers on the stick
and pedal controls sense pilot commands and signal the
system to move the flight controls to change attitude.
The AFCS is a redundant installation, using two
separate but interconnected systems. Normally, both
systems operate at the same time, with each providing
half the input to the flight controls. Each system is said
to have half gain and half authority. If one system fails,
all input comes from the remaining system. However,
this input is limited to three-fourths of that provided
when both systems are working, up to the maximum
travel available from the good system. This maximum
travel stays at half of that available when both systems
are working. In this case, the remaining system is
said to have three-fourths gain and half authority. The
pilot can manually select either system at any time.
Major parts of the AFCS are the control panel,
computers, ILCAs, DASH actuator, and LCT actuators.