Learjet 60 - Heading Control Switches

Learjet 60

Pilot's Manual
ATTITUDE HEADING SYSTEM
Aircraft avionics displays and
equipment requiring attitude
or head-
ing information
are supplied that information
from the dual, indepen-
dent Collins Attitude
Heading Systems (AHS 1
and AHS 2) . Each sys-
tem consists of an
attitude heading
computer with internal
compensator, a magnetic
flux sensor in the
associated wing tip,
two
HEADING control
switches, and associated
aircraft wiring . The atti-
tude
heading computer is
composed of inertial
instruments, electron-
ics,
interface hardware, processing
and memory circuits
to provide at-
titude and
heading information to
other aircraft
systems . One
magnetic slaving
unit is located in each
wing tip and is
used to sense
the earth's magnetic
field . The HEADING
SLAVE-FREE
switch al-
lows the crew to
select either Free or
Slaved Magnetic
Heading mode .
The system has
two operating modes,
normal and basic .
During nor-
mal operation, a true
airspeed input is supplied
by the air data
system
to improve accuracy .
If the true airspeed
input is lost, the system
will
continue to operate
in the basic mode .
AHS operation is
automatic
and both systems
will initialize when
battery power is
applied to the
aircraft . During
the nominal 70 second
alignment, the
system deter-
mines its
orientation with the local
vertical and
magnetic North and
performs a series
of self-test and calibration
functions . The AHS
1 and
2 systems
are powered by 28 VDC
5-amp AHS 1 and
AHS 2 circuit
breakers on the
pilot's and copilot's
circuit breaker
panels . Both AHS
1 and AHS
2 will be powered
during EMER BUS
operations . In the
event
of a power loss,
approximately 11 minutes
of back-up power
(28 VDC)
will be supplied to AHS
1 and AHS 2 by
EMER BAT 2 . This
feature
makes it unnecessary to
reinitialize the system
should a mo-
mentary power loss be
experienced . Should one
of the systems fail,
the functions of the failed system
may be assumed
by the remaining
system
using the AHS/AHS
reversionary mode .
Attitude/heading data is
provided for the following
using systems :
PM-123
Change 2
EFIS Displays -
attitude and heading
displays
Flight
Control System - attitude,
heading and
acceleration data
Weather
Radar - pitch and
roll data for antenna
stabilization
Flight Management System
- heading data
StormScope (if installed) -
pitch and roll data for
heading sta-
bilization
HEADING CONTROL SWITCHES
The
HEADING control switches,
located in the AVIONICS group
on
the pilot's
and copilot's switch panels, are
used to control the
heading
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