TM 1-1520-238-10
3-34
Change 4
3.13.4 Operating Procedures.
a. ANT (audio only) Operation.
1. Mode selector switch – ANT.
2. MAN-2182-500 switch – As desired. If MAN is
selected, set the desired frequency with the five
frequency switches.
3. VOL control – As desired.
4. If cw operation is desired, TEST-TONE switch –
TONE.
b. ADF Operations.
1. Mode selector switch – ADF.
2. MAN-2182-500 switch – As desired. If MAN is
selected, set the desired frequency with the five
frequency switches.
3. VOL control – As desired. The HSI No. 2 bear-
ing pointer and the RMI pointer will indicate rela-
tive bearing to the selected ground station.
4. If cw operation is desired, TEST-TONE switch –
TONE.
c. Self-Test Operation.
NOTE
The ADF system must be in ADF mode and
receiving a valid ground station signal to
perform the self-test.
1. Set to ADF mode (para. d.2). Note position of
HSI No. 2 bearing pointer and RMI pointer.
2. TEST-TONE switch – Momentarily TEST.
3. HSI No. 2 bearing pointer and the RMI pointer
rotate 90 from their original positions and then
return to their original positions.
3.14 NON–INTEGRATED NAVIGATION SYSTEM
WARNING
The non integrated navigation system
does not meet FAA requirements for use
as a primary navigation system for IFR
operations in IMC.
The non–integrated navigation system consists of a
Heading Attitude Reference System (HARS) and either
the AN/ASN-128 or AN/ASN-137 Doppler Navigation Set
(DNS). The non–integrated navigation system is not con-
nected to, and operates independently of, the Mission
System 1553 multiplex (MUX) bus. The MUX bus is re-
sponsible for passing the DNS velocity data from the
ARINC bus to the HARS through special hardware inter-
faces in the CPG and DASE MRTUs. The MUX bus is also
responsible for tracking/filtering MAGVAR changes that
are calculated in the DNS and passing these changes to
the HARS via the same special interfaces. In this configu-
ration the HARS is dependent upon receiving DNS veloc-
ity for internal velocity damping and maintaining proper
heading and/or attitude, and the DNS is dependent upon
receiving HARS heading/attitude in order to perform the
navigation calculations. Additionally, the HARS is depen-
dent upon proper MAGVAR updates for driving the HSI,
RMI, and DNS magnetic heading inputs. The MUX bus
controller (FCC or BBC) uses the HARS inertial data out-
puts to drive all the inertial symbology presented on the
video displays. This includes the heading tape, velocity
vector, acceleration cue, horizon line, hover position box
and trim ball. The Hover Position Box will drift during a sta-
tionary hover, and conversely, the aircraft will drift if the
aircraft is flown to hold the Hover Position Box centered
on the display. The amount of drift may reach as much as
21 feet per minute, and the drift may be random in nature.
This drift is caused by HARS velocity errors, which are
strongly influenced by the DNS velocity characteristics at
these hover velocities. The following paragraphs provide
a description of the HARS and DNS internal operations
and the controls and displays used by the crew to operate
the non–integrated navigation system.
3.14.1 Heading Attitude Reference System (HARS).
a. System Description
The HARS is a doppler aided strapdown inertial reference
system. The HARS provides all attitude, velocity, and ac-
celeration data for the helicopter. The HARS aligns itself
by adjusting its own vertical axis to coincide with the
earth’s gravity vector and by measuring the rotational
speed of the earth about its inertial axis.
